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Bacteriology > Gram Positive Rods > Flashcards

Gram Positive Rods Flashcards

1
Q

Which three gram positive rods are endospore formers?

A

1) Bacillus anthracis
2) Bacillus cereus
3) Clostridium

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2
Q

Which two gram positive rods are regular rods that do not form spores?

A

1) Listeria monocytogenes (food-borne pathogen)

2) Erysipelothrix rhusiopathiae (rare zoonotic/skin infection)

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3
Q

Which three gram positive rods are classified as irregular/pleomorphic?

A

1) Corynebacterium diphtheria
2) Mycobacterium/Propionibacterium/Actinomyces (Anaerobes)
3) Nocardia asteroides

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4
Q

Which virulence factor of Bacillus cereus causes projectile vomiting, nausea, and cramping

A

Emetic enterotoxin/cerulide toxin

Binds 5-HT (serotonin) receptor, stimulating the afferent vagus nerve

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5
Q

T/F B. cereus emetic enterotoxin is heat-stable and proteolysis-resistant

A

TRUE

It is for this reason that it can be found in cooked rice/pasta dishes

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6
Q

T/F Emetic gastroenteritis caused by B. cereus toxin is classified as an infection

A

FALSE

It is classified as an intoxication because only the toxin (no organism) is consumed,

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7
Q

What virulence factor of Bacillus cereus causes symptoms of diarrhea, nausea, and cramps about 24 hours after ingestion that last for about a day?

A

Diarrheal enterotoxin.

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8
Q

T/F B. cereus diarrheal enterotoxin can be eliminated from contaminated food when it is cooked

A

TRUE

B. cereus diarrheal enterotoxin is a heat labile protein complex that can be destroyed when the food it contaminates is cooked.

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9
Q

_____ is a hemolysin produced by B. cereus that punches holes in cell membranes of erythrocytes?

A

Cereolysin

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10
Q

What two virulence factors produced by B. cereus act as spreading factors, allowing the organism to disseminate throughout the tissue by degrading skin, etc.?

A

Collagenase & Serine protease

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11
Q

What are the four diseases B. cereus can cause?

A

1) Emetic gastroenteritis (intoxication by cerulide toxin consumed in pasta/rice dishes)
2) Diarrheal gastroenteritis (Infection with cells or spores in undercooked/uncooked food)
3) Panopthalmitis (contamination of a penetrating ocular wound)
4) Disseminated infections (septicemia, CSF infxn, lung infxn, necrotizing skin lesions from collagenases/serine proteases)

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12
Q

Extreme overdose of B. cereus emetic enterotoxin can lead to _____ because it can impair _____

A

Liver failure

Emetic enterotoxin can impair mitochondrial fatty acid metabolism

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13
Q

What four groups are susceptible to disseminated infection by B. cereus?

A

1) Immucompromised
2) IVDU
3) Pts. w/ exposed wounds
4) Pts. w/ indwelling shunts

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14
Q

T/F Fecal cultures are useful in diagnosing B. cereus infxns?

A

FALSE

Not useful because B. cereus can be found as regular gut flora

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15
Q

What test differentiates B. cereus from the other gram positive rods?

A

Spore stain

Gram(+) AND positive pore stain = B. cereus

Gram(+) only = other Bacillus species

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16
Q

What is the treatment for systematic/skin infxns by B. cereus (4 options)?

A

1) Vancomycin
2) Clindamycin
3) Gentamicin
4) Ciprofloxacin

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17
Q

T/F Beta-lactams may be used in the treatment of B. cereus

A

FALSE

B. cereus produces beta-lactamase

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18
Q

Listeria monocytogenes is an _____ pathogen, making it protected from innate defenses, complement system, and abx. What type of immunity is important in combating Listeria because of this?

A

Intracellular pathogen

Cell-mediated immunity

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19
Q

Which virulence factor of Listeria induces phagocytosis of Listeria? What does this factor bind to?

A

Internalin A (InlA)

Binds to E-cadherin

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20
Q

What virulence factor of Listeria allows it to escape the phagosome before its fusion with the lysosome? How does this factor work?

A

Listeriolysin O (LLO)

LLO is a hemolysin that punches holes in cell membrane

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21
Q

What hemolysin produced by Listeria acts synergistically with LLO to help Listeria escape the phagosome? What does this virulence factor disrupt to accomplish this?

A

Phospholipase C

Disrupts signal transduction pathways

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22
Q

What virulence factor of Listeria directs host cell actin to polymerize behind it, propelling it, and allowing it to move from cell to cell?

A

ActA

Lagniappe: The movement from cell to cell reduces its exposure to the humoral immune response

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23
Q

What three groups are especially susceptible to Listeria?

A

1) Fetuses
2) Neonates
3) Immunocompromised adults

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24
Q

In what kind of products does Listeria thrive?

A

Contaminated refrigerated products (grows well at 4 degrees Celsius)

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25
Q

T/F The symptoms of Listeria emerge quickly

A

FALSE

Listeria begins with flu-like symptoms or GI problems (cramps, diarrhea) before progressing to full blown symptoms

26
Q

Pregnant women infected with Listeria may be asymptomatic, but the fetus may be infected, causing _____, fetal death, or miscarriage. How does Listeria access the fetus?

