In vitro activity of rifaximin against clinical isolates of Escherichia coli and other enteropathogenic bacteria isolated from travellers returning to the UK.

Rifaximin is licensed in the EU and USA for treating travellers' diarrhoea caused by non-invasive bacteria. Selection for resistance mechanisms of public health significance might occur if these are linked to rifamycin resistance. Rifaximin MICs were determined by agar dilution for 90 isolates each of Escherichia coli, Shigella spp., nontyphoidal Salmonella enterica, typhoidal S. enterica and Campylobacter spp., an additional 60 E. coli with CTX-M ESBLs isolated from patients with travellers' diarrhoea, and 30 non-diarrhoeal carbapenemase-producing E. coli. Comparators were rifampicin, ciprofloxacin, azithromycin, trimethoprim/sulfamethoxazole and doxycycline. Isolates with rifaximin MICs>32 mg/L were screened for arr genes, and critical rpoB regions were sequenced. Rifaximin was active at ≤32 mg/L against 436/450 (96.9%) diverse Enterobacteriaceae, whereas 81/90 (90%) Campylobacter spp. were resistant to rifaximin at ≥128 mg/L. Rifaximin MICs were ≥128 mg/L for two Shigella and five MDR E. coli producing NDM (n = 3), OXA-48 (n = 1) or CTX-M-15 (n = 1). Two of the five MDR E. coli had plasmids harbouring arr-2 together with bla(NDM), and two (one each with bla(NDM) and bla(CTX-M-15)) had His526Asn substitutions in RpoB. The rifamycin resistance mechanism remained undefined in one MDR E. coli isolate (with bla(OXA-48)) and the two Shigella isolates. Rifaximin showed good in vitro activity against diverse Enterobacteriaceae but was largely inactive against Campylobacter spp. Rifaximin has potential to co-select MDR E. coli in the gut flora, but much stronger associations were seen between ESBL and/or carbapenemase production and resistance to alternative treatments for travellers' diarrhoea, notably ciprofloxacin and azithromycin.

Widespread acquisition of antimicrobial resistance among Campylobacter isolates from UK retail poultry and evidence for clonal expansion of resistant lineages.

BACKGROUND: Antimicrobial resistance is increasing among clinical Campylobacter cases and is common among isolates from other sources, specifically retail poultry - a major source of human infection. In this study the antimicrobial susceptibility of isolates from a UK-wide survey of Campylobacter in retail poultry in 2001 and 2004-5 was investigated. The occurrence of phenotypes resistant to tetracycline, quinolones (ciprofloxacin and naladixic acid), erythromycin, chloramphenicol and aminoglycosides was quantified. This was compared with a phylogeny for these isolates based upon Multi Locus Sequence Typing (MLST) to investigate the pattern of antimicrobial resistance acquisition. RESULTS: Antimicrobial resistance was present in all lineage clusters, but statistical testing showed a non-random distribution. Erythromycin resistance was associated with Campylobacter coli. For all antimicrobials tested, resistant isolates were distributed among relatively distant lineages indicative of widespread acquisition. There was also evidence of clustering of resistance phenotypes within lineages; indicative of local expansion of resistant strains. CONCLUSIONS: These results are consistent with the widespread acquisition of antimicrobial resistance among chicken associated Campylobacter isolates, either through mutation or horizontal gene transfer, and the expansion of these lineages as a proportion of the population. As Campylobacter are not known to multiply outside of the host and long-term carriage in humans is extremely infrequent in industrialized countries, the most likely location for the proliferation of resistant lineages is in farmed chickens.

Duck liver-associated outbreak of Campylobacteriosis among humans, United Kingdom, 2011.

Campylobacter- spp.-related gastroenteritis in diners at a catering college restaurant was associated with consumption of duck liver pâté. Population genetic analysis indicated that isolates from duck samples were typical of isolates from farmed poultry. Campylobacter spp. contamination of duck liver may present a hazard similar to the increasingly recognized contamination of chicken liver.

Characterization of water and wildlife strains as a subgroup of Campylobacter jejuni using DNA microarrays.

