Antimicrobial Drug Resistance and Plasmid Profiles of Salmonella Isolates from Humans and Foods of Animal Origin in Uganda


Salmonella organisms are among the most common causes of human bacterial gastroenteritis worldwide, and food animals are important reservoirs of these bacteria. A further danger lies in the development of drug resistance in these organisms, primarily driven by non-prudent overuse of antiinfectives. The current study compared the plasmid profiles and drug susceptibility patterns of Salmonella isolates from man and foods of animal origin in Uganda. A total of 92 Salmonella isolates (58 from man and 34 from foods of animal origin) were analyzed. Identification was done by using biochemical tests; plasmid profiling by agarose gel electrophoresis while susceptibility testing to tetracycline, ampicillin, chloramphenicol, nalidixic acid, trimethoprim-sulphamethoxazole, ciprofloxacin, ceftriaxone and tetracycline were done by the Kirby Bauer Disc Diffusion method. Among the human isolates, 57/58 (98.3%, 95% CI, 91.8% - 99.9%) were susceptible to Ciprofloxacin compared to 32/34 (94.1%, 95% CI, 81.9% - 91%) of animal-derived isolates. On the other hand, 48/58 (82.7%, 95% CI, 71.4% - 91%) human-derived isolates were resistant to Trimethoprim sulfamethoxazole compared to 29/34(85.3%) of the animal-derived isolates. Fifty four percent (n = 50) of the all the isolates were resistant to at least three antibiotics whereas only 2.2% (n = 2) were susceptible to all the seven drugs tested. Most worrying, however, was the fact that only 45% percent of the isolates were sensitive to all the three drugs (chloramphenicol, nalidixic acid and ciprofloxacin) commonly used in the treatment of salmonellosis in this setting. The risk of ampicillin resistance was three times more likely to occur in animal-derived as compared to human-derived isolates (Odds Ratio = 2.705, 95% CI, 1.3 - 5.8) as was that to nalidixic acid (Odds Ratio = 2.895, 95% CI, 1.17 - 7.2). Plasmid profile analysis showed eight clusters comprising of 68.7% (46/67) of the isolates. In five of the eight clusters, there were both animal and human-derived isolates. Resistant strains of Salmonella are common in this setting and meat/meat products are the commonest source of infection. A majority of the isolates are multi-drug resistant, and there is evidence of cross-species transmission of plasmids, and possibly drug resistance, between animals and humans.

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K. J. Bosco, D. H. Kaddu-Mulindwa and B. B. Asiimwe, "Antimicrobial Drug Resistance and Plasmid Profiles of Salmonella Isolates from Humans and Foods of Animal Origin in Uganda," Advances in Infectious Diseases, Vol. 2 No. 4, 2012, pp. 151-155. doi: 10.4236/aid.2012.24025.

Conflicts of Interest

The authors declare no conflicts of interest.


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