title: Genetic characterization of commensal Escherichia coli isolated from laboratory rodents.
abstract: BACKGROUND
  Escherichia coli, a commensal in the intestines of vertebrates, is capable of colonizing many different hosts and the environment. Commensal E. coli strains are believed to be the precursor of pathogenic strains by means of acquisition of antimicrobial resistant and virulence genes. Laboratory rodents are inherently susceptible to numerous known infectious agents, which could transfer virulence determinants to commensal E. coli. Hence, in this study, the genetic structure of commensal E. coli found in laboratory rodents and their antimicrobial resistance profiles were investigated.
  
  
  RESULTS
  E. coli strains belonging to phylogroup A were the predominant strain obtained from the animals used in the study. Four novel sequence types (ST746, ST747, ST748 and ST749) were discovered using the multi locus sequence typing, together with one common ST357 in the gastrointestinal tract, liver and, the trachea and lung. Serotyping demonstrated that these commensal E. coli strains were non-Shiga toxin-producers. Phenotypic and genotypic analyses of extended spectrum beta lactamases were also negative.
  
  
  CONCLUSIONS
  These findings implied that the E. coli strains recovered from the laboratory rodents were truly commensal in nature. Further study is required to investigate the possible influence of gender on the susceptibility of hosts to E. coli colonization in laboratory rodents.
authors.affiliation: Tropical Infectious Diseases Research and Education Centre, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Shih Keng
authors.initials: SK
authors.lastname: Loong
authors.affiliation: Tropical Infectious Diseases Research and Education Centre, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Nur Hidayana
authors.initials: NH
authors.lastname: Mahfodz
authors.affiliation: Tropical Infectious Diseases Research and Education Centre, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Nurul Asma Anati
authors.initials: NA
authors.lastname: Che Mat Seri
authors.affiliation: Animal Experimental Unit, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Haryanti Azura
authors.initials: HA
authors.lastname: Mohamad Wali
authors.affiliation: Animal Experimental Unit, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Syahar Amir
authors.initials: SA
authors.lastname: Abd Gani
authors.affiliation: Animal Experimental Unit, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia ; Department of Pharmacology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Pooi-Fong
authors.initials: PF
authors.lastname: Wong
authors.affiliation: Tropical Infectious Diseases Research and Education Centre, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia ; Department of Medical Microbiology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Sazaly
authors.initials: S
authors.lastname: AbuBakar
keywords: Commensal; Escherichia coli; Malaysia; Rodent