Epidemiology and Infection

Research Article

A large outbreak of human salmonellosis traced to a local pig farm

H. C. F. Maguirea1, A. A. Codda2, V. E. Mackaya3, B. Rowea4 and E. Mitchella1

a1 PHLS Communicable Disease Surveillance Centre, 61 Colindale Avenue, London NW9 5EQ

a2 PHLS Newcastle Laboratory

a3 North West Durham Health Authority

a4 PHLS Division of Enteric Pathogens

Abstract

An outbreak of Salmonella typhimurinm definitive type (DT) 193 affecting 206 persons occurred in July and August 1989 in a small town in northern England. A descriptive study suggested that cold meats including pork from a butcher's shop in the town were vehicles of infection. An analytical study of a cohort attending a function in the town showed a significant association between illness and consumption of cold roast pork supplied by the butcher's shop (P = 0·00000004). S. typhimurium DT 193 with the same antibiotic resistance pattern (to ampicillin, streptomycin, sulphonamides and tetracyclines) as the outbreak strain, and possessing a single plasmid of 80 MDa was isolated from samples of meat bought from the shop and implicated in illness, and from samples of pig faeces taken from the farm supplying the shop. It was concluded that inadequate processing of infected pork meat at the shop may have contributed to this outbreak but that cross contamination also played an important part in transmission. Control measures included a temporary closure of the shop and subsequent implementation of a detailed protocol for meat processing and monitoring of all procedures at the shop.

(Accepted October 22 1992)

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