Novel β-Lactamase bla(ARL) in Staphylococcus arlettae

Whole-genome sequencing of penicillin-resistant Staphylococcus arlettae strain SAN1670 from bovine mastitis milk revealed a novel β-lactamase operon consisting of the β-lactamase-encoding gene bla(ARL), the antirepressor-encoding gene blaR1(ARL), and the repressor-encoding gene blaI(ARL). The functionality of bla(ARL) was demonstrated by gene expression in Staphylococcus aureus. The bla(ARL) operon was chromosomally located in SAN1670 and present in 10 additional unrelated strains, suggesting intrinsic penicillin resistance in S. arlettae. Furthermore, a GenBank search revealed more unique potential β-lactamases in Staphylococcus species. IMPORTANCE Penicillins are an important group of antibiotics used to treat various types of infections caused by Gram-positive bacteria. So far, the blaZ gene was the only known β-lactamase gene in staphylococci. However, other putative β-lactamases were identified, and one of them was shown to be a novel functional β-lactamase encoded by bla(ARL) in Staphylococcus arlettae, further limiting treatment options.