A

Granulomatosis infantiseptica

Listeria can cross the placenta

27
Q

Listeria infxn presents as _____ or _____ in the immunocompromised

A

Septicemia or meningitis

28
Q

Gram stain of blood or CSF reveals _____

A

Short gram(+) rods

29
Q

When cultured on blood agar, Listeria demonstrates a _____ pattern of hemolysis due to LLO and other toxins.

A

Beta hemolysis

30
Q

When grown in broth cultures at 20 degrees Celsius, Listeria demonstrates a characteristic _____ generated from is flagellum.

A

Tumbling motion

31
Q

What are the three treatment options for Listeria?

A

1) Ampicillin + gentamicin (synergism)
2) Amoxicillin
3) Bactrim (sulfamethoxazole + trimethoprim)

Drugs must be able to cross into eukaryotic cells

32
Q

T/F Listeria is an obligate intracellular organism

A

FALSE

Its entrance into host cells is only a method of immune evasion

33
Q

Diphtheria toxin has two subunits linked by _____. The A-subunit has a _____, while the B-subunit has _____ regions

A

Diphtheria toxin has two subunits linked by DISULFIDE BONDS The A-subunit has a CATALYTIC DOMAIN, while the B-subunit has TRANSLOCATION AND RECEPTOR BINDING regions.

34
Q

What is the host cell receptor for the B-subunit of Diphtheria toxin? What does the binding of this subunit initiate?

A

Heparin binding epidermal growth factor (HB-EGF)

Binding initiates endocytosis of the organism

35
Q

When _____, the A-subunit of Diphtheria toxin enters the cytoplasm. Once here, function does the A-subunit have?

A

When the pH of the endocytic vesicle drops, the A-subunit enters the cytoplasm.

Here, it catalyzes ADP-ribosylation of EF2, shutting down protein synthesis, resulting in cell death.

36
Q

The A-subunit of DTx catalyzes _____, stopping _____, which causes _____.

A

Catalyzes ADP-ribosylation of EF2, stopping protein synthesis, which causes cell death

37
Q

T/F DTx is encoded in the bacterial chromosome

A

FALSE

DTx is encoded by a lysogenic phage, not C. diphtheriae

38
Q

_____, an iron responsive protein, is encoded by C. diphtheriae. What effect do iron levels have on this protein?

A

Diphtheria Toxin Repressor

Increased levels of iron decreases the amount of toxin produced

39
Q

How is C. diphtheriae spread?

A

Respiratory route or direct contact

40
Q

What symptom of Diphtheria is pathognomonic for the disease?

A

Exudate in the throat that forms a pseudomembrane

41
Q

What are the symptoms of Diphtheria? When do they appear?

A

Fatigue, myalgia, sore throat 2-6 days after infection

42
Q

The distinctive lymphadenopathy caused by Diphtheria, so called because of its appearance, is known as _____.

A

Bull neck

43
Q

T/F Diphtheria exists exclusively as a local infection

A

FALSE

Diphtheria can disseminate through the blood. 1/10 pts. will die from a heart-related infxn

44
Q

The very rare cutaneous form of Diphtheria manifests as a _____

A

Chronic non-healing ulcer

45
Q

Diphtheria appears as _____ on a stain of nasopharyngeal sample.

A

Club shaped pleomorphic rods (Chinese symbols)

46
Q

_____ are polyphosphate storage for Diphtheria, and are seen as pink inclusion bodies

A

Metachromati granules

47
Q

The _____ for toxigenic Diphtheria is based on antigen-antibody precipitation on filter paper soaked in antibodies.

A

Elek test

48
Q

T/F A Diphtheria strain showing precipitation on an Elek test has not received the gene for DTx from a lysogenic phage

A

FALSE

Precipitation on an Elek Test demonstrates the production of DTx by the strain. Because DTx is encoded by a lysogenic phage and not in the bacteria itself, precipitation on an Elek Test tells you the organism MUST have received the gene from a lysogenic phage.

49
Q

T/F Diphtheria is susceptible to penicillin and erythromycin

A

TRUE

50
Q

What is used as passive immunization for Diphtheria? Hint: There is a potential for serum sickness because of the source of passive immunization.

A

Horse anti-toxin

51
Q

T/F The vaccination for Diphtieria covers other organisms.

A

TRUE

The diphtheria vaccine (DTaP) covers tetanus and pertussis as well.

52
Q

The Schick Test is used to test an individual’s immunity to DTx. If the patient has no reaction, then _____. If the patient has a reaction of localized edema and necrosis then _____

A

No reaction: You have protective antibodies to DTx

Reaction (localized edema and necrosis): Time to get a booster

53
Q

Nocardia asteroides is found worldwide in _____.

A

Soil and water

54
Q

N. asteroides grows in _____ macrophages

A

Non-activated macrophages

55
Q

N. asteroides spreads by _____.

A

Inhalation of dirt/dust

56
Q

N. asteroides causes _____ in the immunosuppressed

A

Bronchopulmonary disease

57
Q

T/F Diagnosis of N. asteroides infxn can be accomplished by evaluation of sputum or abscess material

A

TRUE

58
Q

What appearance characterizes N. asteroides when it is cultured on blood agar?

A

Orange, waxy, wrinkled colonies

59
Q

T/F N. asteroides appears as filamentous slender rods that are non-acid-fast

A

FALSE

N. asteroides does appear as filamentous slender rods, but they are PARTIALLY acid-fast, not non-acid-fast.

60
Q

What two treatment options are available for infxns by N. asteroides?

A

1) Sulfonamides

2) Amikacin + Beta-lactam

Bacteriology (19 decks)

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