Antibiotic susceptibility patterns of Salmonella isolates from clinical, food, and environmental sources in Addis Ababa and surrounding towns, Ethiopia

ABSTRACT The increasing prevalence of antimicrobial resistance in Salmonella poses significant challenges to public health globally, particularly in low-resource settings such as Ethiopia. This study aimed to assess the antimicrobial resistance profiles of Salmonella isolates from human, food, and environmental sources in Addis Ababa and surrounding towns, with a focus on multidrug resistance (MDR) patterns. A total of 552 samples, consisting of 386 stool samples from patients with diarrhea and 166 food (meat) and environmental samples (such as waste water, cutting board, knife, and chicken dropping), were collected from 12 health facilities and two slaughterhouses. Salmonella was isolated and screened through selective culture methods and biochemical tests. Antimicrobial sensitivity tests were done by the Kirby-Bauer disk diffusion method. Among the 61 Salmonella isolates tested, the highest resistance was observed against tetracycline (63.9%), followed by ampicillin (55.7%). Resistance to trimethoprim-sulfamethoxazole and chloramphenicol was noted in 24.6% and 19.7% of isolates, respectively. Azithromycin resistance was also sensible at 27.9%. In contrast, ciprofloxacin showed relatively low resistance at 8.2%. Multidrug resistance defined as resistance to three or more antimicrobial classes was detected in 37.7% of isolates. Notably, clinical isolates exhibited significantly higher resistance levels compared to food and environmental sources, with 40% of clinical isolates demonstrating MDR patterns. Gentamicin (3.3%), ceftriaxone (6.6%), and amoxicillin-clavulanic acid (9.8%) remained largely effective, showing low resistance rates. This is one of the few comprehensive studies from Ethiopia examining Salmonella resistance across clinical, food, and environmental samples. High antimicrobial resistance, especially to ampicillin and tetracycline, highlights the urgent need for improved surveillance, rational antibiotic use, and infection control. The presence of multidrug-resistant strains stresses the importance of a coordinated national strategy. Future research should focus on developing simple, effective, and point-of-care applicable rapid diagnostic test kits to enable early detection and targeted treatment of multidrug-resistant Salmonella in resource-limited settings. IMPORTANCE Antibiotic-resistant Salmonella is a growing public health threat, particularly in low-resource settings like Ethiopia, where delayed detection and limited treatment options worsen disease outcomes. This study provides a comprehensive analysis of Salmonella isolates from clinical, food, and environmental samples in Addis Ababa and nearby towns, offering current data on antimicrobial resistance patterns. By using updated laboratory standards and sampling diverse sources, the findings highlight the urgent need for improved food safety practices, sanitation, and antimicrobial stewardship.