Antimicrobial resistance in pig faecal samples from The Netherlands (five abattoirs) and Sweden

The prevalence and degree of antibiotic resistance of faecal indicator bacteria, Escherichia coli and enteroccoci, were determined in 1321 faecal samples collected from pigs at five abattoirs in The Netherlands and in 100 samples from Swedish pigs. In the Dutch samples a high prevalence of resistance was observed in E. coli for three commonly used antibiotics in pig medicine, amoxycillin (70-94%), oxytetracycline (78-98%) and trimethoprim (62-96%). Also, the prevalence for chloramphenicol (55-67%) and neomycin (38-67%) was relatively high. For the other compounds tested the prevalence was less than 10%. The percentage of samples with a high degree of resistant E. coli showed the same tendency in all Dutch abattoirs although significant differences between the abattoirs were observed. The percentage of Swedish samples with a high degree of resistant E. coli was significantly lower for all antibiotics except nitrofurantoin, gentamicin, flumequin and ciprofloxacin. All enterococci were susceptible to amoxycillin and high-level resistance to gentamicin was observed in 4-6% of the Dutch samples. A high prevalence of resistance and a high degree of resistance was found for erythromycin and oxytetracycline. The prevalence of resistance to dalfopristin-quinupristin ranged from 6 to 8% and for vancomycin from 24 to 46%. Significant differences between the abattoirs were found for all compounds tested except amoxycillin. In the Swedish population both the prevalence and degree of resistance in enterococci were significantly lower except for amoxycillin and gentamicin. This point prevalence study showed that the prevalence and degree of antibiotic resistance in indicator bacteria, E. coli and enterococci, in faecal samples from pigs differed between two countries and reflected differences in antibiotic usage in pigs. To analyse the differences observed between the slaughterhouses, additional information about the farms of origin and antibiotic consumption is necessary.