This paper should be cited as: Samadi Kafil,H. Mohebati Mobarez,A. Forouzandeh Moghadam,M.

Comparing MALDI-ToF Mass Spectrometry with Molecular and Biochemical Methods in Identifying Enterococcus Faecium and Enterococcus Faecalis Isolated from Clinical Samples

Samadi Kafil,H.(MSc)1, Mohebati Mobarez,A.(PhD)*2, Forouzandeh Moghadam,M.(PhD)

1 PhD student of Bacteriology,Department of Medical Bacteriology, Faculty of Medical Sciences, Tarbiat modares University

2 Associat Professor of Bacteriology.Department of Medical Bacteriology, Faculty of Medical Sciences, Tarbiat modares University

3 Associat Professor of Biotechnology, Department of Biotechnology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran

Abstract
Background and Objective: Enterococci are Gram-positive members of human gastrointestinal flora, in Dairy products and environment. they have emerged as important causes of opportunistic nosocomial infections in recent years. In this study we aimed to investigat and compare the efficiency of MALDI-TOF mass spectroscopy method through Biochemical and Molecular methods for detecting Enterococcus faecalis and Enterococcus faecium.

Materials and Methods: seventhy five clinical samples were collected for biochemical, molecular and mass spectroscopy investigations. Samples were treated with Esculin hydrolysis, Catalase, Pyrrolidonyl aminopeptidase, 6.5% NaCl solution, motility, 0.04% Tellurite, L-Arabinose and Sorbitol. Using specific primes allele specific PCR was used.The samples were then analyzed by MALDI-TOF mass spectroscopy and Biotyper 3 software.

Results: Enterococcus faecium and Enterococcus faecalis were detected in thirty and forty two samples, respectively whereas three samples showed both bacterial infections. Using biochemical analysis, two E. faecium isolates were Arabinose negative and one E. faecalis isolates was Telliurite negative. All samples were showed correct bands in PCR results but two of them didn't show clear bands(on agarose gel). In mass spectroscopy analysis all strains were correctly detected and well defined.

Conclusion: According to our results, MALDI-TOF mass spectrometry in comparison with Molecular and Biochemical Methods could be a reliable and accurate method that can easily and quickly identify and differentiate Enterococcus faecium and Enterococcus faecalis in clinical samples.

Key words: Enterococcus faecalis, Enterococcus faecium, MALDI-TOF mass spectrometry, PCR

Corresponding Author: Mohebati Mobarez,A.

Email: mmmobarez@modares.ac.ir

Received 19 Dec 2012 Revised 14 Jun 2013 Accepted 14 Jun 2013