Moving towards the immunodiagnosis of staphylococcal intramammary infections.

Bovine mastitis is the primary disease of dairy cattle that has a great impact on the dairy industry. It is estimated that worldwide economic losses due to mastitis range between US$82 and US$131 per cow/year. A fast and efficient diagnosis of the disease remains a major bottleneck that directly influences the speed with which treatment decisions and management are undertaken. Microbiological culture remains the gold standard in the identification of bacteria that cause mastitis, but the method has inherent limitations, such as a delay in obtaining results and cost, and requires special care during the collection and processing of the sample. For this reason, multiple groups have devoted efforts to develop alternative methods that, preferably, can be easily accomplished in the field. The specificity of the antigen-antibody reaction has enabled the emergence of major diagnostic methods used in clinical practice, such as immunoassays, which have significant advantages in terms of speed, sensitivity, specificity, and portability. Commercially, immunodiagnostics have been used in the detection of various diseases in cattle. However, in several cases, only a presumptive diagnosis can be made, which requires confirmation using culture-based methods. This review discusses the immunological-based assays developed since the 1990s for the detection of Staphylococcus aureus, which is considered the primary pathogen of contagious bovine mastitis. Although no ideal antigens ensure the accurate performance of tests and the costs need to be reduced to allow for good market competitiveness, immunoassays, particularly lateral flow immunoassay and immunoagglutination, have emerged as promising tests to be used in the field.

Immunorelevant proteins for the diagnosis of bovine staphylococcal mastitis.

Staphylococcus aureus is a leading cause of bovine mastitis, a condition in which the udder of the cow is inflamed, reducing the quality and quantity of milk produced. Staphylococcal mastitis is a common infection that can develop into a chronic form. The segregation of infected animals is an important preventive practice but relies on an effective diagnostic method. For this purpose, we constructed a genomic library of S. aureus, and a screening step was conducted with antiserum produced using the total protein extract of the pathogen. The nucleotide sequences of the immunoselected clones were aligned with the genome of bovine S. aureus RF122, which enabled the identification of 65 different loci, including proteins related to metabolism, adhesion and cell wall production, toxins, regulatory proteins, and hypothetical proteins. The subcellular location of the immunoreactive polypeptides was also determined. Fifty-two percent were cytoplasmic, 34 % were located in areas exposed to the host's immune system, and for 14 %, the location could not be determined. In silico analysis of the presence of these proteins in mastitis pathogens showed that Fib, ClfA, and the hypothetical protein SAB0166 were the only proteins specific for S. aureus. Therefore, these proteins are promising candidates for the serodiagnosis of staphylococcal mastitis.