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DEN 7102 Micro & Immuno Concepts > Exam 2 Gram Positive Cocci > Flashcards

Exam 2 Gram Positive Cocci Flashcards

Split over 10/9 and 10/12

1
Q

Infectivity

A

ability to infect

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2
Q

Equation for infectivity

A

Number infected/number susceptible x100

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3
Q

Pathogenicity

A

ability to cause disease

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4
Q

Equation for pathogenicity

A

Number with clinical disease/number infected x100

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5
Q

Virulence

A

ability to cause death

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6
Q

Equation for virulence

A

Number of deaths/number with disease x100

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7
Q

What are 3 gram positive species?

A
  1. staphylococci
  2. streptococci
  3. enterococci
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8
Q

What are enterococci shaped like?

A

Not completely round or or oblong, kind of in between

Fat rods

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9
Q

Staphylococci grow in ____

A

Clusters

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10
Q

Streptococci grow in ___

A

chains

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11
Q

Streptococci have what direction plane of splitting?

A

Vertical –> forms chains

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12
Q

Diplococci have what direction plane of splitting?

A

Vertical, then vertical
or
Vertical, then horizontal

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13
Q

Staphylococci have what direction plane of splitting?

A

diagonal – forms clusters

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14
Q

____ are aerobic or facultative anaerobic

A

Staphylococci

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15
Q

_____ grows in 7.5% NaCl

A

Staphylococci (halophilic)

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16
Q

Which produces catalase, staph or strep?

A

Staph

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17
Q

Products of catalase activity

A

oxygen (bubbles) and h2o

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18
Q

____ are mostly facultative anaerobes, some anaerobes

A

Streptococci

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19
Q

Streptococci are ____ organisms, needing enriched media to grow

A

fastidious

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20
Q

True or false: staphylococci ferment well

A

False - streptococci are more known for fermentation

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21
Q

Streptococci perform ____ ____ to produce lactic acid from glucose

A

homolactic fermentation

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22
Q

_____ do not produce catalase

A

Streptococci

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23
Q

Describe S. aureus colonies

A

Large colonies, “golden” cream color

Non s. aureus is white in color

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24
Q

What type of hemolysis can staphylococci do?

A

Often beta hemolysis

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25
Q

Describe streptococci colonies

A

Small, white

wider

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26
Q

What type of hemolysis can streptococci do?

A

Some can do alpha hemolysis, some species cannot do hemolysis at all

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27
Q

Where does S. aureus colonize?

A

anterior nares and/or skin of 30% of normal individuals

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28
Q

More than 80% of patients with ______ carry S. aureus

A

eczema/atopic dermatitis
(due to skin barrier being compromised)

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29
Q

S. aureus is often associated with _____ infection, transmission by carriers

A

nosocomial

acquired at hospital, not present during the time of admission

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30
Q

What virulence factor distinguishes S. aureus from other staphylococci?

A

Coagulase

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31
Q

Coagulase is an enzyme that clots ____. It is produced by:

A

plasma; S. aureus (but not other staphylococci)

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32
Q

Function of coagulase

A

cross-link bacteria in the clot to escape host immune system

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33
Q

True or false: S. aureus has a polysaccharide capsule

A

True - inhibits phagocytosis

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34
Q

Most strains of S. aureus encode _______

A

penicillinase (beta lactamase) on plasmid

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35
Q

Staphylokinase

A
  • converts plasminogen to plasmin, which cleaves C3b opsonin and IgG
  • inhibits phagocytosis by PMN
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36
Q

Staphylokinase is a virulence factor of:

A

S. aureus

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37
Q

Superoxide dismutase is found in:

A

S. aureus

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38
Q

Superoxide dismutase causes resistance to:

A

phagocytes, which release superoxides

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39
Q

Chemotaxis inhibitory protein is a virulence factor of:

A

S. aureus

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40
Q

Chemotaxis inhibitory protein

A
  • competitively binds to neutrophil formyl peptide receptor and C5a receptor
  • harder to contain and kill pathogens
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41
Q

True or false: S. aureus can resist lysozymes

A

True - they have altered muramic acid in NAM, harder to damage cell walls

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42
Q

Where are exotoxins produced?

