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Darlene Miller, Heather Ann Durkee, Mariela C Aguilar, Alejandro Arboleda, Nidhi Relhan, Guillermo Amescua, Jean-Marie A Parel; Impact of Riboflavin Photodynamic Antimicrobial Therapy (PDAT) on S. aureus Virulence Factors. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3899.
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© ARVO (1962-2015); The Authors (2016-present)
MRSA keratitis is the most common cause of bacterial keratitis worldwide. Corneal pathogenicity is determined predominantly by a repertoire of secreted virulence factors (in the presence and absence of the organism) and increasing antibiotic resistance. PDAT is an effective alternative therapy for multidrug resistant MRSA. Its impact in eliminating or inhibiting secreted virulence factor expression is unknown. Our purpose was to investigate the effect of PDAT on the neutralization and or inhibition of S. aureus virulence factors.
We use whole genome sequencing (wgs), post riboflavin PDAT, to detect changes in secreted virulence factors (toxins, defense mechanisms, stress response) expression for 2 MRSA isolates (1 community associated-CA-MRSA SCCmec IV, Panton Valentine Leukocidin (PVL+), accessory gene regulator (agr) type 1 and 1 healthcare –associated, HA-MRSA , SCCmec II, Panton Valentine Leukocidin (PVL -), accessory gene regulatory group 2) collected from patients with microbial keratitis. Following riboflavin PDAT (0.1% riboflavin plus 5.4 J/cm2 UV-A irradiation), surviving colonies were collected from the irradiation zone, DNA extracted and wgs performed. The number of WGS unique matches were compared between the two isolates.
A total of 35 different S. aureus virulence factors were identified among the two isolates. Tissue damaging toxins were the most frequent group at 40% (14/35) followed by global immune defense virulence factors, at 34.3% (12/35), super antigens 20% (7/35) and oxidative stress neutralizers 5.7% (2/35). Toxin production was significantly more frequently expressed in the CA-MRSA (71.4%, 10/14) than HA-MRSA (35.7%, 5/10). Alpha toxin expression was dampened less than 10% between the CA-MRSA control and PDAT treated isolate. No Alpha toxin was expressed by the HA-MRSA isolate. Global immune virulence factors were more frequently in the CA-MRSA isolate (83% vs 75%). Expression reduction was less than 15% for this group.
Impact of PDAT on S. aureus secreted virulence factors is strain dependent. The CA-MRSA was less susceptible to Riboflavin photo inactivation.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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