Streptococci Flashcards
alpha hemolytic streptococci?
s pneumo, s mutans, and s viridans
beta hemolytic streptococci?
strep pyogenes (GAS), strep agalactiae (GBS)
gama (non hemolytic) streptococci?
enterococcus
- gram positive cocci arranged in chains
- normal flora of skin and mouth
- facultative anaerobes
- catalase negative
streptococci
- present in mucosal epithelium of URT or epidermis
- transmission via direct contact or respiratory droplets (sneezing and coughing)
- invades mucus membrane of new host
GAS S. pyogenes
- most common bacterial infection of the throat
- organisms persist 1-4 weeks w/o treatment
- treat with penicillins
acute streptococcal pharyngitis
- complication of GAS pharyngitis
- produces SpeA/SpeC exotoxins
- diffuse erythematous sandpaper rash on chest
- raw strawberry tongue, desquamation
- circumoral pallor around moth
- can lead to rheumatic fever or glomerulonephritis
scarlet fever
skin infections of group A strep pyogenes?
- impetigo: young kids 2-5
- erysipelas: raised bright red plaques with sharply defined borders
- wound infections, cellulitis
- toxic shock syndrome and necrotizing fasciitis
Group A strep pyogenes virulence factors?
- M protein
- hyaluronic acid capsule (non antigenic)
- streptolysin O: pore forming toxin, lyses target cells
- Spe: superantigen causes scarlet fever and toxic shock syndrome
- streptokinases
drug of choice for strep throat?
amoxacillin
drug of choice for GAS strep pyogenes cellulitis?
penicillin, ceftriaxone
drug of choice for bacteremia/toxic shock syndrome due to GAS strep pyogenes?
penicillin + clindamycin (suppresses toxin production)
diagnosis of strep throat?
RADT of group A capsule antigen, culture if negative for more sensitivity
- encapsulated
- group B antigen
- Beta hemolytic, weakly
- colonization of GI and GU tracts
GBS s. agalactiae
- person to person transmission
- bacteremia, skin and soft tissue infections, pneumonia, endocarditis
- risk factors: diabetes, cancer, kidney disease, advanced age
GBS disease in adults
- normal vaginal flora
- prenatal screening cultures at 35-37 WGA
GBS
- pneumonia, meningitis, sepsis
- risk factors: maternal colonization, premature rupture of membranes
- early onset or late onset
GBS disease in neonates
GBS virulence factors?
polysaccharide capsule, adhesins, c5a peptidase inhibits neutrophils, beta hemolysin, CAMP factor
drug of choice for group B strep meningitis/bacteremia?
penicillin G
drug of choice for GBS endocarditis?
penicillin G + gentamycin
DOC for GBS neonates?
ampicillin + gentamycin
- alpha hemolytic
- commensal and opportunistic pathogen (subacute endocarditis, intra abdominal abscesses, dental caries)
- bind fibrin platelet aggregates at damaged heart valves
- resistant to optochin and bile insoluble
strep viridans
- gram positive lancet shaped coccus growing in pairs or short chains
- carbohydrate capsule
- naturally competent for DNA transformation
- transmission via respiratory droplets
- bacteremia higher in African Americans and native Americans
strep pneumonia
- most common cause of CAP
- common cause of sinusitis and otitis media
- can develop into meningitis in children
- respiratory viral infection a predisposing factor
strep pneumonia
- aspiration of bacteria and replication in alveolar spaces
- 1-30 day incubation
- abrupt onset of fever and shaking chills
- pleurisy, productive cough, blood tinged sputum
- bactermia
pneumonia
risk factors for pneumonia?
antecedent viral infection (esp influenze), smoking, age less than 2 or greater than 65, hematologic disorders, asplenia, COPD, diabetes
atypical walking pneumonia?
slow onset, moderate fever, non productive cough
strep pneumonia virulence factors?
polysaccharide capsule, C polysaccharide present in urine and serum
strep pneumonia toxins?
pneumolysin toxic to bronchial epithelial cells, autolysin degades peptidoglycan, IgA protease
lab diagnosis of strep pneumonia?
- lancet shaped gram (+) diplococci
- bile soluble, optochin sensitive (Kirby Bauer testing)
- Quellung reaction visualizes capsule
- C polysaccharide: capsular anitgen detected in CSF or urine
treatment of strep pneumo?
- penicillin
- vancomycin
- fluoroquinolone + 3rd gen cephalopsorin (tax, tri, taz)
strep pneumo prevention?
- Pneumovax PPSV23: adults >65, chronically ill, immunocompromised
- PCV7 prevnar, PCV13
- E faecalis and E faecium most common
- cell wall modification to D-lactate
- group D streptococcus
enterococcus
- opportunistic pathogen
- subacute endocarditis
- biliary tract infections, UTIs
enterococcus
enteroccocus virulence:
- growth in 6.5% _____ or 40% _____
- high level antibiotic resistance often encoded on ________
NaCl, bile salts
conjugative plasmids
enterococcus lab tests?
- non hemolytic, grows in presence of high salt and bile salts
- positive reaction with group D antisera
enterococcus treatment?
penicillin, vancomycin, or ampicillin + beta lactamase inhibitor
