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03 BP1 > 06 Gram Positive Organisms > Flashcards

06 Gram Positive Organisms Flashcards

1
Q

Catalase test

A

Bubble = positive = Staphylococcus

No bubble = neg = Streptococcus

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2
Q

Coagulase

A

Clotting = positive = S. aureus

No clotting = negative = S. saprophyticus / S. epidermidis

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3
Q

Susceptibility test

A

Disk diffusion test (Kirby-Bauer method)

S. saprophyticus = novobiocin resistant

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4
Q

Mannitol test

A

High salt content
Growth and yellow in color = positive = S. aureus
No growth and no yellow color = neg = not S. aureus

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5
Q

Staph culture

A 
grey-yellow = hemolytic in media = S. aureus
grey-white= non-hemolytic in media = S. epidermidis
grey = non-hemolytic in media = S. saprophyticus
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6
Q

Antigenic structures (Staph)

A

Peptidoglycan: IL1 -> complement system, PMN, neutrophil
Teichoic acid: antigenic but nonvirulent
Capsules: inhibits phagocytosis; conjugate vaccines (capsule + carrier protein)
(MSCRAMM) Protein A: adhesin to Fc of IgG, decreases opsonization and phagocytosis
(MSCRAMM) Clumping factor: adhesin fo coagulase -> fibrinogen and platelets; aggregates bacteria
Coagulase: bind with prothrombin -> fibrin on bacterial cell wall; hides bacteria

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7
Q

Enzymes (Staph)

A
  1. Catalase: H2O2 -> H2O + O2
  2. Coagulase: clotting
  3. Hyaluronidase: spreading factor, degrades ECM/CT
  4. Staphylokinase: forms plasmin -> fibrinolysis -> bacteria can enter
  5. Beta lactamase: antibiotic resistance
  6. Proteinases and Lipases
  7. Hemolysin (alpha, beta, delta, gamma)
  8. PVL + gamma hemolysin: lyse WBC; seen in MRSA; bacteriophage mediated
  9. Exfoliative toxin: dissolves mucopolysaccharide in skin; toxin a (heat stable), toxin b (heat labile)
  10. TSST1: binds with MHC II, TSS
  11. Enterotoxin: resistant to gut enzymes, heat stable, pathogenicity islands in bacteriophages
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8
Q

Pathogenesis (Staph)

A

Fomites
Normal microbiota
Food poisoning
Furuncle

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9
Q

Clinical manifestations (Staph)

A
  1. Skin and soft tissue
  2. Direct Organ Dissemination (hematogenous spread)
  3. Toxin release (food poisoning, TSS, SSSS [neonates], blood and catheter infections)
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10
Q

Classification (Strep)

A
  1. Hemolysis patterns (B = complete lysis, yellow; a = partial/incomplete lysis, dark and green; Gamma = no lysis)
  2. Specific antigens: A (S. pyogenes) B (S. agalactiae),D (Enterococcus), no group (S. pneumoniae/S. viridans)
  3. Capsular polysaccharides
  4. Biochemical tests (bile esculin, sodium hippurate, CAMP factor production, susceptibility to chemical reagents)
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11
Q

Bile-esculin test

A

For group D strep
Black = pos = Enterococcus
No black = neg = Viridans

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12
Q

Sodium Hippurate test

A

for group B (S. agalactiae)
precipitation/purple = pos = S. agalactiae
no precipitation/purple = neg = group a/b

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13
Q

Group A Strep antigenic structure

A

M protein: prevents phagocytosis, inhibits complement activation, mediates bacterial attachment, can cross react with connective cardiac tissue -> rheumatic heart disease

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14
Q

Group a strep toxins and enzymes

A
  1. Streptokinase: escape blood clots. treats pulmonary emboli and coronary artery thrombosis
  2. Deoxyribonuclease (streptodornase): positive antibody after infection
  3. Streptococcal pyrogenic exotoxins: scarlet fever, STSS
  4. Hemolysins: streptolysin s (not antigenic) O (antigenic)
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15
Q

Local invasion/exotoxin release of strep

A 
erysipela (superficial)
cellulitis (deep)
necrotizing fasciitis (Strep w M protein, cannot be phagocytosed)
puerperal fever (after fever)
bacteremia (bacteria in blood)/sepsis
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16
Q

Local infections of strep

A

strep sore throat (red tonsils)

streptococcal pyoderma

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17
Q

Systemic invasion of strep

A 
Strep Shock Syndrome (soft tissue infection -> bacteremia, M type 1 and 3, pyrogenic toxin a and b)
Scarlet Fever (pharyngitis, pyrogenic toxin a-c)
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18
Q

Post streptococcal diseases

A 
Acute glomerulonephritis
Rheumatic fever (M protein vs heart tissue = deformed valves and aschoff bodies)
19
Q

