M. Fantasia et al., CONVENTIONAL AND MOLECULAR APPROACHES TO ISOLATES OF SALMONELLA HADARFROM SPORADIC AND EPIDEMIC CASES, Journal of applied microbiology, 82(4), 1997, pp. 494-498
In September 1994 an outbreak of gastroenteritis occurred in 437 peopl
e who had consumed lunch in the canteen of a factory in Central Italy.
Salmonella sp. was isolated from stools of 99 patients and in 73 of t
hem Salmonella hadar was identified. This is the first outbreak caused
by this serotype described in Italy. In order to examine the genotypi
c basis of the epidemic strains, molecular typing was applied to spora
dic strains isolated before and after the outbreak episode. For this p
urpose phage type, resistance to antibiotics, DNA plasmid profile and
sites of insertion of the mobile element of IS200 were determined. The
epidemic strains were genetically distinct from the non-epidemic isol
ates; they were shown to be phage type 26, harbouring four small plasm
ids, were resistant to nalidixic acid and showed a unique characterist
ic IS200 fingerprint. The typing methods used in this study allowed th
e identification and discrimination of the outbreak strains from relat
ed isolates. They can thus be considered as a tool for epidemiological
purposes. In addition we should point out the emerging resistance to
nalidixic acid, largely used in veterinary medicine, in Salm. hadar.