ABSTRACT
Many ocular infections arise from contaminated topical ophthalmic medication most especially when standards of care are compromised during handling and administration. These infections may even be worse in situations where the eyes have sustained injury.
To assess the level of bacterial contamination of in-use ophthalmic solutions and evaluate their effects on injured eyes, 154 immediate-post-use eye drop residues were recovered from the two major hospitals in Benin City. They contained a variety of 7- antibiotics and 17–non-antibiotic drugs used for different eye conditions. These were microbiologically assessed for contamination using conventional techniques. To ascertain that the eye drops were most probably contaminated in-use, 5 unopened eye drops of different drug types were equally evaluated for sterility. In addition, preservative effectiveness of fresh eye drops was appraised by challenging 3 eye drops with 1x103 – 1x106 cfu/ml using washed isolates of Ps. aeruginosa and Staph. aureus from contaminated residues. Finally, the same isolates were used to contaminate freshly opened eye drops and 2 drops instilled into groups of rabbits eyes that were chemically injured with 1 M Sodium Hydroxide solution to induce alkali-burn corneal ulceration. Normal rabbits eyes (non-alkali burn) were similarly infected as control group.
Results showed an incidence of 10.39% contamination of the recovered eye drop residues out of which 23 different micro-organisms were isolated. The microbial load ranged between 1.8x103 – 1.4x107 cfu/ml. Most of the isolates were human flora types of Gram positive bacteria such as Bacillus subtilis(2), Staphylococcus aureus (6), Staphylococcus epidermidis (2). Gram negative bacteria such as Klebsiella pneumonia (3), Proteus vulgaris (3), Escherichia coli (1), as well as air–borne fungi, yeast (5). Of particular interest is the isolation of Pseudomonas aeruginosa (1) from one of the eye drops. The level of contamination between the antibiotic and non-antibiotic containing eye drops showed no significant difference at P > 0.05. However, comparism of contaminated eye drops recovered from wards and clinics indicated a significant difference with P < 0.05. Sterility tests on the fresh eye drops showed no growth. The contaminated eye drops therefore were ascribed to improper in-use procedures. Furthermore no viable microorganisms were detected 24 hours after fresh eye drops were opened and tested for preservative effectiveness. Ocular status of normal and injured rabbit eyes were critically and visually assessed. These showed that alkali–damaged ocular status was generally bacteria–inoculum size dependent. Eyelids were found to be generally inflamed and lacrimation was copious with higher inoculum size. Photophobia was present but more apparent was the mucopurulent discharge which was very copious with large doses of the inocula. However, there appeared to be no marked difference between the observed outcomes produced by the two organisms Ps. aeruginosa and Staph. aureus used for infecting the injured eyes. It can thus be concluded that: Eye drops can be inadvertently contaminated during use. Secondly, inherent antimicrobial property of an eye drop does not prevent it from contamination. Furthermore, incidence of eye drop contamination in the hospital wards is far higher than in the clinics and finally, the degree and extent of infection of injured eyes by contaminated eye drops is much higher than in intact eyes.
