Showing papers in "Journal of Antimicrobial Chemotherapy in 2012"

Identification of acquired antimicrobial resistance genes

Abstract: Objectives Identification of antimicrobial resistance genes is important for understanding the underlying mechanisms and the epidemiology of antimicrobial resistance. As the costs of whole-genome sequencing (WGS) continue to decline, it becomes increasingly available in routine diagnostic laboratories and is anticipated to substitute traditional methods for resistance gene identification. Thus, the current challenge is to extract the relevant information from the large amount of generated data.

OXA-48-like carbapenemases: the phantom menace

Abstract: OXA-48-type carbapenem-hydrolysing class D β-lactamases are increasingly reported in enterobacterial species. To date, six OXA-48-like variants have been identified, with OXA-48 being the most widespread. They differ by a few amino acid substitutions or deletions (one to five amino acids). The enzymes hydrolyse penicillins at a high level and carbapenems at a low level, sparing broad-spectrum cephalosporins, and are not susceptible to β-lactamase inhibitors. When combining permeability defects, OXA-48-like producers may exhibit a high level of resistance to carbapenems. OXA-163 is an exception, hydrolysing broad-spectrum cephalosporins but carbapenems at a very low level, and being susceptible to β-lactamase inhibitors. The bla(OXA-48)-type genes are always plasmid-borne and have been identified in association with insertion sequences involved in their acquisition and expression. The current spread of the bla(OXA-48) gene is mostly linked to the dissemination of a single IncL/M-type self-transferable plasmid of 62 kb that does not carry any additional resistance gene. OXA-48-type carbapenemases have been identified mainly from North African countries, the Middle East, Turkey and India, those areas constituting the most important reservoirs; however, occurrence of OXA-48 producers in European countries is now well documented, with some reported hospital outbreaks. Since many OXA-48-like producers do not exhibit resistance to broad-spectrum cephalosporins, or only decreased susceptibility to carbapenems, their recognition and detection can be challenging. Adequate screening and detection methods are therefore required to prevent and control their dissemination.

Mycobacterium abscessus: a new antibiotic nightmare

Abstract: The intrinsic and acquired resistance of Mycobacterium abscessus to commonly used antibiotics limits the chemotherapeutic options for infections caused by these mycobacteria. Intrinsic resistance is attributed to a combination of the permeability barrier of the complex multilayer cell envelope, drug export systems, antibiotic targets with low affinity and enzymes that neutralize antibiotics in the cytoplasm. To date, acquired resistance has only been observed for aminoglycosides and macrolides, which is conferred by mutations affecting the genes encoding the antibiotic targets (rrs and rrl, respectively). Here we summarize previous and recent findings on the resistance of M. abscessus to antibiotics in light of what has been discovered for other mycobacteria. Since we can now distinguish three groups of strains belonging to M. abscessus (M. abscessus sensu stricto, Mycobacterium massiliense and Mycobacterium bolletii), studies on antibiotic susceptibility and resistance should be considered according to this new classification. This review raises the profile of this important pathogen and highlights the work needed to decipher the molecular events responsible for its extensive chemotherapeutic resistance.

Miltefosine: a review of its pharmacology and therapeutic efficacy in the treatment of leishmaniasis

Abstract: Miltefosine is an alkylphosphocholine drug with demonstrated activity against various parasite species and cancer cells as well as some pathogenic bacteria and fungi. For 10 years it has been licensed in India for the treatment of visceral leishmaniasis (VL), a fatal neglected parasitic disease. It is the first and still the only oral drug that can be used to treat VL and cutaneous leishmaniasis (CL). The standard 28 day miltefosine monotherapy regimen is well tolerated, except for mild gastrointestinal side effects, although its teratogenic potential severely hampers its general use in the clinic and roll-out in national elimination programmes. The pharmacokinetics of miltefosine are mainly characterized by its long residence time in the body, resulting in extensive drug accumulation during treatment and long elimination half-lives. At the moment, different combination therapy strategies encompassing miltefosine are being tested in multiple controlled clinical trials in various geographical areas of endemicity, both in South Asia and East Africa. We here review the most salient pre-clinical and clinical pharmacological aspects of miltefosine, its mechanism of action against Leishmania parasites and other pathogens, and provide a systematic overview of the efficacy and safety data from all clinical trials of miltefosine, either alone or in combination, in the treatment of VL and CL.

Guidelines for the diagnosis and antibiotic treatment of endocarditis in adults: a report of the Working Party of the British Society for Antimicrobial Chemotherapy

Abstract: The BSAC Guidelines on Endocarditis were last published in 1998. The Guidelines presented here have been updated and extended to reflect changes in both the antibiotic resistance characteristics of causative organisms and the availability of new antibiotics. Randomized, controlled trials suitable for the development of evidenced-based guidelines in this area are still lacking, and therefore a consensus approach has again been adopted. The Guidelines cover diagnosis and laboratory testing, suitable antibiotic regimens and causative organisms. Special emphasis is placed on common causes of endocarditis, such as streptococci and staphylococci, however, other bacterial causes (such as enterococci, HACEK organisms, Coxiella and Bartonella) and fungi are considered. The special circumstances of prosthetic endocarditis are discussed.

