Infectious keratitis: cotton vs steel, do opposites agree? Comparison between two different instruments used for obtaining corneal material for direct inoculation in infectious keratitis

Session Details

Session Title: Presented Poster Session: Medical Cornea

Venue: Poster Village: Pod 3

First Author: : S.Sagerfors SWEDEN

Co Author(s): :    B. Ejdervik-Lindblad   B. Söderquist                    

Abstract Details

Purpose:

To investigate agreement and differences of corneal culture outcome and isolated microbes between knife blade and cotton tip applicator, used for corneal sampling for direct inoculation, in patients with suspected infectious keratitis.

Setting:

A retrospective study of medical records and microbiology reports from patients with suspected infectious keratitis during January 1st 2004 to December 31st 2014 at the three Departments of Ophthalmology in Region Örebro Län, Sweden.

Methods:

Patients with suspected infectious keratitis were included if they met at least one of two inclusion criteria: 1) Positive corneal culture (all growth was considered positive) 2) stromal infiltration with overlying epithelial defect in combination with lesion within/overlapping the central 4 mm of the cornea and/or uveitis and/or pain Corneal samples were first obtained by swabbing the infiltrate with cotton tip applicators and then by scrapings with knife blade, and directly inoculated on agar plates in the following order, GC agar- incubated in CO2 at 36°, Blood agar and Sabouraud agar incubated in air, at 36°C and 30°C respectively.

Results:

In all, 355 episodes were included. Corneal cultures were positive by either or both methods in 46% (165/355) of the patients. Cotton tip applicator rendered a significantly higher rate of culture positive episodes, 43.9% (156/355) than knife blade, 31.3% (111/355) (p<0.00001). On patient level, cotton tip and knife blade agreed completely in 75% of the cases (n=267/355). Of 200 isolated microbes, 97 were isolated by both instruments, 83 by cotton tip only and 20 by knife blade only resulting in a Cohen’s kappa of 0.65 with a 95% CI of 0.58-0.71.

Conclusions:

Corneal sampling by cotton tip applicator yielded a significantly higher proportion of positive cultures compared to knife blade in cases of infectious keratitis. The agreement on microbial level between the two instruments, measured with Cohen’s kappa was good. Future studies with randomized sampling order are needed to establish which instrument, cotton tip applicator or knife blade, is the most effective in picking up microbes for direct inoculation in suspected infectious keratitis.

Financial Disclosure:

None