Retrospective identification of a previously undetected clinical case of OXA-48-producing K. pneumoniae and E. coli: the importance of adequate detection guidelines.

Introduction: The laboratory detection of OXA-48-carbapenemase-producing Enterobacteriaceae is difficult, as minimum inhibition concentrations for carbapenems are often below the clinical breakpoint. In 2011, the Dutch national guideline for the detection of highly resistant micro-organisms was issued, which includes recommendations on the use of carbapenem screening breakpoints for the detection of carbapenemase-producing Enterobacteriaceae.

Materials And Methods: During a validation study of the Check-MDR CT103 microarray (Check-Points, Wageningen, The Netherlands) in 2013, an OXA-48-like carbapenemase gen was identified in two isolates that were previously obtained from a patient with non-Hodgkin lymphoma in 2007. Whole-genome sequencing (WGS) and subsequent BLAST Ringe Image Generator (BRIG) analysis were performed to establish the presence of OXA-48 carbapenemase encoding plasmids and their similarity.

Results: This case report describes the first documented OXA-48-producing Klebsiella pneumonia (ST648) and Escherichia coli (ST866) in the Netherlands. A similar IncL/M plasmid was identified in both strains, suggesting within-patient horizontal transfer.

Conclusion: This case illustrates that OXA-48-carbapenemase-producing Enterobacteriaceae can be unnoticed without adequate laboratory detection procedures. Our observation stresses the importance of uniform and adequate laboratory methods for the timely and accurate detection of important antimicrobial resistance.