What are the disadvantages of the prophylactic use of antibiotics in cell culture?

The prophylactic use of antibiotics in cell culture is generally discouraged for several important reasons.
First, antibiotics can create a false sense of security and may lead users to develop poor aseptic techniques. As a result, low‑level contaminations can occur and remain undetected for extended periods of time. These unnoticed contaminations may then spread within the laboratory and contribute to the development of antibiotic‑resistant strains. 
Second, the routine presence of antibiotics can facilitate mycoplasma infections, which are often introduced together with bacteria or fungi and are not effectively controlled by standard antibiotics. 
Finally, antibiotics are known to have direct negative effects on eukaryotic cells, including:

• reduced proliferation rates of primary cells
• altered cellular metabolism
• effects on differentiation and gene expression

These side effects can compromise experimental reliability and data interpretation. 
For a more detailed discussion, please refer to our blog article “Antibiotics in Cell Culture: Friend or Enemy?”.