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CMMRS > Chapter 4: Streptococci > Flashcards

Chapter 4: Streptococci Flashcards

1
Q

What cocci gram-positive bacteria does not have catalase?

A

Streptococci

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2
Q

What cocci gram positive bacteria are round in clusters and have catalase?

A

Staphlococci

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3
Q

Beta-hemolytic streptococci

A

Completely lyse RBC, leaving a clear zone of hemolysis around the colony

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4
Q

Alpha-hemolytic Streptococci

A

Partially lyse the RBCs, leaving a greenish discoloration

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5
Q

Gamma-hemolytic streptococci

A

unable to hemolyze the RBCs

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6
Q

Lancefield antigens

A

C carbohydrate found on the cell wall of streptococci

A,B,D most important

Strep pneumoniae and viridans do not have lancefield antigens

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7
Q

Group A beta-hemolytic streptococci

A

Streptococcus pyogenes
Pus-producing
Strep throat, scarlet fever, rheumatic fever, poststreptococcal glomerulonephritis

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8
Q

What are the components of the cell wall of Group A beta-hemolytic streptococci that are antigenic?

A

C carbohydrate Group A

M protein - Major source of virulence, inhibits complement and protects from phagocytosis

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9
Q

What are the enzymes that contribute to Group A beta-hemolytic streptococci pathogenicity ?

A

Streptolysin O
Streptolysin S
Pyrogenic Exotoxin
Streptokinase

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10
Q

Streptolysin O

A

Inactivated by oxygen, destroys red and white blood cells
Reason for Group A beta-hemolytic streptococci hemolytic ability
antigenic

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11
Q

Streptolysin S

A

Oxygen stabile
Responsible for beta-hemolhysis
Not antigenic

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12
Q

Pyrogenic exotoxin

A

Only found in a few strands of Group A beta-hemolytic streptococci
leads to scarlet fever
Directly superstimulate T cells to pour out inflammatory cytokines –>streptococcal TSS

Acquired by lysogenic conversion

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13
Q

Streptokinase

A

Activates the proteolytic enzyme plasmin which breaks up fibrin blood clots

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14
Q

Group A beta-hemolytic streptococci causes what four diseases by local invasion and/or exotoxin release?

A

Streptococcal pharyngitis
Streptococcal skin infections
Scarlet fever
Streptocococcal TSS

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15
Q

Group A beta-hemolytic streptococci causes what 2 Delayed antibody mediated diseases?

A

Rheumatic Fever

Glomerulonephritis

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16
Q

streptococcal pharyngitis

A

Strep throat with red swollen tonsils and pharynx, purulent exudate on the tonsils, high temp, and swollen LNs

Group A beta-hemolytic streptococci

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17
Q

Streptococcal Skin infections

A

Folliculitis,
pyoderma: Pustule on extremity or face, forms thick crust, heals slowly, leaves depigmented area
erysipelas: superficial skin, dermis only (raised, bright red rash with sharp border)
cellulitis,
Impetigo: vesicular, blistered, eruption (most common in children) crusty and flaky around mouth

Group A beta-hemolytic streptococci

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18
Q

Necrotizing Fasciitis

A

Flesh-eating
M-proteins block phagocytosis
Follow path along fascia btwn subQ and muscle
Swelling, heat, redness moves rapidly
Red–>blue skin change 24 hours later with large blisters

Group A beta-hemolytic streptococci

19
Q

Fournier’s Gangrene

A

Necrotizing fasciitis involving the male genital area and perineum

Often caused by mixed organisms or by streptococcus pyogenes

20
Q

Scarlet Fever

A

Group A beta-hemolytic streptococci
pyrogenic toxin/erythrogenic toxin

Fever, scarlet-red rash
Rash begins on trunk and neck then spreads to extremities

FACE is spared

21
Q

Streptococcal TSS

A

Pyrogenic toxin
Similar to scarlet fever
TSS is similar to the one caused by staphylococcus aureus
Group A beta-hemolytic streptococci

