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MICROM 442 > Exam 2 Lecture 11 > Flashcards

Exam 2 Lecture 11 Flashcards

Staphylococci

1
Q

As of 2014, the Staphylococci genus consists of __ species and __ sub-species

A

47; 23

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2
Q

Staphylococci is a gram-___ cocci

A

Positive

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3
Q

Staphylococci are arranged as: (4 shapes)

A

singles, pairs, tetrads, clusters

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4
Q

Why are there so many different arrangements of Staphylococci?

A

They can divide in multiple perpendicular planes. This can lead to cluster formation

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5
Q

What is the DNA G/C content of Staphylococci?

A

27-41%

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6
Q

True or false: Staphylococci are motile and are capable of forming spores.

A

False: they are non-motile and non-spore forming.

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7
Q

What is an example of spore forming bacteria?

A

Clostridium and Bacillus species

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8
Q

True or false: all staphylococci are coagulase positive

A

False: they are all catalase positive

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9
Q

What is special about all Staphylococci being catalase positive?

A

This allows us to differentiate Staph from all other gram positive cocci.

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10
Q

What does catalase do?

A

Catalase is an enzyme that detoxifies reactive oxygen species (ROS) by reducing hydrogen peroxide to water and oxygen.

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11
Q

How do you perform a catalase test?

A

Add 3% hydrogen peroxide to a culture/suspended cells. Observe for bubbling.

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12
Q

Signs of a positive catalase test

A

Bubbling

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13
Q

Signs of a negative catalase test. What species would this indicate?

A

No bubbling; may indicate Streptococci or Enterococci

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14
Q

What are two Staphylococci phenotypes on blood agar?

A
  1. Pigment production: S. aureus produces gold-colored colonies, S. epidermis produces white-colored colonies
  2. Hemolysis (S. aureus does beta and S. epidermidis does gamma)
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15
Q

S. aureus hemolysis

A

Beta hemolysis

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16
Q

S. epidermidis hemolysis

A

Gamma (none)

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17
Q

What is coagulase?

A

Bacterial protein that causes clotting of blood plasma

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18
Q

How do you perform the coagulase test?

A

Mix bacteria with rabbit plasma on glass slide or in tube, look for clumping/clot formation

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19
Q

True or false: S. aureus is the most medically important CoPS.

A

True; all other CoPS species usually infect animals

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20
Q

Staphylococci are ____ ____, but only S. aureus can perform ____ fermentation.

A

Facultative anaerobes; mannitol

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21
Q

Acidic fermentation products

A

energy and lactic acid

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22
Q

True or false: Majority of CoNS can ferment mannitol

A

False, they cannot

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23
Q

What are some characteristics of Mannitol Salt Agar?

A
  1. Selective and differential medium
  2. Contains essential nutrients and mannitol
  3. High salt concentration (7.5% NaCl)
  4. Contains phenol red (pH indicator)
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24
Q

True or false: on a mannitol salt agar plate, S. aureus will indicate a yellow to red color change.

A

False: red to yellow

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25
Q

True or false: on a mannitol salt agar plate, S. epidermis will not indicate a color change and the plate will stay red

A

True

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26
Q

What makes Staphylococci “hardy”?

A
  1. Halotolerant
  2. Wide temp (10-45ºC) and pH(4.0 - 9.0) ranges
  3. growth with low water activity
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27
Q

Halotolerant

A

Can grow under high concentration of salt

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28
Q

Where do reactive oxygen species come from?

A

Can be self generated by aerobic respiration or they can come from immune cells

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29
Q

Where can you find coagulase in Staphylococci?

A

Surface bound or extracellularly

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30
Q

What does surface bound coagulase do?

A

Cleaves fibrinogen, resulting in fibrin precipitating out of solution to form clot

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31
Q

What does extracellular coagulase do?

A

Binds prothrombin, cleaves fibrinogen, fibrin precipitates out

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32
Q

When S. aureus ferments ____, this results in the production of ___ ___, which will change the __ indicator from red to yellow color

A

mannitol; lactic acid; pH

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33
Q

What are some rapid diagnostic methods for differentiating S. aureus?

A
  1. Molecular (PCR to amplify genes inherent to Staph genome)

2. Proteomics (ex. mass spectrometry to look at mass/charge ratio of ionized proteins)

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34
Q

What gives S. aureus colonies their characteristic gold color?

