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Medical Micro/Immunology > Chapter 18 > Flashcards

Chapter 18 Flashcards

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USMLE® Step 1 flashcards
1
Q

What part of the body do staphylococcus inhabit?

A

skin and mucous membranes

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2
Q

Responsible for staph infections

A

staphylococcus

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3
Q

Describe the morphology of staphylococcus

A
  • Clusters of short chains (grape racemes)
  • No spores or flagella
  • Sometimes encapsulated
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4
Q

How many species does the genus staphylococcus have? Name 3.

A

31

*S. aureus, S. epidermis, S. capitis

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5
Q

Staphylococcus are not _____________ any more.

A

harmless commensals

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6
Q

Describe the colonies of S. aureus

A

large, round, and opaque

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7
Q

What is the best temp for growth of S. aureus? and the temperature range?

A

37 degrees Celsius

10 - 46 degrees C

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8
Q

Facultative anaerobe

A

S. aureus

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9
Q

S. aureus look _____ under the microscope

A

grape-like

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10
Q

The growth of S. aureus is enhanced with ____ and ____.

A

O2 (oxygen) and CO2 (carbon dioxide)

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11
Q

S. aureus are metabolically versatile meaning…

A

They digest proteins and lipids and ferment sugars

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12
Q

Name 3 things S. aureus can resist

A
  • extremes of pH
  • extremes of temp (60 degrees C in 1 hour)
  • most current antibiotics and many disinfectants
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13
Q

Why is S. aureus a troublesome hosipital pathogen?

A

Because it is highly resistant to most disinfectants and can remain viable after months of air drying. Also highly resistant to most current antibiotics.

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14
Q

No other pathogen produces as many virulence factors as

A

S. aureus

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15
Q

Name the 6 staphylococcal enzymes

A 
Coagulase + 
Hyaluronidase
Staphylokinase
Nuclease
Lipases
Penicillinase
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16
Q

Spreading factor that digest the intercellular ‘glue’ and binds connective tissue

A

Hyaluronidase

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17
Q

intercellular “glue”

A

hyaluronic acid

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18
Q

Enzyme that digests blood clots

A

Staphylokinase

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19
Q

Enzyme that digests DNAse

A

Nuclease

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20
Q

Enzyme that help bacteria colonize oily skin and stay in sebaceous glands

A

Lipases

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21
Q

What enzymes inactivates penicillin?

A

penicillinase

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22
Q

Which enzyme must be positive in order for the bacteria to be S. aureus

A

coagulase

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23
Q

Pathogenic strains of staphylococcus produce which enzyme?

A

coagulase (coagulates plasma and blood)

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24
Q

What does coagulase do?

A

Coagulase causes fibrin to be deposited around staph cells.

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25
Q

Fibrin stops _______ or _____________.

A

phagocytosis; promote adherence to tissues

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26
Q

Which enzyme is present in 97% of all isolates?

A

coagulase

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27
Q

Name the 5 toxins of staphylococcus?

A
  • Hemolysins
  • leukocidins
  • enerotoxins
  • exfoliative toxin
  • toxic shock syndrome toxin
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28
Q

Which toxin will cause damage by lysing the cell membranes of neutrophils and macrophages?

A

Leukocidins

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29
Q

Which toxins act on the gastrointestinal tract?

A

enterotoxins

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30
Q

How does the exfoliative toxin cause damage?

A

Separates the epidermal layer from the dermis.

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31
Q

Which toxin breaks down and disrupts the cell membranes of RBC?

A

hemolysins

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32
Q

Hemolysins produce a zone of _______ in ___________.

A

hemolysis; blood agar

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33
Q

The most powerful toxin

A

alpha toxin

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34
Q

Alpha toxin produces

A

beta hemolysis

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35
Q

Alpha toxins damage the __________, ___________, __________, and ________.

A

leukocytes, muscles, heart, renal tissues

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36
Q

Which toxin is associated with tampons and the binding/absorption of Mg++?

A

Toxic shock syndrome toxin

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37
Q

Which toxin is an intimate human associate?

A

TSST

38
Q

Where is TSST present?

A

in all environments including fomites

39
Q

Name the circumstances that predispose a person to infection?

A
  • poor nutrition
  • poor hygiene
  • immunodeficiency
  • preexisting primary infections
  • diabetes mellitus (people w/ no control)
  • tissue injury
40
Q

Which type of infections are the 3rd most common nosocomial infection in the newborn nursery and surgical wards?

A

staph infections

41
Q

________ can readily spread an epidemic pattern within and outside the hospital.

A

Hospital strains

42
Q

Name the four different types of localized staph infections.

