Molecular epidemiology of invasive isolates of Salmonella enterica serovar Typhimurium in Gauteng, South Africa, 2006-2008

摘要

The clonality of 840 invasive human Salmonella enterica serotype Typhimuriumudisolates isolated in Gauteng Province during January 2006 to May 2008 wasudinvestigated. PFGE analysis revealed 38 clusters: three (clusters 3, 5 and 11) wereudprimary clusters. Most isolates originated from Hospital 2 and were isolated fromudpatients in the age-range of 15-64 years. Ninety-two percent (256/277) of patientsudwith known HIV status were HIV-positive. Antibiotic susceptibility testing showedudthe most commonly expressed antibiotic resistance profiles were ACSSuNa (13%;ud90/671) and ACSSuTNa (12%; 82/671). Thirty-five nosocomial isolates wereudidentified in 12 clusters, of which most isolates came from two of our three majorudclusters: cluster 3 (31%; 11/35) and cluster 5 (23%; 8/35). In South Africa,udSalmonella Typhimurium remains an important opportunistic infection of HIVpositiveudpatients and may circulate as a nosocomial pathogen over prolonged periodsudwithin the hospital environment.udThe study included characterization of 47 Salmonella isolates recovered from a 150udchicken specimens purchased in Gauteng Province during September 2007 to Aprilud2008. Salmonella Heidelberg (34%; 16/47) and Salmonella Infantis (34%; 16/47)udwere the most common serotypes isolated from chickens. PFGE analysis showedudSalmonella Heidelberg and Salmonella Hadar isolates were similar in PFGE profile toudequivalent human serotypes, indicating that for these two serotypes some chicken andudhuman isolates may be related. PFGE analysis and MLVA showed that some chickenudand human Salmonella Typhimurium isolates were similar in molecular profile,udindicating a relationship between these isolates. An epidemiological relationshipudbetween chicken and human isolates could not be confirmed; however results suggest that Salmonella strains with similar molecular profiles circulate in the animal andudhuman communities, supporting the suggestion of animal-to-human transmission orudpossibly human-to-animal transmission. Further work is required to confirm thisudtheory.