Microbial Keratitis: An Analysis Of Corneal Scrape Investigations Over Four Years. A Poster Highlighting Important Quality Improvement Lessons That Can Be Widely Applied.

Microbial keratitis is a common cause of emergency ophthalmology presentations. It can cause significant visual morbidity, and outcomes can be poor and life-changing if treated incorrectly. It is therefore crucial that appropriate investigations are undertaken to direct treatment, and that these are audited against national guidelines. Clinicians should be aware of regional and temporal changes in pathogens and sensitivities, as well as the common underlying risk factors seen in their patient cohort. Through analysing all corneal scrapes performed at our unit, over a four year period, this study aims to highlight important quality improvement lessons and recommendations that can be widely applied.

The data captured and analysed was over a four year period (August 2018 - November 2022) in a regional hospital within South West England.  

Data from all corneal scrapes performed during this period was obtained directly from microbiology, and crossreferenced with the hospital wide pathology reporting system. Corresponding patient notes were found on the electronic patient record system and note made of patient age, sex and any underlying aetiological risk factors. 

For each corneal scrape result, we extracted data on whether:

- a gram stain was performed as per national guidance

- a fungal culture was undertaken as per national guidance

- whether the cultures were positive and if so, the organism cultured, including sensitivities, as well as the panel of antimicrobials tested

- whether a PCR (polymerase chain reaction) test was also sent and whether this changed management

175 consecutive corneal scrapes were analysed. The key findings were:

- gram staining was only being performed in 70% and fungal cultures in only 68.5% despite this being outlined as a national standard. 

- 28.5% of cultures were positive. This percentage is lower than other reported rates.

- The most common organisms identified were pseudomonas, staph aureus and streptococci species. This shows some regional differences in pathogens.

- Antibiotic sensitivities reported are often not the antibiotics used clinically.

- 50% of positive PCR results changed management and acanthomeoba was only detected via PCR in this cohort.

- the most common underlying aetiological risk factor was contact lens use, accounting for 40% of corneal ulcers. 

This analysis has helped identify key lessons which can be widely applied. These include the need to ensure gram testing and fungal cultures for a complete investigation, the utility of PCR testing when suspecting acanthomoeba, and the need to work with microbiology to develop an antibimicrobial testing array/protocol that closely resembles drugs used in clinical practice, such that sensitivities reported are directly relevant to patient management. 

Though contact lens use was responsible for 40% of cases, the majority of patients (60%) had other causative risk factors, including neuropathic corneas, ocular surface disease, trauma, lid malpositions or previous grafts, highlighting the importance of a comprehensive history and examination.