THE EPIDEMIOLOGY OF SALMONELLA-TYPHIMURIUM IN CATTLE - PLASMID PROFILE ANALYSIS OF DEFINITIVE PHAGE TYPE (DT) 204C

During the period 1979-1991, Salmonella Typhimurium DT 204c was the ca use of a major epidemic of salmonellosis in calves in the UK. Plasmid profile analysis of DT 204c isolates from England and Wales commenced in 1986 and isolates from all subsequent incidents were examined by th is technique. Forty-three different plasmid profile types (PPTs) were detected, of which the commonest, designated type E, constituted 44.6- 80.2% of the annual incidents during the study period. Some PPTs, e.g. , F and P, were detected throughout most years of the study, whereas P PTs 0 and 6 persisted for short periods. Until 1984, most isolates wer e resistant to neomycin, but the subsequent predominant PP type E was sensitive to this antibacterial agent. It was concluded that during th e epidemic there was an evolution of new genotypes, of which only some persisted; again, antibacterial resistance genes may be acquired or l ost. The study demonstrated the value of PP typing for epidemiological studies.