Rapid detection of Pseudomonas aeruginosa and Acinetobacter baumannii harboring bla_VIM-2, bla_IMP-1 and bla_OXA-23 genes by using loop-mediated isothermal amplification methods

Background: Carbapenem-resistant Pseudomonas aeruginosa (CRPA) and Acinetobacter baumannii (CRAB) are the leading causes of nosocomial infections. A rapid and sensitive test to detect CRPA and CRAB is required for appropriate antibiotic treatment. We optimized a loop-mediated isothermal amplification (LAMP) assay to detect the presence of bla_VIM-2, bla_IMP-1, and bla_OXA-23, which are critical components for carbapenem resistance. Methods: Two sets of primers, inner and outer primers, were manually designed as previously described. The LAMP buffer was optimized (at 2mM MgSO₄) by testing different concentrations of MgSO₄. The optimal reaction temperature and incubation time were determined by using a gradient thermocycler. Then, the optimized bla_VIM-2, bla_IMP-1, and bla_OXA-23 LAMP reactions were evaluated by using 120 P. aeruginosa and 99 A. baumannii clinical isolates. Results: Only one strain of the 100 CRPA isolates harbored bla_IMP-1, whereas none of them harbored bla_VIM-2. These results indicate that the acquisition of bla_VIM-2 or bla_IMP-1 may not play a major role in carbapenem resistance in Korea. Fifty two strains of the 75 CRAB isolates contained bla_OXA-23, but none contained bla_VIM-2 and bla_IMP-1 alleles. Conclusions: Our results demonstrate the usefulness of LAMP for the diagnosis of CRPA and CRAB.