Colistin resistance of Acinetobacter baumannii: clinical reports, mechanisms and antimicrobial strategies

Abstract: Colistin is the last resort for treatment of multidrug-resistant Acinetobacter baumannii. Unfortunately, resistance to colistin has been reported all over the world. The highest resistance rate was reported in Asia, followed by Europe. The heteroresistance rate of A. baumannii to colistin is generally higher than the resistance rate. The mechanism of resistance might be loss of lipopolysaccharide or/and the PmrAB two-component system. Pharmacokinetic/pharmacodynamic studies revealed that colistin monotherapy is unable to prevent resistance, and combination therapy might be the best antimicrobial strategy against colistin-resistant A. baumannii. Colistin/ rifampicin and colistin/carbapenem are the most studied combinations that showed promising results in vitro, in vivo and in the clinic. New peptides showing good activity against colistin-resistant A. baumannii are also being investigated.

Bacterial stress responses as determinants of antimicrobial resistance

Abstract: Bacteria encounter a myriad of stresses in their natural environments, including, for pathogens, their hosts. These stresses elicit a variety of specific and highly regulated adaptive responses that not only protect bacteria from the offending stress, but also manifest changes in the cell that impact innate antimicrobial susceptibility. Thus exposure to nutrient starvation/limitation (nutrient stress), reactive oxygen and nitrogen species (oxidative/nitrosative stress), membrane damage (envelope stress), elevated temperature (heat stress) and ribosome disruption (ribosomal stress) all impact bacterial susceptibility to a variety of antimicrobials through their initiation of stress responses that positively impact recruitment of resistance determinants or promote physiological changes that compromise antimicrobial activity. As de facto determinants of antimicrobial, even multidrug, resistance, stress responses may be worthy of consideration as therapeutic targets.

Use of hydrogen peroxide as a biocide: new consideration of its mechanisms of biocidal action

Abstract: Hydrogen peroxide is extensively used as a biocide, particularly in applications where its decomposition into non-toxic by-products is important. Although increasing information on the biocidal efficacy of hydrogen peroxide is available, there is still little understanding of its biocidal mechanisms of action. This review aims to combine past and novel evidence of interactions between hydrogen peroxide and the microbial cell and its components, while reflecting on alternative applications that make use of gaseous hydrogen peroxide. It is currently believed that the Fenton reaction leading to the production of free hydroxyl radicals is the basis of hydrogen peroxide action and evidence exists for this reaction leading to oxidation of DNA, proteins and membrane lipids in vivo. Investigations of DNA oxidation suggest that the oxidizing radical is the ferryl radical formed from DNA-associated iron, not hydroxyl. Investigations of protein oxidation suggest that selective oxidation of certain proteins might occur, and that vapour-phase hydrogen peroxide is a more potent oxidizer of protein than liquidphase hydrogen peroxide. Few studies have investigated membrane damage by hydrogen peroxide, though it is suggested that this is important for the biocidal mechanism. No studies have investigated damage to microbial cell components under conditions commonly used for sterilization. Despite extensive studies of hydrogen peroxide toxicity, the mechanism of its action as a biocide requires further investigation.

Time interval of increased risk for Clostridium difficile infection after exposure to antibiotics

Abstract: Background: Clostridium difficile infections (CDIs) are common in developed countries and affect .250000 hospitalized patients annually in the USA. The most important risk factor for the disease is antibiotic therapy. Methods: To determine the period at risk for CDI after cessation of antibiotics, we performed a multicentre case –control study in the Netherlands between March 2006 and May 2009. Three hundred and thirty-seven hospitalized patients with diarrhoea and a positive toxin test were compared with 337 patients without diarrhoea. Additionally, a control group of patients with diarrhoea due to a cause other than CDI (n¼ 227) was included. Results: In the month prior to the date of inclusion, CDI patients more frequently used an antibiotic compared with non-diarrhoeal patients (77% versus 49%). During antibiotic therapy and in the first month after cessation of the therapy, patients had a 7 –10-fold increased risk for CDI (OR 6.7 –10.4). This risk declined in the period between 1 and 3 months after the antibiotic was stopped (OR 2.7). Similar results were observed when the second control group was used. All antibiotic classes, except first-generation cephalosporins and macrolides, were associated with CDI. Second- and third-generation cephalosporins (OR 3.3 and 5.3, respectively) and carbapenems (OR 4.7) were the strongest risk factors for CDI. Patients with CDI used more antibiotic classes and more defined daily doses, compared with non-diarrhoeal patients. Conclusions: Antibiotic use increases the risk for CDI during therapy and in the period of 3 months after cessation of antibiotic therapy. The highest risk for CDI was found during and in the first month after antibiotic use. Our study will aid clinicians to identify high-risk patients.

