BIOCHEMICAL PHENOTYPES OF SALMONELLA-LIVINGSTONE ISOLATED FROM HUMANS, ANIMALS AND FEEDSTUFFS IN SWEDEN

Salmonella Livingstone is occasionaly isolated from humans, animals an d feedstuffs in Sweden. To follow the spread of infection and trace th e source of isolates, adequate typing methods are needed. We have deve loped an automated typing system based on biochemical fingerprinting o f bacteria (the PhP system) for typing of different Salmonella serotyp es. The system measures the kinetics of various biochemical reactions of bacteria grown in liquid medium in microtiter plates and uses numer ical techniques to identify biochemical phenotypes (BPTs) among the te sted strains. In the present study we used a set of 16 highly discrimi natory tests to differentiate strains of Salmonella of serotype Living stone and evaluated the system for its discriminatory ability using a collection of 34 unrelated human isolates of S. Livingstone. We also u sed the system to investigate BPTs of 45 Livingstone strains isolated from animals and feedstuffs in Sweden between 1987 and 1991. Altogethe r 19 different BPFs were found among human isolate giving a diversity index (Di) of 0.930. In contrast, most strains isolated from animals a nd feedstuffs in Sweden belonged to 2 dominating BPTs (Di 0.704). One of these contained 17 strains mainly isolated during 1992 whereas the other contained 18 strains isolated between 1987 and 1991. None of the Swedish human isolates were identical to those of animals and feedstu ffs. These findings suggest that 2 different BPTs of Salmonella Living stone, strains are particularly common among animals and feedstuffs in Sweden and that they are not related to human cases of enteritis in t his country. We also conclude that biochemical fingerprinting with the PhP system is a reliable and highly discriminatory method for detecti ng epidemic strains of Salmonella Livingstone.