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.