Ivermectin is a potent inhibitor of flavivirus replication specifically targeting NS3 helicase activity: new prospects for an old drug

Abstract: Objectives Infection with yellow fever virus (YFV), the prototypic mosquito-borne flavivirus, causes severe febrile disease with haemorrhage, multi-organ failure and a high mortality. Moreover, in recent years the Flavivirus genus has gained further attention due to re-emergence and increasing incidence of West Nile, dengue and Japanese encephalitis viruses. Potent and safe antivirals are urgently needed.

Molecular characterization of two high-level ceftriaxone-resistant Neisseria gonorrhoeae isolates detected in Catalonia, Spain

Abstract: Objectives The aim of this study was to characterize the first two extended-spectrum cephalosporin-resistant and multidrug-resistant (MDR) Neisseria gonorrhoeae isolates collected from two sexually related patients (men who have sex with men) in Spain. Methods Antimicrobial susceptibility was studied by Etest. Genes involved in quinolone, ceftriaxone and multidrug resistance were amplified by PCR and sequenced in both directions. The isolates were typed by N. gonorrhoeae multi-antigen sequence typing (NG-MAST). Results The two isolates had the same MDR profile, showing resistance to penicillin (MIC 0.094 mg/L; β-lactamase negative), ceftriaxone (MIC 1.5 mg/L), cefixime (MIC 1.5 mg/L), cefotaxime (MIC 1 mg/L), ciprofloxacin (MIC >32 mg/L) and tetracycline (MIC 1.5 mg/L). NG-MAST showed that both isolates belonged to sequence type (ST) 1407 (porB-908 and tbpB-110). Ciprofloxacin resistance was due to amino acid substitutions in GyrA (S91F and D95G) and ParC (S87R). An A deletion in the promoter of the MtrCDE efflux pump (mtrR) was detected. No changes were detected in the pilQ gene. The outer membrane protein PorB showed two substitutions at G120K and A121N. An L421P substitution was observed in the PBP1A (ponA) sequence. The sequence of PBP2 (penA) showed a mosaic structure related to genotype XXXIV with a single additional amino acid substitution (A501P). This genotype was identical to a recently described French isolate (F89). Conclusions This is the first reported case of high-level extended-spectrum cephalosporin-resistant N. gonorrhoeae transmission. The molecular typing and MDR genotype suggest possible European spread of this strain, highlighting the need for surveillance and the importance of testing the susceptibility of N. gonorrhoeae to extended-spectrum cephalosporins.

Carbapenems versus alternative antibiotics for the treatment of bacteraemia due to Enterobacteriaceae producing extended-spectrum β-lactamases: a systematic review and meta-analysis

Abstract: Objectives: To study the comparative mortality associated with carbapenems and alternative antibiotics for the treatment of patients with extended-spectrum b-lactamase (ESBL)-positive Enterobacteriaceae bacteraemia. Methods: We searched systematically PubMed and Scopus databases for studies providing data for mortality among patients treated with carbapenems, b-lactam/b-lactamase inhibitor combinations (BL/BLIs) or nonBL/BLIs (mainly cephalosporins and fluoroquinolones), preferably as monotherapy. Studies focusing on patients of all ages with community- and healthcare-associated bacteraemia were eligible. Data were pooled using the technique of meta-analysis. Results: Twenty-one articles, studying 1584 patients, were included. Escherichia coli and Klebsiella pneumoniae were the most commonly studied bacteria. Delay in appropriate treatment up to 6 days was reported. Carbapenems were used mainly as definitive therapy. Carbapenems were associated with lower mortality than non- BL/BLIs for definitive [risk ratio (RR) 0.65, 95% CI 0.47‐0.91] and empirical (RR 0.50, 95% CI 0.33‐0.77) treatment. No statistically significant differences in mortality were found between carbapenems and BL/BLIs administered as definitive (RR 0.52, 95% 0.23‐1.13) or empirical (RR 0.91, 95% CI 0.66‐1.25) treatment. BL/BLIs were not associated with lower mortality than non-BL/BLIs administered either definitively (RR 1.59, 95% 0.83‐3.06) or empirically (RR 0.82, 95% 0.48‐1.41). Data regarding subgroups according to the setting, comorbidity and bacterial species could not be extracted. Conclusions: Based on data from non-randomized studies, carbapenems may be considered the treatment of choice for empirical treatment of patients with ESBL-producing Enterobacteriaceae bacteraemia. The role of BL/ BLIs should be further evaluated for definitive treatment. Further research should focus on faster identification of ESBL-positive pathogens and potential differences in the treatment of each bacterial species.

