AUTHOR=Locatelli Clara , Gattolin Stefano , Monistero Valentina , Castiglioni Bianca , Moroni Paolo , Addis Maria Filippa , Cremonesi Paola 

TITLE=Staphylococcus aureus coa gene sequence analysis can prevent misidentification of coagulase-negative strains and contribute to their control in dairy cow herds

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1120305

DOI=10.3389/fmicb.2023.1120305

ISSN=1664-302X

ABSTRACT=<p>Accurate and precise differentiation of staphylococci isolated from milk is of importance for udder health management. In particular, the rapid and specific identification of <italic>Staphylococcus aureus</italic> plays an essential role in the prevention and treatment programs for bovine mastitis. Plasma gelatinization in coagulase assays is routinely used to discriminate <italic>S. aureus</italic> from other species by detecting the presence of extracellular free staphylocoagulase. However, rarely occurring coagulase-deficient <italic>S. aureus</italic> strains can be responsible for clinical and subclinical mastitis cases. By investigating <italic>S. aureus</italic> isolates from a single herd over a 10-year period we identified the persistence of a phenotypically coagulase-negative <italic>S. aureus</italic> strain and pinpointed the possible cause to a single base pair deletion in the <italic>coa</italic> gene sequence. Our results support the need to integrate primary biochemical tests with molecular/sequence analysis approaches for correctly identifying and discriminating atypical <italic>S. aureus</italic> in bovine herds, as the coagulase test alone may fail to detect persistent mastitis-causing strains.</p>