Efficacy of penicillin G, cefazolin, and gentamicin in M-K medium at 4 degrees C.

Corneal-scleral shells are routinely stored in McCarey-Kaufman (M-K) medium at 4 degrees C. Antibiotics are added to the medium to suppress bacterial growth. We examined the antibacterial activity of penicillin G potassium, 100 microgram/ml, cefazolin sodium, 100 microgram/ml, and gentamicin sulfate, 20 microgram/ml against test organisms in M-K medium at 4 degrees, 23 degrees, and 37 degrees C for periods up to 18 hours. Within the limits of the experimental conditions, none of the antibiotics used could be relied on to sterilize an inoculum of sensitive bacteria in M-K medium at 4 degrees C, the recommended storage temperature.