Hot off the presses! May 01 J Antimicrob Chemother

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Latest Articles Include:

• Guidelines (2008) for the prophylaxis and treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections in the United Kingdom
  - J Antimicrob Chemother 63(5):849-861 (2009)
  These evidence-based guidelines are an updated version of those published in 2006. They have been produced after a literature review of the treatment and prophylaxis of methicillin-resistant Staphylococcus aureus (MRSA). The guidelines aim to complement those recently published for the antibiotic treatment of common and emerging community-onset MRSA infections in the UK. The guidelines have reviewed and updated, where appropriate, previous recommendations, taking into account any changes in the UK epidemiology of MRSA, ongoing national surveillance data and the value of new antistaphylococcal agents licensed for use in UK practice. Emerging therapies that have not been licensed for UK use are not reviewed, but their future potential role has been mentioned where deemed appropriate. Recommendations are given for the treatment of common infections caused by MRSA, elimination of MRSA from carriage sites and prophylaxis of surgical site infection.
• Treatment of congenital cytomegalovirus infection: implications for future therapeutic strategies
  - J Antimicrob Chemother 63(5):862-867 (2009)
  Cytomegalovirus (CMV) infection is the most common cause of congenital infection in the developed world, occurring in [~]1% of all liveborns. Symptomatic disease occurs in 10% of all congenitally infected infants, resulting in a spectrum of clinical manifestations that include microcephaly, chorioretinitis, hepatosplenomegaly and sensorineural hearing loss, among others. Even those children who are asymptomatic at birth have a risk of hearing loss, with [~]8% experiencing this sequela. Overall, congenital CMV infection accounts for one-third of all cases of sensorineural hearing loss. The economic burden of disease exceeds $2 billion annually in the USA. Therefore, this infection has been the target for antiviral therapy. Studies performed by the National Institute of Allergy and Infectious Diseases Collaborative Antiviral Study Group (CASG) have evaluated ganciclovir for the treatment of symptomatic congenital CMV infection with central nervous system involvement. In ! a randomized, controlled clinical trial of ganciclovir treatment (6 mg/kg iv every 12 h for 6 weeks) brainstem-evoked responses were utilized as the primary endpoint and demonstrated stabilization of hearing both at 6 months and >1 year. Treatment was associated with neutropenia in over 60% of treated patients. Since ganciclovir must be given intravenously, studies with its prodrug, valganciclovir, have been performed to assess pharmacokinetics and pharmacodynamics. Currently, a clinical trial of 6 weeks versus 6 months of valganciclovir is being performed by the CASG. Notably, only intravenous ganciclovir and orally administered valganciclovir have been used to treat congenital CMV infection. Hopefully, other drugs such as maribavir will be available for evaluation in this population.
• Spread without known selective pressure of a vancomycin-resistant clone of Enterococcus faecium among broilers
  - J Antimicrob Chemother 63(5):868-872 (2009)
  ObjectivesThe aim of this paper was to describe an increased occurrence of vancomycin-resistant enterococci (VRE) in Swedish broilers since 2000 and to investigate the genetic relatedness of isolates. MethodsCaecal content from slaughtered broilers was cultured for VRE on medium supplemented with vancomycin (16 mg/L). Species identification, antibiotic susceptibility determination, vancomycin resistance genotyping, multilocus sequence typing (MLST) and characterization of Tn1546 were performed. ResultsThe proportion of VRE-positive samples increased gradually from <1% in 2000 to slightly over 40% in 2005. Between 2005 and 2006, the proportion of VRE-positive samples decreased and between 2006 and 2007, it was stable at just below 30%. All isolates tested were Enterococcus faecium and carried the vanA gene. A majority of the isolates had similar antibiograms, the same MLST sequence type and Tn1546 transposon. ConclusionsThe proportion of VRE-positive samples from bro! ilers has increased since 2000, and this is due to the spread of one major clone. Moreover, this has taken place in an environment without any obvious selective pressure.
• Genotypic and phenotypic relationships among methicillin-resistant Staphylococcus aureus from three multicentre bacteraemia studies
  - J Antimicrob Chemother 63(5):873-876 (2009)
  BackgroundAt a time when the molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) was changing, we sought to characterize several genotypic markers and glycopeptide susceptibility features of clinical isolates from patients with bacteraemia. MethodsOne hundred and sixty-eight MRSA bloodstream isolates obtained from three multicentre clinical trials were microbiologically and genotypically characterized. ResultsAll isolates were susceptible to vancomycin (MIC [≤] 2 mg/L); 38% belonged to accessory gene regulator (agr) group I, 52% belonged to group II and 10% belonged to group III. Typing of the staphylococcal cassette chromosome mec (SCCmec) showed that 67% were type II and 33% were type IV. The agr group II polymorphism was associated with SCCmec II (P < 0.001). Fifty-three percent of SCCmec II and 27% of SCCmec IV isolates had vancomycin MICs [≥]1 mg/L (P = 0.001). One hundred percent of agr II strains were predicted to be members of c! lonal complex 5. SCCmec II was the genetic marker most predictive of vancomycin MICs of [≥]1 mg/L. SCCmec IV isolates were more likely to have vancomycin MICs [≤]0.5 mg/L. ConclusionsGiven that SCCmec IV is a marker for a community-based organism for which less prior vancomycin exposure is predicted, we conclude that prior antibiotic exposure in agr group II organisms may account for their increased vancomycin MICs.
• StaphVar-DNA microarray analysis of accessory genome elements of community-acquired methicillin-resistant Staphylococcus aureus
  - J Antimicrob Chemother 63(5):877-885 (2009)
  ObjectivesApproximately 75% of the genome of Staphylococcus aureus (the core' genome) is highly conserved between strains, whereas the remaining 25% (the accessory' genome) is composed of mobile genetic elements (MGEs), containing virulence and resistance genes. We developed a composite microarray focused on resistance and virulence genes located on the accessory or core-variable genome to characterize a collection of Belgian community-acquired methicillin-resistant S. aureus (CA-MRSA) strains. MethodsOligonucleotide probes targeting 403 genes encoding antimicrobial resistance (35%), virulence (28%) and adhesion (31%) factors were designed among eight S. aureus sequenced genomes. The StaphVar Array was validated by testing five of the strains used for the design and utilized to characterize 13 CA-MRSA strains representative of the multilocus sequence typing (MLST) sequence types circulating in Belgium. ResultsAnalysis of the gene content of the five reference strai! ns by the StaphVar Array matched 90% to 97% of the theoretical results. Analysis of CA-MRSA strains showed that 54.4% of the genes tested were strain-dependent. Strains presented specific exotoxin, enterotoxin, cytolysin and adhesin gene profiles by MLST lineage. One exception to these lineage-specific' profiles was the variable presence of the arginine catabolic mobile element (characteristic of the USA300 clone) within ST8 strains. ConclusionsThe StaphVar Array enables the characterization of [~]400 variable resistance and virulence determinants in S. aureus. CA-MRSA strains displayed extensive diversity in virulence and resistance profiles. The presence of the USA300 clone in Belgium was confirmed. Although mainly located on MGEs, associations of virulence genes were highly conserved within strains of the same MLST lineage.
