Association between the use of colistin for short-term treatment of gram-negative bacterial infections and the emergence of colistin-resistant enterobacteriaceae in swine from selected swine farms in thailand

Abstract

Copyright: © 2020 Poolperm et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Long-term use of colistin for preventing Gram-negative bacterial infections in food animals was prohibited in Thailand in 2017, but it is permitted for short-term treatment. This study aimed to investigate association between the use of colistin for short-term treatment of infection and the emergence of colistin-resistant Enterobacteriaceae in swine. The current study was conducted at 2 selected swine farms in Thailand. Neither farm has used colistin to prevent infection for longer than 1 year. Rectal swabs were collected from the same 66 pigs at birth, and on days 7, 14, 21, 28, and 60. Colistin was used to treat sick pigs for up to 3 days. Additional rectal swabs were collected during colistin treatment. Rectal swabs were analyzed for colistin-resistant Enterobacteriaceae and the mcr-1 gene. Results revealed that colistin-resistant Enterobacteriaceae were absent at birth. Some pigs at both farms had diarrhea and received colistin treatment during days 2–27. Colistin-resistant Enterobacteriaceae were detected in 13.3–50.0% of sick and healthy pigs. No sick pigs were observed during days 28–60, and colistin was not used during that period. Colistin-resistant Enterobacteriaceae were detected in 2.8–10.0% of healthy pigs on day 28, and in 0–3.4% of healthy pigs on day 60. The mcr-1 gene was detected in 57.6% of colistin-resistant Enterobacteriaceae isolates. Short-term treatment with colistin was found to be associated with the emergence of colistin-resistant Enterobacteriaceae in swine. Colistin-resistant Enterobacteriaceae rapidly emerged after colistin use, and rapidly decreased or disappeared after its discontinuation.