Rapid detection of carbapenemase genes by multiplex real-time PCR

Abstract: Objectives To develop a single multiplex real-time PCR assay to detect six different genetic types of carbapenemases already identified in Enterobacteriaceae (KPC, GES, NDM, IMP, VIM and OXA-48). Methods A total of 58 bacterial isolates were tested. Thirty were previously characterized as resistant to carbapenems and documented by PCR and sequencing analysis to carry the following genes: bla(KPC) type, bla(GES) type, bla(IMP) type, bla(VIM) type, bla(OXA-48) and bla(NDM-1). These positive strains included 21 Enterobacteriaceae, 1 Acinetobacter baumannii and 8 Pseudomonas aeruginosa isolates. The remaining 28 isolates previously tested susceptible to carbapenems and were negative for these genes. Bacterial DNA was extracted using the easyMag extractor (bioMerieux, France). The real-time PCR was performed using the Rotor-Gene 6000 instrument (Corbett Life Science, Australia) and specific primers for each carbapenemase target were designed using the DNAStar software (Madison, WI, USA). Results Each one of the six carbapenemase genes tested presented a different melting curve after PCR amplification. The melting temperature (T(m)) analysis of the amplicons identified was as follows: bla(IMP) type (T(m) 80.1°C), bla(OXA-48) (T(m) 81.6°C), bla(NDM-1) (T(m) 84°C), bla(GES) type (T(m) 88.6°C), bla(VIM) type (T(m) 90.3°C) and bla(KPC) type (T(m) 91.6°C). No amplification was detected among the negative samples. The results showed 100% concordance with the genotypes previously identified. Conclusions The new assay was able to detect the presence of six different carbapenemase gene types in a single 3 h PCR.

Clofazimine: current status and future prospects

Abstract: Clofazimine, a lipophilic riminophenazine antibiotic, possesses both antimycobacterial and anti-inflammatory activities. However, its efficacy has been demonstrated only in the treatment of leprosy, not in human tuberculosis, despite the fact that this agent is impressively active in vitro against multidrug-resistant strains of Mycobacterium tuberculosis. Recent insights into novel targets and mechanisms of antimicrobial and anti-inflammatory activity coupled with the acquisition of innovative drug delivery technologies have, however, rekindled interest in clofazimine as a potential therapy for multidrug- and extensively multidrug-resistant tuberculosis in particular, as well as several autoimmune diseases. The primary objective of this review is to critically evaluate these recent developments and to assess their potential impact on improving the therapeutic efficacy and versatility of clofazimine.

The Deferasirox–AmBisome Therapy for Mucormycosis (DEFEAT Mucor) study: a randomized, double-blinded, placebo-controlled trial

Abstract: Received 19 July 2011; returned 6 August 2011; revised 6 August 2011; accepted 13 August 2011Objectives: Host iron availability is fundamental to mucormycosis pathogenesis. The combination of liposomalamphotericin B (LAmB) and deferasirox iron chelation therapy synergistically improved survival in diabetic micewith mucormycosis. To determine the safety of combination deferasirox plus LAmB therapy for mucormycosis,a multicentred, placebo-controlled, double-blinded clinical trial was conducted.Methods: Twenty patients with proven or probable mucormycosis were randomized to receive treatment withLAmB plus deferasirox (20 mg/kg/day for 14 days) or LAmB plus placebo (NCT00419770, clinicaltrials.gov). Theprimary analyses were for safety and exploratory efficacy.Results: Patients in the deferasirox arm (n¼11) were more likely than those in the placebo arm (n¼9) to haveactive malignancy, neutropenia and corticosteroid therapy, and were less likely to receive concurrent non-studyantifungal therapy. Reported adverse events and serious adverse events were similar between the groups.However, death was more frequent in the deferasirox than in the placebo arm at 30 days (45% versus 11%,P¼0.1) and 90 days (82% versus 22%, P¼0.01). Global success (alive, clinically stable, radiographicallyimproved) for the deferasirox arm versus the placebo arm at 30 and 90 days, respectively, was 18% (2/11)versus 67% (6/9) (P¼0.06) and 18% (2/11) versus 56% (5/9) (P¼0.2).Conclusions: Patients with mucormycosis treated with deferasirox had a higher mortality rate at 90 days.Population imbalances in this small Phase II study make generalizable conclusions difficult. Nevertheless,these data do not support a role for initial, adjunctive deferasirox therapy for mucormycosis.Keywords: antifungal, fungal infections, mould infections, combination therapy

The role of international travel in the worldwide spread of multiresistant Enterobacteriaceae