A

Inside the cell, then exported out

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43
Q

Example of S. aureus exotoxin

A

Protein A

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44
Q

Most common cause of Impetigo

A

S. aureus

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45
Q

Cellulitis can occur due to infection by _____

A

S. aureus
(also caused by Streptococcus pyogenes)

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46
Q

Cellulitis

A

infection of dermal and subcutaneous connective tissue

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47
Q

Impetigo looks like:

A

Honey colored crusts

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48
Q

True or false: impetigo is not infectious

A

False - highly infectious

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49
Q
A

S. aureus cellulitis (can’t use topical creams)

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50
Q
A

S. aureus cellulitis

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51
Q
A

Furuncle

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52
Q
A

Carbuncle

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53
Q

_____ target intestines

A

Enterotoxins

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54
Q

Difference between exotoxins and endotoxins

A

exotoxins - produced inside cell and exported out
endotoxins - usually part of organism’s cell wall

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55
Q

Enterotoxins can act as ____ when expressed systemically

A

superantigens

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56
Q

What can happen if exotoxins are eaten?

A

Bacterial intoxication (food poisoning)

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57
Q

TSST-1 is a ______

A

Superantigen

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58
Q

What does a superantigen do?

A
  • activate large numbers of T cells by binding outside of MHC-II and TCR complex
  • antigen independent
  • massive release of cytokines (IL-1, TNF), leading to fever, organ failure
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59
Q

True or false: S. aureus exotoxin can also suppress normal immune response

A

True

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60
Q

Name some exotoxins produced by S. aureus

A
  • TSST-1
  • Protein A
  • Enterotoxins (specifically enterotoxin A)
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61
Q

During normal phagocytosis, ___ binds to ____ and then to ____

A

IgG; S. aureus; PMN receptor (Fc region)

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62
Q

Protein A function

Exotoxin: Protein A-mediated immune evasion

A

hinders opsonization/phagocytosis –> IgG now in wrong orientation

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63
Q

How does Protein A hinder phagocytosis?

A

Protein A binds to Fc region of IgG so it cannot bind to PMN. Decreases phagocytosis

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64
Q

Staphylococcal food poisoning is caused by:

A

S. aureus enterotoxin A

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65
Q

Main symptom of S. aureus food poisoning

A

Projectile vomiting 1-6 hours after ingestion, nausea, cramps, diarrhea

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66
Q

True or false: you won’t die from Staph food poisoning unless you are dehydrated

A

True

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67
Q

Enterotoxins directly affect ____

A

intestinal epithelium

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68
Q

TSST-1 is also known as:

A
  • enterotoxin B
  • pyrogenic exotoxin
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69
Q

True or false: males are not affected by TSST

A

False - can acquire through deep tissue infection

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70
Q

Females can acquire TSST via:

A

high-absorbancy tampon

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71
Q

Cytotoxins a, b, d, g, are associated with:

A

S. aureus

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72
Q

Cytotoxins a, b, d, g are toxic for what kinds of cells?

A

Many blood cells, including RBC, WBC

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73
Q

Exfoliatin A and B are toxins of:

A

S. aureus

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74
Q

Exfoliatin A and B are ____. What do they do?

A
  • They are serine proteases that cleave desmoglein-1
  • split desmosomes in epidermis
  • Results in Scalded Skin Syndrome
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75
Q

What is the most common cause of osteomyelitis?

A

S. aureus (exception = osteomyelitis of the mandible)

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76
Q

What is osteomyelitis?

A

Inflammation of bone/marrow

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77
Q

True or false: S. aureus can cause acute endocarditis

A

True

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78
Q

How is acute endocarditis acquired?

A

from staphylococcal bacteremia, which originates from skin infection, surgery, IV catheter

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79
Q

Acute endocarditis can lead to:

A

heart failure, septic emboli

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80
Q

Acute endocarditis mortality rate

A

50%

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81
Q

What is septic emboli?

A
  • can be caused by S. aureus
  • embolism that can dislodge and spread through the body
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82
Q

Most strains of S. aureus are resistant to ______ because _____

A

Penicillin; they produce penicillinase

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83
Q

Penicillinase of S. aureus is mediated by:

A

Plasmid

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84
Q

DOC to S. aureus resistant to penicillin

A

Methicillin (penicillinase resistant penicillin)

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85
Q

MRSA

A

Methicillin resistant Staph Aureus

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86
Q

True or false: methicillin also has a B lactam ring

A

True - but penicillinase from S. aureus has a harder time getting to it

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87
Q

True or false: MRSA is not very common

A

False - now common in around 60% hospital isolates

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88
Q

MRSA is encoded by:

A

mecA

mobile genetic element that inserted itself on the chromosome

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89
Q

MecA gene produces:

A

PBP2a (penicillin binding protein, binds to B lactam antibiotics to prevent binding to transpeptidase

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90
Q

DOC for MRSA

A

Vancomycin

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91
Q

MRSA colonizes ____ of healthy people

A

2%

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92
Q

Majority of MRSA causes what kind of infections?

