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. 2022 May 6;17(5):e0268262.
doi: 10.1371/journal.pone.0268262. eCollection 2022.

Molecular typing and prevalence of antibiotic resistance and virulence genes in Streptococcus agalactiae isolated from Chinese dairy cows with clinical mastitis

Guangli Han  1   2 , Baohai Zhang  1   2 , Zidan Luo  1   2 , Biao Lu  1   2 , Zhengzhong Luo  1   2 , Jieru Zhang  1   2 , Yin Wang  1   2 , Yan Luo  1   2 , Zexiao Yang  1   2 , Liuhong Shen  1   2 , Shumin Yu  1   2 , Suizhong Cao  1   2 , Xueping Yao  1   2
Affiliations

Molecular typing and prevalence of antibiotic resistance and virulence genes in Streptococcus agalactiae isolated from Chinese dairy cows with clinical mastitis

Guangli Han et al. PLoS One. .

Abstract

Bovine mastitis is a common disease occurring in dairy farms and can be caused by more than 150 species of pathogenic bacteria. One of the most common causative organisms is Streptococcus agalactiae, which is also potentially harmful to humans and aquatic animals. At present, research on S. agalactiae in China is mostly concentrated in the northern region, with limited research in the southeastern and southwestern regions. In this study, a total of 313 clinical mastitis samples from large-scale dairy farms in five regions of Sichuan were collected for isolation of S. agalactiae. The epidemiological distribution of S. agalactiae was inferred by serotyping isolates with multiplex polymerase chain reaction. Susceptibility testing and drug resistance genes were detected to guide the clinical use of antibiotics. Virulence genes were also detected to deduce the pathogenicity of S. agalactiae in Sichuan Province. One hundred and five strains of S. agalactiae (33.6%) were isolated according to phenotypic features, biochemical characteristics, and 16S rRNA sequencing. Serotype multiplex polymerase chain reaction analysis showed that all isolates were of type Ia. The isolates were up to 100% sensitive to aminoglycosides (kanamycin, gentamicin, neomycin, and tobramycin), and the resistance rate to β-lactams (penicillin, amoxicillin, ceftazidime, and piperacillin) was up to 98.1%. The TEM gene (β-lactam-resistant) was detected in all isolates, which was in accordance with a drug-resistant phenotype. Analysis of virulence genes showed that all isolates harbored the cfb, cylE, fbsA, fbsB, hylB, and α-enolase genes and none harbored bac or lmb. These data could aid in the prevention and control of mastitis and improve our understanding of epidemiological trends in dairy cows infected with S. agalactiae in Sichuan Province.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Geographical location of sampling.
A, map of China, the colored plate represents Sichuan Province; B, map of Sichuan Province, red star represents Hongya farm, orange star represents Yangba farm, green star represents Yushu farm, blue star represents Qingbaijiang farm, purple star represents Songya farm, and black star represents Ninggang farm, percentages identical to the symbol color indicate the sample collection rate in that dairy farm. All original maps were download from d-maps.com.
Fig 2
Fig 2. Antibiotic susceptibility profiles of 105 isolates.
The first five drugs on the x-axis are aminoglycosides and the last five are β-lactams.
See this image and copyright information in PMC

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