Prospective evaluation of an easy and reliable work flow for the screening of OXA-48-producing Klebsiella pneumoniae in endemic settings

Background: Carbapenemase-producing Enterobacterales (CPE) represent a serious threat to public health. Clinical microbiology laboratories (CMLs) need effective protocols for screening and confirmation of CPE.

Aim: To prospectively evaluate an algorithm for the screening of carbapenemase-producing Klebsiella pneumoniae in an OXA-48 endemic hospital.

Methods: The algorithm was based on a disc diffusion assay using ertapenem and temocillin, which also served as a purity check for routine automated antimicrobial susceptibility testing. All isolates with minimal inhibitory concentrations >0.5 mg/L or zone inhibition diameters <25 mm for ertapenem (Criterion 1) and <12 mm for temocillin (Criterion 2) were tested sequentially by an OXA-48 lateral flow immunochromatographic assay and a multiplex polymerase chain reaction targeting VIM, KPC and OXA-48. If neither test was positive, the modified Hodge test or CARBA NP test was used.

Findings: Over 2 years, 2487 K. pneumoniae were assessed by the algorithm proposed, and 378 (15.20%) met both criteria. Of these, 98.68% (373/378) were either confirmed as OXA-48 producers or originated from patients with a previous CPE isolate that maintained the same resistance phenotype over time. The remaining three K. pneumoniae were VIM producers. Only two of the 378 isolates (0.53%) did not produce carbapenemase, despite meeting Criteria 1 and 2.

Conclusion: The algorithm described combined the most sensitive carbapenem for CPE detection with a cut-off for temocillin that was highly specific for detection of OXA-48. It is reliable and easy to apply in routine CML work flow, allowing rapid detection of CPE isolates and hence prompt implementation of infection control measures and targeted antimicrobial regimens.