AUTHOR=Yang Feng , Shi Wenli , Meng Na , Zhao Yiyu , Ding Xuezhi , Li Qinfan 

TITLE=Antimicrobial resistance and virulence profiles of staphylococci isolated from clinical bovine mastitis

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1190790

DOI=10.3389/fmicb.2023.1190790

ISSN=1664-302X

ABSTRACT=<p>Staphylococci, mainly including <italic>Staphylococcus aureus</italic> and coagulase-negative staphylococci (CNS), are one of the most common pathogens causing bovine mastitis worldwide. In this study, we investigated the antimicrobial resistance and virulence profiles of staphylococci from clinical bovine mastitis in Ningxia Hui Autonomous Region of China. Antimicrobial resistance was determined by disc diffusion combined with <italic>E</italic>-test method. Genes of antimicrobial resistance and virulence factors were determined by PCR. A total of 332 staphylococcal isolates were confirmed from 1,519 mastitic milk samples, including 172 <italic>S. aureus</italic> and 160 CNS isolates. Fifteen CNS species were identified, with <italic>S. chromogenes</italic> being the most frequent found (49.4%), followed by <italic>S. equorum</italic> (13.8%). Noticeably, 2 <italic>S. agnetis</italic> isolates were found among the CNS isolates. To our knowledge, this is the first report documenting the presence of <italic>S. agnetis</italic> from bovine mastitis in China. The <italic>S. aureus</italic> and CNS isolates showed high resistance against penicillin, followed by erythromycin and tetracycline. Multidrug resistance was found in 11.6 and 16.3% of the <italic>S. aureus</italic> and CNS isolates, respectively. Resistance to penicillin was attributed to the presence of <italic>bla</italic>Z, erythromycin resistance to <italic>ermC</italic> (alone or combined with <italic>ermB</italic>) and tetracycline resistance to <italic>tet</italic>K (alone or combined with <italic>tetM</italic>). Notably, one <italic>S. equorum</italic> isolate and one <italic>S. saprophyticus</italic> isolate were both methicillin-resistant and <italic>mecA</italic> positive. Additionally, all <italic>S. aureus</italic> isolates carried the adhesin genes <italic>fnbpA</italic>, <italic>clfA</italic>, <italic>clfB</italic>, and <italic>sdrC</italic>, and most of them contained <italic>cna</italic> and <italic>sdrE</italic>. Conversely, only a few of the CNS isolates carried <italic>clf</italic>A, <italic>cna</italic>, and <italic>fnb</italic>A. Regarding toxin genes, all <italic>S. aureus</italic> isolates harbored <italic>hlb</italic>, and most of them were <italic>hlg</italic> positive. The <italic>lukE</italic>-<italic>lukD</italic>, <italic>lukM</italic>, <italic>sec</italic>, <italic>sed</italic>, <italic>sei</italic>, <italic>sen</italic>, <italic>seo</italic>, <italic>tst</italic>, <italic>seg</italic>, <italic>seh</italic>, and <italic>sej</italic> were also detected with low frequencies. However, no toxin genes were observed in CNS isolates. This study reveals high species diversity of staphylococci from clinical bovine mastitis in Ningxia Hui Autonomous Region of China. The findings for the genetic determinants of antimicrobial resistance and virulence factor provide valuable information for control and prevention of staphylococcal bovine mastitis.</p>