Decreasing the abundance of tetracycline-resistant Escherichia coli in pig feces during nursery using flavophospholipol as a pig feed additive

Junichiro Kimura; Hayami Kudo; Akira Fukuda; Michi Yamada; Kohei Makita; Kentaro Oka; Motomichi Takahashi; Yutaka Tamura; Masaru Usui

doi:10.1016/j.vas.2022.100236

Decreasing the abundance of tetracycline-resistant Escherichia coli in pig feces during nursery using flavophospholipol as a pig feed additive

Vet Anim Sci. 2022 Jan 29:15:100236. doi: 10.1016/j.vas.2022.100236. eCollection 2022 Mar.

Authors

Junichiro Kimura¹, Hayami Kudo², Akira Fukuda¹, Michi Yamada³, Kohei Makita⁴, Kentaro Oka², Motomichi Takahashi², Yutaka Tamura¹, Masaru Usui¹

Affiliations

¹ Laboratory of Food Microbiology and Food Safety, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido, Japan.
² Tokyo R&D Center, Miyarisan Pharmaceutical Co., Ltd., Saitama-shi, Saitama, Japan.
³ Department of Sustainable Agriculture, Rakuno Gakuen University, Ebetsu, Hokkaido, Japan.
⁴ Laboratory of Veterinary Epidemiology, Department of Health and Environmental Sciences, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido, Japan.

Abstract

Tetracyclines (TCs) are widely used for livestock, and the high prevalence of TC-resistant Escherichia coli in livestock has become a serious concern worldwide. In Japan, the National Action Plan on Antimicrobial Resistance in 2016 aimed to reduce the TC resistance rate in E. coli derived from livestock. Flavophospholipol (FPL), used as a feed additive, has an inhibitory effect on the spread of plasmid-mediated antimicrobial resistance. The number of TC-resistant E. coli was determined in pigs administered TCs and/or FPL to clarify the effect of FPL on reducing the number of TC-resistant E. coli in pigs. TC-resistant E. coli and their plasmids were then analyzed. The pigs were divided into four groups: control, doxycycline (DOXY; a TC), FPL, and a DOXY-FPL combination. Their feces were collected from the nursing period to the day before being transported to the slaughterhouse, followed by estimation of TC-resistant E. coli (colony-forming units [CFU]/g). The number of TC-resistant E. coli increased with the use of DOXY, suggesting that DOXY administration provides a selective pressure for TC-resistant E. coli. Supplementation with FPL as a feed additive significantly suppressed the increase in the number of TC-resistant E. coli, especially during the DOXY administration period. Transfer and growth inhibition analyses were performed for TC-resistant isolates. FPL inhibited the conjugational transfer and growth of a few TC-resistant E. coli isolates. These results suggest that FPL is effective against the spread of TC-resistant E. coli.

Keywords: Conjugational transfer; Escherichia coli; Flavophospholipol; Pig; Tetracycline resistance.