A

skin or soft tissue infections

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93
Q

In hospital associated facilities, MRSA is associated with:

Not the majority of S. aureus cases

A
  • bloodstream infections
  • pneumonia
  • surgical site infections
  • sepsis
  • death
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94
Q

What are some risk factors for MRSA colonization?

A
  • recent hospitalization
  • prolonged hospital stay
  • residence in long term care facility
95
Q

True or false: Healthcare-associated MRSA infections are declining and have recently slowed

A

True - declining since 2005

96
Q

True or false: community associates rates of MRSA are decreasing

A

False - increasing

97
Q

Current recommendations of DOC for bacteremia or pneumonia

A
  1. Vancomycin, daptomycin
  2. Second line: linezolid, clindamycin, telavancin, ceftaroline
98
Q

Current recommendations of DOC for skin infections

A
  • incision and drainage if abscessed
  • clindamycin, tetracycline
99
Q

True or false: VRSA has already been identified

A

True - plasmid mediated

100
Q

Linezolid resistance reported in ____

101
Q

Staphylococcus epidermidis is ____ negative

102
Q

Where is Staphylococcus epidermidis found normally?

A

normal flora of skin, mucous membrane

103
Q

Staphylococcus epidermidis has _____ to prevent from drying/salty environment

A

Slime layer (capsule)
Also allows attachment to tissues, foreign bodies

104
Q

Most Staphylococcus epidermidis infections are from:

A

self flora

105
Q

Treatment for Staphylococcus epidermidis

A

Antibiotic susceptibility tests (over 50% resistant to methicillin)

106
Q

On an antibiotic susceptibility, what indicates antibiotic resistance?

A

Lack of zone of inhibition

107
Q

Streptococcus can perform what kind of hemolysis?

A

A, B, gamma

B accounts for most streptococcal diseases

108
Q

Lancefield system classifies streptococci based on:

A

antigens on cell wall

109
Q

Group A Strep also known as:

A

Streptococcus pyogenes

110
Q

Group B Strep contains:

A
  • Streptococcus agalactiae
  • Streptococcus halichoeri
111
Q

Group A strep causes what kinds of infections:

A

Skin and throat infections

112
Q

Group A strep is ___ hemolytic

113
Q

Group B strep causes:

A

neonatal meningitis

114
Q

Group B strep is ___ hemolytic

115
Q

Non-lancefield streptococci lack _____

A

Lancefield carbohydrates

116
Q

Example of Non-lancefield streptococci

A

Streptococcus pneumoniae

bacterial pneumonia

117
Q

M protein is a virulence factor of:

A

Streptococcus pyogenes

118
Q

M protein function

A
  • evasion
  • adhesin (attachment)
  • destroys C3-convertase to inhibit opsonization by C3b

Most important virulence factor

119
Q

F protein of S. pyogenes

A

Adhesin, binds fibronectin

120
Q

S. pyogenes capsule function

A

Evasion, antiphagocytic

121
Q

Spe stands for:

A

Streptococcal pyrogenic exotoxins

122
Q

Spe is made by:

A

Phage (lysogenized strains)

123
Q

Which exotoxins are made by S. pyogenes?

A

A, B, C, F

124
Q

True or false: superantigens of S. pyogenes are structurally and functionally similar to S. aureus TSST-1

125
Q

Superantigens cause:

A

cytokine storm of IL-1 and TNF (overreaction of immune system)

126
Q

Cytokine storm can lead to:

A

shock, organ failure

127
Q

Hemolysins are ________ toxins and associated with _______

A

extracellular; S. pyogenes

128
Q

Which streptolysins are made by S. pyogenes?

