LABORATORY INVESTIGATION AND COMPARISON OF SALMONELLA BRANDENBURG CASES IN NEW-ZEALAND

An apparent increase in the incidence of S. Brandenburg in New Zealand , coupled with the possibility that the virulence of the organism may also be changing, prompted this study. Three typing methods: macro-res triction fragment length polymorphism (MRFLP) profiling using pulsed h eld gel electrophoresis (PFGE), plasmid profiling and antimicrobial su sceptibility profiling were used to determine strain diversity amongst 115 recent and historical isolates of S. Brandenburg from both human cases and non-human sources. Antimicrobial resistance was noted only i n three isolates. Plasmids of varying sizes were found in 31 isolates. MRFLP analysis resulted in 13 different patterns. Combining the three sets of typing data yielded 24 composite types. Comparison of composi te type, isolation date and geographical location of case allowed the retrospective recognition of seven potential clusters during the 5-yea r study period. Composite types of 24 (80 %) of the non-human isolates tested were indistinguishable from human isolates, suggesting that hu man infection may be via a number of vehicles. Although not cost-effec tive for routine use on all salmonella isolates, the methods used in t his study are an important adjunct to serotyping for discrimination wi thin an emerging serotype.