Bacteria in gingivitis change from aerobic Gram-positive to which of the following as disease progresses?

Correct answer: C. Motile anaerobic Gram-negative

• A. Facultative anaerobic Gram-positive bacteria predominate in health — the pathogenic shift is toward motile anaerobic Gram-negative organisms.
• B. The shift is toward ANAEROBIC Gram-negative — not aerobic Gram-negative.
• C. As gingivitis progresses to periodontitis, the subgingival microbiome shifts from aerobic Gram-positive cocci to anaerobic, Gram-negative motile rods/spirochetes. Key pathogens: P. gingivalis, T. forsythia, T. denticola (Red Complex).
• D. Non-motile Gram-positive anaerobes are associated with healthy sites, not progressive periodontal disease.