Changing epidemiology of human salmonellosis in Hong Kong, 1982-93

A comprehensive analysis of the epidemiology of salmonellosis in a major hospital in Hong Kong from 1982-93 is reported. The trend of salmonella isolations over the past 12 years and changes in the occurrence of individual serotypes are delineated. A total of 5328 isolates were analyzed. Groups B (Salmonella typhimurium and S. derby) and E (S. anatum) were the commonest serogroups isolated from the intestinal tract in all age groups. A significant increase in the isolation of group D salmonellae has been observed since 1989. This is accounted for by a substantial rise in S. enteritidis isolation as seen in Western countries, despite a concomitant decrease of S. typhi. The extraintestinal isolation index (EII) is proposed as an index of the virulence potential of individual serotypes and serogroups. Group D salmonella was found to be the most invasive serogroup. While group D was the predominant serogroup isolated from extraintestinal sites in patients older than 1 year, group B serotypes (especially S. typhimurium) were more frequently seen in infants younger than 12 months.