How do biofilms contribute to antibiotic resistance?

• A. They create a protective matrix, reduce antibiotic penetration, and harbor slow-growing cells that are less susceptible.
• B. They secrete enzymes that break down antibiotics completely.
• C. They enhance drug uptake to kill competing microbes.
• D. They cause immediate lysis of embedded bacteria to release nutrients.

Answer: (A)

Biofilms resist antibiotics mainly through three linked features: a protective extracellular matrix, limited antibiotic penetration, and subpopulations of cells that grow slowly or are dormant. The matrix forms a dense barrier around the microbial community, which slows or blocks many antibiotic molecules from diffusing all the way to the cells inside. Because of the gradients of nutrients and oxygen within the biofilm, many cells enter slower growth or dormancy, making antibiotics that target active cellular processes (like cell wall synthesis or protein production) much less effective. Some cells become persisters—metabolically quiet variants that can survive antibiotic treatment and repopulate once the drug is gone. Together, these factors create a strong survival advantage for bacteria in biofilms, explaining why they’re so often hard to eradicate.