Abstract: From international tourists to war-displaced refugees, more people are on the move than ever before. This provides the opportunity for a variety of antimicrobial-resistant bacteria to be carried from one geographic location to another. The Enterobacteriaceae are among the most important causes of serious hospital-acquired and community-onset bacterial infections in humans, and resistance to antimicrobial agents in these bacteria has become an increasingly relevant problem. International travel and tourism are important modes for the acquisition and spread of antimicrobial-resistant Enterobacteriaceae, especially CTX-M-producing Escherichia coli. Infections with KPC-, VIM-, OXA-48- and NDM-producing Enterobacteriaceae in developed countries have been associated with visiting and being hospitalized in endemic areas such as the USA, Greece and Israel for KPCs, Greece for VIMs, Turkey for OXA-48, and the Indian subcontinent for NDMs. To combat the spread of antimicrobial-resistant Enterobacteriaceae, the French Healthcare Safety Advisory Committee recently issued national recommendations for screening and contact isolation precautions for patients transferred from, or hospitalized outside, France. For effective public and patient health interventions, it is important to understand the role of international travel in the spread of antimicrobial-resistant Enterobacteriaceae. We urgently need well-designed studies to evaluate the transmission potential and risks for colonization and infections due to multiresistant Enterobacteriaceae in travellers who have recently visited or have been hospitalized in endemic areas. The emergence of CTX-M-, KPC- and NDM-producing bacteria is a good example of the role that globalization plays in the rapid dissemination of new antibiotic resistance mechanisms.

Reduced susceptibility to chlorhexidine in staphylococci: is it increasing and does it matter?

Abstract: Antiseptic agents are increasingly used for hand hygiene and skin decolonization as key tools for the prevention of healthcare-associated infections. Chlorhexidine, a divalent, cationic biguanide, has a broad spectrum of activity and is one of the most frequently used topical antiseptic agents. Notably, there are an increasing number of prevalence studies that report reduced levels of susceptibility to chlorhexidine. In contrast to bacterial resistance to antibiotics, using parameters such as the MIC to define resistance to antiseptics, including chlorhexidine, is not straightforward. A range of methods have been used for the detection of reduced susceptibility to chlorhexidine, but, importantly, there is no standardized method and no consensus on the definition of chlorhexidine 'resistance'. In this review we have assessed the methods available for the detection of reduced susceptibility to chlorhexidine and the prevalence of coresistance to other antimicrobial agents. We have focused on the development of reduced susceptibility to chlorhexidine and the presence of efflux-mediated resistance genes in staphylococci, and have reviewed the clinical significance of this phenomenon. Lastly, we have identified unanswered questions to further our understanding of this emergent threat. We anticipate that clinical use of chlorhexidine will continue to increase, and it will be important to be alert to the possibility that this may lead to the emergence of new clones with reduced susceptibility. Indiscriminate chlorhexidine use in the absence of efficacy data should be discouraged.

Improving the quality of antibiotic prescribing in the NHS by developing a new Antimicrobial Stewardship Programme: Start Smart—Then Focus

Abstract: There has been dramatic change in antibiotic use in English hospitals. Data from 2004 and 2009 show that the focus on reducing fluoroquinolone and second- and third-generation cephalosporin use seems to have been heeded in NHS secondary care, and has been associated with a substantial decline in hospital Clostridium difficile rates. However, there has been a substantial increase in use of co-amoxiclav, carbapenems and piperacillin/tazobactam. In primary care, antibiotic prescribing fell markedly from 1995 to 2000, but has since risen steadily to levels seen in the early 1990s. There remains a 2-fold variation in antimicrobial prescribing among English General Practices. In 2010, the NHS Atlas of Variation documented a 3-fold variation in the prescription of quinolones and an 18-fold variation in cephalosporins by Primary Care Trusts across England. There is a clear need to improve antimicrobial prescribing. This paper describes the development of new antimicrobial stewardship programmes for primary care and hospitals by the Department of Health's Advisory Committee on Antimicrobial Resistance and Healthcare Associated Infection: Antimicrobial Stewardship in Primary Care Initiative. The secondary care programme promotes the rapid prescription of the right antibiotic at the right dose at the right time, followed by active review for all patients still on antibiotics 48 h after admission. The five options available are to stop, switch to oral, continue and review again, change (if possible to a narrower spectrum) or move to outpatient parenteral antibiotic therapy. A range of audit and outcome tools has been developed, but to maintain optimal antimicrobial usage, monitoring of local and national quantitative and qualitative data on prescribing and consumption is required, linked to the development of key performance indicators in primary, secondary and tertiary care.

A systematic review of gyrase mutations associated with fluoroquinolone-resistant Mycobacterium tuberculosis and a proposed gyrase numbering system

Abstract: Fluoroquinolone resistance in Mycobacterium tuberculosis has become increasingly important. A review of mutations in DNA gyrase, the fluoroquinolone target, is needed to improve the molecular detection of resistance. We performed a systematic review of studies reporting mutations in DNA gyrase genes in clinical M. tuberculosis isolates. From 42 studies that met inclusion criteria, 1220 fluoroquinolone-resistant M. tuberculosis isolates underwent sequencing of the quinolone resistance-determining region (QRDR) of gyrA; 780 (64%) had mutations. The QRDR of gyrB was sequenced in 534 resistant isolates; 17 (3%) had mutations. Mutations at gyrA codons 90, 91 or 94 were present in 654/1220 (54%) resistant isolates. Four different GyrB numbering systems were reported, resulting in mutation location discrepancies. We propose a consensus numbering system. Most fluoroquinolone-resistant M. tuberculosis isolates had mutations in DNA gyrase, but a substantial proportion did not. The proposed consensus numbering system can improve molecular detection of resistance and identification of novel mutations.

