Determination of Virulence factors in Salmonella isolates of Human, Poultry and Dog origin in Lusaka District, Zambia
Ulaya, Dandaulo William
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This study was conducted in Lusaka, Zambia to determine the distribution of the invA, invF,hilA, hilC, hilD, sipC and spiC virulence genes in Salmonella isolates from dogs, chickens and humans using both the Polymerase chain reaction (PCR) and dot blot hybridization methods. In the study, 243 dog fecal samples and 136 chicken specimens were analyzed by the culture and isolation method. A total of 18 Salmonella isolates (prevalence 7.6%) belonging to sero groups E, B, C and untypable serovars from dogs and sero group D (S. enteritidis) from chickens (prevalence 16.2%) were subjected to virulent gene analysis. A further 25 Salmonella isolates belonging to sero group B, C, D and E from humans were also examined for the presence of the virulence genes. The invA gene was found present in all the 66 isolates using both methods. However, using the Dot blot hybridization assay it was observed that isolates from the chicken, dog and human sources varied in the possession of the hilD gene (13%, 55.5% and 72%,respectively) and sipC gene (13%) only from chicken isolates. Using the Polymerase chain reaction (PCR) assay the invF gene was distributed in varying percentages (16.7%, 40%, 20%)as well as the sipC gene (8%, 8.7%, 4%) among isolates from dog, chicken and human sources,respectively. The hilD gene was possessed only by isolates from dogs. Also examined were the antimicrobial susceptibility patterns of the isolates, which showed that dog Salmonella isolates were susceptible to amoxicillin (100%) and nitrofurantoin (94.4%), those from chicken showed susceptibility to nitrofurantoin (100%), amoxicillin (95.7%), ampicillin and tetracycline (82.6% respectively) and those from human showed susceptibility to nitrofurantoin (79.6%) and amoxicillin (68%).It was concluded from the results of the study that dogs and chickens could be important carriers of invasive Salmonella in Lusaka, Zambia. There was no significant difference in the distribution of Salmonella virulence genes in dogs, chickens and humans. However, their degrees of expression varied from one Salmonella source to another showing their pathogenic potential in the infected hosts. Humans were shown to have similar Salmonella serogroups as those found in dogs and chickens, signifying the zoonotic potential of the bacteria. The multiple antimicrobial drug resistance observed from Salmonella in dogs and chickens may be potential sources of human salmonellosis in Zambia which could be difficult to treat.
- Veterinary Medicine