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Biofilm Antimicrobial Resistance — MFDS Part 1 MCQ

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ModerateMicrobiologyBiofilm Antimicrobial ResistanceMFDS Part 1

Compared with genetically similar planktonic cells, bacteria in an established dental plaque biofilm often show markedly reduced susceptibility to antimicrobial agents. Which combination best explains this biofilm-associated tolerance?

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Correct answer: B — Matrix-mediated binding or delayed penetration, nutrient-linked slow growth, and persister phenotypes

Explanation lettering: C = shown as A · A = shown as B · D = shown as C · B = shown as D

A is correct. Biofilm-associated antimicrobial tolerance is multifactorial. The extracellular polymeric matrix may bind or delay penetration of some agents, while oxygen and nutrient gradients produce slow-growing cells that are less susceptible to antimicrobials targeting active cellular processes. Phenotypically tolerant persister cells can survive exposure and repopulate the biofilm. This does not require universal inherited resistance mutations, so B is incorrect. Bacteriophages are not the primary protective mechanism, excluding C. Biofilms contain metabolically heterogeneous populations rather than uniformly inactive bacteria, excluding D. Increased individual bacterial size or universally thickened cell walls does not account for the characteristic biofilm effect, excluding E.

Reference: Liu HY, Prentice EL, Webber MA. Mechanisms of antimicrobial resistance in biofilms. npj Antimicrobials and Resistance. 2024;2:27. https://pubmed.ncbi.nlm.nih.gov/39364333/