Diagnostic challenges in detecting the OXA-244 enzyme

ABSTRACT Background OXA-244 is a β-lactamase capable of hydrolyzing carbapenems and belongs to the OXA-48-like family. Detection of OXA-48-like–producing Enterobacterales, including OXA-244, remains challenging in clinical microbiology laboratories, as isolates may demonstrate susceptibility to carbapenems despite producing a carbapenemase enzyme. Here, we describe a pediatric case of OXA-244–producing Escherichia coli and highlight the challenges and some practical considerations to improve the recognition and confirmation of OXA-48-like–producing Enterobacterales in clinical laboratories. Case Summary A 3-year-old boy with penoscrotal hypospadias and prior urologic surgery in Saudi Arabia presented in Canada with 5 days of dysuria and abdominal discomfort. Urinary tract infection was diagnosed based on the symptoms and growth of E. coli in the urine culture. Initial automated susceptibility testing showed susceptibility to meropenem (MIC, 0.25 mg/L) but intermediate susceptibility to ertapenem (MIC, 1 mg/L), with a positive NG-Test CARBA-5 (NG Biotech, France) for OXA-48-like enzymes. Disk diffusion demonstrated carbapenem susceptibility. Reference laboratory testing confirmed carbapenemase production using a modified carbapenem inactivation method and detected an OXA-48-like carbapenemase gene by real-time PCR. Whole-genome sequencing identified bla OXA-244 , and the isolate was assigned E. coli sequence type 69. The patient was initially treated with cephalexin and switched to oral ciprofloxacin once susceptibility results became available. He completed 7 days of therapy with full symptom resolution and no documented recurrence. Conclusion Detection of OXA-244 and other OXA-48-like carbapenemases is challenging because isolates may retain carbapenem-susceptible phenotypes. Enhanced screening algorithms, coupled with phenotypic confirmation and molecular testing, are warranted to improve clinical laboratory detection.