title: Relatedness of Escherichia coli strains with different susceptibility patterns isolated from beagle dogs during ampicillin treatment.
abstract: The aim of this study was to investigate the effects of ampicillin treatment on selection and diversity of ampicillin-resistant intestinal Escherichia coli in beagles treated with ampicillin, ampicillin + beta-lactamase (targeted to degrade antibiotic residues in the gut) or placebo. Selected faecal (n = 339) and jejunal (n = 63) E. coli isolates with known resistance patterns were typed using pulsed-field gel electrophoresis (PFGE). Among the 25 detected PFGE types, ampicillin resistance was detected in 6, none of which was dominant over others among the dogs. The resistant types increased especially in the ampicillin group, whilst beta-lactamase inhibited their emergence. Selection of genetically unrelated resistant strains rather than emerging resistance among previously susceptible strains accounts for increasing resistance rates during ampicillin treatment.
authors.affiliation: Anaerobe Reference Laboratory, Department of Bacterial and Inflammatory Diseases, National Public Health Institute (KTL), Helsinki, Finland. silja.mentula@ktl.fi
authors.forename: Silja
authors.initials: S
authors.lastname: Mentula
authors.forename: Terhi
authors.initials: T
authors.lastname: Virtanen
authors.forename: Arja
authors.initials: A
authors.lastname: Kanervo-Nordström
authors.forename: Jaana
authors.initials: J
authors.lastname: Harmoinen
authors.forename: Elias
authors.initials: E
authors.lastname: Westermarck
authors.forename: Merja
authors.initials: M
authors.lastname: Rautio
authors.forename: Pentti
authors.initials: P
authors.lastname: Huovinen
authors.forename: Eija
authors.initials: E
authors.lastname: Könönen
mesh_terms: D000667:Ampicillin / Q000494:pharmacology; D000668:Ampicillin Resistance; D000818:Animals; D004285:Dogs; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000187:drug effects* / Q000302:isolation & purification / Q000502:physiology*; D005243:Feces / Q000382:microbiology; D007583:Jejunum / Q000382:microbiology; D012641:Selection, Genetic
chemical_list: D000667:Ampicillin