Frequency and Antimicrobial Resistance of Salmonella spp. Isolates from chicken Meat and from Patients with Acute Diarrhea in Shiraz; A Comparative Study

Background and Objectives: Salmonella is a leading cause of food-borne illnesses. In many countries, the high incidence of salmonellosis in human appears to be caused by infection caused by contaminated poultry meat and meat products. The emergence of antimicrobial resistant Salmonella is associated with the use of antibiotics in animals raised for food. The resistant bacteria can be transmitted to humans through foods, particularly those of animal origin. This study aimed to determine the frequency and antimicrobial resistance of Salmonella isolates from raw chicken meat and human diarrhea stool samples. Materials and Methods: Chicken meat samples came from different municipal districts of Shiraz, and the stool samples were collected from patients with acute diarrhea, referred to the emergency wards of Nemazee, and Dastgheyb hospitals between September of 2018 and of 2019. Isolation of Salmonella was carried out using standard microbiological culture methods. The identification of the colonies suspected of Salmonella was done by biochemical tests. Confirmation was made through PCR, employing primers targeting invA gene. Serogroups of the isolates were determined by agglutination method using antisera against Salmonellas serogroups A to D. The antimicrobial susceptibility testing of the isolates was performed using disk diffusion method on 15 antibiotics. Results: A total of 100 chicken meat and 295 diarrhea stool samples were tested. Seventy (70%) and 5 (1.7%) Salmonella strains were isolated from samples of chicken meat and of stool, respectively. While all Salmonella isolates from human sources belonged to serogroup D, only 20% of the isolates from chicken meat were related to this serogroup. Serogroup C (74.3%) was the most prevalent one among the isolates from chicken source. Multidrug resistant (MDR) phenotype was observed in 85.7% of Salmonella isolates from chicken source. The resistance level of isolates from chicken meat to Nalidixic acid, Tetracycline, Trimethoprim-sulfamethoxazole, Chloramphenicol and Azithromycin were 95.7%, 75.7%, 61.4%, 38.6% and 34.3%, respectively. Ciprofloxacin resistance was observed in 12.85% of isolates of the chicken meat. No resistance to cefotaxime, Ceftazidime or Imipenem was found in the chicken meat isolates. Contrary to those of the chicken meat, Salmonella isolates of the patients were almost susceptible to most tested antibiotics. In the isolates from the latter source, resistance was observed only to Nalidixic acid, Tetracycline and Chloramphenicol with 80%, 20% and 20% rates, respectively. Conclusion: We are reporting here that 70 % of chicken meat of the collected samples have been contaminated with MDR Salmonella strains. Therefore, chicken meat could be a potential vehicle of infections with foodborne resistant Salmonella in humans.