MRSA: the first half century

Abstract: Fifty years ago methicillin-resistant Staphylococcus aureus (MRSA) first revealed themselves to the medical community, having been described in a landmark article published in the British Medical Journal. Among other things, their discovery set off a major response from the scientific and medical professions to control or even eliminate them as major human pathogens. Despite these efforts, however, MRSA have spread throughout the world and a half century after they burst upon the scene they continue to pose major challenges to research scientists and clinicians alike. In a very real sense, this year marks the ‘birthday’ of a remarkably successful pathogen. The major reasons for the ability of MRSA to prosper and cause disease in settings inimical to its survival form the basis of this article.

Occurrence and characteristics of extended-spectrum-β-lactamase- and AmpC-producing clinical isolates derived from companion animals and horses

Abstract: To investigate the occurrence and characteristics of extended-spectrum -lactamase (ESBL)- and AmpC-producing Enterobacteriaceae isolates in clinical samples of companion animals and horses and compare the results with ESBL/AmpC-producing isolates described in humans. Between October 2007 and August 2009, 2700 Enterobacteriaceae derived from clinical infections in companion animals and horses were collected. Isolates displaying inhibition zones of 25 mm for ceftiofur and/or cefquinome by disc diffusion were included. ESBL/AmpC production was confirmed by combination disc tests. The presence of resistance genes was identified by microarray, PCR and sequencing, Escherichia coli genotypes by multilocus sequence typing and antimicrobial susceptibility by broth microdilution. Sixty-five isolates from dogs (n38), cats (n14), horses (n12) and a turtle were included. Six Enterobacteriaceae species were observed, mostly derived from urinary tract infections (n32). All except 10 isolates tested resistant to cefotaxime and ceftazidime by broth microdilution using clinical breakpoints. ESBL/AmpC genes observed were bla(CTX-M-1, -2, -9, -14, -15,) bla(TEM-52), bla(CMY-2) and bla(CMY-39). bla(CTX-M-1) was predominant (n17). bla(CTX-M-9) occurred in combination with qnrA1 in 3 of the 11 Enterobacter cloacae isolates. Twenty-eight different E. coli sequence types (STs) were found. E. coli carrying bla(CTX-M-1) belonged to 13 STs of which 3 were previously described in Dutch poultry and patients. This is the first study among a large collection of Dutch companion animals and horses characterizing ESBL/AmpC-producing isolates. A similarity in resistance genes and E. coli STs among these isolates and isolates from Dutch poultry and humans may suggest exchange of resistance between different reservoirs.

Fosfomycin: evaluation of the published evidence on the emergence of antimicrobial resistance in Gram-negative pathogens

Abstract: Fosfomycin has attracted renewed interest for the treatment of lower urinary tract and even systemic infections caused by Gram-negative pathogens with resistance to traditionally used agents. The main concern regarding the clinical utility of fosfomycin refers to the potential for the emergence of resistance during therapy. In this review, we evaluate the available published evidence regarding the mechanisms and the frequency of in vitro mutational resistance to fosfomycin in Gram-negative pathogens. We also review data regarding the emergence of resistance in clinical studies of fosfomycin therapy in various infectious syndromes and data from studies that evaluate the evolution of fosfomycin resistance over time. There appears to be discordance between the high frequency of mutational resistance to fosfomycin in vitro and the lower extent of this phenomenon in clinical studies. This discordance could at least partly be attributed to a biological cost associated with common mutations that confer resistance to fosfomycin, including decreased growth rate and low adherence to epithelial cells for the resistant mutants. The development of resistance appears to be more frequent both in vitro and in clinical studies for Pseudomonas aeruginosa in comparison with Escherichia coli, whereas relevant data for other Enterobacteriaceae are relatively scarce. The urinary tract seems to provide a favourable environment for the use of fosfomycin with a low associated likelihood for the emergence of resistance, owing to high drug concentrations and acidic pH. Additional data are needed to further clarify the optimal use of fosfomycin for different infectious syndromes caused by contemporary multidrug-resistant pathogens.

