Masks Not Associated with Microbial Keratitis Agents

Microbiological profile of infectious keratitis unchanged during COVID-19 pandemic. Dermot McGrath reports.

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Microbiological profile of infectious keratitis unchanged during COVID-19 pandemic. Dermot McGrath reports. The long-term use of face masks does not seem to promote significant changes in the microbiological-causes of infectious keratitis, a recent Portuguese study concludes. “Most of the microorganisms identified in our study are known commensals of the upper respiratory tract or pathogenic agents associated with respiratory infections. However, our results did not significatively differ from the ones previously published in 2019 regarding the microbiological profile of infectious keratitis in our tertiary centre in Porto, Portugal, from 2009 to 2018,” said Mário Lima Fontes MD. Microbial keratitis (MK) is the most common non-surgical ophthalmic emergency ocular infection. Its potential causes are bacteria, fungi, viruses, or parasites and can rapidly progress, causing irreversible sight loss. Discussing the study’s background, Dr Lima Fontes noted the COVID-19 pandemic introduced profound changes in daily habits, including the frequent use of face masks. There have been observations of an increasing number of patients presenting with dry eye symptoms among regular mask users with no history of ocular surface pathology. “Numerous reports from around the world pointed to an increase in dry eye symptoms due to an upwards route of the exhaled air over the ocular surface. Therefore, we speculated this mechanism could have led to a change in the microbiological profile of infectious keratitis,” he said. Dr Lima Fontes and co-workers carried out a retrospective study based on a survey review of electronic medical records of all patients with presumed infectious keratitis between March 2020 - when the first cases of COVID-19 were identified in Portugal – and October 2021. A total of 194 samples from the same number of patients were included, with a 43% culture-positive rate. The mean age at diagnosis was 49 years, and 54% of the patients were female. Bacteria accounted for 83% of all positive scrapes (61% were Gram positive and 35% were Gram negative), fungi for 12%, and acanthamoeba for 4%. The most frequent Gram-positive agent identified was Corynebacterium macginleyi (23%), followed by staphylococcus aureus (17% each) and streptococcus pneumoniae (8%). The Gram-negative bacteria pseudomonas aeruginosa was found in 17% of cultures. Various strains of candida comprised the main fungi identified in 12% of cases, followed by acanthamoeba in 3.5%. The most common ophthalmologic risk factors identified were the use of contact lenses (41%), previous ocular trauma (12%), and history of corneal ulcers (9%). Diabetes (8%) and poor systemic status/multiple comorbidities (5%) were the most frequent systemic associations. Summing up, Dr Lima Fontes said while most of the organisms identified in the study were known commensals of the upper respiratory tract, there was no evidence that the widespread use of face masks during the pandemic had significantly altered the root causes of infectious keratitis. “The long-term use of face masks does not seem to promote significant changes in the microbiological causes of infectious keratitis,” he said. Dr Lima Fontes presented the study at the ESCRS Virtual Winter Meeting 2022. Mário Lima Fontes MD is an ophthalmology resident at São João University Hospital, Porto, Portugal, and a PhD candidate in Metabolism at Faculty of Medicine of the University of Porto, Portugal. u014996@chsj.min-saude.pt