Morphology (Bacilus)

A

Saprophytic
B anthracis: - hemolysis, nonmotile
B cereus: + hemolysis, motile, food poisoning
B subtilis: contaminant

20
Q

B anthracis virulence factors

A

Capsule: virulence, antiphagocytic
Toxin: PA (protective antigen), LF (lethal factor), EF (edema factor), PA+LF (lethal toxin causing necrosis and death), PA+EF

21
Q

B anthracis clinical pathology

A 
Papules with necrotic ulcer, edema, eschar formation, inflammation
Cutaneous anthrax (spores on skin), inhalation (bioterrorism), gastric
22
Q

Types of B cereus

A

Emetic (nausea, vomiting, occasional diarrhea, found in sporulates of rise)
Diarrheal (no vomiting)
Eye infection
Localized infections

23
Q

Clostridium morphology

A

Saprophytic
C botulinum
C tetani
C perfringes

24
Q

Spore forming species

A

Bacillus (anthracis, cereus, subtilis)

Clostridium (botulinum, tetani, perfringes, difficile)

25
Q

C botulinum characteristics

A

Causes flaccid paralysis
Spores are resistant to heat, decreased in high pH
Toxin: light chain lyses SNARE proteins + heavy chain

26
Q

Types of botulism

A

Adult: eat neurotoxin

Infant/child: eat spores and it germinates in the gut

27
Q

C tetani characteristics

A

Found in soil and feces
Flagellar antigen
Tetanospasmin (neurotoxin): spastic paralysis, non invasive, A and B units

28
Q

C tetani clinical findings

A 
Difficulty swallowing
Vocal cord spasm
Opisthotonos (back arching)
Risus sardonicus (sardonic smile)
Trismus (lockjaw)
29
Q

C tetani prevention

A

Active immunization (toxoid antigen -> antibodies)
Prophylaxis with antitoxin
Wound care
Penicillin

30
Q

C perfringes toxin

A 
Clostridium perfringes enterotoxin
Intense diarrhea
Incubation period: 7-30 h
Hypersecretion in small intestines
Self-limiting
Test: stormy fermentation (coagulates the milk)
31
Q

C perfringes invasive toxin

A

a toxin: lecithinase (skin lecithin, platelet aggregation makes anaerobic environment)

32
Q

C perfringes pathology

A

Gas gangrene (clostridial myonecrosis)
COH ferments and produces gas -> cackling sounds -> distention of tissues -> compromised blood supply
Crepitation (cracking skin from gas)

33
Q

C difficile characteristics

A 
Antibiotic associated diarrhea
Psudomembranous colitis (type a = enterotoxin = watery and bloody diarrhea; type b = cytotoxin = plaques and micro-abscesses in intestine)
34
Q

Non-spore forming species

A

Corynebacterium diptheriae

Listeria monocytogenes

35
Q

C diptheriae characteristics

A 
Metachromic granules (beaded appearance)
Potassium tellurite growth (black)
Loeffler media (white)
Invasive
Toxic (toxigenicity found in bacteriophage)
36
Q

Diptheria

A

Bull neck (swollen lymphs from lymphatic edema)
Toxin produces necrotic epithelium
Psudeomembrane and bacteria grows inside nectrotic tissue

37
Q

L monocytogenes morphology

A 
Facultative anaerobe with short rods
Tumbling motility
Can survive in low temp, pH, and high salt
Catale +
Esculin +
38
Q

L monocytogenes virulence factors

A

Intracellular organism = cell-mediated immunity
Antigenic structure: O somatic antigen / H flagellar antigen
Factors: Adhesin proteins (Ami, fbp a, flagellin proteins), surface proteins (for entrance; internalin a/b, actin a), listerolysin O, iron, filopodia

39
Q

L monocytogenes pathophysio

A

adhesion (adhesin proteins) -> surface proteins for entering -> pH decreases inside vacuole due to listeriolysin O -> filopods+actin propel to another cell

40
Q

B anthracis pathophysio

A

PA binds to surface receptors -> LF+EF enter cell -> EF = edema, LF = death

41
Q

C botulinum pathophysio

A

Botulinum toxin goes to gut -> absorbed to blood -> goes to neuron -> light chain of toxin lyses SNARE SNAP protein -> no release of neurotransmitter -> flaccid paralysis

42
Q

L monocytogenes clinical findings

A

Gastroenteritis
Granulomatous infanseptica (neonatal sepsis, pustular lesions, granuloma in organs, death on delivery)
Listeria meningoencephalitis

43
Q

Actinomycetes characteristics

A

Aerobic
Chains with branches
Long cell wall with mycolic acid

03 BP1 (18 decks)

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