One of the most important aids in the diagnosis of external diseases of the eye is the isolation and identification of the causative organism. Material for cultures, especially from the cornea, is usually obtained after the application of a topical anesthetic. It is therefore important to be aware of the effects of topical anesthetics on bacterial growth.
Topical anesthetics in multidose vials contain a preservative which is chosen for its antibacterial and antifungal properties; such preparations should not be used before material for culture is obtained.
Studies by Erlich have shown that tetracaine in a concentration of 0.05% will inhibit Staphylococcus aureus and Monilia.1 Murphy et al found that 0.5% tetracaine is toxic to Pseudomonas.2 Burns suggests that 0.4% benoxinate hydrochloride or 5% cocaine is less likely to inhibit bacterial growth than 0.5% proparacaine hydrochloride or 0.5% tetracaine hydrochloride.3 This is contradictory to Schlegel and Swan, who
KLEINFELD J, ELLIS PP. Effects of Topical Anesthetics on Growth of Microorganisms. Arch Ophthalmol. 1966;76(5):712-715. doi:10.1001/archopht.1966.03850010714017