• Emergence of high-level fluoroquinolone resistance in emm6 Streptococcus pyogenes and in vitro resistance selection with ciprofloxacin, levofloxacin and moxifloxacin
  - J Antimicrob Chemother 63(5):886-894 (2009)
  ObjectivesTo investigate the prevalence of fluoroquinolone resistance in Streptococcus pyogenes and its in vitro selection by ciprofloxacin and the respiratory fluoroquinolones, levofloxacin and moxifloxacin. MethodsS. pyogenes (n = 5851) recovered from pharyngitis and invasive infections during 2003-06 in Belgium were screened for fluoroquinolone non-susceptibility (ciprofloxacin MIC [≥]2 mg/L) and further studied for mutations in the topoisomerase genes, reserpine-sensitive efflux, clonality by PFGE and emm typing. Fourteen well-characterized fluoroquinolone-non-susceptible or -susceptible isolates were exposed stepwise to increasing levels of ciprofloxacin, levofloxacin and moxifloxacin. Selected mutants with increased MICs were analysed for resistance mechanisms. Mutation frequencies at 2x and 4x MIC of moxifloxacin and levofloxacin were estimated for a clinical emm6 parent strain carrying mutations in both parC and gyrA. ResultsPrevalence of fluoroquinolone-n! on-susceptible S. pyogenes (n = 437; 7.47%) increased significantly from 2.08% and 5.08% to 13.11% during 2003-05 and decreased to 8.93% in 2006 ({chi}2 test; P [≤] 0.001). emm6 constituted 80.09% of the total fluoroquinolone-non-susceptible isolates. Of the 71 S. pyogenes sequenced, 70 harboured first-step parC or gyrA mutations correlating with ciprofloxacin MICs 2-8 mg/L. Reserpine-sensitive efflux was not observed. One emm6parC mutant (Ser79Ala) also showed a second-step mutation in gyrA (Ser81Tyr), with MICs of ciprofloxacin, levofloxacin and moxifloxacin of 32, 8 and 1 mg/L, respectively. Mean mutation frequencies under moxifloxacin selection were 500- to 30 000-fold higher for this strain than those for an emm6 control strain. Selection of the emm6 double mutant with moxifloxacin generated a mutant with a moxifloxacin MIC of 64 mg/L and a levofloxacin MIC of 128 mg/L, and an additional Asp83Tyr substitution in ParC. ConclusionsWe report an emergence of levofloxac! in and high-level ciprofloxacin resistance associated with a s! econd-step gyrA mutation in a clinical emm6 S. pyogenes. The observed high mutation frequency and in vitro selection of high-level resistance to the respiratory fluoroquinolones in the emm6 double mutant is of concern.
• Novel CTX-M {beta}-lactamase genotype distribution and spread into multiple species of Enterobacteriaceae in Changsha, Southern China
  - J Antimicrob Chemother 63(5):895-900 (2009)
  ObjectivesThe aim of this study was to undertake a survey of the occurrence of CTX-M and SHV extended-spectrum {beta}-lactamase (ESBL) genotypes in Enterobacteriaceae from Hunan Province, China. MethodsClinical isolates (425) from three major hospitals in Changsha, Hunan Province, were collected between October 2004 and July 2005, and their antimicrobial susceptibilities of the genotype of blaCTX-M and blaSHV were determined. Random amplified polymorphic DNA was used to characterize the clonality of all of the isolates. ResultsThe overall rate of ESBL-positive isolates was 33.4% (142/425). The dominant ESBLs were CTX-M types, and were found in 109/142 (76.8%) isolates comprising seven different genera/species, namely Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Enterobacter aerogenes, Citrobacter freundii, Proteus vulgaris and Providencia stuartii. The most common blaCTX-M genotypes were blaCTX-M-14 (47.7%), blaCTX-M-3 (29.4%) and blaCTX-M-15 (17.4%! ). A novel gene derived from blaCTX-M-15, blaCTX-M-82 (Ala-40[->]Pro), was identified. ConclusionsThe dominant ESBL genotype in Hunan Province was blaCTX-M. The high prevalence (17.4%) of blaCTX-M-15 has not previously been reported from China. Our results identify that an epidemic of blaCTX-M in Changsha, Hunan Province, has evolved with the appearance and spread of blaCTX-M-15 against the dominant genotypes blaCTX-M-14 and blaCTX-M-3. The worldwide dominance of blaCTX-M-15 could be poised to spread to China, displacing the current prevailing genotypes.
• Identification of blaIMP-22 in Pseudomonas spp. in urban wastewater and nosocomial environments: biochemical characterization of a new IMP metallo-enzyme variant and its genetic location
  - J Antimicrob Chemother 63(5):901-908 (2009)
  ObjectivesThe aim of the study was the biochemical characterization of a new variant of the metallo-{beta}-lactamase, IMP-22. Moreover, the genetic environment of the blaIMP-22 gene was investigated in Pseudomonas fluorescens and Pseudomonas aeruginosa collected from urban wastewater and a teaching hospital in L'Aquila, Italy. MethodsMolecular characterization of genetic elements was carried out by PCR and DNA sequencing methods. The new enzyme was purified from recombinant Escherichia coli BL21(DE)Rosetta/pBC-SK/IMP-22. Steady-state kinetic parameters (Km and Vmax) were determined for a large pattern of substrates. ResultsA new IMP metallo-{beta}-lactamase gene was found in a class 1 integron and in one case, in a plasmid of Pseudomonas spp. The blaIMP-22 encodes for a pre-protein of 246 amino acids and the N-terminus of the mature {beta}-lactamase (NH2-PDLK) was also determined. The molecular mass and pI were 24 930 Da and 6.2, respectively. On the basis of the kin! etic parameters calculated (Km and Vmax), IMP-22 was found to hydrolyse narrow- and extended-spectrum {beta}-lactams. Enzyme activity was found to be inhibited by metal chelators such as EDTA, 1,10-o-phenathroline and dipicolinic acid with an IC50 of 800, 750 and 300 {micro}M, respectively. ConclusionsThe finding of the blaIMP-22 gene in P. fluorescens environmental strains and P. aeruginosa clinical isolate suggests the ongoing spread of blaMBL genes in several bacterial species and in different environments.
• Ciprofloxacin selects for multidrug resistance in Salmonella enterica serovar Typhimurium mediated by at least two different pathways
  - J Antimicrob Chemother 63(5):909-916 (2009)
  ObjectivesThe aim of this study was to understand the role of ramA in conferring multidrug resistance (MDR) in Salmonella enterica serovar Typhimurium. MethodsTwo phenotypically distinct isogenic MDR laboratory mutants derived from Salmonella Typhimurium SL1344 and three human clinical isolates from a patient that failed antibiotic therapy, including with ciprofloxacin, were investigated for the cause of MDR. MICs were determined by agar dilution and efflux activity assessed by monitoring the accumulation of Hoechst 33342. The combination of specific genes and MDR was assessed by inactivation, and complementation RT-PCR was used to assess gene expression and DNA sequencing to identify mutations within genes of interest. ResultsMutation in ramR and the consequent over-production of ramA and acrB were revealed in one laboratory mutant selected with ciprofloxacin and this was associated with cyclohexane tolerance. Complementation of SL1344 ramR::aph with pUC19 ramRmutan! t conferred MDR and cyclohexane tolerance. However, analysis of a second ciprofloxacin-selected MDR mutant, which was susceptible to cyclohexane, revealed no mutation in ramR or altered expression of marA, soxS or rob. There was a mutation in ramR in both the pre- and post-therapy clinical isolates and no difference between the isolates in the level of expression of ramA. ConclusionsThese data show that ciprofloxacin exposure can select for mutations within ramR and consequently mediate MDR. These data also indicate that there is at least one further unidentified gene in addition to marA, soxS, rob and ramA that confers MDR in S. enterica.
• Characterization of fluoroquinolone-resistant Shigella flexneri in Hangzhou area of China
  - J Antimicrob Chemother 63(5):917-920 (2009)
