Class D beta-lactamase (OXA) — Oxacillinase production

Mechanism

Serine beta-lactamases that hydrolyze oxacillin; some variants (such as OXA-48-like and OXA-23) hydrolyze carbapenems.

What it removes from the grid

Penicillins; carbapenems are downgraded for organisms where carbapenem-hydrolyzing OXA enzymes occur.

What it spares

Depends on the variant; avibactam inhibits OXA-48-like enzymes.

A multiplex panel can't say which organism in a mixed specimen carries a detected gene. CORE-ABR applies Class D beta-lactamase (OXA) only to organisms known to carry it, and only to the agents its mechanism defeats — so a detected gene moves the right cells and spares the rest.

Organisms it is applied to

Acinetobacter baumanniiA non-fermenting gram-negative bacillus, notorious in healthcare settings for accumulating resistance.Gram-negative bacteria · UTI · Wound · STI Klebsiella pneumoniae / oxytocaCommon uropathogens and a leading host of ESBL and KPC carbapenemase genes.Gram-negative bacteria · UTI · Wound · STI Escherichia coliThe most common cause of urinary tract infection, and a frequent organism in wound and intra-abdominal specimens.Gram-negative bacteria · UTI · Wound Pseudomonas aeruginosaA non-fermenting gram-negative bacillus common in chronic wounds and complicated UTI, with a long list of intrinsic resi…Gram-negative bacteria · UTI · Wound · STI

Coding

Z16.19 (resistance to other specified beta lactam antibiotics), as documentation supports. CORE-ABR adds resistance findings as supporting codes, not primary, and prints the rationale on the report.

Tagged

Decision support only. The treating clinician decides. Molecular genotype does not replace phenotypic susceptibility testing, culture, or public-health reporting. Absence of a detected resistance gene does not establish susceptibility. Organism targets vary by panel; CORE-ABR is configured to the assay each laboratory runs.