This study was aimed at evaluation of two diagnostic techniques and the cultural isolation of Staphylococcus aureus for the testing of subclinical mastitis in lactating cows. A total of 144 milk samples from 36 cows were examined. Ten (10) ml milk samples were aseptically collected from each quarter into labelled sterile universal bottles. The California Mastitis Test (CMT) and the Methylene Blue Reduction Test (MBRT) were carried out on each sample, before cultural isolation (gold standard test) was conducted. Forty eight milk samples were CMT-positive and 60 samples were MBRT-positive, while the gold standard (S. aureus isolation) had 31 positives. The 89.5 % samples of CMT-positive were correctly identified by the test culture. The proportions of samples that tested negative for Subclinical Mastitis (SCM) that did not have the disease, which is a negative predictive value, are 97.9 % and 92.9 % for CMT and MBRT, respectively. The highest total resistance of S. aureus to antibiotics was detected for gentamycin and chloramphenicol (100 %), followed by streptomycin and amoxicillin at 80.6 % and 74.1 %, respectively. The control and monitoring of subclinical mastitis in lactating cows are of great importance to human health. A good management system constitutes the priority in controlling subclinical mastitis in lactating cows.