  ObjectivesThe aim of this study was to characterize fluoroquinolone-resistant Shigella and determine whether the qnr and aac(6')-Ib-cr genes could contribute to sporadic shigellosis at the clinic in the Hangzhou area of China. MethodsA total of 202 strains of Shigella (79 Shigella sonnei and 123 Shigella flexneri ) isolated from sporadic cases of shigellosis from 1998 to 2007 were analysed for their antimicrobial susceptibility. The gyrA, gyrB, parC, parE, qnr and aac(6')-Ib-cr genes and the profiles and incompatibility of plasmids were characterized. Chromosomal DNA fingerprinting was determined by XbaI-based digestion and PFGE. ResultsAll strains of S. sonnei were susceptible to fluoroquinolones (ciprofloxacin and levofloxacin) while 15 out of 123 strains of S. flexneri were resistant. All of the 15 resistant strains displayed common mutations in the gyrA and parC genes and formed eight distinct groups with unique molecular characteristics. Notably, 10 isolates sho! wed mutations at codon 87 of gyrA, and the other 5 were qnrS-positive. Two strains were positive for the aac(6')-Ib-cr gene. Importantly, this is the first report of qnrS- and aac(6')-Ib-cr-positive Shigella in China, the qnrS-positive S. flexneri serotypes 1a, 2a and 4c and the aac(6')-Ib-cr-positive S. flexneri serotypes 2a and 4c worldwide. ConclusionsThe common mutations at position 83 of gyrA and position 80 of parC were crucial for resistance to nalidixic acid in S. flexneri. The mutation at position 87 of gyrA or the presence of the qnrS gene is necessary for high-level resistance to fluoroquinolones in Shigella isolates from China.
• Evidence that impurities contribute to the fluorescence of the polyene antibiotic amphotericin B
  - J Antimicrob Chemother 63(5):921-927 (2009)
  ObjectivesBased on the assertion that fluorescence spectroscopy detects dimers of the polyene antibiotic amphotericin B (AmB), this technique was recently proposed to analyse the interaction of the drug with cell membranes. However, contradictory results indicate that this dimeric' fluorescence might actually originate from polyene impurities. We used a highly purified AmB to challenge this last proposal. MethodsComparison of the fluorescence of AmB from different origins was made in dimethyl sulphoxide (DMSO); concentration and sodium dodecyl sulphate (SDS) addition dependencies were analysed in water. ResultsExcitation of fluorescence in the absorption band of the AmB monomer (around 410 nm) revealed no difference between the different samples, in contrast with what was observed by excitation in the absorption wavelengths of self-associated AmB (around 325 nm). Furthermore, in this latter case, no concentration dependence was observed, in DMSO or in water. SDS add! ition increased the fluorescence in water. ConclusionsThe fluorescence of AmB observed by excitation in the absorption wavelengths of self-associated species (around 325 nm) is explainable by the presence of impurities. Fluorescence is probably not appropriate for characterization of the drug interaction with cell membranes.
• Inhibition of MptpB phosphatase from Mycobacterium tuberculosis impairs mycobacterial survival in macrophages
  - J Antimicrob Chemother 63(5):928-936 (2009)
  ObjectivesThe secreted Mycobacterium tuberculosis protein tyrosine phosphatase (MptpB) is a virulence factor for M. tuberculosis and contributes to its survival within host macrophages. The aim of this study was to identify potent selective inhibitors of MptpB and to determine the efficacy of these compounds in mycobacterium-infected macrophages. MethodsThe inhibitory effect of a small library of compounds on MptpB was first examined in vitro. The efficacy of these compounds was further examined in mycobacterium-infected macrophages. ResultsWe have identified a new family of double-site isoxazole-based compounds that are potent selective inhibitors of MptpB. Importantly, the inhibitors substantially reduce mycobacterial survival in infected macrophages. In contrast with current anti-tubercular drugs, these MptpB inhibitors do not have bactericidal action but rather, severely impair mycobacterial growth within macrophages. Docking analysis suggests a double-site bindi! ng mechanism of inhibition with the isoxazole head in the active site and a salicylate group in a secondary binding pocket that is a unique structural feature of MptpB. ConclusionsThese results provide the first evidence that inhibition of phosphatases can be exploited against mycobacterial infections. The cell activity of the inhibitors together with the lack of MptpB human orthologues suggests a strong potential for these compounds to be developed as drug candidates against tuberculosis and promises a new therapeutic strategy to tackle clearance and reduce the persistence of M. tuberculosis infection.
• Effect of a solution containing citrate/Methylene Blue/parabens on Staphylococcus aureus bacteria and biofilm, and comparison with various heparin solutions
  - J Antimicrob Chemother 63(5):937-945 (2009)
  ObjectivesSome antibiotic solutions increase bacterial resistance and may cause toxic side effects. Heparin, frequently used as an anticoagulant in catheter lock solutions, may cause bleeding and stimulate biofilm formation. The aim of this study was to investigate the effect of a new antibacterial/antithrombotic solution, citrate/Methylene Blue/parabens (C/MB/P), versus various heparin solutions on the viability and the structure of preformed mature biofilms of Staphylococcus aureus bacteria. The degree of eradication of both planktonic and sessile microorganisms was evaluated. MethodsThe changes in the structure of biofilms after exposure to C/MB/P and several concentrations of heparin were analysed by means of confocal laser scanning microscopy. COMSTAT image analysis was utilized to compare biofilm biomass, average and maximum height, surface coverage and roughness coefficient. Viability studies were performed on both biofilms and supernatant solutions. ResultsC/! MB/P, in contrast to heparin solutions, significantly reduced biofilm biomass and thickness and reduced viability by 5 log when compared with saline treatment. No viable planktonic bacteria were detected and the few remaining biofilm cells appeared to be lysed. In contrast, most heparin solutions only reduced viability up to 1.0 log and failed to eradicate planktonic bacteria. ConclusionsC/MB/P has a rapid bactericidal effect on the preformed, mature biofilm of S. aureus. The structural changes of biofilms treated with C/MB/P, together with the observed log reduction of viable biofilm cells, confirmed the high potential of this solution to eliminate sessile bacteria. Furthermore, the tested solution entirely eliminated planktonic bacteria detached from the biofilm.
• Sensitization of Campylobacter jejuni to fluoroquinolone and macrolide antibiotics by antisense inhibition of the CmeABC multidrug efflux transporter
  - J Antimicrob Chemother 63(5):946-948 (2009)
  ObjectivesThe aim of this study was to investigate the feasibility and efficacy of antisense-mediated gene silencing by peptide nucleic acid (PNA) for specific inactivation of the CmeABC multidrug efflux transporter in Campylobacter jejuni. MethodsPNA was designed to bind to the cmeA transcript and to inhibit the translation of CmeA, the periplasmic component of the RND-type CmeABC efflux transporter of C. jejuni. Inhibition of CmeA production was determined by western blotting. MICs of clinically important antibiotics, including ciprofloxacin and erythromycin, were measured in the presence of the CmeA-specific PNA (CmeA-PNA). ResultsCmeA-PNA greatly reduced the expression level of CmeA. Consistent with the reduced CmeA production, CmeA-PNA rendered C. jejuni strains more susceptible to ciprofloxacin and erythromycin. At a concentration of 2 {micro}M, CmeA-PNA resulted in 8- and 4-fold reductions in the MICs of ciprofloxacin and erythromycin, respectively, in C. jeju! ni NCTC 11168. CmeA-PNA also increased the susceptibility to the antibiotics in C. jejuni strains that were resistant to ciprofloxacin or erythromycin. ConclusionsAntisense technology is a feasible method to suppress the function of the CmeABC multidrug efflux transporter, which may be further exploited to control antibiotic-resistant Campylobacter.
• Vinaxanthone, a new FabI inhibitor from Penicillium sp.
  - J Antimicrob Chemother 63(5):949-953 (2009)
