This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General Microbiology Pa 1 (History, Microscopy, Stains and Structure and Physiology of Bacteria), Subject name: Microbiology
Defence mechanism by the bacteria which produce biofilm are all except? 
Select and explain. 
A. Antibiotics are expelled from the surface, B. They stick to the surface strongly, C. Antibiotics penetration into the biofilm is less, D. They protect from the inflammatory mediators
A: Antibiotics are expelled from the surface
Answer: A: Antibiotics are expelled from the surface 
Explanation: Biofilms: These are well-organised microcolonies of bacteria enclosed in self-produced extracellular polymer matrices known as glycocalyx. They are separated by water channels that remove water and deliver nutrients. Biofilm is one of the mechanisms of antibiotic resistance. They stick to the surface strongly. Antibiotics penetration into the biofilm is less. They protect from the inflammatory mediators. Efflux pumps- Expulsion of the drug from the cell soon after their entry to prevent intracellular accumulation of the drug.