Gram + Bacteria Flashcards
S. Aureus Lab Algorithm
Gram +
Cocci in Clusters
Catalase +
Coagulase +
S. Aureus Virulence Factor, Main Toxin, and Colonization
Virulence Factor: Protein A (binds Fc-IgG, inhibiting complement and phagocytosis)
Toxin: TSST (binds MHCII and TCR, inducing T cells)
Colonization: Commonly colonizes the nose and skin
S. Aureus Diseases (2 main ones)
Inflammatory Disease (skin, organs, pneumonia, endocarditis, osteomyelitis) Toxin-mediated disease (toxic shock:TSST1, scalded skin:exfoliative toxin, food poisoning:entertoxins)
Staph epidermidis Lab Algorithm
Gram + Cocci in clusters Catalase + Coagulase - Novobiocin sensitive
Staph epidermidis Pathology and Flora
Infects prothetic devices and intravenous catheters by producing adherent biofilms
Component of normal skin flora (contaminates blood cultures)
Staph saprophyticus Lab Algorithm and Presentation
Gram + cocci in clusters, catalase +, coagulase -, novobiocin resistant
Second most common cause of uncomplicated UTI in young women (first is E. coli)
Staphylococcus epidermidis and saprophyticus Treatment
Needs to include Vancomycin
Streptococcus pyogenes Lab Algorithm
Gram + cocci in chains, catalase -, beta hemolytic,
Strep pyogenes (Group A) Lab Algorithm
Gram + cocci in chains, catalase -, beta hemolytic, bacitracin sensitive
ASO titer detects regent infection
Strep pyogenes Presentation (3 Main Categories)
Pyogenic: pharyngitis, cellulitis, impetigo
Toxigenic: scarlet fever, toxic shock-like
Immunologic: rheumatic fever, acute glomerulonephritis
JONES Criteria for rheumatic fever
Polyarthritis Carditits Subcutaneous nodules Erythema marginatum Sydenham chorea
Scarlet Fever
Caused by toxins (exotoxin A?) secreted by Strep pyogenes
Scarlet rash with sandpaper-like texture
Strawberry tongue (also kawasaki)
Circumoral pallor
M Proteins
These are proteins on Strep pyogenes
Antibodies to M proteins enhance host defenses against Strep pyogenes, but also can give rise to rheumatic fever
Strep agalactiae (Group B) Lab Algorithm
Gram + cocci in chains, catalase -, beta hemolytic, bacitracin resistant
Strep agalactiae Presentation
Colonizes vagina
Can cause pneumonia, meningitis, and sepsis in babies
Produ
Strep agalactiae Presentation
Colonizes vagina
Can cause pneumonia, meningitis, and sepsis in babies
Produces CAMP factor (enlarges S aureus hemolysis)
Pregnant women screened at 35 weeks and positive cultures receieve intrapartum penicillin prophylaxis
Strep pneumoniae Lab Algorithm
Gram + cocci in chains (diplococci?), catalase -, alpha hemolytic, optochin sensitive
Lancet-shaped
Strep pnuemoniae Presentation
Associated with a "rust colored sputum" Most common cause of: Meningitits Otitis media (in children) Pneumonia Sinusitis
Strep pneumoniae Virulence Factor
IgA protease (cleaves IgA in order to colonize respiratory mucosa) Polysaccharide Capsule
Strep pneumoniae Lab Algorithm
Gram + cocci in chains (diplococci?), catalase -, alpha hemolytic, optochin sensitive, bile soluble (lysed by bile)
Lancet-shaped
Strep pneumoniae Virulence Factor
IgA protease (cleaves IgA in order to colonize respiratory mucosa) Polysaccharide Capsule
Viridans Group Streptococci Lab Algorithm
Gram + cocci in chains, catalase -, alpha hemolytic, optochin resistant, bile insoluble (not lysed by bile)
Viridans Group streptococci Presentation
Normal flora of the oropharynx
Cause dental caries (mutans)
Cause subacute bacterial endocarditis and damaged valves (sanguinis–makes dextrans which bind to fibrin-platelet aggregates on damaged valves)
Viridans Group streptococci Presentation
Normal flora of the oropharynx
Cause dental caries (mutans)
Cause subacute bacterial endocarditis and damaged valves (sanguinis–makes dextrans which bind to fibrin-platelet aggregates on damaged valves)