Exam 2 Gram Positive Cocci Flashcards
Split over 10/9 and 10/12 (233 cards)
1
Q
Infectivity
A
ability to infect
2
Q
Equation for infectivity
A
Number infected/number susceptible x100
3
Q
Pathogenicity
A
ability to cause disease
4
Q
Equation for pathogenicity
A
Number with clinical disease/number infected x100
5
Q
Virulence
A
ability to cause death
6
Q
Equation for virulence
A
Number of deaths/number with disease x100
7
Q
What are 3 gram positive species?
A
- staphylococci
- streptococci
- enterococci
8
Q
What are enterococci shaped like?
A
Not completely round or or oblong, kind of in between
Fat rods
9
Q
Staphylococci grow in ____
A
Clusters
10
Q
Streptococci grow in ___
A
chains
11
Q
Streptococci have what direction plane of splitting?
A
Vertical –> forms chains
12
Q
Diplococci have what direction plane of splitting?
A
Vertical, then vertical
or
Vertical, then horizontal
13
Q
Staphylococci have what direction plane of splitting?
A
diagonal – forms clusters
14
Q
____ are aerobic or facultative anaerobic
A
Staphylococci
15
Q
_____ grows in 7.5% NaCl
A
Staphylococci (halophilic)
16
Q
Which produces catalase, staph or strep?
A
Staph
17
Q
Products of catalase activity
A
oxygen (bubbles) and h2o
18
Q
____ are mostly facultative anaerobes, some anaerobes
A
Streptococci
19
Q
Streptococci are ____ organisms, needing enriched media to grow
A
fastidious
20
Q
True or false: staphylococci ferment well
A
False - streptococci are more known for fermentation
21
Q
Streptococci perform ____ ____ to produce lactic acid from glucose
A
homolactic fermentation
22
Q
_____ do not produce catalase
A
Streptococci
23
Q
Describe S. aureus colonies
A
Large colonies, “golden” cream color
Non s. aureus is white in color
24
Q
What type of hemolysis can staphylococci do?
A
Often beta hemolysis
25
Describe streptococci colonies
Small, white
| wider
26
What type of hemolysis can streptococci do?
Some can do alpha hemolysis, some species cannot do hemolysis at all
27
Where does S. aureus colonize?
anterior nares and/or skin of 30% of normal individuals
28
More than 80% of patients with ______ carry S. aureus
eczema/atopic dermatitis
(due to skin barrier being compromised)
29
S. aureus is often associated with _____ infection, transmission by carriers
nosocomial
| acquired at hospital, not present during the time of admission
30
What virulence factor distinguishes S. aureus from other staphylococci?
Coagulase
31
Coagulase is an enzyme that clots ____. It is produced by:
plasma; S. aureus (but not other staphylococci)
32
Function of coagulase
cross-link bacteria in the clot to **escape host immune system**
33
True or false: S. aureus has a polysaccharide capsule
True - inhibits phagocytosis
34
Most strains of S. aureus encode _______
penicillinase (beta lactamase) on plasmid
35
Staphylokinase
- converts **plasminogen to plasmin**, which cleaves C3b opsonin and IgG
- **inhibits phagocytosis** by PMN
36
Staphylokinase is a virulence factor of:
S. aureus
37
Superoxide dismutase is found in:
S. aureus
38
Superoxide dismutase causes resistance to:
phagocytes, which release superoxides
39
Chemotaxis inhibitory protein is a virulence factor of:
S. aureus
40
Chemotaxis inhibitory protein
- **competitively binds** to neutrophil formyl peptide receptor and **C5a receptor**
- harder to contain and kill pathogens
41
True or false: S. aureus can resist lysozymes
True - they have altered muramic acid in NAM, harder to damage cell walls
42
Where are exotoxins produced?