A
  • streptolysin O (forms pores)
  • streptolysin S (responsible for B hemolysis)
129
Q

S. pyogenes spreading factors

A

Streptokinase (dissolves blood clots)

130
Q

S. pyogenes disease types

A
  1. Primary suppurative (pus) infections
  2. Invasive disease (often toxin-mediated)
  3. Non-suppurative sequelae: Non-pus complications after infection
131
Q

What causes strep throat?

A

S. pyogenes primary suppurative infection (pharyngitis)

132
Q

Symptoms of strep throat

A

Sore throat, fever, malaise, headache, cervical lymphadenopathy

133
Q

True or false: most sore throats are caused by S. pyogenes

A

False - most caused by viruses

134
Q

What are tonsilloliths

A

tonsil stones

135
Q

Tonsil stones are ___

A

calcified bacteria and debris in palatine tonsil crypts

136
Q

_____ may occur if you have tonsil stones

A

Aspiration pneumonia

137
Q

Group A strep causes what kinds of skin infections? (4)

A
  1. pyoderma (any skin disease involving pus)
  2. impetigo
  3. erysipelas (upper dermis)
  4. cellulitis
138
Q

Impetigo tx

A

topical/systemic abx

139
Q

What is erysipelas?

A

Painful, red, swelling of upper dermis, may blister

140
Q

Impetigo of the upper dermis is also known as:

A

St. Anthony’s Fire

Erysipelas

141
Q

Orbital cellulitis can be caused by

A

Streptococcus pyogenes

142
Q

What is puerperal fever?

A

“purple” fever; childbed fever postpartum

143
Q

What was discovered in 1847 by Ignaze Semmelweis?

A

Handwashing drastically reduced puerperal fever incidents

144
Q

Which bacteria can cause primary suppurative infections?

A

Streptococcus pyogenes

145
Q

Examples of suppurative infections caused by S. pyogenes

A
  1. puerperal fever
  2. otitis media (middle ear infection)
  3. sinusitis
  4. pneumonia
  5. mastoiditis
146
Q

What is mastoiditis, and what are the symptoms?

A

Infection of mastoid process right behind the ear, causes swollen area and ear turns forward

147
Q

What invasive diseases can occur from S. pyogenes infection, and what toxin causes them to occur?

A
  1. Scarlet fever
  2. Streptococcal Toxic Shock Syndrome
  3. Necrotizing fasciitis (flesh eating disease)

All caused by streptococcal pyrogenic exotoxins

148
Q

True or false: Staphylococcal TSS has a higher mortality rate than Streptococcal TSS

A

False - Streptococcal TSS has higher mortality

149
Q

Necrotizing fasciitis has a mortality rate of:

150
Q

Streptococcus pyogenes invasive diseases are often caused by:

151
Q

Scarlet fever is a complication of:

A

Streptococcal pharyngitis (strep throat)

152
Q

Another name for strep throat

A

Streptococcal pharyngitis

153
Q

Scarlet fever is caused by ____ strains that produce pyrogenic exotoxins

A

Lysogenized

154
Q

Main physical symptoms of scarlet fever

A

Strawberry tongue, rash, fever

155
Q

Scarlet fever occurs ____ days after onset

156
Q

Rapid diagnosis methods for strep throat

A
  • rapid enzyme immunoassay
  • rapid agglutination test

Throat swabs

157
Q

S. pyogenes drug of choice for treatment

A

Penicillin
(If allergic –> erythromycin, azithromycin)

158
Q

True or false: there are several instances of antibiotic resistance of penicillin by S. pyogenes

A

False - all strains are susceptible so far

159
Q

After infection of S. pyogenes has resolved, what can occur?

A

Non-suppurative sequelae (complications)

160
Q

True or false: during non-suppurative sequelae, S. pyogenes organisms can still be recovered at this stage

A

False - no longer have the infection, so organisms cannot be isolated at this point

161
Q

Complications associated with S. pyogenes non-suppurative sequelae

A
  • rheumatic fever
  • glomerulonephritis
  • erythema nodosum
162
Q

True or false: Rheumatic fever is unusual in the US

A

True - due to access to antibiotics/healthcare

163
Q

What age group does rheumatic fever commonly affect?

A

Children 6-15 years old

164
Q

When does rheumatic fever develop?

A

2-5 weeks after pharyngeal infection

165
Q

What is the likely cause of rheumatic fever?

