Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for rapid identification of Mycobacterium abscessus .

Background: Nontuberculous mycobacteria are increasingly being implicated in infections and have become an important cause of health care associated infections. Mycobacterium abscessus , a rapidly growing mycobacteria, is of particular concern as it tends to be resistant to commonly used therapeutic options. Conventional phenotypic methods for speciation of mycobacteria are time consuming, labor intensive and not always reliable. Molecular methods require expertise and are expensive. The study was used to evaluate the use of matrix associated laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) as a means of rapid identification of M. abscessus .

Methods: 35 isolates of rapidly growing Mycobacterium from an outbreak of surgical site infections at a tertiary care hospital were identified using phenotypic methods. The mycobacterial isolates were inactivated and an extraction protocol was followed. These isolates were then analyzed by MALDI biotyper (Bruker Daltonics) using biotyper software 4.0 and the mycobacterial reference database v 2.0.

Results: All 35 isolates were identified as M. abscessus by MALDI biotyper but the scores obtained according to guidelines of the company were lower than previous studies with only 23 out of the 35 isolates having scores of greater 1.8 which was described as the minimum score to be achieved for reliable identification.

Conclusion: MALDI-TOF MS offers a rapid and inexpensive method for identification of Mycobacteria; however, the scores obtained in our study were lower than reported in other studies.