Phenotypic and Genotypic Characterization of Staphylococcus aureus Isolated from Patients with Chronic Furunculosis and Osteomyelitis from Northwestern Poland

<i>Staphylococcus aureus</i>, a Gram-positive coccus commonly found in the environment, is indeed a common cause of both superficial and deep infections. The aim of the study was to determine the virulence factors of <i>S. aureus</i> characteristic of chronic infections, including chronic furunculosis and chronic osteomyelitis. Phenotypic characteristics of the bacteria (ability to produce hemolysis, clumping factor, and coagulase; antibiotic susceptibility) and genotypic characteristics (presence of genes responsible for the production of enzymes and toxins; ability to form biofilm) were examined. The real-time PCR method was used to determine the presence of virulence genes. Biofilm production was confirmed using the crystal violet method. Antibiotic and chemotherapeutic susceptibility tests were performed using the disk diffusion method. In 90% of cases, <i>S. aureus</i> strains possessed the following virulence genes: clfA, clfB, spa, cna, eap, hlgA, hlgB, hlg, hld, bap, bbp, ebpS, fib, fnbA, fnbB, and pvl. A total of 82% of <i>S. aureus</i> strains showed susceptibility to methicillin (MSSA), whereas 12% of strains were susceptible to methicillin and simultaneously resistant to macrolides, lincosamides, and streptogramin B, including 10.5% with inducible resistance and 1.5% with constitutive resistance (MSSA/MLSB). In addition, 1.5% were methicillin-resistant <i>S. aureus</i> (MRSA) and susceptible to the remaining antimicrobial agents. The predominance of MSSA in the etiology of chronic furunculosis and chronic osteomyelitis was observed. It has been demonstrated that MSSA possesses a similar set of virulence genes to MRSA and that MSSA is responsible for most cases of chronic osteomyelitis and furunculosis. The findings indicate that <i>S. aureus</i> possesses numerous virulence factors that play a key role in the processes of adhesion to and proliferation within host cells.