A

Antibodies to streptococcal antigens that cross react with certain tissues, like joints, heart, skin, nervous system

166
Q

Rheumatic fever causes inflammation of the ____

A

Heart (pancarditis)

combination of myocarditis, endocarditis, pericarditis

167
Q

Rheumatic fever effects in joints

A

Migratory, painful arthritis, large joints

168
Q

Sydenham’s Chorea occurs as a result of:

A

Rheumatic fever
- muscle weakness
- twitching

169
Q

This rash is characteristic of what disease?

A

Rheumatic fever (looks like antigen binding antibody on the skin since it is in a ring)

170
Q

How do you diagnose Rheumatic fever?

A

Elevated anti-streptolysin O (ASO) titer

171
Q

ASO positive indicates:

A

S. pyogenes previous infection and now having sequelae

172
Q

Rheumatic fever prophylaxis DOC

A

Penicillin
If allergic, erythromycin

173
Q

Acute glomerulonephritis can occur following ____ infections

A

Skin or pharyngeal

174
Q

Acute glomerulonephritis - where are antibody-antigen complexes deposited?

A

Glomerular basement membrane

175
Q

Inflammatory subcutaneous nodules are characteristic of:

A

Erythema nodosum

176
Q

Viridans streptococci - what type of hemolysis

177
Q

Viridans streptococci is normal flora of:

A

Oral cavity

178
Q

True or false: viridans streptococci is classifiable by the Lancefield system

179
Q

S.mutans is a part of the ____ streptococci group

A

Viridans streptococci

180
Q

Viridans streptococci - associated diseases

A
  • caries
  • subacute bacterial endocarditis (especially in patients with existing heart damage)
181
Q

Mitral valve vegetations can occur as a result of:

A

Viridans strep - subacute bacterial endocarditis

182
Q

In almost all cases of viridans strep, what occurs?

A

Heart murmurs

183
Q

According to AHA recommendations, what must be given to patients with history of heart valve therapy prior to dental therapy?

A

Prophylactic antibiotics
(pre-med)

184
Q

What medical history would indicate the need for pre-meds before dental therapy?

A
  1. prosthetic cardiac valves
  2. previous infective endocarditis (heart valve or endocardium)
  3. cardiac transplant that develops valve regurgitation
  4. Residual shunt or valvular regurgitation (congenital)
185
Q

Viridans strep can be found in what area of the teeth?

A

Towards the roots

186
Q

Dental procedures that involve ______ pose significant risks of bacteremia with viridans strep

A

Gingiva, periapical region of the teeth, perforation of oral mucosa

187
Q

What does not require antibiotic prophy for viridans strep? (5)

A
  • routine anesthetic injection in non-infected tissue
  • x-rays
  • placement of removable prosthodontic or ortho appliances
  • adjustment of ortho appliances
  • bleeding from trauma to the lips or oral mucosa
188
Q

What is the antibiotics prophylaxis regimen?

A

Single dose of amoxicillin taken orally 30-60 minutes before procedure
- Adults - 2 gm
- Children - 50mg/kg

189
Q

Streptococcus pneumoniae is gram ____ ____ and ____ hemolytic

A

Gram positive diplococcus;
Alpha

190
Q

True or false: S. pneumoniae cannot be classified using the Lancefield system

191
Q

_____ can be lysed by bile

A

S. pneumoniae

192
Q

Most of S. pneumoniae is _____-sensitive

193
Q

Streptococcus mitis is unaffected by:

194
Q

S. pneumoniae virulence factors

A
  1. polysaccharide capsule (antiphagocytic)
  2. IgA protease (cleaves IgA on mucosal surfaces to help bacteria stick to membranes and colonize)
195
Q

Smooth-edge colonies indicated presence of:

A

S. pneumoniae (S strain capsule = smooth strains)

196
Q

Capsule serotype tests (2)

regarding S. pneumoniae

A
  1. Immunofluorescence (test of choice)
  2. Quellung test (capsular swelling)

regarding S. pneumoniae

197
Q

Most common cause of bacterial pneumonia, meningitis, ear infection

A

S. pneumoniae

198
Q

S. pneumonia primarily affects what age groups?

A

Immunocompromised old/young people

199
Q

S. pneumoniae infects you via:

A

Auto inoculation (infecting yourself)

