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. 2024 Jan 24:10:1328552.
doi: 10.3389/fvets.2023.1328552. eCollection 2023.

Prevalence and antimicrobial resistance of Enterococcus spp. isolated from animal feed in Japan

Yohei Yamagami  1 , Miyuki Asao  1 , Akiko Takahashi  1 , Yoshiyasu Hashimoto  1 , Noriko Okuyama  1 , Eiko Arai  1 , Wakana Arihara  1 , Ryota Masui  1 , Yoko Shimazaki  1
Affiliations

Prevalence and antimicrobial resistance of Enterococcus spp. isolated from animal feed in Japan

Yohei Yamagami et al. Front Vet Sci. .

Abstract

The rising prevalence of antimicrobial resistance (AMR) of bacteria is a global health problem at the human, animal, and environmental interfaces, which necessitates the "One Health" approach. AMR of bacteria in animal feed are a potential cause of the prevalence in livestock; however, the role remains unclear. To date, there is limited research on AMR of bacteria in animal feed in Japan. In this study, a total of 57 complete feed samples and 275 feed ingredient samples were collected between 2018 and 2020. Enterococcus spp. were present in 82.5% of complete feed (47/57 samples), 76.5% of soybean meal (62/81), 49.6% of fish meal (55/111), 33.3% of poultry meal (22/66), and 47.1% of meat and bone meal (8/17) samples. Of 295 isolates, E. faecium (33.2% of total isolates) was the dominant Enterococcus spp., followed by E. faecalis (14.2%), E. hirae (6.4%), E. durans (2.7%), E. casseliflavus (2.4%), and E. gallinarum (1.0%). Of 134 isolates which were tested for antimicrobial susceptibility, resistance to kanamycin was the highest (26.1%), followed by erythromycin (24.6%), tetracycline (6.0%), lincomycin (2.2%), tylosin (1.5%), gentamicin (0.8%), and ciprofloxacin (0.8%). All Enterococcus spp. exhibited susceptibility to ampicillin, vancomycin, and chloramphenicol. Of 33 erythromycin-resistant isolates, only two showed a high minimum inhibitory concentration value (>128 μg/mL) and possessed ermB. These results revealed that overall resistance to antimicrobials is relatively low; however, animal feed is a source of Enterococcus spp. It is essential to elucidate the causative factors related to the prevalence of AMR in animal feed.

Keywords: Enterococcus; animal feed; antimicrobial resistance; prevalence; resistance gene.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Map of Japan showing sampling locations of feed mill. All 47 prefectures of Japan were divided into eight regions (Hokkaido, Tohoku, Kanto, Chubu, Kinki, Chugoku, Shikoku, and Kyushu), and 180 feed mills from 36 prefectures were selected. Color indicated the prefectures sampling animal feed. P-values were determined using Fisher’s exact test. No significant differences were found in the prevalence of Enterococcus spp. in animal feed among the regions (p > 0.05). n, number of samples; %, prevalence of Enterococcus spp.
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