A

Staphyloxanthin (carotenoid pigment)

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35
Q

True or false: staphyloxanthin is mainly a pigment and does not have a major function

A

False: is also a virulence factor

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36
Q

In S. aureus, __-hemolysin is secreted and forms pores in erythrocytes, resulting in __-hemolysis

A

alpha; beta

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37
Q

What can S. aureus colonize on the human body?

A

Skin and mucosa of asymptomatic individuals; anterior nares; hand; perineum; pharynx

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38
Q

True or false: If you are a nasal carrier of S. aureus, you have a negligibly higher chance of having S. aureus colonizing other sites of the body.

A

False: being a carrier significantly increases chance

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39
Q

What are the three nasal carriage patterns in healthy individuals?

A
  1. non-carriage
  2. intermittent
  3. persistent
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40
Q

What does MSCRAMM stand for?

A

Microbial Surface Components Recognizing Adhesive Matrix Molecules

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41
Q

What does SERAM stand for?

A

Secretable Expanded Repertoire Adhesive Molecule

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42
Q

What are some examples of S. aureus MSCRAMM?

A

Fibronectin binding protein; Protein A

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43
Q

What are some examples of S. aureus SERAM?

A

Extracellular adherence protein (Eap); extracellular matrix binding protein (Emp); Coagulase (Coa)

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44
Q

What role do teichoic acids play in S. aureus?

A

It is a cell wall component that mediates host cell adherence

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45
Q

What does S. aureus Protein A bind to?

A
  1. von Willebrand factor (vWF), which helps to stick platelets together and adhere to the walls of blood vessels at the site of a wound
  2. Fc portion of antibodies
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46
Q

What does S. aureus Eap bind to in the host?

A

fibrinogen and fibronectin

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47
Q

S. aureus has 4 virulence factors, which are:

A
  1. Adhesins
  2. Invasins
  3. Immune evasion
  4. Miscellaneous toxins (pyogenic)
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48
Q

What are the two major classes of S. aureus adhesins?

A
  1. MSCRAMM

2. SERAM

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49
Q

Examples of S. aureus invasins

A
  1. Cytolytic toxins (pore forming)

2. Exoenzymes (spreading)

50
Q

What is the overall function of invasins?

A

they are extracellular proteins that lyse cells and promote spread

51
Q

S. aureus produces a ____ called __-_____ that lyses erythrocytes and other mammalian cells, which allows for __ hemolysis to occur.

A

cytolytic toxin; alpha-hemolysin; beta

52
Q

Examples of S. aureus exoenzymes

A

hyaluronidase, collagenase, staphylokinase (fibrinolysin), lipase

53
Q

Why does S. aureus produce exoenzymes?

A

Allows spreading from one site of infection to another (i.e. S. aureus translocates through the activity of exoenzymes)

54
Q

An S. aureus cytotoxin called ___-___ _____ lyses neutrophils and macrophages.

A

Panton-Valentine Leukocidin

55
Q

Why is it beneficial for S. aureus to be able to lyse host cells?

A

These cells contain nutrients needed for bacterial growth and replication

56
Q

Hemolysins and PVL bind to ___ ___ ____ and ____, allowing a channel to form within the host cell membrane.

A

host membrane receptor; oligomerize

57
Q

How does pore formation lead to cell lysis?

A

Allows the release of cations like Na+, Ca++, K+ in and out of the cell, changing the osmotic pressure of the host cell, causing lysis

58
Q

Which S. aureus adhesins also serve as factors of immune evasion?

A. Fibronectin binding protein
B. Protein A
C. Coagulase
D. Eap
E. Collagen binding protein (Cna)
A

B and D

59
Q

How does Protein A function in immune evasion?

A

Binds to Fc portion of antibodies that serves as a disguise, so host immune cells cannot differentiate pathogen from self

60
Q

How does Eap function in immune evasion?

A

Impairs T-cell and neutrophil recruitment, preventing a larger immune response from occurring

61
Q

S. aureus may also be coated with ___ ___ ___ that helps prevent recognition by immune cells.

A

Polysaccharide capsule coats

62
Q 
Which of the following S. aureus pyogenic toxins are superantigens?
A. Toxic Shock Syndrome Toxin (TSST)
B. Exfoliative toxins (ETA and ETB)
C. Staphylococcal Enterotoxins
D. none of these
A

A and C

63
Q

S. aureus exfoliative toxins function

A

serine protease that cleaves desmosomes, causing desquamation

64
Q

Superantigens promote non-specific binding of ___ ___ __ to _-__ ___ in the absence of processed antigen

A

MHC Class II; T-cell receptor

65
Q

Superantigens cause _-__ activation and proliferation, which can cause massive ____ production.

