Cocci Flashcards
Virulence factors of Group A streptococci
Structural: Pili; M protein (infect surfaces because of pili)
Toxins: Streptokinase (breaks blood clots, spread b/c break down blood clots); Streptodornase; Hyaluronidase; Pyrogenic toxin (cause fever); Erythrogenic toxin (red skin rash, scarlet fever)
What is the spread of streptococci from a sore throat?
Oropharynx -> tonsils; floor of mouth; middle ear; mastoids; meninges
What are the reservoirs and transmission of Group A streptococci?
From Carriers + infected patients in direct contact with a susceptible person, dogs might be carriers/reservoirs
What are some post-streptococcal conditions (2 weeks, lesions are sterile)?
- Skin infections -> recovery -> pain, blood and protein in urine = post streptococcal nephritis, autoimmune nephritis, no bacteria in kidney
- Sore throat -> recovery -> fever, arthritis, endocarditis = rheumatic fever
- Syndenham’s chorea - neurological symptoms (OCD?)
Two ways to diagnose Group A streptococcal infection
- Swab - culture - Gram stain - bacitracin sensitivity (accurate but slow)
- Rapid office tests with antibody assays (quick but less sensitive)
What are the virulence factors for Group B strep? What is the reservoir and transmission?
Structural : capsule; resistant to phagocytosis
R - genital tract of 25% of women, T - neonatal (fatal meningitis)
How do you prevent neonatal Group B strep infection? (4)
Penicillin prophylaxis if vaginal/rectal swab shows Group B, previous baby with Group B, fever or membranes ruptured for > 18 hrs
What are the virulence factors of pneumococci?
Structural: capsule - anti-phagocytic; polysaccharide antigen; stimulates opsonizing antibody; 80 types; basis of typing sera (can type which pneumonia is going around) and vaccines(no vaccines against other cocci); basis of ‘quellung’ rxn (polyvalent antibody, swelling rxn on agar plate)
Pathogenesis of bacterial pneumonia
Natural resistance to lung infections via mechanical clearance by mucus/cilia - this brings up the pneumococci and then you digest them with stomach acid, inhibition of natural resistance to lung infection (mechanical obstruction disease) smoking; virus; allergy (too much fluid being produced, can’t sweep it away); immobility; mechanical obstruction (tumors and foreign bodies); depressed cough reflex; HF
pneumococci are not very virulent, but these things cause it
How do you manage bacterial pneumonia?
Offer vaccine to susceptible groups; identify and treat the underlying cause; antibiotic sensitivity tests and offer antibiotics - now they are resistant to penicillin
Reservoir and virulence factors of viridans streptococci
Reservoir: Mouth (100% of people)
Virulence factors: Sugar-metabolizing enzymes
Pathogenesis of dental caries and endocarditis
Low MW sugars -> V. streptococci EITHER acids-> decalcification OR High MW sugars -> dental plaque -> bacteremia (biofilm, causes gum disease) -> endocarditis
Following dental surgery, can get into blood and stickiness allows them to clot the heart
What are some other ways of classifying S. aureus?
Coagulase test (clotting) -> positive OR DNAse pos., salt resistant, beta hemolytic
What are the virulence factors of S. aureus?
Structural: Protein A, Capsule, Coagulase (causes clotting, localized tissue death, stops antibiotics from geting in THEREFORE need to drain the abcess)
Toxins: DNase, enterotoxin, exfoliatin, leukocidin, TSS toxin
What is problematic with Staphlococci?
they have accumulated mutations leading to multi-drug resistance - at least 6 resistance genes, 8 strains in existence now
What types of infections are associated with Staphylococcus epidermis?
Infected piercings, fairly non virulent, sticks to plastic much more easily than metal, fairly minor.
Tend to infect catheters, no way to treat it, need to replace catheters in a timely manner
What is a minor cause of UTIs?
Staphylococcus saprophyticus, most are gram neg. e. coli
What the the virulence factors of gram - cocci?
N. Meningitidis - Structural: capsule (infects deeper tissue, can get a vaccine) Toxins: LPS
N. Gonorrhoeae - Structural: pili (attaches to surface, mucous membrane or surface tissue) Toxins: LOS
Reservoir and transmission of Gram - cocci
N. Meningitis - R- resp. tract carriers, T- droplets, prevention - vaccine
N. Gonorrhoeae- R - genital tract, chronic infection (no read carrier state), T - sexual contact and birth, Prevention - behavioral, neonatal eye drops
How can you treat Gram negative cocci?
N. Meningitis - Penicillan
N. Gonorrhoeae - NOT penicillin, (like pneumococci, gon. picked up plasmids, resistance common)
