Microbial keratitis: Causative organisms, susceptibilities and trends at a tertiary eye hospital in South Africa

Background: Microbial keratitis is a sight-threatening disease. Empiric management is based on current regional microbial sensitivity patterns. Aim: This study aimed to describe the demographics and microbial patterns of keratitis at St John Eye Hospital and compare it with data from the same centre 10 years prior. Setting: A tertiary eye care centre in Soweto, South Africa. Methods: A retrospective cross-sectional study of the microbiological reports of patients treated for microbial keratitis between 01 January 2018 and 31 December 2018. Results: The median age of patients was 42 years (interquartile range [IQR]: 3–77) with a male predominance of 57.0% (n = 65/113). Culture positivity rate was 63.0% (n = 84/133). There was a predominance of Gram-positive organisms of 63.0% (n = 84/133). The most common Gram-positive organism was coagulase-negative Staphylococcus (CNS) (32.0%, 42/133), and the most common Gram-negative organism was Pseudomonas aeruginosa (6.0%, 8/133). Other common organisms were Staphylococcus aureus (14.0%, 18/133), Streptococcus pneumoniae (9.0%, 12/133) and Streptococcus viridans (5.0%, 6/133). Commonly used fluoroquinolones ciprofloxacin and moxifloxacin had resistance of 4.2% and 10.0%, respectively. Gentamicin had a resistance of 5.8%. Culture positivity rate increased compared to 2008 from 52% to 63%. There was an increase from 2008 to 2018 of Pseudomonas aeruginosa from 2% to 6%. There was little change in antibiotic resistance profiles between the two study periods (2008 and 2018). Conclusion: Culture positivity rate has increased at our institution and suggests improvements in detecting organisms and antibiotic susceptibilities. There does not seem to be any change in the susceptibilities of organisms between the study periods; therefore, it suggests current empiric management remains appropriate.