Phylogenetic relationship, virulence factors, and biofilm formation ability of human, pet animals, and raw milk Staphylococcus aureus isolates

Document Type : Full paper (Original article)


1 Ph.D. Student in Microbiology, Department of Microbiology, College of Science, Agriculture and Modern Technology, Shiraz Branch, Islamic Azad University, Shiraz, Iran

2 Department of Pathobiology, Faculty of Veterinary Medicine, Amol University of Special Modern Technologies, Amol, Iran

3 Department of Microbiology, Faculty of Basic Sciences, Ayatollah Amoli Branch, Islamic Azad University, Amol, Iran

4 Department of Microbiology, College of Science, Agriculture and Modern Technology, Shiraz Branch, Islamic Azad University, Shiraz, Iran


Background: Identification of genotypic characteristics and pathogenicity of Staphylococcus aureus isolates is very important in the epidemiological study of its related diseases. Aims: The present study was done to compare the S. aureus isolates from different sources on the basis of virulence gene properties, biofilm production ability, and phylogenetic variations. Methods: Seventy S. aureus isolates (including 25 human, 25 raw milk, and 20 pet animal isolates) were subjected to slime production ability testing, polymerase chain reaction (PCR) detection of 14 different virulence genes, and DNA fingerprinting using restriction fragment length polymorphism (RFLP) of coa gene PCR products. Results: Among 70 S. aureus, 64 (91.4%) isolates were slime producers on Congo red agar (CRA) medium. The spa and icaD virulence genes were present in all isolates and the seD and etaA genes were not detected in any of the isolates. In total, 22 different virulence gene patterns and nine distinct clusters of coa-PCR-RFLP were identified among isolates. Conclusion: According to the results, S. aureus strains of human origin showed a significant association with specific virulence gene profiles and genotypes. seB and seC were the most responsible genes for S. aureus enterotoxin among human and animal isolates, respectively. Coa-RFLP showed partially appropriate results in the classification and source detection of S. aureus isolates.


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