A nationwide survey of antimicrobial resistance of isolated from broiler chickens in Malawi.

BACKGROUND

Antimicrobial resistance is a global health challenge with profound implications across sectors. Livestock, a significant field at the One Health interface, lacks sufficient information, particularly in low-resource settings such as Malawi.

OBJECTIVES

We determined the antimicrobial resistance rates of isolated from broiler chickens in Malawi and explored the relationship between resistance genes across sectors using genomic analysis.

METHODS

In 2023, we isolated 115 strains from 116 faecal and caecal samples from broiler chickens across Malawi. Antimicrobial susceptibility tests were performed using agar dilution method according to the Clinical Laboratory Standard Institute guidelines. Whole-genome sequencing was performed using Illumina sequencing.

RESULTS

Notably, 50 isolates (44%) were resistant to cefotaxime. We detected ESBL genes ( , , , , , , and ) in 48 cefotaxime-resistant isolates, which exhibited higher resistance rates to levofloxacin than non-ESBL-encoding isolates (29/48; 60% versus 20/67; 30%). All isolates were susceptible to colistin and carbapenems. High resistance rates were observed for tetracycline and co-trimoxazole commonly used in broiler chickens (90% and 70%, respectively). Sequence type 206 and phylogroup A were predominant (14% and 65%, respectively). In the genetic context of genes, whole-genome alignment of the ESBL-producing isolates with reference plasmids from of various origins indicated significant similarity.

CONCLUSIONS

Antimicrobial resistance is highly prevalent among from broiler chickens in Malawi. Genomic analysis suggests potential transmission pathways for ESBL genes across sectors, necessitating further studies from One Health perspective.