326mbaresp - RESPIRATORY BACTERIAL DISEASES- those that...

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RESPIRATORY BACTERIAL DISEASES- those that affect the upper (oropharynx, nasopharynx) and lower (bronchi, lungs) respiratory tract Streptococci Most important pathogen (frank)- Group A Streptococcus, (Streptococcus pyogenes) Encounter and entry of Group A Streptococcus into host 1. Oropharyngeal (asymptomatic carriage) up to 20% in school-aged children; others have pharyngitis 2. Spread by aerosols or direct (skin - skin, hand to mouth) contact (occasionally contaminated food) 3. Adherence- adhesin-lipoteichoic acid in cell wall are complexed to M protein which also binds to fibronectin host protein 4. Skin or mucous membrane colonization usually remains localized, but can spread easily to deeper tissues Virulence factors 1. M protein- antiphagocytic- fibrinectin bound to coat bacterium's outer surface; strains lacking it are readily opsonized and phagocytosed; Ab to M protein is able to opsonize, but 80 different M proteins exist (b/c of great gene duplication and mutation) 2. Hyaluronic acid capsule- host cannot make Ab against
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326mbaresp - RESPIRATORY BACTERIAL DISEASES- those that...

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