Phenotypic Antimicrobial Resistance Patterns in E. coli, Salmonella, and Enterobacter Species Isolated from Broiler Chicken Meat in Mzimba, Malawi: Insights from the Multiple Antibiotic Resistance Index

Background: Antibiotic resistance is becoming a serious problem in chicken production globally due to the use of antibiotics. In Mzimba, the multiple antibiotic resistance index (MARI) pattern in chicken meat is not known and has not been documented. Objective: To assess the prevalence of antibiotic-resistant Escherichia coli, Salmonella, and Enterobacter species in broiler chicken meat sold in informal markets in Mzimba District, Malawi, using the MAR index. Materials and Method: A cross-sectional study was conducted between March and May 2025. A total of 100 meat samples were collected from the informal markets across the district. A stratified sampling technique was used to select chicken meat samples from various markets. Descriptive statistics and inferential statistics were performed using R version 4.5.3. Results: E. coli (69%) and Enterobacter (12%) species were the most frequently isolated pathogens. The highest prevalence of antibiotic resistance was observed in E. coli against ampicillin (91%), meropenem (83%), and tetracycline (71%). Similarly, Enterobacter spp. showed substantial resistance to tetracycline (83%), ampicillin (83%) and meropenem (75%). The MAR index values were considerably high, ranging from 0.1 to 0.75. A total of 97.1%, 91.7% and 100% of the positive isolates of E. coli, Enterobacter and Salmonella spp., respectively, had MAR index values over 0.2. Location was the most significant predictor of the MAR index (p = 6.096 × 10−5, η2 = 0.372). Conclusions and Recommendations: High levels of the MAR index were revealed in this study. As such, combating MDR requires coordinated multisectoral approaches through One Health programs that integrate surveillance, policies, and innovation to prevent and control antimicrobial resistance.