Gibco™ Antibiotic-Antimycotic is used to prevent bacterial and fungal contamination. This solution contains 10,000 units/mL of penicillin, 10,000 μg/mL of streptomycin, and 25 μg/mL of Gibco Amphotericin B. The antibiotics penicillin and streptomycin prevent bacterial contamination of cell cultures due to their effective combined action against gram-positive and gram-negative bacteria. Amphotericin B prevents fungal contamination of cell cultures due to its inhibition of multi-cellular fungus and yeast.

Penicillin was originally purified from the fungus Penicillium and acts by interfering directly with the turnover of the bacteria cell wall and indirectly by triggering the release of enzymes that further alter the cell wall. Streptomycin was originally purified from Streptomyces griseus. It acts by binding to the 30S subunit of the bacterial ribosome leading to inhibition of protein synthesis and death in susceptible bacteria. Amphotericin B is an antifungal agent that prevents the growth of fungi and yeast by causing an increase in fungal plasma membrane permeability.