Periodontal Pathogenesis and Host Response Flashcards

Which bacterium is considered the 'keystone pathogen' in periodontal disease because it disrupts host immunity disproportionate to its low abundance?

Answer: Porphyromonas gingivalis

P. gingivalis is the keystone pathogen that, even at low colonization levels, subverts innate immunity and reshapes the entire subgingival microbiome toward a dysbiotic state.

Socransky's 'red complex,' the bacterial group most strongly associated with severe periodontitis, consists of which three organisms?

Answer: P. gingivalis, T. forsythia, T. denticola

Socransky's red complex comprises Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola — organisms consistently co-detected in deep periodontal pockets with bleeding.

What is the primary role of Fusobacterium nucleatum within the subgingival biofilm community?

Answer: Bridge organism linking early colonizers to late-colonizing pathogens

F. nucleatum acts as a bridge species, co-aggregating with both early colonizers (streptococci) and late-colonizing pathogens (red complex), allowing the mature pathogenic biofilm to assemble.

Leukotoxin A (LtxA), a major virulence factor that lyses PMNs and macrophages, is uniquely produced by which periodontal pathogen?

Answer: Aggregatibacter actinomycetemcomitans

Aggregatibacter actinomycetemcomitans produces leukotoxin A, which selectively kills human leukocytes bearing the LFA-1 integrin, allowing the organism to evade immune clearance.

Which feature of the subgingival biofilm most contributes to its resistance to systemic antimicrobial agents?

Answer: Extracellular polysaccharide matrix that limits drug penetration and shields bacteria

The extracellular polymeric substance (EPS) matrix of the biofilm impedes antibiotic diffusion, reduces metabolic activity of embedded bacteria, and enables horizontal gene transfer for antibiotic resistance.

Gingipains produced by Porphyromonas gingivalis primarily function to:

Answer: Degrade host defense proteins and cleave complement to evade immunity

Gingipains are cysteine proteases that degrade immunoglobulins, complement proteins, and cytokines, effectively disabling multiple arms of the host immune response.

In Socransky's microbial complexes, which complex serves as the 'bridge' between early colonizers and the pathogenic red complex?

Answer: Orange complex

The orange complex (including F. nucleatum, P. intermedia, P. nigrescens, and others) bridges the early yellow/green colonizers and the late red complex, facilitating ecological succession to a pathogenic biofilm.