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Microbiology > Chapter 1 > Flashcards

Chapter 1 Flashcards

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Biology 101 flashcards
1
Q

Staphylococcus aureus is:

A 
Catalase-positive (the cats)
β-Hemolytic
Coagulase positive
Mannitol Positive
Facultative anaerobe
Hardy (heat and drying resistant)
Cultured on enriched media, containing nutrient broth and/or blood
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2
Q

Predisposing factors for S. aureus infection:

A

1- a break in the skin
2- insertion of a foreign body
3- an obstructed hair follicle (folliculitis)
4- a compromised immune system

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3
Q

S. aureus disease may be a result of:

A

1- invasive infection
2- toxicosis
3- a combination of both

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4
Q

Scalded skin syndrome and Toxic shock syndrome are a result of :

A

a combination of invasive infection and intoxication

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5
Q

S. Aureus healthy Carriers serve as a source of infection to themselves and others by:

A

1- direct contact
2- contamination of fomites
3- contamination of food

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6
Q

Virulence factors are the ………. features that enable an organism to produce disease.

A

genetic, biochemical, or structural

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7
Q

True or False:

mutants lacking the coagulase activity lose their virulence in animal models.

A

False:

mutants lacking the ability to make this factor remain virulent in animal models.

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8
Q

True or False:

majority of diseases caused by S. aureus, pathogenesis depends on the single action of one virulence factor

A

False:

majority of diseases caused by S. aureus, pathogenesis depends on the combined actions of several virulence factors

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9
Q

S.aureus virulance factors:

A
  1. Cell wall virulence factors
  2. Cytolytic exotoxins (hemolysin)
  3. Panton-Valentine leukocidin
  4. Superantigen exotoxins
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10
Q

S.aureus cell wall virulance factors:

A
  • Capsule (very thin, antiphagocytic)
  • Protein A (IgG anti-opsonin effect, antiphagocytic)
  • Fibronectin-binding protein FnBP (binding to mucosal cells and tissue matrices)
  • Clumping factor ( FnBP enhances clumping in the presence of plasma
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11
Q
  • often referred to as hemolysins
  • attack mammalian cell membranes
  • α Toxin: chromosomally encoded, polymerizes into tubes that pierce membranes
A

Cytolytic exotoxins (hemolysins)

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12
Q

α Toxin

A

chromosomally encoded
polymerizes into tubes
results in the osmotic lysis

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13
Q
  • pore-forming toxin lyses PMNs
  • makes strains more virulent.
  • produced predominantly by community-(MRSA) strains
A

Panton-Valentine leukocidin

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14
Q

Superantigen exotoxins:

A
  • affinity for the TC-MHCII
  • stimulate enhanced T-lymphocyte response (as many as 20 % of T cells respond)
  • can cause toxic shock syndrome due to cytokine storm
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15
Q

a ‘’cytokine storm’’:

A

release into the circulation of large amounts of T-cell cytokines.

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16
Q

a ‘’cytokine storm’’:release into the circulation of large amounts of T-cell cytokines such as:

A
  • interleukin-2 (IL2)
  • interferon-γ (IFN-γ)
  • tumor necrosis factor-α (TNF-α)
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17
Q

Toxic shock syndrome toxin 1 results in:

FR VDN FAILURES

A
  • Fever,
  • Rash
  • Nausea
  • Vomiting
  • Diarrhea
  • Failure of many organ systems,
  • circulation failure and Death
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18
Q

True or False:

The high cytokine levels in turn cause capillary leak and shock.

A

True

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19
Q

Superantigen exotoxin types:

A

a. Enterotoxins:
b. Toxic shock syndrome toxin 1
c. Exfoliatin (exfoliative toxin)

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20
Q
  • produced by half of all S. aureus isolates.
  • can cause food poisoning
  • even more heat-stable than S. aureus.
A

Enterotoxins

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21
Q

One of the following is not a symptom of food poisoning by staph:

  • Diarrhea
  • Nausea
  • Pyrexia (fever)
  • Vomiting
  • Abdominal cramps
A
  • Pyrexia (fever)
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22
Q

Incubation of staph

A

short 1-8 hours

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23
Q
  • classic cause of toxic shock syndrome (TSS)