  ObjectivesBacterial enoyl-ACP reductase (FabI) has been validated as a novel antibacterial target for tackling infections caused by multidrug-resistant pathogens. A few FabI inhibitors, however, are known. This study isolated a new FabI inhibitor from Penicillium sp. MethodsA screening programme led to the selection of a Penicillium sp. producing a strong FabI-inhibitory metabolite. The chemical structure of the isolated FabI inhibitor was elucidated by mass spectrometry and nuclear magnetic resonance spectral data. The antibacterial target of the inhibitor was validated by overexpression assays. ResultsThe isolated FabI inhibitor was elucidated to be vinaxanthone. It selectively inhibited Staphylococcus aureus FabI with an IC50 of 0.9 {micro}M; it did not affect FabK, an enoyl-ACP reductase of Streptococcus pneumoniae. Consistent with its inhibition of FabI, the inhibitor prevented intracellular fatty acid synthesis while it did not affect protein biosynthesis. It a! lso prevented the growth of S. aureus as well as methicillin-resistant S. aureus (MRSA) and quinolone-resistant S. aureus. Importantly, fabI-overexpressing S. aureus showed reduced susceptibility to the inhibitor compared with the wild-type strain, demonstrating that its antibacterial action is mediated by inhibition of FabI. ConclusionsVinaxanthone is a new FabI-directed antibacterial of natural origin that could have potential for further development as a new anti-MRSA agent.
• Spectrum of activity and mode of action of REP3123, a new antibiotic to treat Clostridium difficile infections
  - J Antimicrob Chemother 63(5):954-963 (2009)
  ObjectivesThe aim of this study was to characterize the antimicrobial profile of REP3123, a novel inhibitor of methionyl-tRNA synthetase (MetRS) in development for the treatment of Clostridium difficile infection. MethodsThe spectrum of activity of REP3123 was determined by susceptibility testing of C. difficile and non-target organisms. The mode of action was studied by enzyme inhibition assays, macromolecular synthesis assays, target overexpression and selection of spontaneous resistant mutants. ResultsREP3123 was active against a collection of 108 clinical isolates of C. difficile and against epidemic, moxifloxacin-resistant BI/NAP1/027 strains (MIC range=0.5-1 mg/L and MIC90 = 1 mg/L). The spectrum of activity included clinically important aerobic Gram-positive cocci such as Staphylococcus aureus, Streptococcus pyogenes, Enterococcus faecalis and Enterococcus faecium (MIC90s < 1 mg/L), but REP3123 was not active against most Gram-negative bacteria. REP3123 target! ed C. difficile MetRS with a calculated inhibition constant (Ki) of 0.020 nM, and selectivity was >1000-fold over human mitochondrial and cytoplasmic MetRS. The specific mode of action within bacterial cells was demonstrated by macromolecular synthesis assays that showed inhibition of protein synthesis by REP3123, and by metS overexpression, which resulted in a 16-fold increase in MIC for REP3123. Spontaneous REP3123-resistant mutants of C. difficile (MICs, 4-128 mg/L) arose with frequencies of 10-8-10-9 and harboured distinct point mutations within the metS gene, resulting in 13 different amino acid substitutions. Most of the MetRS substitutions caused reduced catalytic efficiency and a growth fitness burden. ConclusionsREP3123 demonstrated a favourable microbiological profile and was found to target C. difficile with high specificity and selectivity.
• Inhibitory effect of REP3123 on toxin and spore formation in Clostridium difficile, and in vivo efficacy in a hamster gastrointestinal infection model
  - J Antimicrob Chemother 63(5):964-971 (2009)
  ObjectivesREP3123 is a fully synthetic methionyl-tRNA synthetase inhibitor in pre-clinical development as a novel agent to treat Clostridium difficile infection (CDI). This novel agent was investigated for its ability to block the production of toxins and spores, and was tested for efficacy in vivo in a hamster model. MethodsClostridial toxin levels were determined qualitatively using monoclonal antibodies and by cytotoxicity assays. Spores were detected by staining and by quantitative dilution plating after ethanol treatment. Efficacy of REP3123 was tested in a clindamycin-induced C. difficile hamster gastrointestinal (GI) infection model. ResultsREP3123 at concentrations as low as 1 mg/L inhibited de novo toxin production in high cell density, stationary phase cultures of C. difficile. Among comparator agents currently used for CDI therapy, vancomycin required much higher levels of 20 mg/L, and metronidazole had no effect on toxin levels. REP3123 caused a >10-fold ! reduction of the sporulation rate in vitro. Vancomycin and, in particular, metronidazole appeared to promote the formation of spores. REP3123, at concentrations as low as 0.5 mg/kg, demonstrated efficacy in the hamster model of CDI and was superior to vancomycin in the overall survival of the animals at the end of the study (33 days). ConclusionsREP3123 inhibited growth of C. difficile, affected the production of toxins and spores and demonstrated superior efficacy compared with vancomycin in the hamster GI infection model. This agent may be a promising candidate for CDI treatment; in particular, the inhibition of toxin production and spore formation may reduce the severity and spread of the disease, respectively.
• Comparative in vitro activity of REP3123 against Clostridium difficile and other anaerobic intestinal bacteria
  - J Antimicrob Chemother 63(5):972-976 (2009)
  ObjectivesThe aim of this study was to determine the anaerobic spectrum of activity of REP3123, a novel diaryldiamine that inhibits bacterial methionyl-tRNA synthetases in Gram-positive bacteria. MethodsFifty recent clinical isolates of Clostridium difficile from patients diagnosed with C. difficile infection and 223 other intestinal normal flora anaerobes were tested for their susceptibility to REP3123 and four or five comparator agents by the agar dilution method using supplemented Brucella agar with 5% laked sheep blood. ResultsAll strains of C. difficile were inhibited by 0.5-1 mg/L REP3123, including those resistant to moxifloxacin and clindamycin. REP3123 lacked activity against many normal flora anaerobes in the gut, including Clostridium ramosum, bifidobacteria, lactobacilli of the Lactobacillus casei-rhamnosus-plantarum group and Gram-negative anaerobes. ConclusionsREP3123 demonstrated good potency against C. difficile, but limited activity against many oth! er intestinal anaerobic species, thus, in theory, maintaining the colonization resistance barrier.
• Daptomycin pharmacodynamics against Staphylococcus aureus hemB mutants displaying the small colony variant phenotype
  - J Antimicrob Chemother 63(5):977-981 (2009)
  ObjectivesStaphylococcus aureus small colony variants (SCVs) are slow-growing morphological variants associated with persistent infections. While vancomycin activity has been shown to be attenuated against SCVs of S. aureus, few data exist regarding daptomycin. The objective was to evaluate the pharmacodynamics of daptomycin against defined S. aureus mutants displaying the SCV phenotype. MethodsTwo S. aureus hemB mutants (Ia48 and III33) displaying the SCV phenotype and their parental strains (COL and Newman) were evaluated. Time-kill experiments were performed using a starting inoculum of 106 cfu/mL at 0, 0.25, 0.5, 1, 2, 4, 8, 16, 32 and 64 times the MIC. Samples were obtained at 0, 1, 2, 4, 6, 8 and 24 h, plated and incubated to determine colony counts. A Hill-type pharmacodynamic mathematical model was fitted to the data to characterize the effect. ResultsBactericidal activity for daptomycin was achieved and occurred in a concentration-dependent manner against bo! th hemB mutants and their parental strains. Against strains with normal phenotype, bactericidal activity was achieved rapidly, within 2 h at concentrations [≥]16 times the MIC, while against SCVs, bactericidal activity was achieved within 6 h at concentrations [≥]16 times the MIC. Against both hemB mutants, daptomycin maintained bactericidal activity at 24 h, with similar profiles of killing activity when compared with their parental strains. ConclusionsDaptomycin achieved bactericidal activity against S. aureus hemB mutants and parenteral isolates. Daptomycin represents a potential therapeutic option for infections caused by S. aureus strains displaying the SCV phenotype and additional studies are warranted.