A

T-cell; cytokine

66
Q

What kinds of cutaneous infections can S. aureus cause?

A

folliculitis, non-bullous impetigo, furuncle, carbuncle

67
Q

How can a furuncle spread to become a carbuncle?

A

S. aureus may secrete exoenzymes to spread to surrounding, uninfected tissue and worsen the infection

68
Q

Abscesses are characterized as:

A

warm, pus-filled, painful pockets

69
Q

Folliculitis is characterized by: (3 things)

A
  1. superficial infection of hair follicles or glands
  2. clusters of small red bumps
  3. pus-filled blisters
70
Q

Non-bullous impetigo is characterized by:

A
  1. superficial skin infection
  2. bubble-like epidermal swelling
  3. vesicles or pustules that rupture and leave a honey-colored crust
  4. primarily occurs in young children
71
Q

Name 5 systemic S. aureus infections

A
  1. Bacteremia
  2. Septic arthritis
  3. Infective endocarditis
  4. Osteomyelitis
  5. Pneumonia
72
Q

True or false: bacteremia cause by S. aureus often has high mortality rates, but incidence decreases with age.

A

False; incidence increases with age

73
Q

Symptoms of bacteremia

A

Fever, chills, weakness, fast respiration, rapid heart rate

74
Q

What is S. aureus induced septic arthritis and what are some symptoms?

A

infection of joint cavity causing inflammation; symptoms include swollen joint, pain, fever, chills

75
Q

True or false: S. aureus induced Septic arthritis may cause hematogenous seeding of vascular synovial membrane

A

True

76
Q

Infective endocarditis causes ~____ cases per year, and some risk factors include:

A

40,000; IV drug abuse, pacemakers, congenital heart disease

77
Q

Osteomyelitis

A

infection of bone or bone marrow

78
Q

____ is the most common cause of pathogen-induced bone destruction and is predominantly found in ____.

A

Osteomyelitis; children

79
Q

Osteomyelitis is ___ in origin and ____ in nature.

A

hematogenous; acute

80
Q

Osteomyelitis commonly colonizes the ____ of the long bone.

A

metaphysis, which is a highly vascularized area of long bones where the growth plate is located

81
Q

Osteomyelitis usually causes:

A

Abscesses, inflammation, remodeling, necrosis (bone becomes brittle)

82
Q

What are 2 factors of S. aureus that detoxify ROS?

A
  1. Catalase

2. Staphyloxanthin (antioxidant that protexts against O2-, H2O2, HOCl)

83
Q

What are 4 factors of S. aureus that lyse immune cells and/or inhibit cell recruitment/migration?

A
  1. Hemolysins
  2. Panton-Valentine Leukocidin
  3. Chemotaxis Inhibiting Protein (CHIP)
  4. Eap
84
Q

S. aureus-induced pneumonia causes ~____ cases per year and is usually ____ or ____-acquired.

A

70,000; community; hospital

85
Q

Necrotizing pneumonia has a ___ mortality rate and is often caused by __ ____-___ S. aureus and preceded by ____

A

high; PV leukocidin-producing; influenza

86
Q

What are 4 toxigenic S. aureus infections?

A
  1. Staphylococcal Scalded Skin Syndrome (SSSS)
  2. Bullous impetigo
  3. Toxic Shock Syndrome (TSS)
  4. Staphylococcal Food Poisoning
87
Q

What is Staphylococcal Scalded Skin Syndrome, and what is it caused by?

A

fluid accumulated and blistering skin often accompanied by desquamation; caused by exfoliative toxins ETA and ETB

88
Q

We have multiple layers of skin that are connected via _____. S. aureus ____ ___ are serine proteases that cleave ______ _, causing desquamation.

A

desmosomes; exfoliative toxins; desmogelin 1

89
Q

Desquamation

A

epidermal-dermal separation

90
Q

Bullous Impetigo is a localized form of ____ and is characterized by:

A

SSSS; fluid-filled vesicles and flaccid blisters (bullae)

91
Q

What is Toxic Shock Syndrome?