- sometimes referred to as staphylococcal enterotoxin F

A

Toxic shock syndrome toxin 1 (TSST –1)

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24
Q

True or False:

staphylococcal enterotoxin F can cause food poisoning when ingested

A

False:

staphylococcal enterotoxin F does not cause food poisoning when ingested

25
Q

Exfoliatin (exfoliative toxin, ET)

A
  • causes scalded skin syndrome in children.
  • cleaves desmoglein 1, which is a component of desmosomes
  • loss of the superficial skin layer
26
Q

True or false:

organisms producing enterotoxin are not always recovered from incriminated food but the toxin may be recovered

A

True

27
Q

toxin cleaves ……….. which is a component of ……….. (cell structures specialized for cell-to-cell adhesion).

A

desmoglein 1, desmosomes

28
Q

portals of entry of streptococcus:

A

1- break in the skin ( needle stick / surgical wound)

2- respiratory tract ( S.pneumonia => influenza)

29
Q

localized host response to staphylococcal infection is inflammation, characterized by SNAP

A

Swelling
Necrosis of tissues
Accumulation of pus

30
Q

Diseases caused by toxins of S.aureus

A
  1. Toxic shock syndrome
  2. Food poisoning
  3. Scalded skin syndrome
31
Q

When the bacteria invade the bloodstream:

  • septicemia
  • bacteremia
A
  • septicemia (the presence and persistence of pathogenic microorganisms or their toxins in the blood) may be rapidly fatal.
  • Bacteremia (the presence of viable bacteria circulating in the bloodstream) may result in seeding internal abscesses, skin lesions, or infections in the lung, kidney, heart, skeletal muscle, or meninges.
32
Q

Bacteremia may result in:

SSI

A
  • seeding internal abscesses
  • skin lesions
  • infections in the lung, kidney, heart, skeletal muscle, or meninges.
33
Q

the common sty (external hordeolum) is created by

A

infection of an eyelash follicle.

34
Q

The most common S. aureus infections are small, superficial abscesses involving

A

hair follicles (folliculitis)
sweat
sebaceous glands.

35
Q

Subcutaneous abscesses
…cles
…cles
impetigo

A
  • furuncles (boils)
  • Carbuncles
  • Impetigo
36
Q

The more common cause of impetigo

A

Streptococcus pyogenes

37
Q

True or False:
Carbuncles are small, superficial, localized skin infections that can lead to septicemia and require antibiotic therapy and debridement.

A

False:
Carbuncles are larger, deeper, multiloculated skin infections that can lead to bacteremia and require antibiotic therapy and debridement.

38
Q

Deep, localized infections may be metastatic from:

sst

A
  • superficial skin infections
  • skin lesions
  • trauma
39
Q

S.aureus is the most common cause of:

A
  • acute and chronic infection of bone marrow

- acute infection of joint space in children (septic joint).

40
Q

True or False:
Septic joints are medical emergencies because pus can rapidly cause irreparable cartilage damage. They must be treated promptly with drainage and an antibiotic

A

True

41
Q
  • associated with intravenous drug abuse
  • caused by the injection of contaminated preparations
  • or by needles contaminated with S.aureus
A

Acute endocarditis

42
Q

True or False:

An abscess in any organ or tissue is cause to suspect S.aureus, although many other bacteria can cause abscesses.

A

True

43
Q

Which of the following is incorrect:

  1. Septicemia is a generalized infection with sepsis or bacteremia that may be associated with a known focus or not
  2. Strep. pneumonia s a cause of severe, necrotizing pneumonia.
  3. S. aureus is one of the most common causes of hospital-associated infections.
  4. Toxicosis caused by S. aureus include: toxic shock syndrome, staphylococcal gastroenteritis, scalded skin syndrome
A
  1. Strep. pneumonia s a cause of severe, necrotizing pneumonia.
    => S.aureus is a cause of severe, necrotizing pneumonia.
44
Q

Which of the following is not caused by TSS:

  • high fever,
  • rash )
  • vomiting,
  • diarrhea,
  • hypertension
  • multi-organ involvement
A

hypertension

REMEMBER/ HRDHMV

45
Q

True or False:
Symptoms of Staphylococcal gastroenteritis, such as nausea, vomiting, and diarrhea, are acute following a short incubation period (less than 6 hours) and are triggered by the infection

A

False:

they are triggered by local actions of the toxin on the GI tract rather than from infection.

