# Detection of carbapenem resistance among third-generation cephalosporin-resistant Enterobacterales from small-scale poultry farms in peri-urban Lusaka, Zambia

## TL;DR

This study found carbapenem-resistant bacteria in poultry from Zambia, highlighting risks to human and animal health and the need for better antibiotic use.

## Contribution

The study reports the emergence of carbapenem resistance in poultry-associated Enterobacterales in Zambia, with insights into resistance genes and patterns.

## Key findings

- 12% of third-generation cephalosporin-resistant isolates were also carbapenem resistant.
- blaCTX-M and blaTEM were the most common β-lactamase genes detected.
- Isolates from both districts showed similar resistance patterns, suggesting shared sources or transmission.

## Abstract

Background. Carbapenem and third-generation cephalosporin (3GC) resistance among Gram-negative bacteria 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 the Chongwe and Chilanga districts of Lusaka Province. The isolates were screened for 3GC and carbapenem resistance using the disc diffusion and broth microdilution methods. PCR and Sanger sequencing were performed for species identification and detection of 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 occurred in 84.3% of the isolates, with the highest resistance to ampicillin, tetracycline and co-trimoxazole. Overall, 80.7% of the isolates harboured 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. The detection of imipenem-resistant isolates indicates the potential for transmission of resistance genes between animals and humans. These findings underscore the need for prudent antimicrobial use, strengthened stewardship and a One Health surveillance approach to contain the spread of carbapenem resistance genes.