Oxa

OXA refers to a family of beta-lactamase enzymes known as oxacillinases, which hydrolyze beta-lactam antibiotics. They belong to class D beta-lactamases in the Ambler classification and are serine enzymes found in various Gram-negative bacteria, most notably Acinetobacter species and members of Enterobacterales. The name derives from their ability to hydrolyze oxacillin and cloxacillin. OXA enzymes are highly diverse, with many variants organized into groups such as OXA-1-like, OXA-2-like, and OXA-48-like, among others. Some enzymes in the family are narrow-spectrum penicillinases, while others contribute to carbapenem resistance.

In Acinetobacter, carbapenem resistance is often mediated by OXA-23-like, OXA-24/40-like, and OXA-58-like enzymes. In Enterobacterales, OXA-48-like carbapenemases are a prominent cause of carbapenem resistance and can complicate detection because their activity against cephalosporins may be limited. The OXA family generally shows limited inhibition by traditional beta-lactamase inhibitors, which complicates treatment and necessitates reliance on susceptibility testing to guide therapy.

Detection and monitoring rely on a combination of phenotypic tests and molecular methods to identify OXA-encoding genes. Clinically, the emergence and spread of OXA-producing organisms pose challenges for infection control and antimicrobial stewardship, given their diverse substrate profiles and variable geographic distribution.

Treatment options depend on the specific OXA variant and the organism, with management guided by susceptibility results and, when appropriate, the use of non-beta-lactam agents or newer therapies with activity against OXA enzymes.