Inside the cell, then exported out
43
Example of S. aureus exotoxin
Protein A
44
Most common cause of Impetigo
S. aureus
45
Cellulitis can occur due to infection by _____
S. aureus
(also caused by Streptococcus pyogenes)
46
Cellulitis
infection of dermal and subcutaneous connective tissue
47
Impetigo looks like:
Honey colored crusts
48
True or false: impetigo is not infectious
False - highly infectious
49
S. aureus cellulitis (can't use topical creams)
50
S. aureus cellulitis
51
Furuncle
52
Carbuncle
53
_____ target intestines
Enterotoxins
54
Difference between exotoxins and endotoxins
exotoxins - produced inside cell and exported out
endotoxins - usually part of organism's cell wall
55
Enterotoxins can act as ____ when expressed systemically
superantigens
56
What can happen if exotoxins are eaten?
Bacterial intoxication (food poisoning)
57
TSST-1 is a ______
Superantigen
58
What does a superantigen do?
- 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
59
True or false: S. aureus exotoxin can also suppress normal immune response
True
60
Name some exotoxins produced by S. aureus
- TSST-1
- Protein A
- Enterotoxins (specifically enterotoxin A)
61
During normal phagocytosis, ___ binds to ____ and then to ____
IgG; S. aureus; PMN receptor (Fc region)
62
Protein A function
| Exotoxin: Protein A-mediated immune evasion
hinders opsonization/phagocytosis --> IgG now in wrong orientation
63
How does Protein A hinder phagocytosis?
Protein A binds to Fc region of IgG so it cannot bind to PMN. Decreases phagocytosis
64
Staphylococcal food poisoning is caused by:
S. aureus enterotoxin A
65
Main symptom of S. aureus food poisoning
**Projectile vomiting 1-6 hours after ingestion**, nausea, cramps, diarrhea
66
True or false: you won't die from Staph food poisoning unless you are dehydrated
True
67
Enterotoxins directly affect ____
intestinal epithelium
68
TSST-1 is also known as:
- enterotoxin B
- pyrogenic exotoxin
69
True or false: males are not affected by TSST
False - can acquire through deep tissue infection
70
Females can acquire TSST via:
high-absorbancy tampon
71
Cytotoxins a, b, d, g, are associated with:
S. aureus
72
Cytotoxins a, b, d, g are toxic for what kinds of cells?
Many blood cells, including RBC, WBC
73
Exfoliatin A and B are toxins of:
S. aureus
74
Exfoliatin A and B are ____. What do they do?
- They are **serine proteases** that cleave desmoglein-1
- split desmosomes in epidermis
- Results in Scalded Skin Syndrome
75
What is the most common cause of osteomyelitis?
S. aureus (exception = osteomyelitis of the mandible)
76
What is osteomyelitis?
Inflammation of bone/marrow
77
True or false: S. aureus can cause acute endocarditis
True
78
How is acute endocarditis acquired?
from **staphylococcal bacteremia**, which originates from skin infection, surgery, IV catheter
79
Acute endocarditis can lead to:
heart failure, septic emboli
80
Acute endocarditis mortality rate
50%
81
What is septic emboli?
- can be caused by S. aureus
- embolism that can dislodge and spread through the body
82
Most strains of S. aureus are resistant to ______ because _____
Penicillin; they produce penicillinase
83
Penicillinase of S. aureus is mediated by:
Plasmid
84
DOC to S. aureus resistant to penicillin
Methicillin (penicillinase resistant penicillin)
85
MRSA
Methicillin resistant Staph Aureus
86
True or false: methicillin also has a B lactam ring
True - but penicillinase from S. aureus has a harder time getting to it
87
True or false: MRSA is not very common
False - now common in around 60% hospital isolates
88
MRSA is encoded by:
mecA
| mobile genetic element that inserted itself on the chromosome
89
MecA gene produces:
PBP2a (penicillin binding protein, binds to B lactam antibiotics to prevent binding to transpeptidase
90
DOC for MRSA
Vancomycin
91
MRSA colonizes ____ of healthy people
2%
92
Majority of MRSA causes what kind of infections?
skin or soft tissue infections
93
In hospital associated facilities, MRSA is associated with:
| Not the majority of S. aureus cases
- bloodstream infections
- pneumonia
- surgical site infections
- sepsis
- death
94
What are some risk factors for MRSA colonization?
