Molecular characterisation and antimicrobial resistance of Streptococcus agalactiae isolates from dairy farms in China

Xiaojiao Ma; He Chen; Fulan Wang; Shuai Wang; Yating Wu; Xianlan Ma; Yong Wei; Wei Shao; Yankun Zhao

doi:10.2478/jvetres-2023-0027

Molecular characterisation and antimicrobial resistance of Streptococcus agalactiae isolates from dairy farms in China

J Vet Res. 2023 Jun 16;67(2):161-167. doi: 10.2478/jvetres-2023-0027. eCollection 2023 Jun.

Authors

Xiaojiao Ma^#^{1

2

3

4}, He Chen^#^{2

3

4}, Fulan Wang^{2

3

4}, Shuai Wang^{2

3

4}, Yating Wu^{2

3

4}, Xianlan Ma^{2

3

4}, Yong Wei⁵, Wei Shao¹, Yankun Zhao^{2

3

4}

Affiliations

¹ College of Animal Science Xinjiang Agriculture University, Urumqi 830052, P. R. China.
² Institute of Quality Standards & Testing Technology for Agro-Products, Xinjiang Academy of Agricultural Sciences, Urumqi 830091, P. R. China.
³ Ministry of Agriculture and Rural Affairs-Laboratory of Quality and Safety Risk Assessment for Agro-Products, Urumqi 830091, P. R. China.
⁴ Key Laboratory of Agro-Products Quality and Safety of Xinjiang, Urumqi 830091, P. R. China.
⁵ Xinjiang Tian'ao Animal Husbandry Co., Ltd, Ili 835000, P. R. China.

^# Contributed equally.

Abstract

Introduction: Streptococcus agalactiae (S. agalactiae) is a pathogen causing bovine mastitis that results in considerable economic losses in the livestock sector. To understand the distribution and drug resistance characteristics of S. agalactiae from dairy cow mastitis cases in China, multilocus sequence typing (MLST) was carried out and the serotypes and drug resistance characteristics of the bacteria in the region were analysed.

Material and methods: A total of 21 strains of bovine S. agalactiae were characterised based on MLST, molecular serotyping, antimicrobial susceptibility testing, and the presence of drug resistance genes.

Results: The serotypes were mainly Ia and II, accounting for 47.6% and 42.9% of all serotypes, respectively. Five sequence types (STs) were identified through MLST. The ST103 and ST1878 strains were predominant, with rates of 52.4% and 28.6%, respectively. The latter is a novel, previously uncharacterised sequence type. More than 90% of S. agalactiae strains were susceptible to penicillin, oxacillin, cephalothin, ceftiofur, gentamicin, florfenicol and sulfamethoxazole. The bacteria showed high resistance to tetracycline (85.7%), clindamycin (52.1%) and erythromycin (47.6%). Resistant genes were detected by PCR, the result of which showed that 47.6%, 33.3% and 38.1% of isolates carried the tet(M), tet(O) and erm(B) genes, respectively.

Conclusion: The results of this study indicate that S. agalactiae show a high level of antimicrobial resistance. It is necessary to monitor the pathogens of mastitis to prevent the transmission of these bacteria.

Keywords: Streptococcus agalactiae; antimicrobial resistance; drug resistance gene; molecular characterisation; serotype.

Grants and funding

This research was supported by the National Natural Science Foundation of China (32060797), China Post-doctoral project (282739), Tianshan Innovation Team (2022D14016), Xinjiang Science and Technology Assistance Project (2022E02012), Major Science and Technology Projects of the Xinjiang Uygur Autonomous Region (2022A020006), and Integration and Application of Key Technologies for Safe Production of High Quality Raw Milk (SR2020001).