Identification of Enterococci in MALDI-TOF MS by Comparison with Slanetz and Bartley and Blood Agar Media

Abstract

Introduction: Matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been used frequently in the last decade as a fast and reliable method for the identification of microorganisms. The fact that only one gram-negative selective medium is recommended in this method causes problems in the diagnosis. There is no information in the scientific literature that Slanetz and Bartley (SB) agar used in the study can be used in MALDI-TOF MS to identify bacteria. Materials and Methods: In this study, it was aimed to compare the identification performance of enterococci isolated from drinking-use and lake waters in Van and its surroundings with blood agar by using MALDI-TOF MS method and to develop a simple and fast sample preparation method that increases this performance. For this purpose, 60 mains and 30 lake water samples were examined for six months. Results: The samples were studied by the membrane filtration method. The isolated enterococci were identified by MALDI-TOF MS method with the isolates taken directly from both blood agar and SB medium, which is a selective medium. The same results were obtained in the species determination in both media. According to these results, 35% of the mains water isolates were Enterococcus casseliflavus, 30% Enterococcus faecalis, 26.7% Enterococcus faecium, 6.6% Enterococcus hirae, 1.7% Enterococcus columbae, and 20% of lake water isolates E. casseliflavus, 40% E. faecalis, 36.7% E. faecium, 3.3% E. hirae, E. casseliflavus in mains water and E. faecalis in lake water are the most frequently isolated enterococci species. Conclusion: Determining that it can also be obtained from selective media such as SB agar, for which there is no data on its suitability for mass spectrometric identification, will contribute to the more effective and rapid use of MALDI-TOF MS in microbiology laboratories. In addition, it has been concluded that all the waters examined are exposed to a significant level of microbial contamination and pose a potential danger to public health. It has been revealed that the consumption of these waters may pose a potential health risk for immunocompromised patients and the elderly, as well as children.