• Pharmacodynamic evaluation of tigecycline against Acinetobacter baumannii in a murine pneumonia model
  - J Antimicrob Chemother 63(5):982-987 (2009)
  ObjectivesTigecycline is an extended-spectrum antibiotic with activity against Acinetobacter spp. (ACB), an increasingly common cause of nosocomial pneumonia. Although this compound is under investigation for this indication, supportive pharmacodynamic data are not yet available at this infection site. The objective of this study was to characterize the exposure-response relationship of tigecycline with ACB in an established murine pneumonia model. MethodsThe pharmacokinetic profile of tigecycline was evaluated in infected neutropenic mice. Tigecycline 6.25, 12.5, 25, 50, 100, 200, 300 and 400 mg/kg, in single or two to six divided subcutaneous doses, were tested against all ACB isolates. Efficacy, defined as the log10 change in bacterial cfu/mL, was assessed after a 24 h course of therapy. Tigecycline exposures in serum were corrected for dose-specific protein binding. The relationship between the area under the free concentration-time curve to MIC (fAUC/MIC) and cha! nge in bacterial density was determined using the sigmoid Emax model. ResultsTigecycline displayed linear pharmacokinetics with a mean half-life of 11.3 {+/-} 1.4 h. Efficacy correlated well with fAUC/MIC (R2 = 0.96). The mean 80%, 50% effective and stasis exposures (fAUC/MIC) were 17, 8 and 6, respectively. Maximal efficacy for the five Acinetobacter baumannii studied was 3.4 log kill. ConclusionsTigecycline efficacy in this murine ACB pneumonia model was well predicted by fAUC/MIC. Requisite tigecycline exposures for efficacy appear to be higher for ACB pneumonia than for other pathogens reported of non-respiratory infections.
• Nevirapine pharmacokinetics in HIV-infected and HIV/HCV-coinfected individuals
  - J Antimicrob Chemother 63(5):988-991 (2009)
  ObjectivesAn increased risk of drug-related liver injury has been repeatedly reported in individuals infected with hepatitis C virus (HCV) receiving the antiretroviral drug nevirapine. This study was undertaken to assess the differences in the pharmacokinetics of nevirapine between patients with HIV/HCV coinfection and HIV infection that could explain higher rates of hepatotoxicity. MethodsA 12 h pharmacokinetic analysis was performed in 18 patients: 7 HIV/HCV-coinfected and 11 HIV-monoinfected. Advanced liver disease was an exclusion criterion in order to assess the impact of chronic HCV infection alone. ResultsComparing the two groups, no difference was observed between minimum and maximum drug levels or total drug exposure in terms of area under the curve. ConclusionsHepatitis C coinfection does not alter the pharmacokinetics of nevirapine in patients with preserved liver function.
• Saquinavir exposure in HIV-infected patients with chronic viral hepatitis
  - J Antimicrob Chemother 63(5):992-997 (2009)
  ObjectivesThe aim of this study was to assess the influence of hepatitis B virus or hepatitis C virus co-infection and the extent of liver fibrosis on saquinavir and ritonavir pharmacokinetics in HIV-infected subjects without liver function impairment. MethodsA cross-sectional, comparative study enrolling HIV-infected adults receiving saquinavir/ritonavir 1000/100 mg twice daily or 1500/100 mg once daily was conducted. Patients with chronic viral hepatitis (HEP+) were grouped as having advanced liver fibrosis (HEP+/FIB+) or not (HEP+/FIB-) based on the FIB-4 index. Saquinavir and ritonavir trough concentrations (Ctrough) in plasma were determined by HPLC. The geometric mean ratio (GMR) was used to compare saquinavir and ritonavir Ctrough between HEP- and HEP+ patients, and the influence of the extent of liver fibrosis on saquinavir and ritonavir pharmacokinetics was explored using analysis of variance. ResultsOne hundred and thirty-eight patients on twice-daily saqui! navir/ritonavir (67 HEP-, 71 HEP+) and 36 patients on once-daily saquinavir/ritonavir (12 HEP-, 24 HEP+) were included. Saquinavir Ctrough was comparable between HEP- and HEP+ patients receiving either saquinavir/ritonavir 1000/100 mg twice daily [GMR 0.91, 95% confidence interval (CI) 0.60-1.37; P = 0.655] or 1500/100 mg once daily (GMR 0.88, 95% CI 0.39-1.97; P = 0.752). Similarly, ritonavir Ctrough was also comparable between HEP- and HEP+ patients. The extent of liver fibrosis was not significantly related to saquinavir or ritonavir Ctrough in patients receiving either of the two studied doses. ConclusionsSaquinavir Ctrough was not increased in HIV-infected patients with chronic viral hepatitis in the absence of liver function impairment. These results confirm that no specific dose modification of saquinavir/ritonavir should be recommended in this setting.
• Peripheral and visceral fat changes following a treatment switch to a non-thymidine analogue or a nucleoside-sparing regimen in HIV-infected subjects with peripheral lipoatrophy: results of ACTG A5110
  - J Antimicrob Chemother 63(5):998-1005 (2009)
  BackgroundSwitching a thymidine analogue to a non-thymidine analogue or changing to a nucleoside-sparing regimen has been shown to partially reverse peripheral lipoatrophy. The current study evaluated both approaches. MethodsSubjects at 15 AIDS Clinical Trial Group sites receiving thymidine analogue stavudine- or zidovudine-containing regimens with plasma HIV RNA [≤]500 copies/mL and lipoatrophy were prospectively randomized to: (i) switch the thymidine analogue to abacavir; (ii) discontinue all antiretrovirals and switch to lopinavir/ritonavir plus nevirapine (LPV/r+NVP); or (iii) delay switching for 24 weeks (ClinicalTrials.gov identifier: NCT00028314 ). Single-slice computer tomography of mid-thigh and abdominal fat and metabolic and virological/immunological parameters were measured at baseline and weeks 24 and 48. ResultsAmong the 101 patients enrolled, there were significant subcutaneous thigh fat and subcutaneous abdominal tissue (SAT) increases over time a! nd decreases in visceral adipose tissue to total adipose tissue (VAT:TAT) ratios for both interventions, and a decrease in VAT for abacavir. CD4 increased in the LPV/r+NVP arm. LPV/r+NVP had a significantly shorter time to grade 3 or higher toxicity (P = 0.007), but discontinuation rates were similar. Glucose levels did not change, but insulin decreased in the LPV/r+NVP arm. Lipids tended to increase in the LPV/r+NVP arm. ConclusionsSwitching stavudine or zidovudine to a non-thymidine analogue or changing to a nucleoside reverse transcriptase inhibitor-sparing regimen is associated with qualitatively similar improvements in thigh fat, SAT and VAT:TAT ratio at 48 weeks. Abacavir also resulted in VAT reductions and LPV/r+NVP resulted in CD4 count increases.
• Design and validation of new genotypic tools for easy and reliable estimation of HIV tropism before using CCR5 antagonists
  - J Antimicrob Chemother 63(5):1006-1010 (2009)
