Molecular epidemiology of community-acquired invasive non-typhoidal Salmonella among children aged 2 29 months in rural Gambia and discovery of a new serovar, Salmonella enterica Dingiri.

ABSTRACT

Sixty-two invasive non-typhoidal Salmonella (NTS) isolates from children aged 2-29 months in rural Gambia were examined for serovar prevalence and antimicrobial susceptibility, and characterized using multilocus sequence typing (MLST) of seven genes, aroC, dnaN, hemD, hisD, purE, sucA and thrA. Salmonella enterica serovar Enteritidis was the most common serovar (80.6 %), followed by S. enterica serovar Typhimurium (8.0 %). Thirty-three per cent of the isolates were resistant to all eight antimicrobials tested, including ampicillin (74.2 %), cotrimoxazole (64.5 %) and tetracycline (63 %). A total of 40.3 % of the NTS cases had an initial clinical diagnosis of malaria, whilst 27.3 % had a diagnosis of clinical pneumonia and 18 % had a diagnosis of septicaemia. MLST of NTS resulted in ten different sequence types (STs), of which five were novel, representing five different NTS serovars. In general, STs were restricted to the same serovar. One type (ST11) encompassed 80.6 % of the NTSs. A new NTS serovar named S. enterica serovar Dingiri was discovered. S. Dingiri was isolated from a 6-month-old male with an initial clinical diagnosis of malaria but a final clinical diagnosis of anaemia and septicaemia. S. Dingiri, which possesses an antigenic formula of 17z1,6, was sensitive to ampicillin, cefotaxime, chloramphenicol, ciprofloxacin, cotrimoxazole and tetracycline but resistant to gentamicin, and was ST338.