Virulence Markers in Staphylococcus aureus Strains Isolated from Hemodialysis Catheters of Mexican Patients

Methicillin-resistant Staphylococcus aureus is an increasingly important cause of nosocomial bacterial infections worldwide. S. aureus is responsible for several pathologies, including skin infections, endocarditis, meningitis, deeptissue ulcers, and sepsis. S. aureus biofilm formation on catheters and other medical devices is a major post-operative concern, because biofilms are often the source of persistent and difficult to treat bacterial infections. While catheterrelated S. aureus infections have been reported, the strains responsible for these infections have not been genetically characterized. We genetically characterized S. aureus strains isolated from hemodialysis catheters in Mexican patients. The frequency of 35 genes coding for adhesins, toxins, and other virulence-associated products in the 55 isolated S. aureus strains was determined using PCR, while real-time PCR was used to examine the level of gene expression. Of the 55 S. aureus strains isolated from 109 patients, 45 (81.8%) were determined to be methicillin-resistant. The icaA, rbf, sarA, and agr genes are involved in biofilm formation and bacterial dispersion and were detected in 96.3%, 40.0%, 74.5%, and 100% of S. aureus strains, respectively, and 70.9% of the strains formed a detectable biofilm. Interestingly, 67.2% of the strains contained the icaA, agr, spa, clfA, sdrC, sdrD, sdrE, seg, seh, and sei genes, suggesting that this gene combination is important for successful catheter colonization. The results of this study provide significant insight into the virulence gene make-up of catheter-colonizing S. aureus strains, and will assist in developing a more targeted treatment approach for persistent S. aureus biofilm contamination of medical devices.