Penicillin-Streptomycin Dual Antibiotic in Animal Cell Culture: Functions and Limitations

Why animal experiments often involve cell culture

In biomedical and animal experiment-related research, many experiments begin with in vitro cell culture. Cell culture can be used for drug screening, toxicity observation, gene function research, etc., and then subsequently proceed to validation in animal models. In this process, cell culture medium is rich in amino acids, glucose, and serum components, which is equivalent to providing a very good "culture medium" for microorganisms. Therefore, bacterial contamination is a problem that laboratories frequently need to face.

To reduce interference caused by common bacterial contamination, many laboratories add a certain proportion of antibiotic combinations to cell culture media. Penicillin-streptomycin is one of the more widely used combinations, often referred to as "dual antibiotics."

What roles do penicillin and streptomycin each play?

Penicillin mainly inhibits cell wall synthesis in Gram-positive bacteria. The cell walls of these bacteria require peptidoglycan to maintain their structure. After penicillin interferes with this synthesis process, the bacteria readily rupture and die. Streptomycin mainly targets some Gram-negative bacteria. It binds to bacterial ribosomes, preventing the bacteria from synthesizing proteins normally, thereby inhibiting their growth.

Animal cells do not have cell walls, and their ribosomal structure is also different from that of bacteria. Therefore, at conventional working concentrations, penicillin-streptomycin causes relatively little direct interference to most animal cells. The combined use of the two antibiotics can cover a broader range of bacterial types, which is one reason it has become a commonly used preventive reagent.

What dual antibiotics can and cannot do

The main value of dual antibiotics lies in reducing the risk of low-dose bacterial contamination in the culture system. If a very small number of bacteria enter the culture flask during handling, antibiotics may inhibit their proliferation and allow the cells to remain temporarily stable. However, it is not a disinfectant and cannot reverse culture that has already been severely contaminated.

It is usually of limited effectiveness against fungi and mycoplasma.

It is not necessarily effective against antibiotic-resistant bacteria.

It cannot replace biosafety cabinets, sterile consumables, and standardized procedures.

In work related to animal experiments, cell status directly affects experimental results. Even when dual antibiotics are used, the color and transparency of the culture medium and cell morphology should still be observed regularly. If the culture medium suddenly becomes turbid, develops an odor, or large numbers of cells detach, contamination should first be considered, and isolation and handling should be carried out immediately.

In summary, penicillin-streptomycin is an auxiliary preventive reagent. Only by understanding the boundaries of its effects can cell culture be made more stable and provide a reliable data foundation for subsequent animal experiments.