- recent hospitalization
- prolonged hospital stay
- residence in long term care facility
95
True or false: Healthcare-associated MRSA infections are declining and have recently slowed
True - declining since 2005
96
True or false: community associates rates of MRSA are decreasing
False - increasing
97
Current recommendations of DOC for bacteremia or pneumonia
1. **Vancomycin**, daptomycin
2. Second line: linezolid, clindamycin, telavancin, ceftaroline
98
Current recommendations of DOC for skin infections
- **incision and drainage** if abscessed
- clindamycin, tetracycline
99
True or false: VRSA has already been identified
True - plasmid mediated
100
Linezolid resistance reported in ____
2010
101
Staphylococcus epidermidis is ____ negative
coagulase
102
Where is Staphylococcus epidermidis found normally?
normal flora of skin, mucous membrane
103
Staphylococcus epidermidis has _____ to prevent from drying/salty environment
Slime layer (capsule)
Also allows attachment to tissues, foreign bodies
104
Most Staphylococcus epidermidis infections are from:
self flora
105
Treatment for Staphylococcus epidermidis
Antibiotic susceptibility tests (over 50% resistant to methicillin)
106
On an antibiotic susceptibility, what indicates antibiotic resistance?
Lack of zone of inhibition
107
Streptococcus can perform what kind of hemolysis?
A, B, gamma
| B accounts for most streptococcal diseases
108
Lancefield system classifies streptococci based on:
antigens on cell wall
109
Group A Strep also known as:
Streptococcus pyogenes
110
Group B Strep contains:
- Streptococcus agalactiae
- Streptococcus halichoeri
111
Group A strep causes what kinds of infections:
Skin and throat infections
112
Group A strep is ___ hemolytic
Beta
113
Group B strep causes:
neonatal meningitis
114
Group B strep is ___ hemolytic
Beta
115
Non-lancefield streptococci lack _____
Lancefield carbohydrates
116
Example of Non-lancefield streptococci
Streptococcus pneumoniae
| bacterial pneumonia
117
M protein is a virulence factor of:
Streptococcus pyogenes
118
M protein function
- **evasion**
- **adhesin** (attachment)
- **destroys C3-convertase to inhibit opsonization by C3b**
| Most important virulence factor
119
F protein of S. pyogenes
Adhesin, binds fibronectin
120
S. pyogenes capsule function
Evasion, antiphagocytic
121
Spe stands for:
Streptococcal pyrogenic exotoxins
122
Spe is made by:
Phage (lysogenized strains)
123
Which exotoxins are made by S. pyogenes?
A, B, C, F
124
True or false: superantigens of S. pyogenes are structurally and functionally similar to S. aureus TSST-1
True
125
Superantigens cause:
cytokine storm of IL-1 and TNF (overreaction of immune system)
126
Cytokine storm can lead to:
shock, organ failure
127
Hemolysins are ________ toxins and associated with _______
extracellular; S. pyogenes
128
Which streptolysins are made by S. pyogenes?
- streptolysin O (forms pores)
- streptolysin S (responsible for B hemolysis)
129
S. pyogenes spreading factors
Streptokinase (dissolves blood clots)
130
S. pyogenes disease types
1. Primary suppurative **(pus)** infections
2. **Invasive** disease (often **toxin**-mediated)
3. Non-suppurative **sequelae**: Non-pus complications after infection
131
What causes strep throat?
S. pyogenes primary suppurative infection (pharyngitis)
132
Symptoms of strep throat
Sore throat, fever, malaise, headache, cervical lymphadenopathy
133
True or false: most sore throats are caused by S. pyogenes
False - most caused by viruses
134
What are tonsilloliths
tonsil stones
135
Tonsil stones are ___
calcified bacteria and debris in palatine tonsil crypts
136
_____ may occur if you have tonsil stones
Aspiration pneumonia
137
Group A strep causes what kinds of skin infections? (4)
1. pyoderma (any skin disease involving pus)
2. impetigo
3. erysipelas (upper dermis)
4. cellulitis
138
Impetigo tx
topical/systemic abx
139
What is erysipelas?
