Gram + Cocci Infections Flashcards
Step pyogenes
Group A Strep
Reservoir: throat, skin
Transmission: direct contact, respiratory dropltes
Pathogenesis: M-protein (antiphagocytic), Hyaluronic Acid, Streptolysin O (titers often used for rheumatic fever)
Spreading Factors: Streptokinase, Streptococcal DNAse, Hyaluronidase, Exotoxins A-C (casuse fever & rash in scarlett fever)
Diseases: Pharyngitis, Scarlett Fever, Pyoderma, Impetigo
Sequelae: Rheumatic fever (after pharyngitis only), acute glomerulonephritis (M12 serotype)
Treatment: Penicillins, Macrolids w/ allergy
Strep agalactiae
Group B strep
Reservoir: vagin, GI tract
Transmission: birth canal
Pathogenesis: capsule, CAMP factor
Disease: neonatal septicemia & meningitis (most common causual agent)
Treatment: Ampicillin w/ aminoglycoside/cephalosporin
Prevention: prophylactic tx of mother before delivery (ampicillin/penicillin)
Strep pneumoniae
Diploccoci
Reservoir: Upper respiratory tract
Transmission: respiratory droplets
Predisposing factors: COPD, CHF, alcoholism, asplenia, antecedent viral infxn
Pathogensis: Polysaccharide capsule (major virulence factor), IgA protease, teichoic acid
Diseases: Pneumonia (rusty sputum), adult meningitis, otitis media, sinusitis- most common cause for all
Lab dx: Quelling rxn: positive (for specific organisms w/ capsule), latex agglutinination test for capsular ag in CSF
Prevention: VACCINE given to all children (pneumococcal conjugate vaccine), adults at risk (pneumococcal polysaccharide vaccine)
Viridians Strep (S. sanguis, S. mutans)
Reservoir: oropharynx
Transmission: endogenous
Pathogenesis: dextran (biofilm) mediated adherence
Disease: dental caries, infective endocarditis (subacute- asoc w/ dental work, prosthetic heart valves, poor oral hygeine)
Enterococcus (E. faecalis, E. faecium)
Group D
Reservoir: colon, urethra, female genital tract
Transmission: endogenous
Pathogenisis: Bile/salt tolerance allows for survival in bowel & gall bladder
Disease: Urinary & biliary infxn, Infective (subacute) endocarditis in elderly w/ damaged heart vavles
Treatment: some strains carry vancomycin resistance (VRE)