  BackgroundGenotypic tools may allow easier and less expensive estimation of HIV tropism before prescription of CCR5 antagonists compared with the Trofile(R) assay (Monogram Biosciences, South San Francisco, CA, USA). MethodsPaired genotypic and Trofile(R) results were compared in plasma samples derived from the maraviroc expanded access programme (EAP) in Europe. A new genotypic approach was built to improve the sensitivity to detect X4 variants based on an optimization of the webPSSM algorithm. Then, the new tool was validated in specimens from patients included in the ALLEGRO trial, a multicentre study conducted in Spain to assess the prevalence of R5 variants in treatment-experienced HIV patients. ResultsA total of 266 specimens from the maraviroc EAP were tested. Overall geno/pheno concordance was above 72%. A high specificity was generally seen for the detection of X4 variants using genotypic tools (ranging from 58% to 95%), while sensitivity was low (ranging fr! om 31% to 76%). The PSSM score was then optimized to enhance the sensitivity to detect X4 variants changing the original threshold for R5 categorization. The new PSSM algorithms, PSSMX4R5-8 and PSSMSINSI-6.4, considered as X4 all V3 scoring values above -8 or -6.4, respectively, increasing the sensitivity to detect X4 variants up to 80%. The new algorithms were then validated in 148 specimens derived from patients included in the ALLEGRO trial. The sensitivity/specificity to detect X4 variants was 93%/69% for PSSMX4R5-8 and 93%/70% for PSSMSINSI-6.4. ConclusionsPSSMX4R5-8 and PSSMSINSI-6.4 may confidently assist therapeutic decisions for using CCR5 antagonists in HIV patients, providing an easier and rapid estimation of tropism in clinical samples.
• Effect of long-term trimethoprim/sulfamethoxazole treatment on resistance and integron prevalence in the intestinal flora: a randomized, double-blind, placebo-controlled trial in children
  - J Antimicrob Chemother 63(5):1011-1016 (2009)
  ObjectivesThe aim of this study was to test the hypothesis that trimethoprim/sulfamethoxazole selects for integron-positive and multidrug-resistant Enterobacteriaceae in the intestinal flora. MethodsDuring 1 year of follow-up, antibiotic susceptibility and the presence of integrons were determined in faecal Enterobacteriaceae isolated from 99 children with chronic active otitis media, randomly assigned to treatment with trimethoprim/sulfamethoxazole or placebo (http://www.clinicaltrials.gov/; trial registration number NCT00189098 ). ResultsAt 6 and 12 weeks of follow-up, 32 (91%) and 24 (67%) children in the trimethoprim/sulfamethoxazole group carried trimethoprim/sulfamethoxazole-resistant Enterobacteriaceae versus 10 (21%) and 8 (17%) children in the placebo group [rate differences (RDs): 70 (95% CI: 55; 85) and 50 (95% CI: 31; 69)], respectively. Multiresistance also increased during trimethoprim/sulfamethoxazole treatment. At 6 weeks of follow-up, the integron pr! evalence was 26 (79%) in the trimethoprim/sulfamethoxazole group and 10 (22%) in the placebo group [RD: 57 (95% CI: 39; 75)]. After 12 weeks the integron prevalence, and after 1 year the susceptibility levels, had returned to baseline values. ConclusionsInitially, trimethoprim/sulfamethoxazole usage was strongly associated with the appearance of integron-positive (multi)drug-resistant Enterobacteriaceae in the intestinal flora. After prolonged exposure to trimethoprim/sulfamethoxazole, however, this population of Enterobacteriaceae was substituted by a population with non-integron-associated resistance mechanisms. After trimethoprim/sulfamethoxazole was discontinued, susceptibility rates to all antibiotics returned to baseline levels.
• Efficacy of levofloxacin-based rescue therapy for Helicobacter pylori infection after standard triple therapy: a randomized controlled trial
  - J Antimicrob Chemother 63(5):1017-1024 (2009)
  ObjectivesThis prospective study was designed to determine the efficacy of a levofloxacin-based rescue therapy for Helicobacter pylori infection after failure of standard triple therapies. We also surveyed the predictors of this rescue therapy. Patients and methodsFrom June 2005 to March 2007, 1036 patients infected with H. pylori received standard triple regimens (proton pump inhibitor, clarithromycin and amoxicillin). H. pylori eradication was achieved in 855 (82.5%) subjects. One hundred and sixty-six eradication-failure patients were enrolled and randomly assigned to receive a 7 day eradication therapy with esomeprazole, bismuth subcitrate, tetracycline and metronidazole (EBTM) or esomeprazole, amoxicillin and levofloxacin (EAL). Follow-up endoscopy was done 16 weeks later to assess the treatment response. Patients' response, CYP2C19 genotypes and antibiotic resistances were also examined. ResultsIntention-to-treat analysis revealed that both groups showed simila! r eradication rates [EBTM 63.9%; 95% confidence interval (CI): 53.6-74.2 and EAL 69.9%; 95% CI: 60.1-79.7] (P = 0.89). Per-protocol results were EBTM = 84.1% (95% CI: 75.1-93.1) and EAL = 75.3% (95% CI: 65.8-84.8) (P = 0.82). Both regimens had similar compliance (P = 0.32), but the EBTM group had more adverse events (P = 0.27). Logistic regression analysis showed that poor compliance, CYP2C19 homozygous extensive metabolizer genotype and levofloxacin resistance were important predictors for eradication failure. ConclusionsThe EAL regimen can achieve an efficacy similar to that of the standard EBTM therapy. It may be very useful in countries where bismuth salts are not available. Compliance, CYP2C19 genotype and resistances to antibiotics may influence the outcome of levofloxacin-based rescue therapy. It seems advisable to reserve levofloxacin for rescue treatment to avoid an increase in the resistance phenomenon.
• Impact of intravenous {beta}-lactam/macrolide versus {beta}-lactam monotherapy on mortality in hospitalized patients with community-acquired pneumonia
  - J Antimicrob Chemother 63(5):1025-1033 (2009)
  ObjectivesGuidelines recommend dual-therapy consisting of a {beta}-lactam/macrolide (BLM) for hospitalized patients with community-acquired pneumonia. Nevertheless, the superiority over {beta}-lactam-monotherapy (BL) remains unproven. MethodsAnalyses from an observational study initiated by the German competence network CAPNETZ were performed. ResultsOne thousand eight hundred and fifty-four patients were treated with either BL (49.0%) or BLM (51.0%). BLM therapy was associated with lower adjusted 14 day mortality [odds ratio (OR) 0.53; 95% confidence interval (CI): 0.30-0.94]. CRB65, neoplastic disease, age and nursing home residency were confirmed as independent predictors of death. Adjusted 14 day mortality risk was clearly reduced in patients with CRB65 = 2 (n = 411; OR 0.35; CI: 0.12-0.99) and CRB65 [≥] 2 (n = 519; OR 0.42; CI: 0.18-0.997). However, this could not be shown for adjusted 30 day mortality. Patients with CRB65 [≤] 1 showed low mortality (2.1%)! without the influence of BLM. BLM therapy was associated with lower adjusted risk of treatment failure at 14 days (n = 1854; OR 0.65; CI: 0.47-0.89) and 30 days (OR 0.69; CI: 0.51-0.94) as well as in the subgroup of patients with CRB65 = 2 and CRB65 [≥] 2. ConclusionsThis study suggests the superiority of BLM therapy in patients with CRB65 risk classes of 2 or higher on 14 day mortality. BLM therapy was also associated with lower risk of treatment failure.
• Community-based outpatient parenteral antimicrobial therapy (CoPAT) for Staphylococcus aureus bacteraemia with or without infective endocarditis: analysis of the randomized trial comparing daptomycin with standard therapy
  - J Antimicrob Chemother 63(5):1034-1042 (2009)
  ObjectivesAdministering outpatient parenteral antimicrobial therapy in the community setting (CoPAT) is becoming more common with the increasing emphasis on controlling costs. However, few controlled trials have evaluated this treatment modality. MethodsUsing data from a recent randomized trial comparing daptomycin with standard therapy (semi-synthetic penicillin or vancomycin, each with initial low-dose gentamicin) for Staphylococcus aureus bacteraemia and infective endocarditis (SAB/IE), patient characteristics and outcomes were evaluated. Patients receiving their full course of therapy in the hospital setting were compared with those who received some portion outside of the hospital (CoPAT). ResultsAmong the 200 patients, 51.5% received CoPAT. These patients were generally younger (median age 50 versus 54 years, P = 0.028). In the CoPAT group, there tended to be fewer patients with endocardial involvement (8.7% versus 18.6%, P = 0.061) and pre-existing valvular he! art disease (7.8% versus 15.5%, P = 0.120). CoPAT patients received longer therapy courses (mean 25.4 versus 13.5 days, P < 0.001) and had higher rates of therapy completion (90.3% versus 45.4%, P < 0.001) and clinical success (86.4% versus 55.7%, P < 0.001). Persisting or relapsing S. aureus was less frequent in the CoPAT group (3.9% versus 15.5%, P = 0.007) and there were fewer deaths (3.9% versus 18.6%, P = 0.001) 6 weeks after the end of therapy. Hospital readmission occurred for 18 of the 103 (17.5%) CoPAT patients. Clinical success rates were similar for CoPAT patients receiving daptomycin (90.0%) or standard therapy (83.0%). ConclusionsWith proper monitoring, stable patients can complete treatment for SAB/IE as outpatients in the community setting. Daptomycin is an appropriate option for this setting.
