Microbial contamination of in-use ocular medications
O. D. Schein, P. L. Hibberd, T. Starck, A. S. Baker and K. R. Kenyon
Dana Center for Preventive Ophthalmology, Wilmer Institute, Johns Hopkins University, Baltimore, Md 21205.
Two hundred twenty in-use medications from 101 patients with nonmicrobial
ocular surface disease were studied by culturing the bottle caps, a drop
produced by simple inversion, and the interior contents removed sterilely.
Conjunctival cultures were taken from these patients and 50 age-matched
controls. Pathogenic organisms were harvested from conjunctivae
significantly more frequently (P less than .01) from cases (34 of 101) than
from controls (five of 50). Sixty-four medications (29%) had microorganisms
cultured from at least one medication site. Gram-negative organisms were
significantly more likely (P less than .00001) to be isolated from all
medication sites than gram-positive organisms. Additionally, when isolated
from medication sites, the gram-negative organisms were highly likely to be
cultured from the conjunctiva as well. This was not true for pathogenic
gram-positive organisms. We conclude that a cycle of contamination between
in-use medications and conjunctivae may represent an important risk factor
for microbial keratitis in patients with ocular surface disease.
