CTX-M-producing Escherichia coli in pigs from a Czech farm during production cycle

We evaluated the prevalence and epidemiology of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli isolates in pigs during production cycle on a Czech farm with the history of previous use of ceftiofur. ESBL-producing E. Coli isolates were obtained from rectal swabs from pigs of different age groups (suckling piglets, weaned piglets, growers and sows). Collected samples were directly cultivated on MacConkey agar with cefotaxime (2 mg l(-1)), whereas intestinal swabs of slaughtered pigs and surface swabs from pig carcasses were also pre-enriched in buffered peptone water without antimicrobials before the cultivation. Clonal relationship of selected isolates was determined byXbaI pulse-field gel electrophoresis and multi-locus sequence typing. The transferability of plasmids carryingbla(CTX-M)genes was tested by conjugation experiments. From all examined samples, 141 (43 center dot 7%,n = 323) were positive for ESBL-producing E. coli. All ESBL-producing isolates showed resistance to multiple antimicrobials and were positive forbla(CTX-M)genes. Thebla(CTX-M-1)was carried by conjugative IncN/ST1 plasmids (c. 40-45 kb) while thebla(CTX-M-15)was located on conjugative F plasmids with F:18:A5:B1 formula (c. 165 kb). This study demonstrated the persistence of CTX-M-positiveE. coliisolates 2 months after banner of ceftiofur usage and indicated possible risk of transmission of these isolates to humans via the food chain.