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KMMS > Microbiology to know for AKT > Flashcards

Microbiology to know for AKT Flashcards

1
Q

Should an asymptomatic person who tests positive for MRSA (nasal swab) while in hospital receive treatment?

A

Yes. The patient should receive eradication with shampoos/nasal creams to protect those around him, and to prevent him from becoming sick with
overgrowth of his current MRSA should his immune system become compromised by
another illness or if antibiotic treatment removes competing commensals.

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2
Q

Which of the following statements best describes a Staphylococcus Aureus infection?
a. S. aureus is not a commensal organism.
b. S. aureus is a coagulase negative bacterium.
c. Ricardo ideally should be moved into a
side room, and the bay he was sleeping in
previously should be deep cleaned.
d. If he does not approach any of the other patients, Ricardo cannot pass on the infection.
e. S. aureus has adhesin proteins, which bind the Fc region of IgG (Fab) to disrupt their function and Protein A, which helps the bacterium adhere to host proteins as well as evade the immune system.

A

a. S. aureus is not a commensal organism. Incorrect. 30% of the population have S.
aureus on their skin; 10% of this is MRSA.
b. S. aureus is a coagulase negative bacterium. Incorrect. Staph Aureus is Coagulase
positive. Coagulase stimulates clotting and plays a role in immune evasion.
c. Ricardo ideally should be moved into a side room, and the bay he was sleeping in
previously should be deep cleaned. Correct. It is important that the chain of infection
is broken. Cleaning items which may act as fomites will prevent indirect transmission
to other patients. In practice, this rarely due to lack of side rooms and patients are
barrier nursed.
d. If he does not approach any of the other patients, Ricardo cannot pass on the
infection. Incorrect. He can still pass it on by indirect transmission. Therefore, he
needs to be moved into a side room or barrier nursed so that he is not touching items
that other patients will then be handling.
e. S. aureus has adhesin proteins, which bind the Fc region of IgG (Fab) to disrupt their
function and Protein A, which helps the bacterium adhere to host proteins as well as
evade the immune system. Incorrect. S aureus has both; however, the functions are
reversed.

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3
Q

Staph aureus is coagulase

A

positive

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4
Q

What action does coagulase have in bacteria?

A

Coagulase stimulates clotting and plays a role in immune evasion.

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5
Q

What do adhesion proteins do, such as those found in Staph aureus?

A

Adhesion proteins help the bacterium adhere to host proteins as well as
evade the immune system.

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6
Q

What the function of Protein A in Staph aureus bacteria?

A

Protein A binds the Fc region of IgG (Fab) to disrupt their function.

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7
Q

Time elapsed between exposure to a pathogen

and developing symptoms.

A

Incubation period

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8
Q

The presence of bacteria on a body surface

without causing harm.

A

Bacterial colonisation

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9
Q

A symbiotic relationship in which one population
derives benefit and the other is neither harmed
nor benefits.

A

Commensalism

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10
Q

Molecules produced by a pathogen that

increase its’ effectiveness at causing disease.

A

Virulence factors

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11
Q

An infection that does not produce symptoms

unless activated but may still be transmissible.

A

Latent infection

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12
Q

An infection caused by multiplication of an

organism that was already present in the body.

A

Endogenous infection

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13
Q

The mechanism by which latent infections begin

to multiply and spread.

A

Reactivation

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14
Q

An infection caused by invasion by a bacterium

from the environment.

A

Exogenous infection

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15
Q

A commensal bacteria of anterior nares

A

Staph aureus

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16
Q

Which type of bacteria forms “golden colonies” on blood agar?

A

Staph aureus

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17
Q

Microscopic appearance/staining of Staph aureus?

A

Gram positive cocci in clusters

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18
Q

What percentage of the population are carriers of Staph aureus?

A

20-60%

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19
Q

What virulence factors of S.aureus provide (host) tissue adherence and immune evasion “cloaking?”

A

Adhesion proteins

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20
Q

Elastin-binding protein, collagen-binding protein, and fibronectin binding protein are examples of

A

Adhesion proteins

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21
Q

Surface proteins such as adhesion proteins are associated with which growth phase of bacteria?

A

Exponential (log) growth phase

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22
Q

Secreted proteins of S. aureus are associated with which growth phase of the bacteria?

A

Stationary phase

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23
Q

How does the capsule of S. aureus play a role in evading the immune system (preventing opsonisation?)

A

It blocks antibodies from binding to antigens such as the peptidoglycan layer, and also by binding of cell wall opsonins to complement receptors and Fc region of antibodies blocks opsonisation

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24
Q

Commonest cause of bacteraemia?

A

Staph aureus

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25
Q

These cytotoxins
-Pore-forming toxins, lyse host cells
- PVL- lyses immune cells
Are associated with what type of bacteria?

A

Staph aureus

26
Q

Staph aureus’s exfoliative toxins (Proteases) target what type of proteins?

A

The exfolative toxins target epidermal structural proteins

27
Q

Enterotoxins are also known as

A

superantigens

28
Q

How does our IMMUNE system respond to enterotoxins from Staph aureus?

