Japanese researchers discovered a vast array of microbes on the ocular surface of Graft-vs.-host (GVHD) patients, and this diversity of microflora may be tied to the pathogenic process of chronic ocular GVHD.

Investigators researched the transformation in the composition of ocular surface microflora since evidence shows microbial diversity correlates with autoimmune disorders—but the relation of the microbial status, especially in the ocular surface, and chronic ocular GVHD is still unknown.

Researchers prospectively harvested conjunctival microorganisms from three groups: group one had 32 eyes from 20 ocular GVHD patients; group two consisted of 28 eyes from 20 non-GVHD cases that were defined as post hematopoietic stem cell transplantation and without ocular GVHD; and 20 eyes of 11 controls made up the third group. Investigators performed nonconventional culture-based methods to examine the microbial community.

The study found ocular surface microbes in the GVHD patients were more complex in diversity compared with the non-GVHD patients and the control group. Researchers found Staphylococcus species, alpha-hemo Streptococcus, Corynebacterium species, Propionibacterium acnes, Aerobic gram-positive cocci, Haemophilus influenzae and Aerobic gram-positive rod in the GVHD patients, while only a few species were detected in the other groups.

Investigators noted ocular surface microbes in the GVHD patients were more diverse than those found in non-GVHD patients and controls. “These results suggest the alternation of microbes are involved in the pathogenic process of the chronic ocular GVHD,” the researchers wrote in their study. “Further examination using state-of-the-art methods will be needed to gain greater insights into the diversity of microflora on the chronic GVHD-affected ocular surface.”

Shimizu E, Ogawa Y, Saijo Y, et al. Commensal microflora in human conjunctiva; characteristics of microflora in the patients with chronic ocular graft-versus-host disease. Ocul Surf. February 8, 2019. [Epub ahead of print].