Original article
Does In Vitro Susceptibility Predict Clinical Outcome in Bacterial Keratitis?

https://doi.org/10.1016/j.ajo.2007.11.004Get rights and content

Purpose

To determine whether clinical outcomes in bacterial keratitis are associated with antibiotic susceptibility.

Design

Retrospective, ancillary study using data and samples from a completed randomized clinical trial.

Methods

Forty-two patients were enrolled with culture-confirmed bacterial keratitis at Aravind Eye Hospital in South India. All patients received topical moxifloxacin and were randomized to receive either topical prednisolone phosphate or placebo. Outcomes included time to epithelialization, best spectacle-corrected visual acuity (BSCVA), and infiltrate/scar size at three months. Bacterial isolates were cultured, and minimum inhibitory concentration (MIC) to moxifloxacin was measured using Etests. Multiple linear regression was used to assess the effect of MIC on outcome, adjusting for enrollment characteristics.

Results

MIC was associated with three-month infiltrate/scar size: each two-fold increase in MIC was associated with a 0.33-mm average diameter increase in scar size (P = .01). MIC was not associated with three-month BSCVA (P = .71) or time to epithelialization (P = .35).

Conclusions

MIC was associated with infiltrate/scar size in bacterial keratitis. An ongoing larger, multicenter trial should provide further information on whether this association is maintained across subgroups of organisms.

Section snippets

Methods

This study used samples and data collected in a pilot study conducted in preparation for the Steroids for Corneal Ulcers Trial (SCUT). The SCUT pilot was a randomized, double-masked clinical trial conducted at the Aravind Eye Hospital in Madurai, India, with the primary objective to assess the effect of topical corticosteroid treatment on bacterial corneal ulcers. Aravind Eye Hospital is both a primary and a tertiary care eye hospital in South India with a well-established cornea subspecialty

Results

Forty-two culture-confirmed bacterial keratitis patients were enrolled in the SCUT pilot study. Thirty-seven organisms were grown successfully from the stored specimens, and 34 of these had available outcome data and were analyzed for this study. Five patients with missing outcome data at three months had their three-week results carried forward to three months for the purpose of analysis. Among these 34 cases, Streptococcus pneumoniae and Pseudomonas aeruginosa were the most common organisms

Discussion

In this study, we found that antibiotic susceptibility to moxifloxacin is associated with infiltrate/scar size at three months in culture-proven bacterial corneal ulcers. Specifically, each two-fold increase in MIC is associated with a 0.33-mm larger infiltrate/scar size. However, we could not demonstrate an association between MIC and BSCVA or time to epithelialization. One explanation for this finding may be that final visual acuity may be dependent on other factors, including preexisting

Aiyin Chen is a medical student at the University of California, San Francisco and is planning on pursuing a residency in ophthalmology. She has an interest in international health and implemented the project presented in the article during a research elective at Aravind Eye Hospital in Madurai, India.

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Aiyin Chen is a medical student at the University of California, San Francisco and is planning on pursuing a residency in ophthalmology. She has an interest in international health and implemented the project presented in the article during a research elective at Aravind Eye Hospital in Madurai, India.

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