The surveillance and control of resistance to betalactam among Gram-negative bacteria remains a big concern for microbiologists worldwide. Descriptions of bacterial infections associated with the oxacillinase OXA-48 are increasing, revealing a huge impact on antimicrobial treatment and patient morbidity.
For clinical laboratories, OXA-48 and its variants represent the most challenging resistance mechanism to detect infections that are often under-detected by routine diagnostic methods. OXA-48 exhibits a weak hydrolytic activity on carbapenem and broad-spectrum cephalosporin, and is not inhibited by clavulanate or tazobactam.
Today, multiple allelic variants of OXA-48 have been described, with diverse hydrolytic profiles. As an example, the single amino acid substitution and four amino acid deletion described in OXA-163 confer an increased hydrolytic activity against cephalosporins, coupled to a loss of resistance to carbapenems and an inhibition by clavulanate and tazobactam.
This particular hydrolytic profile confuses its correct detection at the laboratory level and control at the clinical level. Treatment failures can impede patient recovery and favour the selection of new resistant strains.
For a long time, efficient identification of OXA-163-expressing strains relied on gene sequencing, which is not practical for a clinical laboratory's daily routine. The recently available immunochromatographic lateral flow test developed by Coris BioConcept to specifically differentiate OXA-163 from OXA-48 proteins replaces costly and lengthy genotypic methods.
This phenotypic test is an easy-to-use and instrumentfree test that provides a fast (15 minute) and accurate (100%) identification of variants. Today, precise detection of other carbapenemases will be included in the test to reach a fiveparameters assay. This up-coming RESIST-5 OOKNV test, commercialised by the same company, is the ideal tool to precisely identify the most prevalent carbapenemase-mediated resistance mechanisms on a single phenotypical assay. Its use on a daily routine in healthcare facilities will enable a broader surveillance of worldwide-disseminating new carbapenemase variants and help clinicians in the daily care of patients.