Emerging Microbial Trends That Could Affect Your Practices

The end isn’t nigh, but challenges do lurk beyond the horizon. In a recent presentation, Kyung Sun Na MD, PhD outlined the three primary emerging trends in the microbial sphere that ophthalmology needs to contend with: the microbiome and its impact on human health, antimicrobial resistance, and environmental changes.

The ocular surface was once excluded from the microbiome as a ‘low biomass niche,’ Professor Na said. However, she added it is now known that commensal microbiota in the eye play an important role in immune tolerance, metabolism, and normal mucosal barrier function.

“The microbiome, tear film, and immune response work together to control ocular surface homeostasis,” she explained. “Current research indicates that the lacrimal gland should also be included in the microbiome as it controls the ocular surface’s immune reaction and resulting inflammation.”

She further explained microbiome changes in disease show a reduction in Gram-positive organisms, a relative increase in Gram-negative organisms, and “a trend towards a decrease in alpha diversity.” The last point is particularly apparent in dry eye disease, where alpha diversity is falling; however, the presence of Corynebacterium and Staphylococcus aureus is increasing.

Regarding microbial resistance, Prof Na noted ophthalmology has yet to escape the effects of COVID-19, adding there has been a shift in the microbiological profile of bacterial keratitis, both during and after the pandemic, with a higher resistance observed in Staphylococcus epidermidis, Corynebacterium spp., and Streptococcus spp. to fluoroquinolones.

“We can see that antimicrobial resistance dropped significantly during the COVID-19 pandemic and has not returned to pre-COVID-19 levels,” Prof Na said. “This is apparent in resistance to gatifloxacin, which is commonly used in ophthalmology, and growing resistance to it [in the treatment of] Staphylococcus epidermidis, Corynebacterium spp., Streptococcus spp., and Pseudomonas.”

Turning to the third trend, Prof Na discussed how environmental factors are affecting diseases like infectious keratitis. As global temperatures continue to rise and more regions adopt a more tropical climate, the incidence and spectrum of pathogens involved in infectious keratitis intensify.

Increased travel and cultural exchanges in the wake of the pandemic are also facilitating the appearance of pathogens once considered rare as well as others new to science. Prof Na pointed to the 2024 outbreak of microsporidial keratoconjunctivitis in Japan and patients receiving corneal ulcer diagnoses as a result of monkeypox virus infections as examples.

“Air quality is also an important issue. Corneas exposed to particulate matter showed early perforation and thinning after infection with Pseudomonas aeruginosa,” Prof Na said.

“New infectious threats and antimicrobial resistance are constantly emerging. Multidisciplinary collaboration and global cooperation are essential to stay ahead.”

Prof Na presented at the 2025 EuCornea congress in Prague.

Kyung Sun Na MD, PhD is a professor at the Catholic University of Korea’s College of Medicine, Seoul. drna@catholic.ac.kr