A Rapid Tigecycline and Polymyxin B Susceptibility Test for Klebsiella pneumoniae Using Direct-on-Target Micro-droplet Growth Assay

Background: Tigecycline (TGC) and polymyxin B (PMB)are important antibiotics for the treatment of multidrug-resistant bacterial infections. However, with the widespread applications, the resistant strains have been isolated. To optimize the use of TGC and PMB, there is an urgent need to develop a rapid detection method for the antibiotics. In recent years, a novel Direct-on-Target Micro-droplet Growth Assay (DOT-MGA) has been developed that can detect antibiotic resistance within hours. The study aims to verify the feasibility and accuracy of DOT-MGA in rapidly identification of TGC and PMB-susceptible and non-susceptible bacteria. Methods A total of 67 strains of Klebsiella pneumoniae were collected for DOT-MGA. According to FDA/EUCAST breakpoint concentrations, 6 µL droplets with or without TGC or PMB were added in triplicate into the wells of the MALDI plate with four incubation time points (3 h, 4 h, 6 h, and 8 h). The results were compared with standard databases using Bruker Biotyper software and classified as susceptible and non-susceptible based on the scores. Results Compared with the micro-broth dilution method, the DOT-MGA achieved the best detection performance after 4 h of incubation. The results showed that the growth efficiency of TGC and PMB were both 100%, and the classification agreement rates were 98.15% and 96.15%, respectively. Conclusion With the 4h incubation time, DOT-MGA can accurately identify the resistance of TGC and PMB, which has good consistency compared with the micro-dilution method. DOT-MGA can provide rapid and reliable drug susceptibility diagnosis, which is of great significance for the clinical anti-infective treatment.