Detection of Virulence Genes in Staphylococcus aureus and Streptococcus agalactiae Isolated from Mastitis in the Middle East

Aims: The current study was carried out to genotypically characterize Staphylococcus aureus (S. aureus) and Streptococcus agalactiae (S. agalactiae) isolated from clinical and subclincal cases of bovine mastitis.

Study Design: The S. aureus and S. agalactiae strains were characterized phenotypically, and were further characterized genotypically by polymerase chain reaction (PCR) using oligonucleotide primers that amplified genes encoding the fibronectin-binding proteins A (fnbA), the clumping factors A (clfA), the surface protein A (spa) and the coagulase (coa) genes for S. aureus and the surface immunogenic protein (sip), hyluronidase (hyl), CAMP factor (cfb), surface enzyme (scpB), β-hemolysin/cytolysin (cylE) and alpha-C-protein (bca) for S. agalactiae.

Place and Duration of Study: A total of 61 S. aureus and 43 S. agalactiae isolates were obtained from milk samples collected from 160 apparently healthy cows and 54 clinical cases during a survey conducted for six months at different localities in El-Behira province, Egypt and Al-Qassim region, Kingdom of Saudi Arabia.

Results: 59 (~97%) of S. aureus isolates illustrated a positive coagulase-test and 100% were positive when tested with the BBL™ Staphyloslide™ Latex. All identified strains of S. aureus were PCR positive for thefnbA, clfA, spa (x-region) and spa (IgG Binding region) genes which displayed a single size amplicon of approximately 1226 bp (73.77%), 1000 bp (88.52%), 500 bp (80.32%) and 300 bp (19.67%), respectively. In contrast, the amplification of the coa-gene exhibited three dissimilar size polymorphisms with around 500 bp (57.37%), 600 bp for (8.19%) and 900 bp (8.19%). Furthermore, 42 (~98%) out of 43 S. agalactiae isolates were positive by agglutination of the blue latex particles within 20 second in the test circle and 100% demonstrated a positive results in the CAMP test. All confirmed S. agalactiae isolates were also PCR positive for the sip gene (90.69%), hyl gene (81.39%), cfb gene (93.02%), cylE gene (90.69%), scpB gene (67.44%) and bca gene (20.93%).

Conclusion: The high frequency of virulence genes detected in the current study will help in the understanding of the distribution of infectious S. aureus and S. agalactiae strains in the Middle East and contribute to the establishment of preventive approaches to reduce the spread of infection.