# The Prevalence Rates of Colistin Resistance Among Third-Generation Cephalosporin-Resistant E. coli Isolates From Thai Patients

## TL;DR

This study found a low but notable rate of colistin resistance among E. coli isolates from Thai patients, with specific resistance genes identified.

## Contribution

The study reports the prevalence of colistin resistance and identifies specific mcr genes in E. coli isolates from Thailand.

## Key findings

- 1.45% of third-generation cephalosporin-resistant E. coli isolates showed colistin resistance.
- Five isolates carried mcr-1 or mcr-3 resistance genes, with one carrying both.
- The findings highlight the importance of monitoring resistance genes in public health.

## Abstract

Drug-resistant infections, such as colistin resistance, are reportedly increasing due to the inappropriate use of antibiotics, lack of good control, and the use of excessive quantities of antibiotics. Colistin resistance has been observed in bacteria of the order Enterobacterales exhibiting resistance to third-generation cephalosporins or carbapenems. Currently, the prevalence of colistin resistance in third-generation cephalosporin-resistant E. coli obtained from patients at Nopparat Rajathanee Hospital, Thailand, in 2023 was determined by broth microdilution. Among 343 isolates, 1.45% (95% CI: 0.19%–2.73%, n = 5/343) exhibited a minimum inhibitory concentration (MIC) of colistin between 4 and 8 μg/mL, indicating colistin-resistant E. coli. Nevertheless, five isolates were positive for resistant genes by multiplex PCR: two isolates for mcr-1, two isolates for mcr-3, and one isolate for both mcr-1 and mcr-3. This study reveals crucial data on resistance genes, informing surveillance of antibiotic resistance, treatment decisions, and public health initiatives to combat resistant bacteria.