A

multisystem inflammatory response

92
Q

In menstrual TSS, S. aureus multiples rapidly when _____, and favorable conditions will stimulate the production of ____.

A

Tampon is inserted; TSST-1

93
Q

True or false: When TSST-1 is produced, it is absorbed and enters the bloodstream.

A

True

94
Q

Symptoms of toxic shock syndrome

A
  1. high fever
  2. erythematous rash
  3. hypotension
  4. skin desquamation
95
Q

Nonmenstrual TSS mainly occurs in ____ and is usually caused by:

A

women; barrier contraceptives, surgery, lesions

96
Q

What causes Staphylococcal Food poisoning?

A

Staphylococcal enterotoxins, specifically SEA (80% of cases)

97
Q

Staphylococcal enterotoxins are usually resistant to:

A

heat, acid, and inactivation by GI proteases

98
Q

Staphylococcal food poisoning occurs when you ______. Symptoms start to occur __-__ after ingestion.

A

consume SEA (preformed toxin); 30 min-8 hours

99
Q

Staphylococcal food poisoning causes ____ ___ in the GI tract. SEs will stimulate ___ ___ in intestines. This sends a signal via the ___ and ___ nerves to the ____ brain center. Lastly, the brain sends a signal back to the ____.

A

inflammatory changes; neural receptors; vagus and sympathetic; emetic; stomach

100
Q

SFP food sources

A

meats, dairy products, potatoes, eggs, salads (creamy)

101
Q

True or false: CoNS are usually white colored colonies and do not ferment mannitol.

A

True

102
Q

CoNS hemolysis

A

None (gamma)

103
Q

True or false: CoNS colonize skin and mucous membranes of humans and animals and therefore are significant members of human microbiota.

A

True

104
Q

There are __ species categorized as CoNS, and of those, __ species colonize humans.

A

38; 20

105
Q

___ is the most commonly recovered CoNS.

A

S. epidermidis

106
Q

True or false: CoNS are never considered pathogenic.

A

False; they may become opportunistic pathogens in patients with increased risk, such as those that are immunocompromised or use medical devices.

107
Q

CoNS has fewer ___ ___ than S. aureus

A

virulence factors

108
Q

S. epidermidis has 4 main classes of virulence factors, which include:

A
  1. adhesins
  2. Accumulation factors
  3. Exoenzymes
  4. Immune escape
109
Q

What do S. epidermidis adhesins attach to?

A

Hydrophobic surfaces (polystyrene) and host MSCRAMMs

110
Q

S. epidermidis accumulation factors

A

Exopolysaccharide; accumulation-associated protein (Aap)

111
Q

S. epidermidis exoenzymes

A

lipase (GehD), protease (Esp)

112
Q

S. haemolyticus characteristics

A
  • 2nd most common species in CoNS infections
  • colonizes skin microbiome
  • has virulence factors (adhesins and cytotoxins)
  • highest level of antibiotic resistance among CoNS
113
Q

What kinds of infections can S. haemolyticus cause?

A

native valve endocarditis, bacteremia, peritonitis, UTIs, osteomyelitis, can infect wounds/joints

114
Q

S. saprophyticus can cause ___ mainly in young, sexually active women.

A

UTIs

115
Q

S. saprophyticus colonizes the _____ and ___ tracts as well as the ____.

A

genitourinary and GI; perineum

116
Q

True or false: S. saprophyticus virulence factors include adhesins and enzymes such as urease.

A

True

117
Q

S. lugdunensis can cause severe infections similar to _____. It uses virulence factors such as:

A

S. aureus; adhesins, enzymes, cytotoxin

118
Q

What is the primary cytotoxin that S. lugdunensis uses?

A

S. lugdunensis synergistic hemolysins (SLUSH)

119
Q

What infections can S. lugdunensis cause?

A

skin and soft tissue, endocarditis, bacteremia, peritonitis, prosthetic joint, osteomyelitis, septic arthritis, abscess

120
Q

True or false: Staphylococci use quorum sensing in order to regulate its virulence factor production and biofilm formation.

A

True

121
Q

What are the benefits to forming biofilms?

A

protection against immune system and antibiotics

122
Q

Characteristics of small colony variant Staphylococci

A
  • slow-growth on lab media
    -mutations in essential metabolic genes
    resistant to different antibiotics depending on mutation

MICROM 442 (26 decks)

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