Diversity among human non-typhoidal salmonellae isolates from Zimbabwe

Abstract

Background: Non-typhoidal Salmonella infections are an important public health problem in sub-Saharan Africa, especially among children and HIV-seropositive patients in whom they may cause invasive disease.

Methods: In order to better understand the epidemiology of Salmonella infections in southern Africa we typed, using serotyping, phage typing and multilocus sequence typing, 167 non-typhoidal Salmonella strains isolated from human clinical specimens during 1995-2000.

Results: The most common serovars were Salmonella Typhimurium DT56/ST313, Salmonella Enteritidis PT4 and Salmonella Isangi ST216. Isolates of Salmonella Isangi showed a multidrug-resistant phenotype that was resistant to extended-spectrum cephalosporins. Twelve new sequence types and six new serotypes of Salmonella were identified.

Conclusions: Given the diversity detected in the study it seems likely that many new variants of S. enterica are extant in Zimbabwe and by implication across sub-Saharan Africa. We have demonstrated the presence in Zimbabwe of a multidrug-resistant strain of the serovar Salmonella Isangi and demonstrated the diversity of Salmonella circulating in one sub-Saharan African country. Further studies on the characteristics of Salmonella Isangi isolates from Zimbabwe, including plasmid typing and genotyping, are essential if effective control of the spread of this potential pathogen in sub-Saharan Africa is to be achieved.

Keywords: Africa; Multilocus sequence typing; Non-typhoidal Salmonella; Salmonella Enteritidis; Salmonella Isangi ST216; Salmonella Typhimurium ST313.