12-year analysis of the microbiological profile of infectious keratitis (IK) in Cork, Ireland.

OBJECTIVES

To determine the frequency and causative pathogens of infectious keratitis (IK) at Cork University Hospital, Ireland.

METHODS

A retrospective review was performed of IK cases undergoing corneal scraping / swabs between 2010-2022. Specimens were identified from the laboratory information system. Microbiological profiles were analysed using culture and/or polymerase chain reaction (PCR) testing for Acanthamoeba, herpes simplex virus (HSV), and varicella zoster virus (VZV).

RESULTS

A total of 319 specimens from 288 patients were analysed (mean age 52.0 ± 25.6 years). Overall, 189 specimens (60%) were culture positive. Polymicrobial growth was identified in 48 cases (15%). Of 198 isolates, the most frequently identified organisms were coagulase-negative staphylococci (33%), Staphylococcus aureus (17%), Pseudomonas aeruginosa (12%), Streptococcus pneumoniae (8%), and Gram-negative bacilli (8%). Fungal pathogens accounted for 4% of isolates, while mixed skin flora was reported in 8%. Gram staining was performed on 105 samples, with 22 positive results-68% were concordant with culture. Viral PCR testing was performed on 48 samples, identifying HSV-1 in 5 cases (10%) and VZV in 2 cases (4%). Acanthamoeba testing was performed on 387 specimens from 319 patients, with Acanthamoeba spp. detected in 33 cases (10%).

CONCLUSIONS

This is the largest study describing the microbiological profile of IK in Ireland. A high culture-positive rate (60%) with a high rate of isolation of multiple organisms (15%) were observed, likely influenced by skin commensal contaminants such as coagulase-negative Staphylococci. The proportion of Pseudomonas aeruginosa (12%) was lower than expected. No significant antimicrobial resistant isolates were identified, supporting current empiric antimicrobial treatment strategies.