Effects of confounders and intermediates on the association of bacteraemia caused by extended-spectrum β-lactamase-producing Enterobacteriaceae and patient outcome: a meta-analysis

Abstract: Background and objectives: Bacteraemia caused by Enterobacteriaceae (EB) producing extended-spectrum b-lactamase (ESBL+) has been associated with higher mortality compared with non-ESBL-producing (ESBL2) EB bacteraemia in observational studies. We conducted a systematic review and meta-analysis of these studies to assess how adjusting for confounding in multivariate analyses affects the pooled estimate, and whether multivariate analyses that include intermediates in the causal pathway of outcome (sepsis severity and inadequate empirical therapy) have lower estimates of attributable mortality. Data sources: PubMed search on 23 November 2010 followed by manually searching reference lists of included studies. Study eligibility criteria: Cohort studies published in English with separate mortality rates for ESBL+ and ESBL2 EB bacteraemia. Synthesis methods: Random-effects pooling of unadjusted and adjusted ORs followed by subgroup analyses to explore effects of adjustment procedures on adjusted ORs. Results: The pooled OR for the unadjusted mortality associated with ESBL production was 2.35 (95% CI 1.90– 2.91, I 2 ¼ 42%, 32 studies). The pooled adjusted OR was 1.52 (95% CI 1.15– 2.01, I 2 ¼ 32%, 15 studies). Adjustment for more intermediates was associated with decreasing ORs. The pooled OR for the analyses adjusting for inadequate empirical therapy was 1.37 (95% CI 1.04 –1.82). Conclusions: ESBL production in EB bacteraemia is associated with a higher mortality compared with bacteraemia with ESBL2 EB, although the estimate of this association is affected by adjustment procedures. Adjustment for inadequate empirical therapy leads to a reduction in ORs, indicating that higher mortality is likely to be mediated through this phenomenon.

Therapeutic drug monitoring may improve safety outcomes of long-term treatment with linezolid in adult patients

Abstract: Methods: We performed a retrospective study of patients who had trough (Cmin) and peak (Cmax) plasma levels measured during prolonged linezolid treatment. Dosage adjustments were performed when Cmin ≥10 mg/L and/or AUC24 ≥400 mg/L.h. Patients were divided into two subgroups according to the absence or presence of co-treatment with rifampicin (the linezolid group and the linezolid +rifampicin group, respectively). Data on demographic characteristics, disease, microbiology and haematochemical parameters were collected and outcomes in relation to drug exposure were compared between groups. Results: A total of 45 patients were included. Dosage adjustments were needed in 40% versus 0% of patients in the linezolid group (n¼35) versus the linezolid+rifampicin group (n¼10), respectively. Patients in the linezolid group had either significantly higher Cmin [3.71 mg/L (1.43‐6.38) versus 1.37 mg/L (0.67‐2.55), P,0.001] or AUC24 [212.77 mg/L.h (166.67‐278.42) versus 123.33 mg/L.h (97.36‐187.94), P,0.001]. Thrombocytopenia appeared in 51.4% versus 0% of cases in the linezolid group versus the linezolid+rifampicin group, respectively. In 33.3% of those patients who were experiencing thrombocytopenia, therapeutic drug monitoring (TDM)guided dosage reductions allowed recovery from toxicity and prosecution of therapy with good outcome. A logistic regression model for thrombocytopenia estimated a probability of 50% in the presence of Cmin of 6.53 mg/L and/or of AUC24 of 280.74 mg/L.h. Conclusions: MaintenanceovertimeofCminbetween2and7 mg/Land/orofAUC24between160and300 mg/L.h may be helpful in improving safety outcomes while retaining appropriate efficacy in adult patients receiving prolonged linezolid treatment.

Continuous versus intermittent infusion of vancomycin for the treatment of Gram-positive infections: systematic review and meta-analysis

Abstract: Methods: MEDLINE, EMBASE and Cochrane databases were searched. Randomized clinical trials (RCTs) and observational studies that comparatively assessed CoI and InI of vancomycin in terms of mortality, clinical cure, toxicity rates and serum drug exposure [trough concentration (Cmin) for InI and steady-state concentration (Css) for CoI; area under the curve at 24 h (AUC24) for both] were included. Meta-analysis was conducted combining and analysing the relative risk (RR) and computing a summary RR of the effects with 95% confidence interval (CI). The standardized mean difference was calculated for continuous outcomes. The I 2 test was calculated to assess heterogeneity across studies. Results: One RCTand five observational studies were included in the analysis. Compared with InI, CoI of vancomycin was associated with a significantly lower risk of nephrotoxicity (RR 0.6, 95% CI 0.4‐0.9, P¼0.02; I 2 ¼0). Overall mortality was not different between the two groups (RR 1.03, 95% CI 0.7‐1.6, P¼0.9; I 2 ¼0). Conclusions: Our meta-analysis suggests that administration of vancomycin for the treatment of Gram-positive infections by CoI is associated with a significantly lower risk of nephrotoxicity when compared with InI of the drug. RCTs are needed to define the impact on mortality rate and on the pharmacodynamic activity in terms of AUC/MIC ratio.

