Aerobic Bacterial Flora of the Normal Conjunctiva at High Altitude Area of Shimla Hills in India: a Hospital Based Study

Aim: To study the normal aerobic conjunctival flora in lower to mid Himalayan region of Shimla Hills.

Methods: Samples from normal conjunctiva of 200 individuals above the age of 13 years who visited Indira Gandhi Medical College Hospital Shimla for refraction or cataract surgery were taken by anaesthetising the conjunctival sac with sterile 4% Xylocaine solution. Samples were obtained by gently rubbing lower fornix with a sterile cotton wool swab moistened with normal saline and keeping the eye lids wide apart to avoid contamination from lid margins. It was immediately inoculated in Brain Heart infusion and subjected to standard aerobic culture and identification techniques.

Results: Totally, 72 eyes (36%) conjunctival sacs were sterile. Predominant aerobes isolated were Staphylococcus spp. in 120 (60%) followed by Haemophilus in 16 (8%), diphtheroids in 10 (5%), and Escherichia.coli (E. coli) in 4 (2%). A single aerobe was isolated from 98 eyes (49%) while 30 eyes (15%) yielded more than 1 aerobe. Staphylococcus epidermidis (S. epidermidis) was the most common bacterium, found alone in 58 eyes (29%) and in combination with another aerobe in 30 eyes (15%), followed by Staphylococcus aureus (S. aureus) in 18 (9%) and 10 eyes (5%) respectively.

Conclusion: S. epidermidis is the most common commensal organism followed by Haemophilus species. diphtheroids occupied the third position which otherwise are found more abundantly in literature. Pathogens like S. aureus, Staphylococcus citreus and E. coli were also found. Therefore, preoperative administration of topical broad spectrum antibiotics is extremely important in prophylaxis against ocular infection. The variation in microflora of normal conjunctiva in this part of world can be attributed to geographical, climatic and ethnic characteristics of the population under study.