Detection of icaA and icaD genes of Staphylococcus aureus isolated in cases of bovine mastitis in the Republic of Serbia

Staphylococcus aureus (S. aureus) is the most common agent of contagious mastitis that causes serious health and economic problems. The ability to form biofilms is an important virulence factor of S. aureus for the establishment of persistent infections. This study is aimed to investigate the presence of icaA and icaD, two genes of importance for the biofilm formation in S. aureus bovine mastitis isolates. In order to isolate and identify S. aureus, 1555 milk samples were collected from 401 cows, located in different regions of the Republic of Serbia. Using the conventional microbiological methods 100 isolates were characterized as coagulase-positive staphylococci. After primary biochemical identification, the species confirmation of 44 S. aureus isolates was done using MALDI-TOF Mass Spectrometry and PCR technique, targeting the S. aureus-specific nuc gene. Among all investigated S. aureus isolates 25.0% harbored both icaA gene and icaD genes. The presence of icaD gene alone was confirmed in 40.9% of cases totaling icaD positive isolates to 65.9%. The remaining 34.1% of S. aureus isolates were negative for the presence of both genes. The results of the present study indicate the existence of potential biofilm-producer strains in different regions of the Republic of Serbia, both under intensive and semi-extensive cows breeding