Correlation of Pseudomonas aeruginosa genotype with antibiotic susceptibility and clinical features of induced central keratitis.

PURPOSE: To determine the association of type III secretion system (T3SS) genotype with antibiotic susceptibility, serotypes, and clinical manifestation of centrally located Pseudomonas aeruginosa keratitis.

METHODS: Clinical characteristics of P. aeruginosa keratitis cases from 2001 to 2011 were analyzed. Each strain was serotyped and genotyped for T3SS exotoxin genes. Antibiotic sensitivity and minimum inhibitory concentrations were determined with agar dilution method. Prognostic factors affecting final visual outcomes and time to re-epithelialization were analyzed using linear and Cox regression models.

RESULTS: Forty-four invasive and 28 cytotoxic strains were identified. Invasive strains occurred mostly in males (P = 0.03) with older age (P = 0.009) and ocular surgery or trauma history (P = 0.006), poor presenting (P = 0.04) and final (P < 0.0001) best spectacle-corrected visual acuity (BSCVA), and larger infiltration size (P = 0.03). Cytotoxic strains were associated with contact lens wear (P < 0.0001). Poor prognostic factors for final BCVA after adjusting for sex, age, and contact lens wear included invasive strains (P = 0.02), larger infiltration area (P = 0.02), deeper infiltrations (P = 0.02), and presence of hypopyon (P = 0.09). Factors affecting complete re-epithelialization time included invasive strains (P = 0.02), infiltration area (P = 0.01), depth (P = 0.02), and hypopyon (P = 0.03) after adjusting for age and sex. Serotypes 2, 6, and 11 were more commonly found among all isolates. A trend to increased fluroquinolone resistance is noted for invasive strains, although not reaching statistically significant difference.

CONCLUSIONS: Cytotoxic strains are associated with contact lens wear while invasive strains are related to poor prognosis and increased resistance to fluoroquinolones. Clinicians should be aware of the two different genotypes of P. aeruginosa affecting prognosis.