Novel β-Lactamase blaARL in Staphylococcus arlettae

Abstract

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.

Keywords: antibiotic resistance; beta-lactamases; coagulase-negative staphylococci; penicillinase.

FIG 1

Phylogenetic tree of β-lactamases encoded by staphylococci. Evolutionary analysis was performed for amino acid sequences by the unweighted pair group method using average linkages in MEGA7. Evolutionary distances were computed by the Poisson correction method and were measured as the number of amino acid substitutions per site. The percentages of amino acid and nucleotide sequence identity between bla_ARL and other β-lactamases were determined by sequence alignment with Clustal Omega (http://www.ebi.ac.uk/Tools/msa/clustalo/). Roman numerals indicate β-lactamase groups as follows: I, blaZ; II, bla_ARL; III, β-lactamases of the class E mec gene complex; IV, group of diverse uncharacterized β-lactamases.