200
Q

Common cause of U.S. vaccine-preventable death

A

S. pneumoniae

201
Q

Predisposing factors to getting pneumonia from S. pneumoniae

A

Sickle cell disease (splenic insufficiency), impaired immunity, HIV

202
Q

47% of all meningitis cases in the U.S. are caused by:

A

S. pneumoniae (leading cause)

203
Q

Pneumonia caused by S. pneumoniae is usually localized to:

A

Lower lobes of the lungs –> lobar pneumonia

204
Q

Generalized bronchopneumonia may occur in ____ people due to this bacteria:____

A

Very young/old people; S. pneumoniae

205
Q

Meningitis definition

A

Infection of the meninges covering the brain and spinal cord

206
Q

Encephalitis definition

A

Infection of the brain

207
Q

Meningoencephalitis infects:

A

Meninges and the brain

208
Q

Symptoms of meningitis

A

In adults
- Fever
- headache
- stiff neck
- Photophobia
- Altered mental status/seizures
- Nausea and vomiting

209
Q

What is the fatality rate of meningitis caused by S. pneumoniae?

A

30%, up to 80% in elderly

210
Q

Bacterial meningitis is ____ and presentation includes ____

A

Purulent; acute, rapid onset, life threatening

211
Q

Characteristics of CSF in bacterial meningitis (WBC count, cell type, glucose and protein levels?)

A

WBC = 0 - 60,000
Cell type = neutrophil
Glucose = very low (bacteria is using it all up)
Protein = high (increased antibodies and bacterial proteins)

212
Q

What does CSF look like if someone has bacterial meningitis?

A

Appears turbid/cloudy (high number of neutrophils)

213
Q

What does bacterial meningitis look like on histology?

A

Leptomeninges is infiltrated with neutrophils

214
Q

True or false: susceptibility testing is needed to treat S. pneumoniae meningitis due to prevalence of multidrug-resistance strains

215
Q

According to the American Academy of Pediatrics, what is the recommended DOC for bacterial meningitis?

A

Vancomycin and cephalosporin for initial diagnosis until organism is identified

Vancomycin used for highly resistant strains of S. pneumoniae

216
Q

S. pneumoniae is resistant to many drugs due to:

A

Transposons jumping onto R plasmid

217
Q

True or false: Vaccines are not available for S. pneumoniae

A

False

Polyvalent (23) vaccine; Conjugate (13) vaccine

218
Q

Which S. pneumoniae vaccine is given to people older than 2 years?

A

Polyvalent (23)

219
Q

Polyvalent vaccine (S. pneumoniae) is T-_______

A

independent (B cells produce antibodies without stimulation from T cells)

220
Q

True or false: Polyvalent vaccine for S. pneumoniae is efficient and has good memory

A

False - inefficient, poor memory

221
Q

Which S. pneumoniae vaccine is given to people younger than 2 years?

A

Conjugate polyvalent (13)
- polysaccharide and diphtheria toxin

222
Q

Conjugate polyvalent vaccine (S. pneumoniae) is T-_______

A

Dependent
(Efficient and good memory)

223
Q

How does conjugate polyvalent vaccine induce T cell response?

A
  • Polysaccharide(poorly antigenic) is linked to toxin carrier which is strongly antigenic
  • MHCs bind to protein carrier and present polysaccharide to T cell
  • induces T cell response
224
Q

Streptococcus agalactiae is classified as ____ in Lancefield

A

Group B Strep

225
Q

If Group B strep is present, positive ____ will occur

A

Agglutination

226
Q

Most common infectious cause ofneonatal morbidity and mortality/neonatal meningitis

A

S. agalactiae

227
Q

A thin rim of beta hemolysis on blood agar may indicate presence of:

A

S. agalactiae

weakly hemolytic

228
Q

At what age does S. agalactiae affect the most?

A

Less than one month old

229
Q

Streptococcus dysgalactiae is classified as:

A

Group L Strep (also found in Group D –> subspecies have similarities between group C, G, L antigens)

230
Q

S. dysgalactiae causes _____ like S. pyogenes

A

pharyngitis

231
Q

Enterococcus Faecalis is classified as Group ____ Strep

A

Group D strep

232
Q

Enterococcus faecalis is a major cause of:

A

Nosocomial/healthcare facilities infection
- UTI most common

233
Q

Vancomycin resistance is common in which bacteria?

A

Enterococcus faecalis

DEN 7102 Micro & Immuno Concepts (26 decks)

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