Molecular Epidemiology of Multiple-Drug Resistant Salmonellae from the Sudan

Abstract

This study was designed to evaluate the antimicrobial resistant salmonellae isolates from man and animals. Assessment was done by in vitro, in vivo and molecular assay. Different strains of salmonellae were isolated from naturally infected man, cattle, poultry and camels. The prevalence of salmonella infection studied in the three areas of Khartoum States: Khartoum, Khartoum North and Omdurman. Infection rates in animals was found to be 10.36%, 56.31% and 6.97% in cattle, poultry and camels, respectively. Mortality rate was found to be 1.82% and 27.3% in cattle and poultry, respectively. In human the infection rate was found to be 11.02% calculated from the tested individuals. All isolated strains (119 isolates) were tested for drug resistance by the in vitro Methods. Ten antimicrobial drugs were used for sensitivity assays. Tetracycline revealed the highest resistance (65%), followed by furazolidone, cephalixin, colistin, and ampicillin, 204 respectively. All isolates were sensitive to ciprofloxacin and gentamicin. The MICs to S. enteritidis for ciprofloxacin, cephalixin, ampicillin and sulfamethoxazole + trimethoprim were found to be 0.063, 2.25, 0.25, and 120 μg/ml, respectively, while the MBC was found to be for the same antimicrobial drugs 0.063, 4.5, 1.0 and 240 μg/ml, respectively. This indicates a resistance to sulfamethoxazole + trimethoprim . Chemotaxonomy was used to compare the cell wall of the isolated salmonellae by free lipid analysis. Nine strains showed one pattern and belong to one cell wall free lipid group. Molecular analysis was used for the characterization of three salmonella strains. The three strains showed the same 16S rDNA Sequencing pattern, and belonged to one group. The 16S rDNA genes proved to be unsuitable for the epidemiological typing of salmonella strains below the species level. RAPD-PCR molecular techniques were used to detect the mechanism by which three salmonella strains has give accumulated resistance to chloramphenicol, tetracycline, ampicillin and cephalixin. Although the two isolated multiple-drug resistant strains have been isolated from human and cattle, amplification of the same resistant genes indicated that it could be transferred between man and animals.