Development of a one-step rapid immunochromatographic test kit for detecting bovine mastitis-causing Staphylococcus aureus and streptococci

Major pathogens causing mastitis, such as Staphylococcus aureus and streptococci can be transmitted between cows. Specific antibiotics are needed to exterminate these pathogens. However, bacterial culture for pathogen identification requires at least 18 h. Thus, a rapid diagnostic method is needed for identifying pathogens. A previously reported immunochromatographic strip (ICS) test, based on a lateral flow assay, uses individual lysis buffers for different mastitis-causing pathogens, which may produce technical errors. In this study, a one-step rapid ICS test kit using simple procedures to detect bovine mastitis-causing S. aureus and streptococci was developed. In the ICS test version (ver.) 2, the new test-strip design integrated bacteriolytic enzymes, while a common lysis buffer (consisting of 3 % Triton X-100, 0.5 % sodium N-lauroylsarcosinate, and 0.15 % Zwittergent 3–12) simplified the testing procedure. In refrigerated fresh milk samples from cows with clinical mastitis (n = 77), the sensitivity, specificity, and κ statistic values (the agreement between the results of the ICS test and bacterial culture) of the ICS test ver. 2 for S. aureus were 0.864, 0.909, and 0.752, respectively, and those for streptococci were 0.778, 0.956, and 0.700, respectively, as compared to traditional bacterial culture. Thus, S. aureus and streptococci can be detected in the milk with a simple one-step procedure. Some cross-reactivity with non-aureus staphylococci was observed in ICS test ver. 2 for S. aureus. Nonetheless, the improved ICS test kit may serve as an effective detection tool for staphylococci and streptococci mastitis, supporting timely and appropriate control of mastitis on farms.