Determination of Antibiotic Resistance and Identification of Tetracycline (tet) Resistance Genes in Salmonella enteritidis Strains Isolated from Food Sources

Salmonellosis is an important disease among human animals and which is caused by different serovars of Salmonella enterica. Serovars enteritidis and typhimurium are the most prevalent serovars among human and animals which are the causes of foodborne infections. This study aimed to detect the antibiotic resistance pattern in Salmonella strains isolated from red meat as well as the molecular identification of tetracycline resistance genes.
In this study, 230 red meat samples were collected during 2015 from slaughterhouses,distribution centers and industrial processing plants around Tehran and were examined using culture and biochemical tests for the presence of Salmonella isolates. Serotyping was performed using O and H antisera. Antimicrobial susceptibility testing was done for all the strains. Detection the tetracycline resistance gene was performed using Multiplex PCR and specific primers for the tetA, tetB, tetC and tetD genes.
Results and A total of 60 Salmonella samples were isolated and identified. The serotyping results showed that all of the 60 samples belonged to group D and serovar enteritidis. The highest resistance was against amoxicillin and the lowest resistance against gentamicin. Twenty five percent of the samples showed phenotypical resistance to tetracycline, among which 60% had the tet genes, 7 isolates (46.6%) having the tetA gene, one isolate having the tetB and one isolate possessing the tetC gene. This study showed the prevalence of Salmonella isolates in red meat samples and and the presence of tetracycline resistance genes among these isolates.