Phenotype Detection and Drug Resistance Analysis of Carbapenem-Resistant Gram-Negative Bacilli

The increasing prevalence of infections caused by carbapenem-resistant organisms (CRO) represents a global health issue. Therefore, a rapid and accurate method for detecting these microbes in any clinical microbiology laboratory is crucial for the prevention and control of their transmission, as well as for clinical treatment. This study aimed to evaluate the phenotypic detection methods, PBA-EDTA, mCIM, PCR, and immunocolloidal gold kit for CRO.

We collected 99 samples from the inpatients in Sun Yat-Sen University Cancer Center (SYSUCC) from March 2019 to February 2022 and classified the drug resistance and genotype of various strains by various enzyme-type experiments.

Out of 99 multidrug-resistant Gram-negative bacilli resistant to carbapenems, 58 (58.59%) were identified as carbapenemase-positive using the mCIM test. The carbapenemase genotypes included 19 NDM strains, 4 KPC strains, 1 IMP strain, and 5 OXA-23 strains. Enzyme detection revealed 21 strains positive for metallo-β-lactamase, 50 for serine-β-lactamase, and 2 positive for both, with a total positive rate of 73.74%. 26 strains were negative for enzyme detection, and mCIM showed limited effectiveness in detecting strains coproducing NDM and KPC. The immunocolloidal gold assay had a sensitivity of 96.9% and specificity of 98.5%.

This study used an immunocolloidal gold kit for carbapenemase detection, providing results within 15 min. This cost-effective method can quickly assist in identifying carbapenemase genotypes and holds potential as a new rapid detection and diagnostic tool for CRE in clinical and lab settings.