Bacterial Flora Changes in Conjunctiva of Rats with Streptozotocin-Induced Type I Diabetes

The microbiota of both humans and animals plays an important role in their health and the development of disease. Therefore, the bacterial flora of the conjunctiva may also be associated with some diseases. However, there are no reports on the alteration of bacterial flora in conjunctiva of diabetic rats in the literature. Therefore, we investigated the changes in bacterial flora in bulbar conjunctiva of rats with streptozotocin (STZ)-induced type I diabetes.

A high dose of STZ (60 mg/kg, i.p.) was injected into Sprague-Dawley (SD) rats to induce type I diabetes mellitus (T1DM). The diabetic rats were raised in the animal laboratory and at 8 months post-injection of STZ swab samples were taken from the bulbar conjunctiva for cultivation of aerobic bacteria. The bacterial isolates were identified by Gram staining and biochemical features. The identified bacteria from both diabetic and healthy rats were then compared.

The diabetic and healthy rats had different bacterial flora present in their bulbar conjunctiva. In total, 10 and 8 bacterial species were found in the STZ and control groups, respectively, with only three species (Enterococcus faecium, Enterococcus gallinarum and Escherichia coli) shared between the two groups. Gram-positive bacteria were common in both groups and the most abundant was Enterococcus faecium. However, after the development of T1DM, the bacterial flora in the rat bulbar conjunctiva changed considerably, with a reduced complexity evident.

STZ-induced diabetes caused alterations of bacterial flora in the bulbar conjunctiva in rats, with some bacterial species disappearing and others emerging. Our results indicate that the conjunctival bacterial flora in diabetic humans should be surveyed for potential diagnostic markers or countermeasures to prevent eye infections in T1DM patients.