AUTHOR=Liu Kangjun , Tao Luyao , Li Jianji , Fang Li , Cui Luying , Li Jun , Meng Xia , Zhu Guoqiang , Bi Chongliang , Wang Heng 

TITLE=Characterization of Staphylococcus aureus Isolates From Cases of Clinical Bovine Mastitis on Large-Scale Chinese Dairy Farms

JOURNAL=Frontiers in Veterinary Science

VOLUME=7

YEAR=2020

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2020.580129

DOI=10.3389/fvets.2020.580129

ISSN=2297-1769

ABSTRACT=<p>Bovine mastitis is a prevalent disease that causes serious economic problems globally in the dairy industry. <italic>Staphylococcus aureus</italic> is an important pathogen of bovine mastitis. This study was conducted to characterize <italic>S. aureus</italic> isolates from clinical bovine mastitis cases in large-scale dairy herds in China. <italic>S. aureus</italic> was isolated from 624 clinical mastitis cases and confirmed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). In total, 62 <italic>S. aureus</italic> isolates were obtained. Cluster analysis, genetic diversity, quantification of biofilm formation, antimicrobial resistance, and detection of virulence genes were performed on these isolates of <italic>S. aureus</italic>. Eight isolates harbored the <italic>mecA</italic> gene and were sensitive to oxacillin. MALDI-TOF MS cluster analysis revealed that the 62 isolates were divided into three major clusters (I, II, III) and eight main groups (A–H) at the distance level of 700. The <italic>agr</italic> II was the most prevalent (56.5%). The 62 <italic>S. aureus</italic> isolates were assigned to seven <italic>spa</italic> types. The most common <italic>spa</italic> type was t529(58.1%), followed by t2196 (14.5%), t518 (14.5%), t571(6.5%), t034 (3.2%), t2734 (1.6%), and t730 (1.6%). Five STs were identified from seven representative isolates as follows: ST630/CC8, ST97/CC97, ST50, ST398, and ST705. All isolates had the ability to form biofilm. Antimicrobial resistance was most frequently observed to ciprofloxacin (29%), followed by penicillin (24.2%), and streptomycin (9.6%). All isolates harbored the <italic>fnbA, clfB</italic> (100%), <italic>icaA</italic>, and <italic>icaD</italic> genes. This study provides the basis for the development of bovine mastitis prevention program on large-scale dairy farms.</p>