Development and Evaluation of a Loop-Mediated Isothermal Amplification Assay for Rapid and Specific Identification of Carbapenem-Resistant Acinetobacter baumannii Strains Harboring bla_OXA-23, and the Epidemiological Survey of Clinical Isolates

Acinetobacter baumannii is an important nosocomial pathogen in hospital-acquired infections, and carbapenem resistance has been increasingly observed worldwide. Oxacillinase production by bla(OXA-23) is a predominant and prevalent carbapenem resistance mechanism of A. baumannii, especially in China. Rapid and specific detection of bla(OXA-23) may offer valuable insight for administration of directed antimicrobial therapy. In this study, we aimed to develop a loop-mediated isothermal amplification (LAMP)-based method for identifying carbapenem-resistant A. baumannii (CRAB) harboring the bla(OXA-23) gene. High-specificity primers for screening bla(OXA-23) were designed and synthesized, and the LAMP reactions were performed. Clinical A. baumannii strains isolated from the Former 307th Hospital of People's Liberation Army were used to determine the sensitivity and specificity of this method compared with those of phenotypic antimicrobial susceptibility testing and the traditional PCR method. Multilocus sequence typing (MLST) was performed to investigate the epidemiology of the A. baumannii bacterial population. Compared with antimicrobial susceptibility testing, the sensitivity and specificity of LAMP in detecting bla(OXA-23) were 88.4% and 97.7%, respectively. However, the LAMP method is much simpler and less time-consuming (within 60 minutes) than conventional PCR and phenotypic susceptibility testing. The 113 isolates could be clustered into 30 sequence types, and most strains (83/113) belonged to clonal complex (CC) 92, which is also the dominant CC in China. The LAMP-based method detected bla(OXA-23) in a simpler manner and could provide rapid results for identifying CRAB. Consequently, bla(OXA-23) may serve as a surrogate marker for the presence of CRAB in patients with serious infections in clinical practice.