46
Q

True or False:
S. Aureus infections elicit strong long-lasting immunity, as demonstrated by the non-susceptibility of individuals to S. aureus infections throughout life after being infected before.

A

False:
S. Aureus infections do not elicit strong or long-lasting immunity, as demonstrated by the continuing susceptibility of individuals to S. aureus infections throughout life.

47
Q

All of the followings are true except:
a. all community and hospital-acquired S. aureus infections are now resistant to penicillin G

b. replacement of penicillin G, by β-lactamase-resistant penicillins: methicillin or oxacillin.
c. increased use of methicillin and related antibiotics has resulted in S. aureus that is resistant to a number of β-lactam antibiotics, such as methicillin, oxacillin, and amoxicillin (MOA)
d. These strains are known as methicillin-resistant S. aureus (MRSA)
e. None of the above

A

e. None of the above

48
Q

All of the followings are true except:
a. all community and hospital-acquired S. aureus infections are now resistant to penicillin G

b. replacement of penicillin G, by β-lactamase-resistant penicillins: methicillin or oxacillin.
c. increased use of methicillin and related antibiotics has resulted in S. aureus that is resistant to a number of β-lactam antibiotics, such as methicillin, oxacillin, and amoxicillin
d. These strains are known as methicillin-resistant S. aureus (MRSA)
e. all S. aureus isolates resistant to methicillin or oxacillin.

A

e.

50 % of hospital S. aureus isolates resistant to methicillin or oxacillin.

49
Q

True or False:

S. aureus infections are resistant to penicillin G due to penicillinase-encoding chromosomes.

A

False:

S. aureus infections are now resistant to penicillin G due to penicillinase-encoding plasmids or transposons

50
Q

True or false:

Some MRSA strains are resistant to vancomycin but frequently responsive to many other antibiotics

A

False:

Some MRSA strains are sensitive only to vancomycin but frequently resistant to many other antibiotics

51
Q

The most common clinical manifestations of CA-MRSA are:

A
  • skin and
  • soft tissue infections such as: - abscesses or
    - cellulitis
52
Q

CA-MRSA can also cause severe diseases such as:

nos

A
  • necrotizing pneumonia,
  • osteomyelitis, and
  • septicemia
53
Q

The incidence of vancomycin resistance has increased steadily, prompting the use of alternative drugs such a:
liquid

A
  • linezolid
  • quinupristind-alfopristin
  • daptomycin
    Against: VIRSA and gram-positive bacterial pathogens
54
Q

True or False:

There is an effective vaccine against S. aureus

A

There is no effective vaccine against S. aureus.

55
Q

All of the following are true except:
a. S. epidermidis is present in large numbers as part of the normal flora of the skin

b. Despite its low virulence, it is a common cause of infection of implants such as heart valves and catheters.
c. Acquired drug resistance by S. epidermidis is even less frequent than by S. aureus.
d. S. epidermidis produces a polysaccharide intercellular adhesin (called “slime”), facilitates adherence to bioprosthetic material surfaces

A

c.

Acquired drug resistance by S. epidermidis is even more frequent than by S. aureus.

56
Q

All of the following are correct about Staphylococcus saprophyticus except:
a. is a frequent cause of cystitis (bladder & uriters) in women

b. it is part of normal vaginal flora.
c. Resistant to most antibiotics, including penicillin G
d. can be distinguished from S. epidermidis and most other coagulase-negative staphylococci by its natural resistance to novobiocin.
e. Urinary coagulase-negative staphylococcus is often presumed to be S. saprophyticus; but novobiocin resistance can be used for confirmation

A

c

It is ensitive to most antibiotics, even penicillin G.

57
Q

Which of the following is novobiocin resistent:

a. S.aureus
b. S.epidermedis
c. S. saprophyticus

A

c. S. saprophyticus

58
Q

True or False:
S.saprophyticus produces a polysaccharide intercellular adhesin (called “slime”), facilitates adherence to bioprosthetic material surfaces

A

False:
S. epidermidis produces a polysaccharide intercellular adhesin (called “slime”), facilitates adherence to bioprosthetic material surfaces

Microbiology (4 decks)

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