Phenotypic and Genotypic Characterization of Salmonella Isolated from Asymptomatic Carriers in the Suburb of Dakar

Niang Aissatou Ahmet, Sambe Ba

Abstract

Salmonellosis is a major public health problem, especially with the emergence of multi-resistant Salmonella. The healthy carrier, an important factor of dissemination of Salmonella in the environment ensures inter-human transmission especially in children. In Senegal, studies on (carrying Salmonella are lacking. Thus, this work was (was conducted) to determine the (carrying rate of Salmonella), characterize phenotypically and genotypically salmonella strains isolated from healthy carriers in Dakar. This is a prospective study of five community sites (Jeddah Thiaroye Kao, Guinaw Rail South, North Pikine, Pikine East Guinaw North Rail) between January 2013 and April 2014. Phenotypic and molecular analysis PCR detection simplex virulence genes and typing by Multi-Locus Sequence Typing were performed at the Experimental Bacteriology Unit of the Institut Pasteur in Dakar. Sixteen salmonellae (16) of one thousand eight hundred and eighty-eight (1888) stool specimens were identified to be a carrier rate of 0.84% for a variety of serotypes (Brancaster, Chester, Give, Poona, Agona, Johannesburg, Istanbul, Enteritidis, Corvalis). If all the Salmonella strains were sensitive to beta-lactams, 25% were resistant to at least one antibiotic (nalidixic acid, trimethoprim-sulfamethoxazole and tetracycline). All isolates show all virulence genes (invA, orfL, Pipd, SpiC, Misl). Meanwhile, the SpvR virulence gene was detected in one isolate associated with Serovar enteritidis. This reflects the pathogenicity degree of Salmonella strains and therefore their ability to cause human disease. The MLST technique has revealed that phenotypically identical serotypes had no allelic variation. This suggests that these clones were widely distributed geographically and are probably outstanding in a wide range of hosts. Two new ST were found with Chester and Brancaster. Considering the characteristics of isolated Salmonella in this study and the impact of carriers on public health, monitoring of healthy carriers is needed.