Phenotypic and genotypic analysis of clinical isolates Salmonella serovar Typhimurium in western Kenya

Background: Salmonella spp. are recognized as some of the most common causes of enteritis worldwide. This study aimed to identify clinically isolated S. Typhimurium in western Kenya and to assess antimicrobial resistance profiles and strain inter-relatedness. Methods: The study was performed in rural Maseno, Nyanza province in Kenya, between February 2004 and June 2005. Sixty-three patients with diarrhoea and fever were recruited. S. Typhimurium isolates were confirmed using serotyping, biochemical testing, and 16S rRNA sequencing. Susceptibility to 20 antimicrobials was determined and specific resistance genes were identified by polymerase chain reaction (PCR). Strain diversity was further analyzed using pulsed-field gel electrophoresis (PFGE), fluorescence amplified fragment length polymorphism (fAFLP), and multi-locus-variable-number- tandem regions (MLVNTR). Results: Twenty S. Typhimurium strains were isolated in the course of the study and their identity was confirmed by 16S rRNA gene sequencing. All 20 S. Typhimurium strains were resistant to ampicillin, streptomycin and sulfamethoxazole; ciprofloxacin resistance and phage DT104 were not detected. PFGE, plasmid profiling, and analysis of selected VNTR loci revealed further heterogeneity among the strains in the study. Conclusion: S. Typhimurium was commonly isolated from patients with diarrhoea and fever in Maseno. Considerable phenotypic and genotypic diversity was observed among isolates, suggesting that strains belonging to multiple lineages are responsible for disease in the study region. Multiple resistance was common and mediated by a variety of resistance genes but not by phage DT104. Copyright © 2009 Onyango et al.