Microbial Keratitis Isolates at a Midwestern Tertiary Eye Care Center

Microbial keratitis in the subtropical region of Korea: a comprehensive 12-year retrospective review at a single referral center

OBJECTIVES

To investigate the epidemiological characteristics and clinical outcomes of culture-proven bacterial and fungal keratitis at a single tertiary referral centre on Jeju Island, South Korea.

DESIGN

A retrospective study design.

SETTING

Data from a solitary referral centre on Jeju Island spanning January 2011 to December 2022.

PARTICIPANTS

Among the 245 patients clinically diagnosed with infectious microbial keratitis, 110 individuals had culture-positive results.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome was the identification of causative microbial profiles and epidemiological characteristics, while the secondary outcome was the correlation of these factors with treatment outcomes.

RESULTS

Of 245 patients, 110 (44.9%) had culture-positive infectious keratitis, showing 69 bacterial, 32 fungal, 4 superimposed bacterial and 5 cases with coinfection by bacteria and fungus. The most common pathogen was Pseudomonas species in 14.4% of the bacterial keratitis cases, followed by Staphylococcus epidermidis (9%), Staphylococcus aureus (8%) and Moraxella species (7%). The total treatment success rate for bacterial keratitis was 67.5%. The frequency of methicillin-resistant Staphylococcus on Jeju Island did increase during the study period. Fusarium species had the highest incidence at 22.2%, followed by Candida (16.7%) and Colletotrichum species (11.1%). 56.7% of fungal keratitis patients were successfully treated. An initial large corneal lesion (>3 mm) showed a statistically significant association with treatment failure.

CONCLUSION

The incidence of Moraxella and Colletotrichum species in our study was higher than that reported in other districts with different climates and environments. The results reported here reflect the unique environmental features of Jeju Island, characterised by high humidity and temperatures.

Factors Associated With Laboratory Test Negativity Following a Transition in Specimen Collection in Microbial Keratitis Cases

PURPOSE

Negative laboratory results make targeting microbial keratitis treatment difficult. We investigated factors associated with laboratory negativity in patients with microbial keratitis in the context of a transition to a new specimen collection method.

METHODS

Microbial keratitis patients with associated laboratory tests were identified in the electronic health record of a tertiary care facility from August 2012 to April 2022. Patient demographics and laboratory results were obtained. Random sampling of 50% of charts was performed to assess the impact of the ocular history and pretreatment measures. The relationship between probability of negative laboratory results with demographics, ocular history, pretreatment measures, and utilization of a new specimen collection method (i.e. ESwab) was evaluated by multivariable logistic regression.

RESULTS

Of 3395 microbial keratitis patients identified, 31% (n = 1051) had laboratory tests. Laboratory testing increased over time (slope = 2.5% per year, p < 0.001; 19.6% in 2013 to 42.2% in 2021). Laboratory negative rate increased over time (slope = 2.2% per year, p = 0.022; 48.5% in 2013 to 62.3% in 2021). Almost one-third of patients (31.2%, n = 164) were pretreated with steroids. Over two-thirds of patients were pretreated with antibiotics (69.5%, n = 367). 56.5% (n = 297) of patients were outside referrals. In multivariable regression, patients with corticosteroid pretreatment had lower odds of negative laboratory results (odds ratio [OR] = 0.49, p = 0.001). There were higher odds of negative laboratory results for every additional antibiotic prescribed to a patient prior to presentation (OR = 1.30, p = 0.006) and for specimens collected using ESwabs (OR = 1.69, p = 0.005). Age, prior eye trauma, outside referrals, and contact lens wear were not significantly associated with negative laboratory results.

CONCLUSION

More microbial keratitis associated laboratory tests are being taken over time. Over 60% of tests were negative by 2022. Factors associated with negative laboratory test results included pretreatment with antibiotics and specimens collected with the new collection method.

Corneal Specialists' Confidence in Identifying Causal Organisms of Microbial Keratitis

PURPOSE

Microbial keratitis (MK) is a potentially blinding corneal disease caused by an array of microbial etiologies. However, the lack of early organism identification is a barrier to optimal care. We investigated clinician confidence in their diagnosis of organism type on initial presentation and the relationship between confidence and presenting features.

METHODS

This research presents secondary data analysis of 72 patients from the Automated Quantitative Ulcer Analysis (AQUA) study. Cornea specialists reported their confidence in organism identification. Presenting sample characteristics were recorded including patient demographics, health history, infection morphology, symptoms, and circumstances of infection. The association between confidence and presenting characteristics was investigated with 2-sample t-tests, Wilcoxon tests, and Chi-square or Fisher's exact tests.

RESULTS

Clinicians reported being "confident or very confident" in their diagnosis of the causal organism in MK infections for 39 patients (54%) and "not confident" for 33 patients (46%). Confidence was not significantly associated with patient demographics, morphologic features, or symptoms related to MK. MK cases where clinicians reported they were confident, versus not confident in their diagnosis, showed significantly smaller percentages of previous corneal disease (0% versus 15%, p = 0.017), were not seen by an outside provider first (69% versus 94%, p = 0.015), or had no prior labs drawn (8% versus 33%, p = 0.046), and a significantly larger percentage of cases wore contact lenses (54% versus 28%, p = 0.029).

CONCLUSION

In almost half of MK cases, cornea specialists reported lack of confidence in identifying the infection type. Confidence was related to ocular history and circumstances of infection but not by observable signs and symptoms or patient demographics. Tools are needed to assist clinicians with early diagnosis of MK infection type to expedite care and healing.