PHENOTYPICAL AND MASS SPECTRAL ASSESSMENT METHODS FOR IDENTIFICATION OF SOME CONTAGIOUS MASTITIS PATHOGENS

Abstract

Mastitis is one of the most economic disease affecting dairy cows worldwide. Identification of mastitis pathogens still depends principally on culture and phenotypical method, which is a difficult and time-consuming. Newly, microbiologists have focused their attention on the use of Mass Spectrometry (MS) for microbial identification, especially Matrix Assisted Laser Desorption Ionization Time-Of-Flight (MALDI-TOF). Therefore, this study was designated to evaluate the ability of MALDI-TOF to identify some contagious mastitis pathogens comparing with phenotypical methods such as API panels and VITEK 2 system. A total of one hundred twenty of Staphylococcus aureus (S. aureus), Coagulase Negative Staphylococci (CNS) and Streptococcus agalactiae (Strept. agalactiae) strains isolated from milk of cows affected by clinical and subclinical mastitis were used in the study. According to the results, ~95% of S. aureus, 100% of CNS and Strept. agalactiae were correctly identified by MALDI TOF MS. All S. aureus isolates were then confirmed by a nuc-based PCR technique. While ~92% of S. aureus, 87% of Strept. agalactiae and 76% of CNS were identified by VITEK 2 system. Moreover, ~89% of S. aureus, 80% of Strept. agalactiae and 72% of CNS were identified by API system. In brief, the results demonstrated that MALDI-TOF is a fast and truthful technique which has the capability to replace conventional identification of several bacterial strains usually isolated in clinical laboratories of microbiology. Therefore, it is recomended that MALDI-TOF MS technology can be regularly used in veterinary laboratories for identification of different species of bacteria, particularly when failure of phenotypic methods forces clinical microbiologists.