Host association of Campylobacter genotypes transcends geographic variation.

Genetic attribution of bacterial genotypes has become a major tool in the investigation of the epidemiology of campylobacteriosis and has implicated retail chicken meat as the major source of human infection in several countries. To investigate the robustness of this approach to the provenance of the reference data sets used, a collection of 742 Campylobacter jejuni and 261 Campylobacter coli isolates obtained from United Kingdom-sourced chicken meat was established and typed by multilocus sequence typing. Comparative analyses of the data with those from other isolates sourced from a variety of host animals and countries were undertaken by genetic attribution, genealogical, and population genetic approaches. The genotypes from the United Kingdom data set were highly diverse, yet structured into sequence types, clonal complexes, and genealogical groups very similar to those seen in chicken isolates from the Netherlands, the United States, and Senegal, but more distinct from isolates obtained from ruminant, swine, and wild bird sources. Assignment analyses consistently grouped isolates from different host animal sources regardless of geographical source; these associations were more robust than geographic associations across isolates from three continents. We conclude that, notwithstanding the high diversity of these pathogens, there is a strong signal of association of multilocus genotypes with particular hosts, which is greater than the geographic signal. These findings are consistent with local and international transmission of host-associated lineages among food animal species and provide a foundation for further improvements in genetic attribution.

Non-susceptibility trends among Enterobacteriaceae from bacteraemias in the UK and Ireland, 2001-06.

BACKGROUND: Enterobacteriaceae are common agents of bacteraemia, with Escherichia coli accounting for 20% of the cases. Reflecting this importance, members of the family constitute 4 of the 12 collection groups in the British Society for Antimicrobial Chemotherapy (BSAC) Bacteraemia Surveillance Programme. METHODS: MICs from the BSAC surveillance programme were reviewed, along with bacteraemia reports received by the Health Protection Agency (HPA) via its CoSurv/LabBase system. Isolates with unusual resistances were subjected to molecular analysis. RESULTS: The BSAC and HPA systems both revealed dramatically increasing resistance to cephalosporins, ciprofloxacin and gentamicin among E. coli and Klebsiella spp., with cephalosporin resistance largely contingent on the spread of CTX-M extended-spectrum beta-lactamases (ESBLs); fluoroquinolone resistance also increased among Proteus mirabilis and ESBL-negative E. coli. Carbapenem resistance remained extremely rare, but two Enterobacter spp., from the same patient in different years, had KPC carbapenemases, while a few isolates had carbapenem resistance contingent upon combinations of beta-lactamase and impermeability, and ertapenem MICs for AmpC-derepressed Enterobacter spp. rose over time. Three new agents-ceftobiprole, doripenem and tigecycline-were tested. Ceftobiprole was broadly active, except against ESBL producers and Klebsiella oxytoca hyperproducing K1 enzyme, and was variable against AmpC-derepressed Enterobacter spp. and against Proteus vulgaris. Doripenem was more potent than imipenem. Tigecycline was almost universally active against E. coli, but low-level non-susceptibility (MIC 2 mg/L) was frequent among Klebsiella spp. CONCLUSIONS: E. coli and Klebsiella spp. showed dramatic shifts, with sharply rising non-susceptibility to cephalosporins, ciprofloxacin and gentamicin. The rise in cephalosporin resistance reflected dissemination of CTX-M ESBLs. Carbapenems remain broadly active and new agents offer potential.

Non-susceptibility trends among Pseudomonas aeruginosa and other non-fermentative Gram-negative bacteria from bacteraemias in the UK and Ireland, 2001-06.

BACKGROUND: Pseudomonas and Acinetobacter spp. are important opportunists, notorious for resistance. Pseudomonas spp. are collected in the British Society for Antimicrobial Chemotherapy (BSAC) bacteraemia surveillance, with Acinetobacter spp. and Stenotrophomonas maltophilia well represented in the 'other Gram-negatives' group. METHODS: Data for collected isolates were reviewed together with LabBase bacteraemia reports to the Health Protection Agency (HPA). Isolates with unusual resistances were subjected to molecular investigation. RESULTS: From 2001 to 2006, the BSAC surveillance collected 1226 Pseudomonas aeruginosa, 240 Acinetobacter spp.-125 of them Acinetobacter calcoaceticus/baumannii (Acb) complex-and 165 S. maltophilia. Among P. aeruginosa, non-susceptibility rates to beta-lactams and gentamicin fluctuated, without trend, below 10%; those to ciprofloxacin ranged from 16% to 22%. One P. aeruginosa isolate from 2001 had VIM-2 metallo-beta-lactamase. For Acb, the BSAC data indicated frequent non-susceptibility, except to imipenem, where only five non-susceptible isolates were collected, all after 2003, four of them belonging to the OXA-23 clone 1 lineage which is prevalent in Southeast England. Reports to the HPA indicated rising imipenem non-susceptibility in Acb (P < 0.0001). Co-trimoxazole retained near-universal activity against S. maltophilia. Among new antibiotics, doripenem MICs were /=16 mg/L for Acb OXA-23 clone 1. Ceftobiprole had higher MICs than ceftazidime for P. aeruginosa, but 81% of the isolates were inhibited at

Non-susceptibility trends among staphylococci from bacteraemias in the UK and Ireland, 2001-06.

