Relatedness of Escherichia coli strains with different susceptibility patterns isolated from beagle dogs during ampicillin treatment.
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.
Mentula
Silja
S
Anaerobe Reference Laboratory, Department of Bacterial and Inflammatory Diseases, National Public Health Institute (KTL), Helsinki, Finland. silja.mentula@ktl.fi
Virtanen
Terhi
T
Kanervo-Nordström
Arja
A
Harmoinen
Jaana
J
Westermarck
Elias
E
Rautio
Merja
M
Huovinen
Pentti
P
Könönen
Eija
E
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
D000667:Ampicillin