Characterization of a novel EAST-negative enteropathogenic E. coli strain implicated in a food-borne outbreak of diarrhoea in adults

YesEnteropathogenic Escherichia coli (EPEC) is usually associated with outbreaks and sporadic cases of severe infantile diarrhoea in the developing world, and less commonly with sporadic cases in developed countries. Very little evidence indicates that EPEC is a food-borne pathogen for adults. In a previous study, two groups of adult travellers became ill, and eae+ E. coli of serogroup O111 was isolated from affected individuals and epidemiologically linked to food consumption. Here the strain responsible was further investigated and characterized as an unusual atypical EPEC. PCR analysis of the designated type isolate showed the presence of the rorf1 and espB genes of the LEE pathogenicity island, which was inserted at the chromosomal selC locus. The isolate was negative for the enteroaggregative E. coli EAST-1 toxin present in other strains of EPEC associated with food-borne outbreaks. The strain adhered sparsely to HEp-2 cell monolayers in a diffuse manner, but fluorescent actin staining demonstrated that it was capable of inducing polymerization of actin at the sites of bacterial attachment. Strain P2583 is the first EAST-negative EPEC to be confirmed as a cause of outbreaks of infection in adults following the consumption of contaminated food or water

Carriage of antimicrobial resistant Escherichia coli in dogs: prevalence, associated risk factors and molecular characteristics

Resistance to antimicrobials, in particular that mediated by extended spectrum β-lactamases (ESBL) and AmpC β-lactamases are frequently reported in bacteria causing canine disease as well as in commensal bacteria, which could be a potential health risk for humans they come into contact with. This cross-sectional study aimed to estimate the prevalence and investigate the molecular characteristics of ESBL and plasmid encoded AmpC (pAmpC)-producing E. coli in the mainland UK vet-visiting canine population and, using responses from detailed questionnaires identify factors associated with their carriage. Faecal samples were cultured for antimicrobial resistant (AMR), ESBL and pAmpC-producing E. coli. A subset of ESBL and pAmpC-producing isolates were subjected to multi-locus sequence typing and DNA microarray analyses. Multivariable logistic regression analysis was used to construct models to identify risk factors associated with multidrug resistant (MDR, resistance to three or more antimicrobial classes), fluoroquinolone resistant, ESBL and AmpC-producing E. coli. AMR E.coli were isolated from 44.8% (n = 260) of samples, with 1.9% and 7.1% of samples carrying ESBL and pAmpC-producing E. coli, respectively. MDR E. coli were identified in 18.3% of samples. Recent use of antimicrobials and being fed raw poultry were both identified as risk factors in the outcomes investigated. A number of virulence and resistance genes were identified, including genes associated with extra-intestinal and enteropathogenic E. coli genotypes. Considering the close contact that people have with dogs, the high levels of AMR E. coli in canine faeces may be a potential reservoir of AMR bacteria or resistance determinants

Carriage of antimicrobial-resistant Escherichia coli and Staphylococci in dogs in the community : molecular mechanisms

While previous studies have determined the prevalence of meticillin resistant Staphylococcus aureus (MRSA) and antimicrobial resistant (AMR) Escherichia coli in canine populations, few have included sufficiently large sample sizes and fewer still have characterised the isolates or investigated risk factors that might be associated with their carriage. The main aims of the work presented in this thesis were; to determine the nasal prevalence of MRSA and other AMR staphylococci and the faecal prevalence of AMR E. coli in faeces in the canine population of mainland UK. The study also aimed to characterise the bacteria isolated using molecular techniques in order for comparisons to be made with isolates of human origin, and to determine the presence of potential risk factors associated with faecal carriage of AMR E. coli. These objectives were achieved by carrying out two studies. The first study used frozen canine faecal samples collected during a cross sectional study of a semi-rural community in Cheshire to determine the prevalence of AMR E. coli. The second study collected faecal and nasal swabs from dogs visiting veterinary practices across mainland UK. Antimicrobial resistance of the isolates obtained from both studies were characterised using disc diffusion methods and PCR assays. In addition, isolates collected during the second study were subjected to multi-locus sequence typing and DNA micro array analysis of resistance and virulence genes. For antimicrobial resistant E. coli, risk factors associated with carriage were investigated. The prevalence of MRSA in the canine population was found to be low at 1% and all isolates were identical to EMRSA-15, the main human endemic strain in many UK hospitals. The overall S. aureus prevalence was 7.5%, with a higher prevalence of 11.0% of S. pseudintermedius, in which no meticillin resistance was found. Meticillin resistant coagulase negative Staphylococcus spp. was found in 5.5% of dogs. AMR in the isolates varied between species; however resistance to fusidic acid was consistently high. AMR E. coli was common in both studies (29.0% in community study and 44.8% in nationwide study). Resistance to ampicillin (24.0% and 37.2%), tetracycline (19.7% and 30.0%), trimethoprim (16.9% and 23.8%) and resistance to three or more antimicrobial classes (15.3% and 18.1%) was found to be high in both studies (community and nationwide respectively), while resistance to augmentin, chloramphenicol, ciprofloxacin and nalidixic acid was below 10% in both studies. A variety of genes responsible for resistance to expanded spectrum β-lactams was identified; including blaCTX-M-15 and blacmy2, both of which have previously been identified in humans and dogs. A number of variables were found to be associated with resistance to antimicrobials, with previous prescription of antimicrobials and consumption of raw poultry meat remaining in the final model of more than one resistance outcome. The carriage of MRSA and antimicrobial resistant E. coli could pose a potential problem both in terms of the welfare of the dogs carrying such bacteria as well as the zoonotic potential of the bacteria and resistance determinants.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Carriage of 'Staphylococcus' species in the veterinary visiting dog population in mainland UK : molecular characterisation of resistance and virulence

This study investigated the prevalence of nasal carriage of staphylococci in dogs and determined the characteristics of the isolates. A total of 724 dogs from 87 veterinary practices across the mainland UK were screened for carriage of Staphylococcus spp. All isolates were examined for meticillin resistance (MR) and the presence of the mecA gene investigated in those isolates showing resistance. All coagulase-positive staphylococci and MR coagulase-negative staphylococci (MRCoNS) were subjected to antimicrobial susceptibility testing. Spa typing and DNA microarray analysis of resistance and virulence genes was carried out on all MR S. aureus (MRSA) and a subset of meticillin susceptible S. aureus (MSSA). Staphylococci were isolated from 399 (55.1%) of the dogs; only seven (1%) carried MRSA, all of which were identified as the dominant UK healthcare-associated strain (EMRSA-15, ST22). MSSA was identified in 47 (6.5%) dogs, the sequence types of which have been suggested as precursors to successful MRSA clones. Forty (5.5%) dogs carried MRCoNS, while no dogs carried MR S. pseudintermedius, although this is increasingly reported in mainland Europe. Resistance to antimicrobials among the isolates varied between species, with multidrug resistance (MDR) in 87.5% of MRCoNS and 21.8% of coagulase positive staphylococci. Microarray analysis of MRSA and a subset of MSSA isolates identified numerous virulence genes associated with pathogenesis, which are commonly identified in isolates of human origin. However, no isolates carried Panton-Valentine leukocidin (PVL) genes. This study suggests that MRSA carriage is low in the vet visiting dog population, but there is a diverse range of virulence and resistance determinants in canine S. aureus and MRCoNS isolates