OXA48

OXA-48 is a class D beta-lactamase that acts as a carbapenemase in Enterobacterales. The blaOXA-48 gene is usually carried on transferable plasmids, facilitating spread among bacteria. OXA-48 was first described in 2004 in Klebsiella pneumoniae isolates from Turkey and has since been reported worldwide in hospital and community-associated strains. The OXA-48 family includes several variants (such as OXA-181, OXA-232, and OXA-244) that share core enzymatic activity but differ in genetic context and epidemiology.

Enzymatic activity and resistance patterns: OXA-48-like enzymes hydrolyze penicillins and show relatively weak activity against carbapenems, which can result in carbapenem MICs that are only modestly elevated or even within susceptible ranges in routine testing. This can complicate detection of carbapenemase production. They typically have limited activity against most expanded-spectrum cephalosporins, though activity varies by variant. Because the gene is plasmid-borne, co-resistance with other beta-lactamases and resistance determinants is common, contributing to multidrug-resistant phenotypes.

Detection and epidemiology: OXA-48-like carbapenemases are often identified through molecular methods that detect blaOXA-48 or related variant genes. Phenotypic screening can be aided by temocillin susceptibility testing, as many OXA-48 producers retain susceptibility to temocillin. The enzymes have disseminated across continents, with outbreaks reported in healthcare settings and continuing regional spread.

Clinical implications and treatment: Infections caused by OXA-48 producers limit therapeutic options and require tailored susceptibility-guided therapy. Treatment may involve combinations or non-beta-lactam agents such as aminoglycosides, tigecycline, polymyxins, or newer regimens including ceftazidime-avibactam, which is active against many OXA-48 producers, and aztreonam-avibactam for difficult cases. Infection control and surveillance are essential to curb transmission.