DETECTION OF CARBAPENEM RESISTANCE AMONG THIRD-GENERATION CEPHALOSPORIN-RESISTANT ENTEROBACTERALES FROM SMALL-SCALE POULTRY FARMS IN PERI-URBAN LUSAKA, ZAMBIA.

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Background Carbapenem and third-generation cephalosporin (3GC) resistance among Enterobacterales poses a serious threat to human and animal health. This study aimed to identify and characterize carbapenem- and 3GC-resistant Enterobacterales isolated from poultry in Lusaka Province, Zambia. Methods Ninety pooled cloacal samples were collected from market-ready broiler chickens in Chongwe and Chilanga districtsof Lusaka Province. The isolates were screened for 3GC and carbapenem resistance using disk diffusion and broth microdilution. PCR and Sanger sequencing were performed for species identification and detection of the β-lactamase-encoding (bla) genes, including blaCTX-M, blaTEM, blaOXA-1, and blaSHV. Hierarchical clustering was used to assess phenotypic and genotypic relationships. Results A total of 83 3GC-resistant Gram-negative isolates were recovered, of which 12% were also carbapenem-resistant. Escherichia coli was the most prevalent species, followed by Klebsiella pneumoniae and Enterobacter spp., then Pseudomonas aeruginosa, other Pseudomonas spp., Acinetobacter baumannii, Citrobacter freundii, and Aeromonas caviae. Multidrug resistance (MDR) occurred in 84.3% of the isolates, with the highest resistance to ampicillin, tetracycline, and co-trimoxazole. Overall, 80.7% of the isolates harbored at least one of the four tested bla genes, with blaCTX-M and blaTEM being the most common. Hierarchical clustering revealed that isolates from both districts shared similar phenotypic and genotypic resistance patterns. Conclusions The presence of multidrug- and carbapenem-resistant Enterobacterales from poultry highlights the emergence of carbapenem resistance in Zambia’s food production sector. Imipenem-resistant isolates indicate the potential for transmission of resistance genes between animals and humans. These findings underscore the need for prudent antimicrobial use, strengthened stewardship, and One Health surveillance to contain the spread of carbapenem resistance genes.

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