Genomics of <i>Staphylococcus aureus</i> Strains Isolated from Infectious and Non-Infectious Ocular Conditions

• Main Authors: Madeeha Afzal (Author), Ajay Kumar Vijay (Author), Fiona Stapleton (Author), Mark D. P. Willcox (Author)
• Format: Book
• Published: MDPI AG, 2022-07-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.
• Notes: 10.3390/antibiotics11081011; 2079-6382
• Keywords: <i>Staphylococcus aureus</i>; ocular infectious isolates; whole genome sequencing; virulence factors; Therapeutics. Pharmacology; RM1-950
• Source: Antibiotics, Vol 11, Iss 8, p 1011 (2022)

<i>Staphylococcus aureus</i> is a major cause of ocular infectious (corneal infection or microbial keratitis (MK) and conjunctivitis) and non-infectious corneal infiltrative events (niCIE). Despite the significant morbidity associated with these conditions, there is very little data about specific virulence factors associated with the pathogenicity of ocular isolates. A set of 25 <i>S. aureus</i> infectious and niCIEs strains isolated from USA and Australia were selected for whole genome sequencing. Sequence types and clonal complexes of <i>S. aureus</i> strains were identified by using multi-locus sequence type (MLST). The presence or absence of 128 virulence genes was determined by using the virulence finder database (VFDB). Differences between infectious (MK + conjunctivitis) and niCIE isolates from USA and Australia for possession of virulence genes were assessed using the chi-square test. The most common sequence types found among ocular isolates were ST5, ST8 while the clonal complexes were CC30 and CC1. Virulence genes involved in adhesion (<i>ebh</i>, <i>clfA</i>, <i>clfB</i>, <i>cna</i>, <i>sdrD</i>, <i>sdrE)</i>, immune evasion (<i>chp</i>, <i>esaD</i>, <i>esaE</i>, <i>esxB</i>, <i>esxC</i>, <i>esxD</i>), and serine protease enzymes (<i>splA</i>, <i>splD</i>, <i>splE</i>, <i>splF)</i> were more commonly observed in infectious strains (MK + conjunctivitis) than niCIE strains (<i>p =</i> 0.004). Toxin genes were present in half of infectious (49%, 25/51) and niCIE (51%, 26/51) strains. USA infectious isolates were significantly more likely to possess <i>splC</i>, <i>yent1</i>, <i>set9</i>, <i>set11</i>, <i>set36</i>, <i>set38</i>, <i>set40</i>, <i>lukF-PV</i>, and <i>lukS-PV</i> (<i>p</i> < 0.05) than Australian infectious isolates. MK USA strains were more likely to possesses <i>yent1</i>, <i>set9</i>, <i>set11</i> than USA conjunctivitis strains (<i>p =</i> 0.04). Conversely USA conjunctivitis strains were more likely to possess <i>set36 set38</i>, <i>set40</i>, <i>lukF-PV</i>, <i>lukS-PV</i> (<i>p</i> = 0.03) than MK USA strains. The ocular strain set was then compared to 10 fully sequenced non-ocular <i>S. aureus</i> strains to identify differences between ocular and non-ocular isolates. Ocular isolates were significantly more likely to possess <i>cna</i> (<i>p</i> = 0.03), <i>icaR</i> (<i>p =</i> 0.01), <i>sea</i> (<i>p</i> = 0.001), <i>set16</i> (<i>p</i> = 0.01), and <i>set19</i> (<i>p =</i> 0.03). In contrast non-ocular isolates were more likely to possess <i>icaD</i> (<i>p</i> = 0.007), <i>lukF-PV</i>, <i>lukS-PV</i> (<i>p =</i> 0.01), <i>selq</i> (<i>p</i> = 0.01), <i>set30</i> (<i>p</i> = 0.01), <i>set32</i> (<i>p =</i> 0.02), and <i>set36</i> (<i>p</i> = 0.02). The clones ST5, ST8, CC30, and CC1 among ocular isolates generally reflect circulating non-ocular pathogenic <i>S. aureus</i> strains. The higher rates of genes in infectious and ocular isolates suggest a potential role of these virulence factors in ocular diseases.