Biology 431 Gram (+) Cocci Chapters 22-24
Dec 22, 2015
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.