Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) for the Identification of Bacteria Causing Urinary Tract Infections

Document Type : New and original researches in the field of Microbiology.

Authors

1 Specialist of Medical Microbiology, Central lab of armed force, Egypt

2 Professor of Medical Microbiology and Immunology Department, Ain Shams University, Egypt

3 Medical Microbiology &Immunology ,Ain Shams University ,Cairo ,Egypt

Abstract

Background: Matrix assisted laser desorption/ionization-time of flight (MALDI-TOF) technology is a technique which allows microbial identification in clinical microbiology laboratories based on microbial protein profiles. A promising application of the MALDI-TOF technique comprises carrying out identification from direct urine samples. Objectives: The aim of this study is to evaluate the performance of MALDI-TOF MS system for the rapid identification of clinically relevant urinary tract pathogens in urine samples to the species level. Methodology: two hundred (200) urine samples with findings suggestive of urinary tract infections (UTI) were identified directly by MALDI-TOF MS, and same samples were identified from culture on MALDI-TOF MS. 73 colonies from 73 samples were further identified by Bd Phoneix and PCR. Results: MALDI-TOF MS directly from samples identified 174 samples (91 to the species level 83 to genus level), while MALDI-TOF MS after culture identified 191 samples (187 to the level of species, and 4 to genus level). In addition, 9 samples gave no results from the direct method and no growth in culture. The sensitivity and specificity of direct method compared to after culture method was 91.1% and 100%, respectively. Colonies of 73 samples were detected by the BD Phoneix automated identification system and by PCR. The results were identical among the three systems. Conclusion: The ability of MALDI-TOF MS’s to detect microorganisms from urine samples directly can provide early diagnosis of UTIs and avoid the inadequate or unnecessary empirical antimicrobial treatment. 

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