OBJECTIVES: Investigation of the antibiotic susceptibilities and trends for staphylococci collected from bacteraemia cases in the UK and Ireland, from 2001 to 2006, as part of the British Society for Antimicrobial Chemotherapy's Bacteraemia Surveillance Programme. METHODS: Twenty-five hospitals from the UK and Ireland each collected up to 10 consecutive isolates of both Staphylococcus aureus and coagulase-negative staphylococci (CoNS) per year from 2001 to 2006. MIC determination and identification to species level were carried out centrally. mecA and also mupA alleles were sought by PCR in S. aureus and CoNS from 2005 and 2006, respectively. RESULTS: One thousand four hundred and forty-eight S. aureus and 1214 CoNS were collected. The overall prevalence of methicillin resistance was 42% (with

Non-susceptibility trends among enterococci and non-pneumococcal streptococci from bacteraemias in the UK and Ireland, 2001-06.

OBJECTIVES: To describe the current patterns and trends in antimicrobial susceptibility in enterococci and streptococci (excepting pneumococci) from bacteraemia in the UK and Ireland from 2001 to 2006. METHODS: In each year 2001-06, blood culture isolates were collected by 25 laboratories distributed across the UK and Ireland. In total, there were 1408 isolates of enterococci, 1332 of beta-haemolytic streptococci and 1012 of alpha- and non-haemolytic streptococci. A single central laboratory re-identified the isolates and measured MICs by the BSAC agar dilution method. RESULTS: The prevalence of reduced susceptibility in streptococci and enterococci did not change significantly for most antibiotics, but trends were noted to increased ampicillin, imipenem and vancomycin resistance in Enterococcus faecium. The prevalence of reduced susceptibility to macrolides and tetracycline in streptococci, to tetracycline and gentamicin (high level) in enterococci and to beta-lactams and glycopeptides in E. faecium were all high, with some differences in the prevalence among species or groups. CONCLUSIONS: Reduced susceptibility to some antimicrobial agents among streptococci and enterococci remains common and continued surveillance is warranted.

Non-susceptibility trends and serotype distributions among Streptococcus pneumoniae from community-acquired respiratory tract infections and from bacteraemias in the UK and Ireland, 1999 to 2007.

OBJECTIVES: Pneumococcal disease is prevalent and is a cause of significant morbidity and mortality in the UK and Ireland. We describe the antimicrobial susceptibility and serotype distributions of Streptococcus pneumoniae causing bacteraemia and community-acquired pneumonia in these countries from 1999/2000 to 2006/7, predominantly prior to the introduction of the heptavalent pneumococcal conjugate vaccine (PCV7) into the standard vaccination schedule in September 2006. METHODS: The BSAC Respiratory and Bacteraemia Resistance Surveillance Programmes collected S. pneumoniae from sentinel laboratories distributed across the UK and Ireland. A central laboratory for each programme re-identified the isolates, determined their serotypes and measured MICs by the BSAC agar dilution method. RESULTS: The prevalence of antimicrobial non-susceptibility, although significant, was generally below the global average. There was no convincing evidence of increasing non-susceptibility over time in either study. The results showed clear differences in the serotype distribution between respiratory and blood isolates, but suggested that PCV7 would provide adequate coverage of invasive isolates in the UK and Ireland. A significant and rapid increase of the non-vaccine serotype 1 among blood isolates from 2001 to 2006 was worrying, given the spread of hypervirulent serotype 1 clones elsewhere in the world. CONCLUSIONS: Continued surveillance of both antimicrobial non-susceptibility and serotype distribution changes following the introduction of PCV7 into the routine immunization schedule in the UK and Ireland is imperative. The data presented here, largely obtained prior to the introduction of PCV7 in the UK, provide a valuable baseline against which to monitor changes in antimicrobial non-susceptibility and serotype distribution and hence to identify the expansion of any significant clones.

Is Panton-Valentine leucocidin associated with the pathogenesis of Staphylococcus aureus bacteraemia in the UK?

BACKGROUND: The morbidity and mortality associated with Panton-Valentine leucocidin (PVL)-positive Staphylococcus aureus suggest that this toxin is a key marker of disease severity. Nevertheless, the importance of PVL in the pathogenesis of primary bacteraemia caused by S. aureus is uncertain. We have determined the prevalence of PVL-encoding genes among isolates of S. aureus from bacteraemic patients. METHODS: Consecutive bacteraemia isolates of S. aureus (n=244) from patients hospitalized in 25 centres in the UK and Ireland during 2005 were screened for PVL and mecA genes. PVL-positive isolates were characterized by toxin gene profiling, PFGE, spa-typing and MIC determinations for a range of antimicrobials. RESULTS: Four out of 244 isolates (1.6%) were PVL-positive and susceptible to oxacillin [methicillin-susceptible S. aureus (MSSA)]. Eighty-eight out of 244 (36%) were oxacillin-resistant (methicillin-resistant S. aureus), but none was PVL-positive. The four patients (two males: 30 and 33 years; two females: 62 and 80 years) had infection foci of: skin and soft tissue, unknown, indwelling line, and surgical site, and were located at one centre in Wales, one in England and two in Ireland. One of four PVL-positive isolates was resistant to penicillin and fusidic acid, the remainder were susceptible to all antibiotics tested. Genotypic analyses showed that the four isolates represented three distinct strains; the two isolates from Ireland were related. CONCLUSIONS: We found that 1.6% of S. aureus (all MSSA) from bacteraemic patients were PVL-positive. This low incidence suggests that PVL-positive S. aureus are of no particular significance as causative agents of S. aureus bacteraemia.