Investigating antimicrobial resistance in <i>Salmonella</i> strains isolated from food in Syria

Background: The emergence of multiple drug resistance in Salmonella typhi and Salmonella paratyphi poses a significant challenge, necessitating the development of effective treatments to combat these bacteria and reduce infection rates. This in vitro study aimed to evaluate the minimum inhibitory concentration (MIC) of various antibiotics against S. typhi and S. paratyphi. Methods: Overall, 116 samples were collected from diverse markets in Syria. Molecular techniques, including polymerase chain reaction, were utilized to identify the bacterial genus. Antimicrobial susceptibility testing, employing the disk diffusion method and MIC determination, was conducted to assess the effectiveness of various antibiotics. Results: Among the isolates, 46 were identified, consisting of 23 S. typhi and 23 S. paratyphi strains. Resistance to nalidixic acid was observed in 9 out of 23 S. typhi and 11 out of 23 S. paratyphi isolates. Notably, these nalidixic acid-resistant strains exhibited elevated MIC50 values for other fluoroquinolones. Furthermore, most of these resistant isolates, specifically 8 out of 9 S. typhi and 11 out of 11 S. paratyphi, displayed complete resistance to ciprofloxacin (MIC50≥2 μg/L). Conclusion: Based on our findings, only gentamicin, third-generation cephalosporins, and some fluoroquinolones demonstrated efficacy effects against S. typhi and S. paratyphi isolates in this study.