Campylobacter jejuni is the leading cause of human bacterial gastroenteritis worldwide, but source attribution of the organism is difficult. Previously, DNA microarrays were used to investigate isolate source, which suggested a non-livestock source of infection. In this study we analysed the genome content of 162 clinical, livestock and water and wildlife (WW) associated isolates combined with the previous study. Isolates were grouped by genotypes into nine clusters (C1 to C9). Multilocus sequence typing (MLST) data demonstrated that livestock associated clonal complexes dominated clusters C1-C6. The majority of WW isolates were present in the C9 cluster. Analysis of previously reported genomic variable regions demonstrated that these regions were linked to specific clusters. Two novel variable regions were identified. A six gene multiplex PCR (mPCR) assay, designed to effectively differentiated strains into clusters, was validated with 30 isolates. A further five WW isolates were tested by mPCR and were assigned to the C7-C9 group of clusters. The predictive mPCR test could be used to indicate if a clinical case has come from domesticated or WW sources. Our findings provide further evidence that WW C. jejuni subtypes show niche adaptation and may be important in causing human infection.

Campylobacter epidemiology: a descriptive study reviewing 1 million cases in England and Wales between 1989 and 2011.

OBJECTIVES: To review Campylobacter cases in England and Wales over 2 decades and examine the main factors/mechanisms driving the changing epidemiology. DESIGN: A descriptive study of Campylobacter patients between 1989 and 2011. Cases over 3 years were linked anonymously to postcode, population density, deprivation indices and census data. Cases over 5 years were anonymously linked to local weather exposure estimates. SETTING: Patients were from general practice, hospital and environmental health investigations through primary diagnostic laboratories across England and Wales. PARTICIPANTS: There were 1 109 406 cases. OUTCOME MEASURES: Description of changes in Campylobacter epidemiology over 23 years and how the main drivers may influence these. RESULTS: There was an increase in Campylobacter cases over the past 23 years, with the largest increase in people over 50 years. Changes in the underlying population have contributed to this, including the impacts of population increases after World War I, World War II and the 'baby boom' of the 1960s. A recent increase in risk or ascertainment within this population has caused an increase in cases in all age groups from 2004 to 2011. The seasonal increase in cases between weeks 18 (Early May) and 22 (Early June) was consistent across ages, years and regions and was most marked in children and in more rural regions. Campylobacter prevalence by week in each region correlated with temperature 2 weeks before. There were higher prevalences in areas with a low population density, low deprivation and lower percentage of people of ethnic origin. Data from sero-phage and multilocus sequence typing show a few common types and many uncommon types. CONCLUSIONS: The drivers/mechanisms influencing seasonality, age distribution, population density, socioeconomic and long-term differences are diverse and their relative contributions remain to be established. Surveillance and typing provide insights into Campylobacter epidemiology and sources of infection, providing a sound basis for targeted interventions.

Prevalence, characterisation and antimicrobial resistance of Campylobacter and Salmonella in raw poultrymeat in the UK, 2003-2005.

This study was conducted to determine the prevalence and antimicrobial resistance of Campylobacter and Salmonella isolates from retail poultrymeat in the UK during 2003-2005. Poultrymeat (n = 2104) were more frequently contaminated with Campylobacter (57.3%) than with Salmonella (6.6%). Chicken exhibited the highest contamination from Campylobacter (60.9%), followed by duck (50.7%), turkey (33.7%) and other poultrymeat (34.2%). Duck had the highest contamination from Salmonella (29.9%), compared with chicken (5.6%), turkey (5.6%), and other poultrymeat (8.6%). C. jejuni predominated in raw chicken, whereas C. coli predominated in turkey and duck. C. coli isolates were more likely to exhibit antimicrobial drug resistance, including quinolones, than C. jejuni. Salmonella Enteritidis was the most frequent Salmonella serotype isolated. Salmonella isolates from turkey exhibited higher rates of multiple drug resistance (55.6%) than isolates from chicken (20.9%) and duck (13.6%). The findings reinforce the importance of thorough cooking of poultrymeat and good hygiene to avoid cross-contamination.

Physiological and molecular analysis of a mecA-negative Staphylococcus aureus clinical strain that expresses heterogeneous methicillin resistance.

Staphylococcus aureus clinical isolate 61/5896 exhibited methicillin resistance (MIC 64 mg/L), but lacked mecA, which encodes penicillin-binding protein 2'. The strain was isolated in England in 1961, and exhibited unstable heterogeneous methicillin resistance. When cultivated in drug-free medium, the methicillin resistance of 61/5896 increased after three daily passages, then decreased and was completely lost after 12 days' passage. Electron microscopy revealed that strain 61/5896 had a thicker and rougher cell wall than its methicillin-susceptible derivatives. It produced about three times more penicillin-binding protein 2 (PBP2) than methicillin-susceptible derivatives. The strain was characteristically a non-producer of autolytic enzyme, though the phenotype, which was lost easily, was not directly correlated with methicillin resistance.