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Medical Microbiology 16- > Lecture 18 > Flashcards

Lecture 18 Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

Virulence is determined by two properties. Which are they?

A

Invasiveness and toxigenicity

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2
Q

Recite the formula for virulence

A

V=I+T

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3
Q

Define Invasiveness

A

The ability of a microorganism to establish itself to a host.

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4
Q

What are the contributing factors or invasiveness? Name the five.

A
  1. The ability to avoid phagocytosis
  2. Production of the enzyme hyaluronidase
  3. Production of enzyme collagenase
  4. Production of the enzyme streotikinase
  5. Production of the enzyme coagulase
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5
Q

Describe the avoidance of phagocytosis in respect to the process of invasiveness. Name the two processes.

A
  1. The possession of a capsule makes a bacterial cell resistant to phagocytosis.
  2. The production of leukocidins
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6
Q

What is leukocidins

A

A substance that kill phagocytic white blood cells.

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7
Q

Describe the process of the enzyme hyalurinidase

A

Hyalurinidase degrades the hyaluronic acid which is a constituent of the glue that holds the cells together. Pathogens can spread more easily through the tissues.

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8
Q

Explain the process of the collagenase

A

Collagenase degrades collagen making easier for pathogens to spread through the tissue.

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9
Q

What is collagen

A

Collagen is a structural supporting substance in muscle, bone and cartilage.

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10
Q

Explain the role of the fibrin clot

A

In some infections, the host walls off the infection focus by the formation of this clot.

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11
Q

In the case of the fibrin clot, what does the streptococcus species produce to dissolve he clots.

A

The enzyme produced is the streptokinase

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12
Q

What is the function the enzyme coagulase?

A

Some bacteria produce this enzyme which causes the formation of fibrin clots. Pathogens producing coagulase (staphylococci) are able to cause localized infections such as boils.

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13
Q

Define toxigenicity

A

Toxigenicity is the ability of a microorganism to produce substance that are poisonous to the host’s tissues.

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14
Q

Name the two types of toxins that are produced

A

Endotoxins and exotoxins

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15
Q

True or false. Endotoxins are lipopolysaccharides

A

True

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16
Q

Are endotoxins part of the cell wall of Gram negative or Gram positive bacteria cells.

A

Gram- Negative

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17
Q

True or false. Endotoxins are not part of the outer membrane of the cell.

A

False. They are

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18
Q

During what process are endotoxins released of the bacterial cells.

A

During the bacterial cell lyse.

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19
Q

Endotoxins cause what kind of symptoms in the host.

A

Fever

20
Q

True or false. Exotoxins are soluble proteins that are produced by some Gram- negative and few Gram-positive bacteria.

A

False. Some Gram-positive and few Gram negative

21
Q

Name three examples of exotoxins

A
  1. Clostridium botulinum
  2. Clostridium tetani
  3. Colustridium diptheriae
22
Q

What exotoxin does Clostridium botulinum produce?

A

botulism

23
Q

Are exotoxins considered very toxic and potent?

A

Yes

24
Q

Is Corynebacterium diphtheriae weakly invasive or invasive and why?

A

Weakly invasive as it infects only one area of the body (throat).

25
Q

Is Corynebacterium diphtheriae virulent or not virulent

A

Highly virulent at it can spread to the entire body.

26
Q

Is Streptococcus pneumoniae toxic or not toxic?

A

Not toxic

27
Q

Is Streptococcus pneumoniae virulent or not virulent and why?

A

Highly virulent because of its invasiveness (multiply).

28
Q

Is Treponema pallidum toxic or invasive?

A

Highly invasive and not toxic.

29
Q

Is Clostridium botulinum invasive?

A

Not Invasive at all, however very virulent du to its potency of its toxins.

30
Q

Name the five principal ways pathogens are transmitted.

A
  1. Direct contact
  2. Intellect contact (dispersed on objects)
  3. Air
  4. Water and food
  5. Direct inoculation (the bites of arthropods and other animals, and wounds).
31
Q

What are blood sucking arthropods?

A

Fleas, lice and ticks.

32
Q

Name the five principal ways of a pathogens to access the host.

A
  1. Respiratory system
  2. Digestive system
  3. Broken skin
  4. Unbroken skin
  5. Genitourinary system
33
Q

Name two diseases that are known to enter by unbroken skin as a way of entry.

A
  1. Bricellosis

2. Tuleremia

34
Q

True or false, broken skin is a route of exit for the pathogen.

A

False.

35
Q

Name routes of exit for the respiratory system

A

Saliva, nasal route in the respiratory exudates, and perhaps exhalation.

36
Q

Name the routes of exit fro the digestive system

A

Feces and sometimes urine

37
Q

True or false, pathogens can leave through pus

A

True

38
Q

True or false. Pathogens can’t exit the bites of arthropods

A

False. They can

39
Q

True or false. For pathogens to be transmitted from one host to another, they must survive the passage.

A

True

40
Q

True or false. All pathogens are able to survive outside the host making their survival via the passage viable.

A

False. Some pathogens can survive better than others outside the host thus surviving the passage.

41
Q

True or false. Salmonella typhi, the causative agent of typhoid fever can not survive in hostile environments.

A

Fasle. It can survive in hostile environments for weeks

42
Q

True or false. Neissseria gonorrhoea and Treponema pallidum can rarely be transmitted to one host to another due to the fact that they are less hardy.

A

True

43
Q

Define a carrier

A

A carrier is an individual who possesses the pathogen in their body but do not demonstrate symptoms of the disease.

44
Q

Name the four possibilities in respect to a carrier of a disease and explain each.

A
  1. Incubation stage of a disease- they are about to have a clinical attack ( show symptoms).
  2. Convalescent stage of a disease
  3. No symptoms shown because they are immune
  4. No symptoms because they are mildly infected. They are called inapparent infections.
45
Q

With respect to a carrier, an individual who shows no symptoms because they are mildly infected have inapparent infections. Are these common, yes or no.

A

Yes.

46
Q

True or false. Food handlers in restaurants and processing plants can be a source of infection for the public.

A

True

Medical Microbiology 16- (17 decks)

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