Detection of Carbapenem-resistance in CRE by Comparative Assessment of RAPIDEC^® CARBA NP and Xpert™Carba-R Assay

Carbapenem-resistant Enterobacteriaceae (CRE) infections resist nearly most available antimicrobials, resulting in poor clinical outcomes. Saudi Arabia has a relatively high CRE prevalence. This study aims to evaluate the sensitivity of Rapidec Carba NP test and GeneXpert Carba-R assay compared with conventional manners for detection of carbapenemase-producing Enterobacteriaceae.

This is a cross-sectional study including a total of 90 CRE isolates examined at two tertiary hospitals in KSA from October 2020 to December 2021. Gram-negative Enterobacteriaceae were identified by using Vitek 2 system and were furtherly tested for imipenem and meropenem susceptibility by E- test strips, followed by Rapidec Carba NP test and the Xpert™Carba-R assay.

Carbapenem-resistant K. pneumoniae (78.9%) and carbapenem-resistant E. coli (14.4%) were the two most common isolates species. Colistin (98.9%) and tigecycline (88.9%) were the most effective antibiotics against CRE isolates, followed by amikacin (52.2%), gentamicin (33.3%), cotrimoxazole (15.6%), and ciprofloxacin (8.9%). blaOXA-48 was the predominant carbapenemase gene (44.4%), followed by blaNDM (32.2%). blaKPC gene was not detected. The Rapidec Carba NP and the Xpert™Carba-R demonstrated an overall sensitivity of 69.3% and 88%, respectively, in comparison to gold standard detection of meropenem and imipenem resistance by Vitek 2 system and E- test strips.

RAPIDEC^® CARBA NP may be a beneficial screening test for detecting CRE, but for confirmation of the results, Xpert Carba-R assay is more sensitive, significantly lowering the turnaround time compared to reference traditional methods. The information on carbapenemase genes may be used for epidemiologic purposes and outbreak management.