Comparison of Culture-Positive and -Negative Microbial Keratitis

Objectives: To evaluate and compare the risk factors, presenting features, and outcomes of patients with culture-positive and culture-negative microbial keratitis (MK) who presented to a tertiary referral center. Materials and Methods: We conducted a retrospective review of the medical records of 314 patients who were diagnosed with MK in our clinic between 2012 and 2019. Results: Among 314 patients, 142 had positive cultures (45.2%). The mean ages of the culture-positive and-negative patients at the time of diagnosis were 51.39 +/- 21.31 (range, 14-90) years and 56.68 +/- 21.34 (7-94) years, respectively (p=0.028). The mean best corrected visual acuity (BCVA) of the culture-positive and-negative patients were1.74 +/- 1.25 (0-3.1) LogMAR and 1.91 +/- 1.23 (0-3.1) LogMAR prior to treatment and increased to 1.21 +/- 1.30 (0-3.1) LogMAR and 1.27 +/- 1.29 (0-3.1) LogMAR at last visit, respectively. There was no statistically significant difference between culture-positive and-negative patients' BCVA levels at presentation or last visit. Ninety-two patients (64.7%) were infected with bacteria and 50 patients (35.2%) with fungi. The most common pathogen was Pseudomonas aeruginosa (18.3%), followed by Streptococcus pneumoniae (11.2%) and Fusarium spp. (11.2%). Keratitis foci were either centrally or paracentrally located in 105 eyes (73.9%) of culture-positive patients and 149 eyes (86.6%) of culture-negative patients. Multiple foci were present mostly in culture-positive patients (p=0.001). There was no significant difference between the culture-positive and-negative groups in terms of hypopyon presence (p=0.364). The proportion of contact lens (CL) wearers was 33% (n=47) among culture-positive MK patients and 13.3% (n=23) among culture-negative MK patients, respectively (p<0.001). Culture positivity was found to be significantly higher in keratitis associated with CL use (p=0.0001). Conclusion: Microbiological analysis and culture evaluation are important steps in order to manage proper treatment in microbial keratitis. Prognosis mostly depends on the infectivity of the microbiological agent.

Automated summary

This study evaluated and compared the risk factors, presenting features, and outcomes of patients with culture-positive and culture-negative microbial keratitis. The results showed that contact lens wear and younger age were more common in the culture-positive group. Bacterial infection was the most common pathogen, with Pseudomonas aeruginosa being the most common single pathogen.