Development and testing of a set of chromogenic media for rapid diagnosis of bovine mastitis

Introduction. Bovine mastitis remains one of the most prevalent and economically significant diseases in dairy cattle production. Three chromogenic media have been proposed for the diagnosis, each specifically designed for isolation and differentiation of certain mastitis pathogen groups: Medium I is intended for Enterobacteriaceae family bacteria, Medium II – for Staphylococcus genus microorganisms, Medium III – for Streptococcus genus bacteria. Objective. The objective is to evaluate the sensitivity, specificity, differentiation capacities and inhibitory properties of these chromogenic media, and to test the media using milk samples from mastitic cows. Materials and methods. For sensitivity testing, the control strains ( Streptococcus agalactiae , Staphylococcus aureus and Escherichia coli ) at concentrations of 1×10 0 , 1×10 1 , and 1×10 2 CFU/mL were used. Microbial growth was assessed following 24-hour incubation at 37 °C. Specificity and differentiation capacities were studied using 22 microbial strains, their growth patterns and colony coloration in chromogenic and control media were compared. Inhibitory properties were determined based on presence/absence of culture growth. The media were evaluated using milk samples from mastitic cows and standardized culturing methods. Results. The chromogenic media demonstrated sensitivity comparable to the control media (Columbia agar supplemented with 5% defibrinated sheep blood), p > 0.05. Medium I enabled reliable color-based differentiation but showed limited inhibitory effects. Medium II ensured selective isolation of staphylococci while effectively suppressing growth of other bacteria. Medium III supported growth of both enterococci and streptococci, including Streptococcus agalactiae . The tests conducted in milk samples confirmed genus level differentiation capability. Conclusion. The developed chromogenic media ensure high-accuracy mastitis diagnosis due to their sensitivity, specificity and differentiation properties. Their implementation makes it possible to cover an extensive range of microorganisms and to selectively isolate the targeted bacterial groups. Further work will be aimed at improving the media for fungal growth suppression and increasing the diagnostic accuracy.