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Purpose: To determine whether the cif gene is present in pathogenic Pseudomonas aeruginosa isolates from patients with bacterial keratitis at Aravind Eye Hospital, a referral eye care center in southern India, and from corresponding environmental isolates., Methods: Polymerase chain reaction amplification was performed on strains of P. aeruginosa isolated from ocular infections and environmental soil samples were collected from the area surrounding Aravind Eye Hospital. DNA sequencing of 16S ribosomal DNA amplicons was performed to verify strain identity., Results: We determined that 45 of 48 patient isolates carry a genomic copy of cif. Analysis of a catalog of environmental strains previously isolated from the surrounding area revealed that only 4 of 10 P. aeruginosa strains and 1 of 14 strains of related species carry the cif gene., Conclusions: This is the first study to show that P. aeruginosa strains with ocular pathogenicity carry the cif gene and that the presence of this gene may be enriched over its prevalence in the environment. Taken together, these results suggest a potential role for Cif in acute bacterial keratitis.

P. aeruginosa and S. pneumoniae are major bacterial causes of corneal ulcers in industrialized and in developing countries. The current study examined host innate immune responses at the site of infection, and also expression of bacterial virulence factors in clinical isolates from patients in south India. Corneal ulcer material was obtained from 49 patients with confirmed P. aeruginosa and 27 patients with S. pneumoniae, and gene expression of Toll Like Receptors (TLR), cytokines and inflammasome proteins was measured by quantitative PCR. Expression of P. aeruginosa type III secretion exotoxins and S. pneumoniae pneumolysin was detected by western blot analysis. We found that neutrophils comprised >90% cells in corneal ulcers, and that there was elevated expression of TLR2, TLR4, TLR5 and TLR9, the NLRP3 and NLRC4 inflammasomes and the ASC adaptor molecule. IL-1α IL-1β and IFN-γ expression was also elevated; however, there was no significant difference in expression of any of these genes between corneal ulcers from P. aeruginosa and S. pneumoniae infected patients. We also show that 41/49 (84%) of P. aeruginosa clinical isolates expressed ExoS and ExoT, whereas 5/49 (10%) of isolates expressed ExoS, ExoT and ExoU with only 2/49 isolates expressing ExoT and ExoU. In contrast, all 27 S. pneumoniae clinical isolates produced pneumolysin. Taken together, these findings demonstrate that ExoS/T expressing P. aeruginosa and pneumolysin expressing S. pneumoniae predominate in bacterial keratitis. While P. aeruginosa strains expressing both ExoU and ExoS are usually rare, these strains actually outnumbered strains expressing only ExoU in the current study. Further, as neutrophils are the predominant cell type in these corneal ulcers, they are the likely source of cytokines and of the increased TLR and inflammasome expression.

Purpose: To compare the clinical course of Nocardia species keratitis with keratitis resulting from other bacterial organisms and to assess the effect of corticosteroids as adjunctive therapy using data collected from the Steroids for Corneal Ulcers Trial., Design: Subgroup analysis of a randomized controlled trial., Methods: setting: Multicenter randomized controlled trial. study population: Five hundred patients with bacterial keratitis randomized 1:1 to topical corticosteroid or placebo who had received at least 48 hours of topical moxifloxacin. intervention/observation procedure: Topical prednisolone phosphate 1% or placebo and clinical course of Nocardia keratitis. main outcome measures: Best spectacle-corrected visual acuity and infiltrate or scar size at 3 months from enrollment., Results: Of 500 patients enrolled in the trial, 55 (11%) had a Nocardia corneal ulcer. Patients with Nocardia ulcers had better presentation visual acuity compared with non-Nocardia ulcers (median Snellen visual acuity, 20/45, compared with 20/145; P < .001) and comparable 3-month visual acuity (median, 20/25, vs 20/40; P = .25). Nocardia ulcers had approximately 2 lines less of improvement in visual acuity compared with non-Nocardia ulcers (0.21 logarithm of the minimal angle of resolution; 95% confidence interval, 0.09 to 0.33 logarithm of the minimal angle of resolution; P = .001). This difference may reflect the better starting visual acuity in patients with Nocardia ulcers. In Nocardia ulcers, corticosteroids were associated with an average 0.4-mm increase in 3-month infiltrate or scar size (95% confidence interval, 0.03 to 0.77 mm; P = .03)., Conclusions: Nocardia ulcers responded well to treatment. They showed less overall improvement in visual acuity than non-Nocardia ulcers, but had better presentation acuity. Corticosteroids may be associated with worse outcomes., (Copyright © 2012 Elsevier Inc. All rights reserved.)