Modified tissue culture medium for corneal storage I. Investigation of the effect of antibiotics on bacterial contamination.

A series of experiments were performed to determine the effect of modified tissue culture medium (MTCM), temperature, time, and antibiotics on the replication of Staphylococcus epidermidis and Pseudomonas aeruginosa. A known inoculum of the organisms (usually 10(6)/mL) was introduced, and the recovery of viable organisms was compared by different methods of culturing, including techniques of diluting, inactivating, or removing the antibiotic from the system. The invalidity of techniques that failed to remove the antibiotic from the system was substantiated. The newly developed antibiotic removal device was superior to all other culturing techniques. Penicillin G potassium was ineffective in the MTCM system, and gentamicin reagent solution was not uniformly effective against a gentamicin-sensitive strain of P aeruginosa. Placement of the MTCM at room temperature for two hours enhanced the antibacterial activity of gentamicin, although organisms may still be recovered in small numbers.