Biology 431Gram (+) CocciChapters 22-24

StaphylococcusMajor groups - coagulase (+) aureus vs. (-) others.

External Structures

Capsule - polysaccharide, 11 serotypes, antiphagocytic

Peptidoglycan endotoxin-like - fever, WBC, complement

Teichoic acid binds host mucosal fibronectin receptors

Protein A - binds IgG, prevents Ab clearance

Toxins - mostly aureus

Cytotoxins (A, B, D, G) - hemolytic, mostly WBC/RBC

Exfoliative - protease, target skin desmosomes…

causes SSSS/neonates; impetigo/nosocomial, AIDS…

Enterotoxins (50%) - 8 different, acid/heat-stable, Sag

TSS (15%) - tampon-associated, invasive and SAg

Flesh-Eating/Invasive Enzymes - most aureus

Catalase: neutralize H2O2, metabolic or phagocytic

Hyaluronidase: hydrolyze connective tissue, spread

Lipase: survival in sebaceous areas, invasion

Fibrinolysin/Staphylokinase: dissolve fibrin clots

Penicillinase: plasmid-passed antibiotic resistance

Coagulase: covered in lab

Other aureus Diseases - Most Hematogenous

Enterocolitis - C. difficile-like, long-term antibiotics

Bacteremia - bacteria in blood, 50% nosocomial

Endocarditis - 50% fatal rapid deterioration

Pneumonia - several, all associated with abscesses

Osteomyelitis - bone infection, pain, high fever

Non-aureus Diseases

UTI - mostly saprophyticus, lab

Endocarditis - mostly epidermidis and lugdunensis…

Native heart valves - malformed, genetic, disease

Nosocomial plastic devices, prosthetics - 1 year later

StreptococcusHemolysis subgroups - lab

External Structures - pyogenes

Capsule - polysaccharide, Lancefield (surface A-G)…

pyogenes = Group A - 10% weight, NAG/rhamnose

M Protein - 100 types, antiphagocytic/opsonization

Lipoteichoic acid binds host mucosal fibronectin

Other Virulence Factors - pyogenes

Pyrogenic Exotoxins - SAg, toxic shock, rash, fever…

Streptolysin - hemolytic for RBC, WBC - more in lab

Streptokinase - lysis of fibrin clots, disease spread

DNAse - nucleases, target pus to reduce viscosity

C5a Peptidase - destroys key complement protein

Outcomes - pharyngitis, varying skin infections, Scarlet & Rheumatic Fever/Arthritis, glomerulonephritis.

agalactiae - Group B, beta hemolyticHistorically puerperal sepsis - childbirth, war woundsCurrently - neonatal septicemia, pneumonia, meningitis

Group B Carbohydrate - NAG/rhamnose/galactose

Colonize lower GI & GU, 10-30% pregnant women GU

60% infants colonized, increases with premature or prolonged delivery; post-delivery infection possible.

pneumoniae - Nongroupable, alpha hemolytic

Diseases: pneumonia, sinusitis, otitis, meningitis

Polysaccharide capsule - 90 types, antiphagocytic

IgA protease - digests IgA, prevents binding

Pneumolysin - digests cholesterol, pores

Pneumococcal vaccine, anti-capsule for 23 strains

Viridans group also nongroupable - cavities, endocarditis.

Enterococcus Will not cover extensive list of others, Table 24.1-2

Enterococcus - Virulence, Disease, Treatment

Surface adhesin protein - bind GI and vaginal mucosa

Secrete - hemolysins, proteases, bacteriocins

Inherently resist many antibiotics; serious nosocomial...

UTI, surgical (peritoneum/heart), blood (endocarditis)

Careful antibiotic selection, use - new drug development

gallinarum more prominent human GI flora; faecalis more disease-associated.