Chapter 4: Streptococci Flashcards Preview

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Flashcards in Chapter 4: Streptococci Deck (44):
1

What cocci gram-positive bacteria does not have catalase?

Streptococci

2

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

Staphlococci

3

Beta-hemolytic streptococci

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

4

Alpha-hemolytic Streptococci

Partially lyse the RBCs, leaving a greenish discoloration

5

Gamma-hemolytic streptococci

unable to hemolyze the RBCs

6

Lancefield antigens

C carbohydrate found on the cell wall of streptococci

A,B,D most important

Strep pneumoniae and viridans do not have lancefield antigens

7

Group A beta-hemolytic streptococci

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

8

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

C carbohydrate Group A
M protein - Major source of virulence, inhibits complement and protects from phagocytosis

9

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

Streptolysin O
Streptolysin S
Pyrogenic Exotoxin
Streptokinase

10

Streptolysin O

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

11

Streptolysin S

Oxygen stabile
Responsible for beta-hemolhysis
Not antigenic

12

Pyrogenic exotoxin

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

13

Streptokinase

Activates the proteolytic enzyme plasmin which breaks up fibrin blood clots

14

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

Streptococcal pharyngitis
Streptococcal skin infections
Scarlet fever
Streptocococcal TSS

15

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

Rheumatic Fever
Glomerulonephritis

16

streptococcal pharyngitis

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

Group A beta-hemolytic streptococci

17

Streptococcal Skin infections

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

18

Necrotizing Fasciitis

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

Fournier's Gangrene

Necrotizing fasciitis involving the male genital area and perineum

Often caused by mixed organisms or by streptococcus pyogenes

20

Scarlet Fever

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

Streptococcal TSS

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

22

Rheumatic fever

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

Acute post-streptococcal glomerulonephritis

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

Group B Streptococci

Streptococcus agalactiae
Acquired during delivery

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

Pregnant women - bacteremia and sepsis

25

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?

Listeria monocytogenes
E coli
Group B streptococcus

26

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

Neisseria meningitides and Haemophilus influenzae

27

Viridans group Streptococci

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

Viridans streptococci cause what 3 main types of infections?

Dental infection: cavities
Endocarditis
Abscesses

29

What causes subacute bacterial endocarditis?

viridans Streptococcus
and Group D Streptococci

Settle on heart valves, especially valves that are previously damaged

30

What causes acute bacterial endocarditis ?

Staphylococus aureus

31

Group D streptococci

Can be alpha or gamma hemolytic
Two subgroups: enterococci and non-enterococci

32

Enterococcus

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

33

Non-enterococci

Streptococcus bovis and Equinus
Grows better in bile, can lead to Colon cancer

34

Streptococcus pneumoniae

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

35

What are the two lab tests for Streptococcus pneumoniae?

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

What are the symptoms of Streptococcus pneumoniae

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

37

What is Otitis Media caused by?

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

38

What bacteria is associated with colonic malignancies?

S. Bovis
non-enterococci

39

What is the major virulence factor for group A streptococcus?

M protein

40

What is the major virulence factor of pneumococcus?

Polysaccharide capsule

41

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

Extracellular dextran - helps them bind to heart valves

42

What is subacute bacterial endocarditis?

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

What is acute infective endocarditis?

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

44

What are the Anginosus species group?

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