A
  • folliculitis
  • furuncles
  • carbuncles
  • impetigo
43
Q

Osteomyelitis

A

systemic staph infection

44
Q

Every 20 mins bacteria _____ in population.

A

double

45
Q

_____ of certain strains responsible for the most common type of food infection in the USA

A

Enterotoxins

46
Q

Toxigenic strains are found in

A

custards, sauces, pastries, processed meats, ham… anything salty

47
Q

Toxigenic strains are dangerous because….

A

toxigenic strains are not noticible in food because they do not alter the smell or taste of food.

48
Q

Toxigenic strains are heat-stable and have in activation at ______ for ______.

A

100 degrees celsius for 30 mins

49
Q

Toxigenic strains usually last how long?

A

one day

50
Q

toxins act on _________ and stimulate ______.

A

gastrointestinal epithelium; nerves

51
Q

Effects of toxins are…..

A

cramping, nausea, vomit, diarrhea

52
Q

Staph responsible for a large % of nosocomial infections since the 1970s.

A

Coagulase -

53
Q

coagulase - are _______. They infect immunocompromised people.

A

opportunistic

54
Q

Name the types of staph that infect via instruments through the skin.

A
  • S. epidermitis
  • S. hominis
  • S. capitis
55
Q

Which type of staph infects exclusively young sexually active women?

A

S. saprophyticus

56
Q

The 2nd most common cause of urinary infections in staph.

A

S. saprophyticus

57
Q

How is staphylococcus identified?

A
  • Catalase test. (Plasma clots if it is +)

* Sugar fermentation

58
Q

All types of staph are coagulase negative except ________ which is coagulase +.

A

S. aureus

59
Q

Which type of staph is novobiocin-resistant?

A

S. saprophyticus

60
Q

How is S. epidermidis identified?

A

S. epidermidis ferments mannose

61
Q

S. capitis lacks ________.

A

urease

62
Q

Which type of staph lacks anaerobic growth?

A

S. hominis

63
Q

Is there a vaccine for staph? why or why not?

A

No, because it mutates so much so immunization is not successful.

64
Q

How is staph treated?

A

pus must be removed (pyogenic cocci)

65
Q

What are the clinical concerns for staph?

A
  • They are notorious for in their resistance to many drugs

* Difficult to control

66
Q

What is the biggest concern with S. aureus?

A

95% of S. aureus strains have acquired genes for penicillase making them resistant to penicillin and ampicillin.

67
Q

MRSA can only be controlled by ________?

A

vancomycin

68
Q

Name 3 antibiotics that MRSA is resistant to.

A

Erythromycin, tetracyclins, cephalosporins

69
Q

How can nosocomial staph infections be prevented in a hospital?

A

consistent practice of universal precautions by all hospital staff

70
Q

Family of gram- cocci.

A

Neisseriaceae

71
Q

Two pathogen types of Nesseria

A
  • Neisseria gonorrhoeae

* Neisseria meningitidis

72
Q

What is unique about the shape of Neisseriaceae

A

coffee bean shaped.

73
Q

Nesseria are found in pairs or ________ with flat side touching.

A

diplococci

74
Q

Neisseria gonorrehoae are also known as

A

gonococcus

75
Q

What kind of incubator do Neisseria need?

A

Capnophylic incubator … produces more CO2

76
Q

How would Neisseria be identified in a lab?

A

Neisseria are catalase + so it should make bubbles when combined with Hydrogen peroxide
*it can also be identified with cytochrome oxidase

77
Q

Respiration of Neisseria?

A

aerobic or microaerophilic

78
Q

Neisseria will survive for how long outside?

A

2 hours

79
Q

What affects Neisseria?

A

light, temp, pH

80
Q

Neisseria gonorrhoeae are often confused with _______________.

A

syphilis

81
Q

Claudius Geller thought gonococcus was caused by ___________________.

A

excess flow of semen

82
Q

Humans are the only resevoirs for

A

N. gonorrhoeae

83
Q

Among the top 5 reported STD’s.

A

Neisseria gonorrhoeae

84
Q

How many cases of gonorreah are reported each year

A

400,000.

85
Q

What type of media is N. gonorrohoea grown in?

A

Martin - Tayer media(chocolate agar)

86
Q

How is neisseria gonorrhoea identified?

A

gram stain (stains pink bc it’s negative) and oxidase test

87
Q

special type of neisseria?

A

has no fimbriae

88
Q

antibiotic formulated for control of gonorrohea?

A

spectinomycin

89
Q

causes epidemic cerebrospinal meningitis

A

Neisseria meningitidis

90
Q

How is Neisseria meningitidis transferred?

A

respitory secretion or droplets from carrier

91
Q

Most common in US

A

meningococcus

Medical Micro/Immunology (8 decks)

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