Phenotypic and genotypic characterization of bacterial isolates causing bovine mastitis with reference to MALDI-TOF-MS for isolates’ identification

Abstract

In this investigation, we assessed the phenotypic and genotypic traits of bacterial and Mycoplasma species associated with bovine mastitis.  We examined ninety milk samples taken from cows with mastitis by conventional bacteriological methods, testing for antimicrobial susceptibility, virulence profile, and molecular techniques to determine the presence of resistance genes. The most common pathogens identified as part of this investigation were: E. coli, Enterococcus faecalis, and Mycoplasma spp. Additionally, our examination of cows with mastitis revealed many cows had mixed infections, thus demonstrating the polymicrobial nature of mastitis. The antimicrobial susceptibility of the mastitis causative agents was evaluated through antimicrobial susceptibility testing and revealed that most commonly used classes of antibiotics had demonstrated high levels of resistance being present. Foundationally, the molecular analysis of the pathogens confirmed the presence of multiple critical resistance genes. Biofilm formation, as well as enzymes, were found to be elevated demonstrating the pathogens had the capacity to survive within their host's mammary tissues. This investigation document MALDI-TOF-MS as a rapid and effective tool for identification of the causative agents of bovine mastitis. The results from this study support and reinforces the need for ongoing disease monitoring and responsible antibiotic usage for the control of mastitis in dairy cattle as well as for preventing the development of antibiotic resistance in dairy herds.