Salmonella serovars and their antimicrobial resistance in British turkey flocks in 1995 - 2006
Résumé
Serovar and antimicrobial resistance data from the scanning surveillance of British turkey flocks for Salmonella between 1995 and 2006 were analysed and compared with prevalence data from other livestock and animal feed. A total of 2,753 incidents of 57 different serovars were reported. The five most prevalent serovars were S. Typhimurium (20.8%), S. Newport (14.7%), S. Derby (10.6%), S. Indiana (8.3%) and S. Agona (6.4%). S. Typhimurium reports peaked in the mid to late 1990s; this occurred in parallel with the S. Typhimurium DT104 epidemic in other livestock species. S. Enteritidis reports peaked in mid to late 1990s, followed by a considerable decrease after 2000, which was also noted in flocks of domestic fowl. S. Newport, S. Montevideo, S. Senftenberg and S. Binza occurred in marked clusters indicating that they were introduced into one or more flocks at a certain time, i.e. via contaminated feed or infected day old chicks. A proportion of 43.1% of the reported Salmonella isolates were resistant to at least one antimicrobial while 17.7% were multi-resistant. No isolates were resistant to ciprofloxacin or to the third generation cephalosporins ceftazidime and cefotaxime. Resistance to ampicillin, chloramphenicol, streptomycin, sulphonamide compounds and tetracycline was common and it was mainly a characteristic of S. Typhimurium DT104 compared to S. Typhimurium non-DT104 and non-S. Typhimurium isolates (P<0.001). Resistance to nalidixic acid decreased from 16.9% in 1995 to 11.8% in 2006. Nalidixic acid resistance was most frequently found in S. Hadar (71.4%), S. Typhimurium DT104 (30.0%), S. Newport (17.9%) and S. Typhimurium non-DT104 (11.1%).
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