Abstract
Rapid diagnostic technologies for bovine mastitis caused by Staphylococcus aureus (S. aureus) are urgently needed. In the current study, we generated an anti-ribosomal protein-L7/L12 antibody to detect S. aureus and an anti-ribosomal protein-L7/L12 antibody-coated immune-chromatographic strip (ICS) test. Moreover, we determined the ability of the ICS test to detect S. aureus from milk samples collected from cows with clinical mastitis. The developed ICS reacted to S. aureus in a bacteria load-dependent manner with a detection limit of ~104 CFU/mL. In the evaluation of possible cross-reactivity of the ICS test, six strains of coagulase-negative Staphylococci showed slightly positive reactions, although at a lower level; however, other bacteria were completely negative. Next, we investigated the sensitivity and specificity of the ICS test compared with the bacteriological culture method using milk samples from clinical bovine mastitis. The results of the experiments demonstrated that the ICS test had high sensitivity [100%, 95% confidence interval (CI): 91.3–100%] and specificity (91.9%, CI: 90.5–91.9%) compared with culture tests. In addition, the kappa statistic demonstrated that ICS tests showed substantial agreement (k = 0.77, CI: 0.66–0.87) with culture tests. Positive correlations were observed for the statistical analysis between S. aureus (nuc gene) copy numbers and ICS test scores in mastitic milk infected by S. aureus. Therefore, we assume that this new detection method using ICS may be useful as a highly sensitive S. aureus-screening method for the diagnosis of bovine mastitis. Our findings support the ongoing effort to develop an ICS method for bovine S. aureus-induced mastitis, which can contribute to the rapid diagnosis of this disease.
Highlights
Staphylococcus aureus (S. aureus) is one of the most significant bovine mastitis pathogens and is related to major economic losses [1, 2]
Staphylococcus chromogenes, Staphylococcus sciuri, Staphylococcus hominis, Staphylococcus xylosus, Staphylococcus intermedius, and Staphylococcus lentus showed positive results at a detection limit higher than that of S. aureus; Staphylococcus haemolyticus was negative in the test
The developed anti-Ribosomal protein (RP)-L7/L12 monoclonal antibodies (mAbs)-coated immune-chromatographic strip (ICS) tests reacted to S. aureus in a bacteria load-dependent manner
Summary
Staphylococcus aureus (S. aureus) is one of the most significant bovine mastitis pathogens and is related to major economic losses [1, 2]. In case of japan, guidebook of antibiotic treatment for bovine mastitis by Ministry of Agriculture, Forestry and Fisheries of Japan recommends that clinical cases in lactating cows should be treated with an appropriate intramammary antibiotic based on Roberson’s recommendations [4]. For S. aureus which is a contagious mastitis pathogen, an efficient diagnostic assay would constitute a real progress for the improvement of herd management. Bacterial culture and isolate identification are the gold standard diagnostic methods for bovine mastitis diagnosis [5]. Rapid diagnostic technologies for bovine mastitis caused by S. aureus are urgently needed
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