AUTHOR=Zhang Dexian , Lu Ximing , Feng Xiangyan , Shang Xuzeng , Liu Qingyou , Zhang Nan , Yang Hong 

TITLE=Molecular characteristics of Staphylococcus aureus strains isolated from subclinical mastitis of water buffaloes in Guangdong Province, China

JOURNAL=Frontiers in Veterinary Science

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2023.1177302

DOI=10.3389/fvets.2023.1177302

ISSN=2297-1769

ABSTRACT=<p>Intramammary infections (IMI) in animals reared for milk production can result in large economic losses and distress to the animals. <italic>Staphylococcus aureus</italic> is an important causative agent of IMI in dairy cows, but its prevalence in water buffaloes has not been determined. Therefore, the current study was conducted to investigate the prevalence of subclinical mastitis in water buffaloes and the antimicrobial susceptibility, virulence genes and biofilm formation abilities of <italic>Staphylococcus aureus</italic> isolates recovered from water buffaloes in Guangdong, China. <italic>Staphylococcus aureus</italic> strains were isolated from milk samples of water buffaloes with subclinical mastitis, and twofold microdilution, PCR and crystal violet staining methods were used to determine antimicrobial susceptibility, distributions of virulence and antimicrobial resistance genes and biofilm formation ability, respectively. Our results indicated that 29.44% of water buffaloes were diagnosed with subclinical mastitis, and the most prevalent pathogens were <italic>Escherichia coli</italic> (96.17%), coagulase-negative staphylococci (CoNS) (67.60%) and <italic>S. aureus</italic> (28.57%). Most <italic>S. aureus</italic> isolates showed resistance to bacitracin, doxycycline, penicillin, florfenicol, and tetracycline but were susceptible to ciprofloxacin, ceftizoxime, cefoquinoxime, and ofloxacin. Moreover, 63.72% of <italic>S. aureus</italic> isolates were positive for <italic>tetM,</italic> and the prevalence of <italic>msrB</italic>, <italic>blaZ</italic>, <italic>mecA</italic>, <italic>fexA</italic>, and <italic>tetK</italic> ranged from 21.24 to 6.19%. All <italic>S. aureus</italic> isolates harbored <italic>clfB</italic> and <italic>icaA</italic> genes, and the virulence genes <italic>hla</italic> (93.8%), <italic>hld</italic> (91.15%), <italic>clfA</italic> (90.27%), <italic>fnbA</italic> (86.73%), and <italic>hlb</italic> (83.19%), and <italic>tsst</italic>, <italic>icaD</italic>, <italic>sec</italic>, <italic>see</italic>, <italic>fnbB</italic>, and <italic>sea</italic> showed a varied prevalence ranging from 3.5 to 65.49%. All <italic>S. aureus</italic> isolates possessed the ability to form biofilms, and 30.09% of isolates showed strong biofilm formation abilities, while 19.47% of isolates were weak biofilm producers. Our results indicated that subclinical mastitis is prevalent in water buffaloes in Guangdong, China, and <italic>S. aureus</italic> is prevalent in samples from water buffaloes with subclinical mastitis. Most <italic>S. aureus</italic> isolates were susceptible to cephalosporins and fluoroquinolones; thus, ceftizoxime and cefoquinoxime can be used to treat subclinical mastitis in water buffaloes.</p>