• Eight years' experience of an extended-interval dosing protocol for gentamicin in neonates
  - J Antimicrob Chemother 63(5):1043-1049 (2009)
  BackgroundDosing of gentamicin in neonates in Christchurch has been carried out since 2000 using a locally developed extended-interval dosing protocol. All dosing data have been recorded in a database. AimsThe aims of this study were to analyse the database to determine what percentage of neonates achieved target values for Cmax, Cmin and AUC, and to use the pharmacokinetic values of gentamicin to simulate new dosing protocols. MethodsCmax, Cmin and AUC were compared with target values. Clearance (CL), volume of distribution (V) and half-life (t1/2) were estimated, and used to produce new predictive dosing protocols that were tested and compared with the results of the original protocol. ResultsGentamicin concentrations from 1461 individual doses were recorded in the database. Four hundred and eight were excluded. Of the remaining 1053, 84% achieved the target Cmax (>10 mg/L), 77% the target Cmin (<1 mg/L) and 63% the target AUC (within 80% to 125%). The number achi! eving target Cmax and Cmin values was improved markedly by prolonging the dosing intervals, but not by altering the predictive equations. Since the majority of the neonates only received a single dose of gentamicin, a new V-based model was also tested, and performed well. CL (L/kg) increased, while V (L/kg) and t1/2 (h) both decreased with respect to weight. ConclusionsExtending the dose interval improved the success in achieving target Cmax and Cmin, while revision of the dosing equation did not. A V-based model provides an alternative approach to the first dose of gentamicin in neonates.
• Development and evaluation of vancomycin dosage guidelines designed to achieve new target concentrations
  - J Antimicrob Chemother 63(5):1050-1057 (2009)
  ObjectivesThe aims of this study were to develop a population pharmacokinetic model of vancomycin in adult patients, to use this model to develop dosage guidelines targeting vancomycin trough concentrations of 10-15 mg/L and to evaluate the performance of these new guidelines. MethodsAll data analyses were performed using NONMEM(R). A population pharmacokinetic model was first developed from vancomycin dosage and concentration data collected during routine therapeutic drug monitoring in 398 patients, then new vancomycin dosage guidelines were devised by using the model to predict vancomycin trough concentrations in a simulated dataset. Individual estimates of CL and V1 were then obtained in an independent group of 100 patients using the population model and the POSTHOC option. These individual estimates were used to predict vancomycin trough concentrations and steady-state AUC24/MIC ratios using the current and new dosage guidelines. ResultsThe population analysis fo! und that the vancomycin data were best described using a bi-exponential elimination model with a typical CL of 3.0 L/h that changed by 15.4% for every 10 mL/min difference from a CLCR of 66 mL/min. Vss was 1.4 L/kg. The proposed dosage guidelines were predicted to achieve 55% of vancomycin troughs within 10-15 mg/L and 71% within 10-20 mg/L, which is significantly higher than current guidelines (19% and 22%, respectively). The proportion of AUC24/MIC ratios above 400 was also higher, 87% compared with 58%. ConclusionsNew vancomycin dosage guidelines have been developed that achieve trough concentrations of 10-15 mg/L earlier and more consistently than current guidelines.
• Impact of a computer-generated alert system prompting review of antibiotic use in hospitals
  - J Antimicrob Chemother 63(5):1058-1063 (2009)
  ObjectivesThe aim of this study was to measure the impact on antibiotic use of a computer-generated alert prompting post-prescription review and direct counselling in hospital wards. MethodsA computer-generated alert on new prescriptions of 15 antibiotics was reviewed weekly by an infectious disease physician for 41 weeks. During the first 6 months of the study, criteria selected for potential intervention were: (i) a planned duration of treatment of [≥]10 days; (ii) discordance between the spectrum of the prescribed antibiotic and available microbiological results; or (iii) prescriptions of broad-spectrum {beta}-lactams, fluoroquinolones, glycopeptides or linezolid. During the following 5 months, the alert was restricted to any prescription of the 15 antibiotics in the 9 wards where overall antibiotic use had not decreased in the past year. ResultsWe analysed 2385 prescriptions, 932 (39%) of which generated an alert for potential intervention. Among the latter, 4! 82 (51.7%) prescriptions prompted direct counselling, mainly for shortening the planned duration of therapy (18.9%), withdrawing antibiotics (16.2%) or streamlining therapy (15.5%). The attending physicians' compliance with the recommendations was 80%. The overall median (interquartile range) days of therapy prescribed by the attending physicians was reduced from an initial duration of 8 (7-14) to 7 (6-11) days (P < 0.0001), resulting in 26.5% less antibiotic days prescribed. The time required for the intervention was 6 h per week. ConclusionsThis computer-prompted post-prescription review led physicians to modify one half of the antibiotic courses initially prescribed and was well accepted by the majority, although they had not requested counselling.
• Quantifying changes in incidences of nosocomial bacteraemia caused by antibiotic-susceptible and antibiotic-resistant pathogens
  - J Antimicrob Chemother 63(5):1064-1070 (2009)
  ObjectivesThe aim of this study was to determine, over time, changes in annual trends of nosocomial bacteraemia (NB) and to quantify pathogen-specific changes and emergence of antibiotic resistance. MethodsA retrospective cohort study in a 997 bed tertiary care centre in the Netherlands was performed. All adult patients ([≥]18 years old) admitted for >48 h between 1 January 1996 and 31 December 2005 were included. ResultsA total of 163 525 patients, comprising 1 826 852 patient-days and 1785 episodes of NB, were analysed. The number of admissions per year and length of hospital stay decreased over time. Crude incidence of NB per year remained unchanged, but cumulative incidence (cases/10 000 admissions) and incidence densities (cases/100 000 patient-days at risk) increased, on average, by 2.0% and 4.0% per year, respectively, primarily because of infections caused by Enterococcus spp. and Pseudomonas aeruginosa. The incidence density of NB caused by highly resista! nt microorganisms increased, on average, by 26.1% [95% confidence interval (CI): 17-37] per year, when compared with an annual increase of 3% (95% CI: 1-5) for NB caused by susceptible pathogens. Ratios of increased incidence densities of resistant and susceptible bacteria were 8.7, 3.5, 2.6 and >37.9 for all pathogens, Enterococcus spp., P. aeruginosa and Enterobacteriaceae, respectively. ConclusionsDue to changes in the patient population, increased incidences of NB over time are only evident when expressed as cumulative incidence or incidence densities. Despite overall low levels of antibiotic resistance, the incidence of NB caused by multiresistant pathogens rapidly increased, adding to the total burden of NB.
• Diversity of plasmid-mediated carbapenem-hydrolysing oxacillinases among carbapenem-resistant Acinetobacter baumannii isolates from Kingdom of Bahrain
  - J Antimicrob Chemother 63(5):1071-1073 (2009)
  
