A comperative study of the serotypes, plasmid profiles and resistance patterns of salmonella isolates from foods of animal origin and man from 4 hospital laboratories and the Central Vet laboratory in Uganda.

Abstract

Salmonellosis is a disease of man and animals which could present as a gastroenteritis and or enteric fever in the susceptible host. In Uganda, more than 80 percent of the districts continue to report cases of typhoid fever to the Ministry of Health. The majority of the reported salmonellosis cases are not confirmed according to standard procedures and no attempt has been made to study both human and animal derived isolates countrywide. Furthermore, the emergence of multi drug-resistant strains of salmonella is a recipe for major health problems in developing countries.

The current study compared the plasmid profiles, resistance patterns, and sensitivity patterns of salmonella isolates from foods of animal origin and man in Uganda. A total of ninety two (92) salmonella isolates were analyzed with 58 isolates from man, and 34 isolates from animals. Identification was done by using biochemical tests; plasmid profiling was by agarose gel electrophoresis while susceptibility testing to tetracycline, ampicillin, chloramphenicol, nalidixic acid, Trimethoprim Sulphamethoxazole, ciprofloxacin, Ceftriaxone and tetracycline was done by the Kirby Bauer Disc Diffusion method.

Salmonella typhimurium (1,4,5,12:i:1,2) accounted for 70.1% of the salmonella isolates, with meat and meat products(76.4% of the animal isolates) being the most likely sources of salmonella. Most of the isolates from both man (92%) and animals (94.1%) were susceptible to Ciprofloxacin, while as most (83.1%) of the human and animal(85.1%) isolates were resistant to Trimethoprim-Sulphamethoxazole. A total of 20(58.8%)of the animal isolates were resistant to chloramphenicol, while as 33(56.9%) of the human isolates were resistant to chloramphenicol. Fifty four percent (54%) of the isolates were resistant to at least three antibiotics whereas only 0.05% of the isolates were susceptible to all the seven antibiotics tested. Of the 70 isolates with plasmid, analysis showed eight clusters(A,B,C,D,E,F,Gand H) comprising of 65.7% (46/70 isolates).These clusters represented 100% homology in plasmid profile signatures. In five of the eight clusters formed, there were both animal and human isolates, suggesting cross-species transmission.

Meat and meat products are the commonest food source of Salmonella infection in the study sample. There was clustering of strains of human and animal origin, suggesting cross-species transmission of plasmids, and possibly drug resistance.