Integrated poultry production as a reservoir of tet(X4) and mcr-1.1 encoding Escherichia coli in Pakistan.

Authors

Muhammad Ahmed Mushtaq, Peter Schierack, Muhammad Yousaf, Fariha Fatima, Tayyaba Qamar, Mashkoor Mohsin, Muhammad Moman Khan

Published in

Microbial genomics. Volume 12. Issue 8.

Abstract

Plasmid-mediated colistin and tigecycline resistance threatens last-resort therapeutic options. We investigated the farm-to-fork dissemination of Escherichia coli encoding mcr-1.1 and tet(X4) in a vertically integrated broiler production system. A total of 200 samples were collected in 2024, representing four sequential production stages: broiler breeders, day-old chicks, day-30 broilers and retail meat. All positive [mcr-1.1 and/or tet(X4)] isolates underwent Illumina short-read sequencing, with long-read sequencing of three representatives. The study was enriched and analysed with mcr-1.1 and tet(X4) encoding 213 publicly available E. coli genomes from Pakistan. Of 18 isolates, tet(X4) was detected in 11 and mcr-1.1 in 7 isolates with a single breeder isolate (ST-398) co-harbouring both on separate plasmids. tet(X4) predominated breeders and day-30 broilers, whereas mcr-1.1 was distributed across all four stages. ST-1011 exhibited a pattern of clonal farm-to-fork transmission of tet(X4) via IncFIB(AP001918)-IncFII providing molecular evidence suggestive of clonal transmission. Analysis of 231 genomes across 87 sequence types (STs) revealed contrasting evolutionary trajectories: mcr-1.1 with post-mobilization stabilization marked by complete absence of ISApl1 and highly conserved IncI2 plasmid (93%), whereas tet(X4) retained active transposition within IS26-bounded elements. tet(X4) carriage was also associated with elevated resistance gene burden, driven by the IncF megaplasmids. All 18 isolates exhibited adhesion to chicken intestinal epithelial cells (CHIC-8E11), with high adhesion capacity among tet(X4)-positive isolates. This study demonstrates that mcr-1.1 and tet(X4) disseminate through poultry production via distinct mechanisms. These findings highlight the need for integrated One Health surveillance of antimicrobial resistance dissemination.

PMID:
42545337
Bibliographic data and abstract were imported from PubMed on 03 Aug 2026.

Read full publication at:
Please sign in to see all details.

Stats

1-terrible, 9-excellent. How would you rate this publication? Sign in in to submit your rating.

Post a comment

You need to be signed in to post comments. You can sign in here.

Comments

There are no comments yet.