Molecular fingerprinting defines a strain of Salmonella anatum responsible for an international outbreak associated with formula-dried milk

Abstract

In January 1997 the Laboratory of Enteric Pathogens (LEP) of the Public Health laboratory Service of England and Wales recognised that the number of isolates of Salmonella anatum from infants aged 1 to 11 months had risen in November and December 1996. The Scottish Centre for Infection and Environmental Health also reported four cases of S.anatum in infants in the period October 1996- January 1997. By the end of January 1997, of 52 isolates of S. anatum received in LEP in the 13-month period January 1 1996- January 31 1997, 18 were from infants and two were from relatives of cases. Molecular analyses based on plasmid profile typing and pulsed-field gel electrophoresis (PFGE) defined an epidemic strain of S. anatum associated with the consumption of particular brand of infant dried milk and the product was withdrawn from sale in the UK. The epidemic strain was subsequently identified in two of three isolates of S. anatum from infants in France, which prompted a withdrawal of the product in that country and two weeks later the epidemic strain was isolated from the product. The role of DNA fingerprinting in the 1996-97 international outbreak of S. anatum is discussed.