Flashcards in Streptococci Deck (44):
3 main gram positive cocci that cause disease
Streptococcus, Enterococcus, and Staphylococcus
What is main host defense of GPC (gram positive cocci)?
Phagocytosis (mainly) and neutrophils
Collection of pus in a body cavity, especially pleural cavity
General characteristics of streptococci
Reservoir for pneumococcus
Nasopharynx / throat
Transmission of pneumococcus
Strep pneumoniae morphology
Lancet-shaped (elliptical) diplococci
Hemolysis for strep pneumoniae
O2 conditions for pneumoniae
Grow better w/ 10% CO2 (capnophile)
How do you differentiate pneumococcus from Strep Viridans?
Both are Gram positive and alpha hemolytic. Pneumococcus is highly susceptible to Optochin disk (Cu compound). Strep viridans is NOT.
What is most common childhood illness?
Acute otitis media from Strep pneumoniae
Major host defense against pneumococcus
Phagocytosis, augmented by IgG
Effect of capsule in pneumococcus
Antiphagocytic by inhibiting complement opsonization (C3b)
Stimulates intense inflammatory response
Main immunogen (Ab detection)
Conjugated vaccine uses capsule
Can’t make Abs to opsonize / phagocytose organisms; includes myeloma, lymphoma, leukemia, and nephritic syndrome
Who gets pneumococcal vaccine?
Children (> age 2), elderly, immunocompromised.
Which diseases caused by pneumococcus are resistant to penicillin?
Meningitis and bacteremia
Tx for otitis media
Amoxicillin or erythromycin
Tx for sinusitis
Amoxicillin-clavulinate or FQ
Tx for Meningitis
Ceftriaxone + Vancomycin
Risk factors for acquiring penicillin-resistant pneumococcal infection
Prior becta-lactam AB therapy (amoxicillin / oral cephalosporins)
Contact w/ kids in daycare
Exposure to healthcare setting
Recent respiratory infection
Beta hemolytic strains
Group A, B, C, or G
Based on C-polysaccharide (in cell wall)
What test is used to rule out GAS?
Alpha hemolytic strains
How do you differentiate?
Strep viridans and Strep pneumoniae
Optochin testing (pneumococcus is vulnerable)
What test is used to rule out Group D strep?
Bile esculin test
What determines Lancefield groupings?
What determines Lancefield typings?
Group A Strep
5-10% of people are carriers in throat, skin, anus, and vagina
Transmitted via air or direct contact
Susceptible hosts to GAS
College students, military recruits, neonates, post-partum women, damaged skin (burns, measles, chickenpox, impetigo), surgery
Function of Lipoteichoic acid and Protein F
Mediate attachment to epithelial cells by binding to fibronectin
Cause of scarlet fever
GAS erythrogenic toxin (exotoxin) is produced after virulence factor is added by lysogenic phage.
Location of rash
Caused by GAS
Erythema / edema w/ well-demarcated edges
Most common in kids and elderly
More common on legs than face
Caused by GAS
Erythroderma, strawberry tongue, skin desquamation
What 2 strains cause Toxic Shock Syndrome and which is worse?
GAS is worse than Staph aureus
GAS Toxic Shock Syndrome
Initial site of infection?
Complications (4 things)
Most often due to soft tissue infection or bacteremia
May cause necrotizing fasciitis, strep gangrene, bacteremia, or shock
Tx w/ penicillin and surgical debridement
Due to which strain?
Location of prior infection
Prophylaxis for RHD
Due to GAS
Jones Criteria: 2 major or 1 major + 1 minor + lab evidence of GAS
Due to prior pharyngitis (not skin)
Tx w/ aspirin, steroids, or penicillin
Prophylaxis w/ penicillin or sulfadiazine
Location of prior infection
Typically skin infection (sometimes pharyngitis)
Most common in kids
Sxs: oliguria (due to renal failure), dark urine, hematuria, proteinuria, seizures, HTN, edema.
Only supportive tx
Which AB is GAS highly susceptible to?
Group B Strep
Asymptomatic colonization of genital tract and lower GI tract. 30% of women are carriers in vagina.
Diseases: #1 cause of bacterial sepsis in newborns. Can also cause puerperal sepsis (in pregnant mother). SSTIs / UTIs in diabetics.
Capsule interferes w/ phagocytosis and complement activation
Tx w/ pencillin. Vancomycin if allergic.
2 main types of Group D Strep
Enterococci and Non-Enterocci (Strep bovis)
E. Faecalis and E Faecium
Major cause of nosocomial infections. Grow in bile and salt. Catalase negative
Reservoir: soil, food, water, animals. Normal microbiota of GI and Gyn tracts.
Transmission: endogenous, contact, surfaces
Risk factors: invasive devices, broad spectrum AB's, surgery, >60 y/o
Antigens – adhesins and bacteriocins inhibit competing flora
Diseases: catheter-associated UTI's, endocarditis, surgical infections (especially after colonic / vaginal surgery).
Does NOT cause pneumonia
Tx w/ ampicillin or vancomycin (however resistance is growing). Linezolid / Daptomycin if VRE.
2 other names
Non-enterococci, Strep gallolyticus
Associated w/ colon cancer
Penicillin is tx of choice. Erythromycin / vancomycin if allergic.
Normal microbiota of where?
Normal microbiota of mouth, GI, and GU
Causes dental carries, bacteremia, and SBE
Tx for GAS endocarditis
Penicillin + gentamicin (aminoglycoside)