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MAD Exam 2 > Streptococci > Flashcards

Streptococci Flashcards

1
Q

streptococcus species - overview

A

*gram POSITIVE coccus
*grows aerobically and facultative anaerobically
*differentiated by hemolytic pattern
*short and long CHAINS
*CATALASE NEGATIVE

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2
Q

which strep strains are BETA hemolytic

A

*Group A (strep. pyrogenes)
*Group B

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3
Q

which strep strains are alpha hemolytic

A

*strep viridans
*strep pneumoniae

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4
Q

which strep strains are GAMMA hemolytic

A

*enterococcus strep

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5
Q

strep pyrogenes (Group A Strep - GAS) overview

A

*colonizes oropharynx, esp of children
*can cause suppurative and nonsuppurative infections
*infections range from minor (pharyngitis) to life threatening (necrotizing fasciitis)

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6
Q

strep pyogenes - virulence factors

A

*lipotechoic acid
**M protein
*capsule
*streptococcal pyrogenic exclusions (Spe)
*streptolysins & streptokinase
*DNases A to D

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7
Q

streptococcal pyrogenic exclusions (Spe) - virulence factor of S. pyogenes

A

*exotoxins & superantigens
*produced by lysogenic strains
*responsible for the rash of scarlet fever, toxic shock, and necrotizing fasciitis

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8
Q

DNases A to D - virulence factor of S. pyogenes

A

depolymerize free DNA that is present in pus

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9
Q

strep pyogenes - pathophysiology

A

*acquired through respiratory droplets, direct contact, or fomite
*colonizes and attaches to oropharyngeal mucosa or other mucous membranes
*IMMUNITY through M protein specific immunoglobulin

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10
Q

what is the best host defense (immune response) against strep pyogenes

A

antibodies against the M protein!

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11
Q

strep pyogenes - suppurative clinical infection

A

-pharyngitis
-scarlet fever
-pyoderma
-erysipelas
-cellulitis
-necrotizing fasciitis
-streptococcal toxic shock syndrome
-bacteremia & septic shock

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12
Q

necrotizing fasciitis (s. pyogenes)

A

deep infection of skin that involves destruction of muscle and fat layers

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13
Q

streptococcal toxic shock syndrome

A

multiorgan systemic infection resembling staph toxic shock syndrome, but pts are bacteremic and have evidence of fasciitis
*Spe gets T cells so revved up that cytokine production can’t maintain homeostasis

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14
Q

strep pyogenes - non-suppurative infections

A

-rheumatic fever
-post-strep glomerulonephritis

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15
Q

non-suppurative infection: rhematic fever & strep pyogenes

A

*complication following streptococcal PHARYNGITIS
*antibody against M protein cross-reacts with host cell structural proteins (antigenic mimicry)
*can cause inflammation of heart structures, joints, CNS, subcutaneous tissues

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16
Q

diagnosis of rheumatic fever & post-streptococcal glomerulonephritis

A

anti-DNAase, - ASO or hyaluronidase antibodies

17
Q

non-suppurative infection: post-streptococcal glomerulonephritis & strep pyogenes

A

*complication following streptococcal CELLULITIS
*antigen-antibody complexes deposit in the glomeruli, causing renal dysfunction

18
Q

diagnosis of strep pyogenes

A

*culture & gram stain (looking for beta hemolysis and gram + cocci in chains)

19
Q

strep agalactiae (Group B Strep - GBS)

A

*robust capsule (type-specific capsular polysaccharides)
*gram positive in chains
*beta hemolytic
*catalase negative

20
Q

group B strep - virulence factors

A

***polysaccharide capsule (most important - helps avoid opsonization, interferes with phagocytosis, etc)

21
Q

group B strep - epidemiology

A

*normal flora of lower human intestine and vagina
*colonization of neonates upon birth, which can cause disease in the babies

22
Q

what is the most common cause of meningitis in babies in the first month of life

A

group B strep

23
Q

group B strep infection in adults

A

*usually in older adults with comorbidities
*presents as pneumonia, bacteremia, etc

24
Q

prevention of Group B Strep

A

*screen ALL pregnant women (vaginal PCR or culture)
*if positive, we treat mom and baby with antibiotics

25
Q

enterococcus (group D strep)

A

*GAMMA hemolytic
*short chains of gram positive cocci
*can live in bile and high salt concentrations

26
Q

enterococcus - virulence

A

*ability to adhere to tissue and form biofilms
*antibiotic resistance

27
Q

enterococcus - clinical infection

A

**usually in immunocompromised individuals
*skin and soft tissue
*bloodstream catheter
*urinary tract
*prosthetic and native valve endocarditis

28
Q

strep viridans

A

*ALPHA hemolytic
*gram positive cocci in short chains
*part of the normal flora of oropharynx, periodontal areas, large intestine, and vagina

29
Q

strep viridans - infections

A

*dental caries
*periodontal disease
*endovascular
*native (damaged) and prosthetic valve endocarditis
*prosthetic joints

MAD Exam 2 (37 decks)

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