Diversity of salmonella isolates from wildlife and domestic animals in selected areas of Zambia.

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Mubita, Charles Miyanda
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The University of Zambia
Domestic animals and wildlife are considered important reservoirs from which Non-Typhoid Salmonella serotypes have emerged to cause public health concerns worldwide. Identification of the zoonotic origin of such organisms is important to understand the risk factors associated with a diversity of host types. In this study, phenotypic and genetic properties of Salmonella strains isolated from domestic animals and wildlife sources were characterized to determine their potential for causing invasive salmonellosis. The isolates were characterized into serogroups, serotypes, fermentative groups, resistotypes, and beta-lactamase activity types. Further, Salmonella plasmid virulence genes responsible for extraintestinal manifestations were determined among Salmonella serotypes from domestic animals (bovine, horse, dogs, and chickens) and wildlife (Leopard, Sable and Impala). Sequencing of the invA gene of Salmonella strains from different hosts and locations was performed and compared with reference sequences on the Gene-Bank. Thirty-four Salmonella strains belonging to four sero-groups; B, C1, D1, and a non- reactive group, were isolated and identified from the various animal hosts studied. The most prevalent sero-group was D1 (50.0%; 17/34) Salmonella strains, all from domestic animals followed by a non-reactive group (29.4%; 10/34) strains. Further, 12 serotypes, were detected among the strains. The most predominant serotype was Salmonella enterica serotype Enteritidis (47.1%; 16/34) isolated from horse and chicken, followed by S. Mbandaka (8.8%; 3/34) from dog and chicken. All Salmonella isolates were resistant to at-least four antimicrobial agents. Ampicillin, erythromycin, gentamicin, nitrofurantoin and penicillin G were observed as the most frequently resisted antimicrobial agents. Salmonella Enteritidis and S. Mbandaka isolated from the horse and dog respectively, each displayed multidrug resistance to 6 antimicrobial agents. All strains harboured Salmonella invasion A gene unique to the genus, while some strains possessed Salmonella plasmid virulence locus gene. The horse, leopard and chickens were found to be reservoirs of Salmonella isolates carrying spvA virulence genes and by consequence; these animals could serve as a reservoir for transmission of extra intestinal salmonellosis to humans and other animals through contamination of the environment. The homology percentage of nucleotide sequence (74.0 ~ 100.0) and amino acid sequence (60.0 ~ 100.0), showed genotypic differences between the strains isolated from domestic animals and wildlife, and the published sequences on the Gene-Bank. In conclusion, the present study isolated and identified multi-drug resistant Salmonella serotype strains that possess virulence genes which are of potential public health concern.
Thesis of Doctor of Philosophy In Microbiology.