Purpose: Staphylococcus aureus, cause a range of ocular diseases in humans, including noninfectious corneal infiltrative events (niCIE), infectious conjunctivitis and sight threatening microbial keratitis (MK). This study aimed to determine the possession of known virulence genes of S. aureus associated with MK and conjunctivitis, in strains isolated from these conditions and niCIE.
Methods: Sixty-three S. aureus strains-23 from MK, 26 from conjunctivitis, and 14 from niCIE-were evaluated for possession of genes. Polymerase chain reaction was used for the detection of mecA and 10 known virulence genes involved in MK (clfA, fnbpA, eap, coa, scpA, sspB, sspA, hla, hld, and hlg), 2 associated with conjunctivitis (pvl and seb).
Results: mecA was present in 35% of infections and 7% of niCIE strains (P = 0.05). It was not seen in infection strains from Australia. Adhesion genes were found in all strains except clfA, which was found in 75% of infection and 93% of niCIE strains. Invasion genes were found in higher frequency in infections strains-hlg (100% vs. 85%; P = 0.04) and hld (94% vs. 50%; P = 0.005)-compared with niCIE strains. Evasion genes were common in infection strains except scpA, which was found at a significantly higher frequency in niCIE strains (86%) compared with infection strains (45%; P = 0.001).
Conclusions: The higher rates of hlg and hld in strains isolated from infections than niCIE may have a role in pathogenesis, whereas scpA may be an important virulence factor during niCIEs.
Translational relevance: This study has identified virulence factors involved in the ocular pathogenesis of S. aureus infections and niCIE.