A

Stimulate massive T cell activation and immune invasion

29
Q

What type of illness is produced when Staph aureus (a strain with enteroxins) is ingested?

A

Food poisoning
Rapid, brief illness
+++vomiting
Minimal diarrhea

30
Q

Staph aureus virulence factors:

Substances involved in adherence to nasal mucosa?

A

Adhesions

31
Q

Staph aureus virulence factors:

Ability to invade tissues? (2)

A

Cytotoxins and enzymes

32
Q

Staph aureus virulence factors:

What two things help the bacteria evade immune clearance?

A

Protein A and polysaccharide capsule

33
Q

Lipoteichoic and teichoic acid are found in what type of bacteria- gram positive or gram negative?

A

Gram positive

34
Q

What substance do gram negative bacteria have in their outer membrane?

A

Lipopolysaccharide

35
Q

Which branch of our immune system is very sensitive to lipopolysaccharide?

A

Innate

36
Q

Lipopolysaccharide interacts with ______-_____ receptors (esp TLR4) on monocyte/macrophage lineage cells, as well as endothelium

A

Toll-like

37
Q

_______________ interaction with toll-like receptors results in activation of inflammatory pathways, coagulation and clotting pathways, and changes endothelial integrity

A

Lipopolysacharride

38
Q

What is the main reason why people get very sick with gram negative infections?

A

The lipopolysaccharide acts as an endotoxin in the blood, which produces a systemic activation of immune responses

39
Q

Do gram positive bacteria have endotoxins?

A

No

40
Q

Lipoteichoic acid and peptidoglycan are components of what type of bacterial cell wall?

A

Gram positive

41
Q

Neisseria meningitidis produces what disease?

A

Meningococcal septicaemia

42
Q

A non-blanching “purpuric” rash (glass test) is indicative of what type of infection?

A

Meningococcal septicaemia

43
Q

N.meningitidis has adhension proteins that adhere to which two host tissues?

A

Respiratory epithelium and meninges

44
Q

What three components contribute to pathogenicity of N.meningitidis?

A
  1. Adhesions
  2. LPS
  3. Capsule
45
Q

In microscopy, the N.meningitidis __________ is the result of shedding endotoxin

A

blebbing

46
Q

Pneumococcal pneumonia shows what type of bacteria under the microscope?

A

Gram-positive diplococci (pneumococcus)

47
Q

What bacteria has specific adhesions for respiratory mucosa, pneumolysin, secretory IgA protease, and a capsule?

A

Streptococcus pneumoniae

48
Q

This virulence factor binds host cell membrane cholesterol, forms pores and lyses in ciliated cells, and lyses host phagocytic cells

A

Pneumolysin

49
Q

This substance breaks down secreted IgA, preventing mucosal clearance

A

Secretory IgA protease

50
Q

What are the four virulence factors for Streptococcus pneumoniae? (Think- StreptoCAPS pneumonia)

A
  1. Adhesion molecule specific to respiratory mucosa
  2. Pneumolysin
  3. Secretory IgA protease
  4. Capsule
51
Q

What is the commonest cause of pneumonia?

A

Streptococcus pneumonae

52
Q

In its disseminated form, this bacteria can cause bacteraemia, endocarditis, sinusitis, OM, and meningitis

A

Streptococcus pneumonia

53
Q

What are five types of toxins produced by bacteria?

A
  1. Lysins
    1. Tissue enzymes like elastase, collagenase, coagulase
    2. Exfoliative toxins, enterotoxins
    3. Enzymes targeting host immune responses (Secretory IgAase
    4. Endotoxin
54
Q

Classification of Clostridium difficile? (shape and stain?)

A

Gram positive rods

55
Q

C.diff bacteria- aerobic or anaerobic?

A

Anaerobic

56
Q

C.difficile is a ________-forming bacteria

A

spore

57
Q

Which patients are especially susceptible to C.diff infection?

A

Elderly patients on antibiotics

58
Q

Pseudomembranous colitis is a severe form of diarrhea associated with which bacteria?

A

Clostridium difficile

59
Q

Some virulent strains of C.difficile, such as 027, lose regulation of toxin ____, and become hyper-producers of additional ______

A

genes, toxins

60
Q

What causes the diarrhea in C. diff infection?

A

The bacteria produces toxins which cause fluid secretion into the gut, which leads to diarrhea

61
Q

__________ pathogens always cause disease, while ________ pathogens only cause disease in immunocomprimised patients

A

professional, opportunistic

62
Q

The chain of infection is composed of 6 parts:

1. \_\_\_\_\_\_\_\_\_\_\_ agent
2. r\_\_\_\_\_\_\_\_\_\_\_
3. Portal of \_\_\_\_\_
4. Mode of \_\_\_\_\_\_\_\_\_\_
5. Portal of \_\_\_\_\_\_\_\_
6. \_\_\_\_\_\_\_\_\_\_\_\_ host
A
  1. Causative
  2. Reservoir
  3. Exit
  4. Transmission
  5. Entry
  6. Susceptible

KMMS (58 decks)

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