Isolation of nuc mutant isolates of Staphylococcus aureus from bovine clinical mastitis.

Isolates of Staphylococcus aureus with a mutation in the nuclease (nuc) gene were recovered from cases of bovine mastitis in Poland. Three S. aureus isolates from cows in one herd had a 42 base pair duplication in the nuc gene. These isolates belonged to sequence type 97 (ST97) and clonal complex 97 (CC97). They had a different spa type and multiple-locus variable-number tandem-repeat fingerprinting (MLVF) subtype than a S. aureus isolate without the nuc mutation from the same herd. Isolation of nuc mutant S. aureus strains from cases of bovine mastitis may confound diagnostic PCRs based on detection of the nuc gene.