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Published on: March 16, 2012
Complete sequence of pSAM7, an IncX4 plasmid carrying a novel blaCTX-M-14b transposition unit isolated from
1Department of Bacteriology, Animal Health and Veterinary Laboratories Agency (AHVLA), Addlestone, United Kingdom.
Abstract:
The same plasmid carrying blaCTX-M-14b was identified from an Escherichia coli isolate and an Enterobacter cloacae isolate collected from cattle in the United Kingdom by complete plasmid sequencing. This 35,341-bp plasmid, pSAM7, had an IncX4 backbone that is 99% identical to that of pJIE143 from a human isolate in Australia. PCR screening identified pSAM7-like plasmids in three other E. coli isolates of different multilocus sequence types isolated from cattle on different farms in the United Kingdom.
Insights
A plasmid carrying the blaCTX-M-14b gene was found in both E. coli and Enterobacter cloacae from UK cattle. This IncX4 plasmid, pSAM7, was also detected in other cattle E. coli isolates across different farms.
Area of Science:
- Veterinary Microbiology
- Antimicrobial Resistance
- Plasmid Biology
Background:
- The blaCTX-M-14b gene confers resistance to extended-spectrum cephalosporins, a critical concern in both human and animal health.
- Plasmid-mediated antimicrobial resistance is a significant driver of resistance spread in bacterial populations.
- Escherichia coli and Enterobacter cloacae are important opportunistic pathogens in livestock.
Purpose of the Study:
- To characterize the plasmid carrying blaCTX-M-14b identified in cattle isolates.
- To investigate the genetic relatedness and distribution of this plasmid in United Kingdom cattle populations.
Main Methods:
- Complete plasmid sequencing of pSAM7 from Escherichia coli and Enterobacter cloacae isolates.
- Comparative genomic analysis of pSAM7 against known plasmids.
- Polymerase Chain Reaction (PCR) screening to detect pSAM7-like plasmids in additional isolates.
Main Results:
- A 35,341-bp plasmid, designated pSAM7, carrying blaCTX-M-14b was identified in both E. coli and E. cloacae from cattle in the UK.
- pSAM7 possesses an IncX4 backbone, showing 99% identity to a plasmid found in a human isolate from Australia.
- pSAM7-like plasmids were detected in three additional, distinct E. coli isolates from cattle on different UK farms.
Conclusions:
- The IncX4 plasmid pSAM7 is circulating among cattle in the United Kingdom.
- The presence of this plasmid in both E. coli and E. cloacae highlights the potential for interspecies transmission of antimicrobial resistance genes in livestock.
- The findings underscore the importance of monitoring plasmid-borne resistance in animal populations to mitigate public health risks.