22
Q

Rheumatic fever

A

Uncommon
Usually strikes children 5-15
Follows untreated pharyngitis by Group A beta-hemolytic streptococci
Fever, myocarditis, joint swelling (acute migratory polyarthritis)
chorea (dance-like moves)
Subcutaneous nodules
Rash - erythema marginatum

Ags in heart similar to Ags of strep

23
Q

Acute post-streptococcal glomerulonephritis

A

Occurs one week after infection of pharynx or skin by nephritogenic strains of Group A beta-hemolytic streptococci

Puffy face (retention of fluids)
Darker urine (hematuria - tea)
Hypervolemia (cause HTN)
Sore throat or skin infection one week prior

24
Q

Group B Streptococci

A

Streptococcus agalactiae
Acquired during delivery

Neonatal meningitis, pneumonia, spesis
Symptoms of meningitis: fever, vomiting, poor feeding and irritability

Pregnant women - bacteremia and sepsis

25
Q

What are the three bacteria that are responsible for most meningitis acquired by the baby coming out of the birth canal within the first 3 months of age?

A

Listeria monocytogenes
E coli
Group B streptococcus

26
Q

What are the two bacteria that cause meningitis later in life after the maternal Abs passively given to fetus wane?

A

Neisseria meningitides and Haemophilus influenzae

27
Q

Viridans group Streptococci

A

Big, heterogeneous group of streptococci that are not identified based on one Lancefield group
Most alpha-hemolytic causing greenish-yellow discoloration

Normal human GI tract flora found in nasopharynx and gingival crevices

28
Q

Viridans streptococci cause what 3 main types of infections?

A

Dental infection: cavities
Endocarditis
Abscesses

29
Q

What causes subacute bacterial endocarditis?

A

viridans Streptococcus
and Group D Streptococci

Settle on heart valves, especially valves that are previously damaged

30
Q

What causes acute bacterial endocarditis ?

A

Staphylococus aureus

31
Q

Group D streptococci

A

Can be alpha or gamma hemolytic

Two subgroups: enterococci and non-enterococci

32
Q

Enterococcus

A

Faecalis and faecium
Normal flora
Variably hemolytic
UTI, biliary tract infection, bacteremia, subacute bacterial endocarditis
2nd-3rd most common cause of HA-infection

33
Q

Non-enterococci

A

Streptococcus bovis and Equinus

Grows better in bile, can lead to Colon cancer

34
Q

Streptococcus pneumoniae

A

No Lancefield antigen;
MAJOR cause of pneumonia and meningitis in adults and otitis media in children
Pneumococci
Major virulence: polysaccharide capsule

35
Q

What are the two lab tests for Streptococcus pneumoniae?

A

Quellung reactions -> pneumococci on a slide smear are mixed with a small amount of anti-serum and methylene blue, capsule will swell

Optochin sensitivity ->Optochin is added, Strep pneumoniae will be inhibited; Strep viridans will continue to grow

36
Q

What are the symptoms of Streptococcus pneumoniae

A

Shaking and chills, high fevers, chest pain with respirations, shortness of breath

37
Q

What is Otitis Media caused by?

A

Streptococcus pneumoniae, haemophilus influenzae, moraxella (decreasing order of infection)

38
Q

What bacteria is associated with colonic malignancies?

A

S. Bovis

non-enterococci

39
Q

What is the major virulence factor for group A streptococcus?

A

M protein

40
Q

What is the major virulence factor of pneumococcus?

A

Polysaccharide capsule

41
Q

What are the major virulence factors of Strep viridans and Lancefield group D?

A

Extracellular dextran - helps them bind to heart valves

42
Q

What is subacute bacterial endocarditis?

A

SBE is the slow growth and piling up of bacteria on the heart valve
Slowly develops low-grade fever, fatigue, anemia, and heart murmurs secondary to valve destruction

43
Q

What is acute infective endocarditis?

A

Abrupt onset of shaking chills, high spiking fevers, and rapid valve destruction

44
Q

What are the Anginosus species group?

A

Streptococcus intermedius group
part of normal GI tract flora
Hate oxygen
Found in abscesses in brain or abdominal organs
If in blood, suspect there is an abscess hiding somewhere

CMMRS (27 decks)

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