• Emergence of extended-spectrum-AmpC-expressing Escherichia coli isolates in Belgian hospitals
  - J Antimicrob Chemother 63(5):1073-1075 (2009)
  
• Reduced susceptibility of multidrug-resistant Acinetobacter baumannii to tigecycline in combination with 1-(1-naphthylmethyl)-piperazine is not a pH-dependent phenomenon
  - J Antimicrob Chemother 63(5):1075-1076 (2009)
  
• In vitro effect of metronidazole and vancomycin in combination on Clostridium difficile
  - J Antimicrob Chemother 63(5):1076 (2009)
  
• Detecting streptomycin in apples from orchards treated for fire blight
  - J Antimicrob Chemother 63(5):1076-a-1077 (2009)
  
• Comment on: Resistance of planktonic and biofilm-grown Burkholderia cepacia complex isolates to the transition metal gallium
  - J Antimicrob Chemother 63(5):1078-1079 (2009)
  
• Resistance of planktonic and biofilm-grown Burkholderia cepacia complex isolates to the transition metal gallium--authors' response
  - J Antimicrob Chemother 63(5):1079 (2009)
  
• Comment on: High rate of early virological failure with the once-daily tenofovir/lamivudine/nevirapine combination in naive HIV-1-infected patients
  - J Antimicrob Chemother 63(5):1080 (2009)
  
• High rate of early virological failure with the once-daily tenofovir/lamivudine/nevirapine combination in naive HIV-1-infected patients--authors' response
  - J Antimicrob Chemother 63(5):1080-a-1081 (2009)
  
• Comment on: Aminoglycoside drugs in clinical practice: an evidence-based approach
  - J Antimicrob Chemother 63(5):1081-1082 (2009)
  
• Aminoglycoside drugs in clinical practice: an evidence-based approach--authors' response
  - J Antimicrob Chemother 63(5):1082-1083 (2009)
  
• Comment on: The higher the number of daily doses of antibiotic treatment in lower respiratory tract infection the worse the compliance
  - J Antimicrob Chemother 63(5):1083-1084 (2009)
  
• The higher the number of daily doses of antibiotic treatment in lower respiratory tract infection the worse the compliance--author's response
  - J Antimicrob Chemother 63(5):1084-1085 (2009)
  
• Antimicrobial Drugs: Chronicle of a Twentieth Century Medical Triumph
  - J Antimicrob Chemother 63(5):1086 (2009)