Virulence Genes of Staphylococcus aureus Associated With Keratitis, Conjunctivitis, and Contact Lens–Associated Inflammation

Abstract

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.

Genomics of Staphylococcus aureus Strains Isolated from Infectious and Non-Infectious Ocular Conditions

“…The current study’s genotypic data shows that infectious isolates from USA harbored more antimicrobial resistance genes (ARGs) compared to Australian isolates, which supports the phenotypic data of the previous study. Similarly, PCR results for a subset of 12 known virulence genes had previously reported that genes involved in evasion and invasion ( hlg and hld ) were more commonly found in infectious isolates than niCIE [ 13 ]. The current study results for hld are consistent with the previous report [ 13 ].…”

“…Similarly, PCR results for a subset of 12 known virulence genes had previously reported that genes involved in evasion and invasion ( hlg and hld ) were more commonly found in infectious isolates than niCIE [ 13 ]. The current study results for hld are consistent with the previous report [ 13 ]. However, hlg which was more common in infectious strains than niCIE strains in the previous study [ 13 ] was found in ≥96% of all S. aureus isolates in the current study.…”

“…This study investigated genomic differences in resistance and virulence genes of S. aureus isolates from different infectious (MK and conjunctivitis) and non-infectious (niCIE) ocular conditions from USA and Australia. Based on previous phenotypic susceptibility [ 12 ] and PCR data [ 13 ] it was expected that there would be differences in the resistance and virulence determinants between infectious and non-infectious disease. Most (n = 22, 88%) of the isolates used in the study were MDR [ 12 ].…”

“…MK strains from Australia were more susceptible to antibiotics (ciprofloxacin, oxacillin) compared to MK strains from USA [ 12 ]. Whilst several studies have examined which virulence factors might be involved in the development of keratitis by S. aureus , there is much less information on the association of virulence factors with conjunctivitis or niCIE [ 13 ]. Similarly, as outlined previously [ 13 ], infectious isolates (MK + conjunctivitis) had a higher frequency of genes involved in evasion of the immune system and invasion of the host ( hlg , hld ) compared to niCIE strains.…”

“…Whilst several studies have examined which virulence factors might be involved in the development of keratitis by S. aureus , there is much less information on the association of virulence factors with conjunctivitis or niCIE [ 13 ]. Similarly, as outlined previously [ 13 ], infectious isolates (MK + conjunctivitis) had a higher frequency of genes involved in evasion of the immune system and invasion of the host ( hlg , hld ) compared to niCIE strains. On the other hand, scpA , that encodes a staphylococcal cysteine proteinase, was more common in niCIE strains.…”