Salmonella enterica serovars Typhimurium and Enteritidis causing mixed infections in febrile children in Mozambique.

Background and purpose: Invasive nontyphoidal salmonellosis, mostly caused by serovars Typhimurium and Enteritidis of Salmonella enterica , has emerged as a major public health problem in sub-Saharan Africa. The aim of this study was the clinical and microbiological characterization of nontyphoidal salmonellosis episodes affecting febrile children in Mozambique.

Patients and methods: The clinical records of the patients were evaluated, and S. enterica isolates were characterized with regard to serovar, phage type, antimicrobial resistance (phenotype/responsible genes), plasmid content, pulsed-field gel electrophoresis, and multilocus sequence typing.

Results: Fifteen S . Typhimurium and 21 S . Enteritidis isolates were recovered from blood samples of 25 children, the majority with underlying risk factors. With regard to phage typing, most isolates were either untypeable or reacted but did not conform, revealing that a number of previously unrecognized patterns are circulating in Mozambique. Most isolates were multidrug-resistant, with nearly all of the responsible genes located on derivatives of serovar-specific virulence plasmids. ST313 and ST11 were the predominant sequence types associated with S . Typhimurium and S . Enteritidis, respectively, and the uncommon ST1479 was also detected in S . Enteritidis. A distinct Xba I fragment of ~350 kb was associated with pulsed-field gel electrophoresis patterns of multidrug-resistant isolates of S . Enteritidis. Nearly half of the children were coinfected with both serovars, a fact expected to aggravate the disease and hamper the treatment. However, particularly poor outcomes were not observed for the coinfected patients.

Conclusion: Mixed Salmonella infections could frequently occur in febrile children in Mozambique. Additional studies are required to determine their actual impact and consequences, not only in this country, but also in other African countries.