Isolation of multiple-triazole-resistant Aspergillus fumigatus strains carrying the TR/L98H mutations in the cyp51A gene in India

Abstract: OBJECTIVES: Azole resistance in Aspergillus fumigatus isolates impacts on the management of aspergillosis since azoles are primary agents used for prophylaxis and therapy. We report the emergence of resistance to triazoles in two A. fumigatus isolates from patients in Delhi, India. METHODS: One hundred and three A. fumigatus isolates, collected from 85 patients suspected of bronchopulmonary aspergillosis during 2005-10, were investigated for susceptibility to itraconazole, voriconazole, posaconazole and isavuconazole. We undertook a mixed-format real-time PCR assay for the detection of mutations leading to triazole resistance in A. fumigatus. The resistant isolates were compared with 25 Dutch TR/L98H-positive isolates by microsatellite analysis. RESULTS: Of the 103 A. fumigatus isolates tested, only 2 had high MIC values of itraconazole (>16 mg/L), voriconazole (2 mg/L), posaconazole (2 mg/L) and isavuconazole (8 mg/L). The resistant A. fumigatus isolates exhibited the TR/L98H genotype and showed identical patterns by microsatellite typing, but were different from 25 Dutch TR/L98H isolates. CONCLUSIONS: We report for the first time from India the occurrence of TR/L98H mutations in the cyp51A gene (responsible for reduced azole susceptibility) in two A. fumigatus isolates from patients with chronic respiratory disease who had not previously been exposed to azoles. The presence of TR/L98H is consistent with a route of resistance development through exposure to azole compounds in the environment. Given the emergence of azole resistance in environmental strains, continued surveillance of resistance in clinical A. fumigatus strains is desirable for successful therapy of aspergillosis.

Good practice recommendations for outpatient parenteral antimicrobial therapy (OPAT) in adults in the UK: a consensus statement

Abstract: These good practice recommendations for outpatient parenteral antimicrobial therapy (OPAT) are an update to a previous consensus statement on OPAT in the UK published in 1998. They are based on previous national and international guidelines, but have been further developed through an extensive consultation process, and are underpinned by evidence from published literature on OPAT. They provide pragmatic guidance on the development and delivery of OPAT services, looking at all aspects of service design, care delivery, outcome monitoring and quality assurance, with the aim of ensuring that OPAT services provide high-quality, low-risk care, whatever the healthcare setting. They will provide a useful resource for teams developing new services, as well as a practical set of quality indicators for existing services.

Prospective study on quantitative and qualitative antimicrobial and anti-inflammatory drug use in white veal calves

Abstract: Results: The average TIADD of antimicrobial treatments was 416.8 ADD per 1000 animals at risk. Predominantly, oral group antimicrobial treatments were used (95.8%). Of the oral group antimicrobial treatments, 12% and 88% were used for prophylactic or metaphylactic indications, respectively. The main indication for group and individual drug use was respiratory disease. The most frequently used antimicrobials (group treatments) were oxytetracycline (23.7%), amoxicillin (18.5%), tylosin (17.2%) and colistin (15.2%). Deviations from the leaflet dosage recommendations were frequently encountered, with 43.7% of the group treatments underdosed (often oxytetracycline and tylosin to treat dysbacteriosis). In 33.3% of the oral antimicrobial group treatments a combination of two antimicrobial preparations was used. Smaller integrations used more antimicrobials in group treatments than larger ones (P,0.05); an integration is defined as a company that combines all steps of the production chain by having its own feed plant and slaughterhouse and by placing its calves in veal herds owned by producers that fatten these calves for this integration on contract. Producers used higher dosages than prescribed by the veterinarian in cohorts with a single caretaker (P,0.01). Conclusions: The present study provided detailed information on the intensive antimicrobial use in the white veal industry. Reduction can only be achieved by reducing the number of oral group treatments.

Population structure, virulence potential and antibiotic susceptibility of uropathogenic Escherichia coli from Northwest England

Abstract: Objectives Multilocus sequence typing (MLST) has been used to characterize diverse pathogens, including uropathogenic Escherichia coli (UPEC). There has been significant interest in the contribution of the O25b:H4-ST131 lineage to UPEC disease, as these isolates are often highly virulent and exhibit multidrug resistance. To reveal the wider impact of sequence type (ST) 131, we have examined its contribution to the overall population structure of UPEC isolates that were not selected on the basis of virulence or antibiotic resistance. Methods Three hundred UPEC isolates were recovered from community and hospital urine samples examined by clinical microbiology laboratories in the Northwest region of England in June 2007 and June 2009. They were characterized by susceptibility profiling, MLST and virulence gene PCR. PFGE was used to examine isolates from key clones. Results The most common lineage was ST73 (16.6%) followed by ST131 (13.3%), ST69 (9%), ST95 (6.3%), ST10 (4.3%) and ST127 (3.6%). ST131 isolates were significantly more likely to exhibit high levels of antibiotic resistance (35% being CTX-M-15 PCR positive) and those of ST127 were the most widely susceptible but carried the highest number of virulence genes. Only when the CTX-M-15-O25b-positive strains were examined was a high level of virulence observed for ST131 isolates. PFGE indicated ongoing local evolution in ST131. Conclusions ST131 isolates are well established in the wider UPEC population. This clone is still evolving and we further support suggestions that it represents a real threat to health. We suggest that ST127 is a recently emerged, community-associated, virulent clone that warrants further study.