Aim: To reduce the inspection time for urinary tract pathogens and provide a rapid and effective therapeutic plan for clinical anti-infection treatment, this study developed a rapid identification (ID) and antimicrobial sensitivity test (AST) method by DOT-MGA.
Methods: We grouped midstream urine samples with single bacteria according to the number of bacteria (≤ 5/5– 15/≥ 15) under per oil microscope after Gram staining. Then we adopted differential centrifugation to process the grouped samples to collect precipitate. MALDI-TOF MS was performed using precipitate directly or after short-term culture. If succeed, we resuspended the precipitate into droplets with or without antibiotics at a MALDI target. Four hours later, mass spectrometer (MS) was used to identify the culture on the target and to analyse AST.
Results: Samples (count ≥ 15), which precipitate can be directly identified by MS; otherwise, the precipitate need a short-term cultured for 3– 6 h before ID. The consistency of the ID results between conventional culture and the precipitate is 100%. Compared with broth microdilution method, DOT-MGA for predicting AST had a high consistency. EA and CA for IPM, LEV, CAZ, NIT, and FOT were 100%/100%, 98%/90%, 98%/92%, 100%/90%, 98%/94%, respectively. No VME was observed in all tests. Besides, MIC50 for the five antibiotics by DOT-MGA and broth microdilution method were ≤ 1/≤ 0.5,> 2/2,≤ 4/≤ 2,≤ 32/≤ 16,≤ 64/≤ 32 and MIC90 were ≤ 1/≤ 0.5, > 2/> 4, 16/16, 128/128, 128/64.
Conclusion: This study can shorten the ID time (minimum 0.5h) and AST (minimum 4h) of the main pathogens of urinary tract infection to 5– 10 hours, which greatly reduce the inspection time and provide substantial help for the rapid diagnosis and treatment of patients with urinary tract infection.
Keywords: MALDI-TOF, DOT-MGA, rapid drug susceptibility test, urinary tract infection, antibiotics resistance