Abstract
PurposeStaphylococcus aureus (S. aureus) is the most important pathogen involved in bovine mastitis in dairy production. S. aureus produces a spectrum of extracellular protein toxins and virulence factors which are thought to contribute to the pathogenicity of the organism. The aim of this work was to isolate and molecular characterize S. aureus associated with bovine subclinical mastitis in the central part of Ethiopia.MethodsA total of 265 lactating dairy cows from various dairy farms in four different geographical locations were screened by the California mastitis test (CMT) for bovine subclinical mastitis. One hundred thirty CMT-positive milk samples were collected and transported to the laboratory. Different biochemical tests and polymerase chain reaction (PCR) were used for the identification of S. aureus isolates. Finally, PCR was performed for molecular detection of virulence genes.ResultsFrom a total of 265 lactating dairy cows screened, 49% (n = 130) were positive for bovine subclinical mastitis. One hundred thirty mastitic milk samples were subjected to bacterial culturing, and one hundred (76%) S. aureus isolates were identified based on phenotypic characters. Sixty-eight confirmed S. aureus isolates were obtained using PCR. The confirmed S. aureus isolates were tested for six virulence genes (tsst-1, hlb, eta, sea, clfA, and icaD) using PCR. Of the six virulence genes screened from all the isolates, only two (clfA and eta) were detected in the isolates. Out of 68 isolates, 25% and 22% were possessed the eta and clfA genes, respectively.ConclusionThe presence of Staphylococcus aureus having virulence genes (eta and clfA) revealed that mastitis is a major concern nowadays affecting animal health, milk quality, and yield. Further genomic study of these isolates will provide broad new insights on virulence.
Highlights
Mastitis is considered to be the most frequent and most costly production disease in dairy herds of developed and developing countries including Ethiopia
Isolation and identification of S. aureus isolates In this study, of the 265 lactating dairy cows screened, 130 (49%) were positive for bovine mastitis based on California mastitis test (CMT)
One hundred and thirty mastitic milk samples were subjected to bacterial culturing, and 100 (76%) S. aureus isolates were identified based on the morphological and biochemical characters
Summary
In addition to specific virulence factor, S. aureus possesses different mechanisms or traits such as biofilm formation, adhesion to and invasion into mammary epithelial cells, and formation of small colony variant (SCV) that enables this pathogen to resist host defense mechanisms. Some of these toxins are known to function as superantigens that cause increased immunological reactivity in the host (Rollin et al, 2015; Bobbo et al, 2017)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