Painful, red, swelling of upper dermis, may blister
140
Impetigo of the upper dermis is also known as:
St. Anthony's Fire
| Erysipelas
141
Orbital cellulitis can be caused by
Streptococcus pyogenes
142
What is puerperal fever?
"purple" fever; childbed fever postpartum
143
What was discovered in 1847 by Ignaze Semmelweis?
Handwashing drastically reduced puerperal fever incidents
144
Which bacteria can cause primary suppurative infections?
Streptococcus pyogenes
145
Examples of suppurative infections caused by S. pyogenes
1. puerperal fever
2. otitis media (middle ear infection)
3. sinusitis
4. pneumonia
5. mastoiditis
146
What is mastoiditis, and what are the symptoms?
Infection of mastoid process right behind the ear, causes swollen area and ear turns forward
147
What invasive diseases can occur from S. pyogenes infection, and what toxin causes them to occur?
1. Scarlet fever
2. Streptococcal Toxic Shock Syndrome
3. Necrotizing fasciitis (flesh eating disease)
All caused by streptococcal pyrogenic exotoxins
148
True or false: Staphylococcal TSS has a higher mortality rate than Streptococcal TSS
False - Streptococcal TSS has higher mortality
149
Necrotizing fasciitis has a mortality rate of:
20-30%
150
Streptococcus pyogenes invasive diseases are often caused by:
Spe
151
Scarlet fever is a complication of:
Streptococcal pharyngitis (strep throat)
152
Another name for strep throat
Streptococcal pharyngitis
153
Scarlet fever is caused by ____ strains that produce pyrogenic exotoxins
Lysogenized
154
Main physical symptoms of scarlet fever
Strawberry tongue, rash, fever
155
Scarlet fever occurs ____ days after onset
1-2 days
156
Rapid diagnosis methods for strep throat
- rapid enzyme immunoassay
- rapid agglutination test
| Throat swabs
157
S. pyogenes drug of choice for treatment
Penicillin
(If allergic --> erythromycin, azithromycin)
158
True or false: there are several instances of antibiotic resistance of penicillin by S. pyogenes
False - all strains are susceptible so far
159
After infection of S. pyogenes has resolved, what can occur?
Non-suppurative sequelae (complications)
160
True or false: during non-suppurative sequelae, S. pyogenes organisms can still be recovered at this stage
False - no longer have the infection, so organisms cannot be isolated at this point
161
Complications associated with S. pyogenes non-suppurative sequelae
- **rheumatic fever**
- glomerulonephritis
- erythema nodosum
162
True or false: Rheumatic fever is unusual in the US
True - due to access to antibiotics/healthcare
163
What age group does rheumatic fever commonly affect?
Children 6-15 years old
164
When does rheumatic fever develop?
2-5 weeks after pharyngeal infection
165
What is the likely cause of rheumatic fever?
Antibodies to streptococcal antigens that cross react with certain tissues, like joints, heart, skin, nervous system
166
Rheumatic fever causes inflammation of the ____
Heart (pancarditis)
| combination of myocarditis, endocarditis, pericarditis
167
Rheumatic fever effects in joints
Migratory, painful arthritis, **large** **joints**
168
Sydenham's Chorea occurs as a result of:
Rheumatic fever
- muscle weakness
- twitching
169
This rash is characteristic of what disease?
Rheumatic fever (looks like antigen binding antibody on the skin since it is in a ring)
170
How do you diagnose Rheumatic fever?
Elevated **anti-streptolysin O (ASO) titer**
171
ASO positive indicates:
S. pyogenes previous infection and now having sequelae
172
Rheumatic fever prophylaxis DOC
Penicillin
If allergic, erythromycin
173
Acute glomerulonephritis can occur following ____ infections
Skin or pharyngeal
174
Acute glomerulonephritis - where are antibody-antigen complexes deposited?
Glomerular basement membrane
175
Inflammatory subcutaneous nodules are characteristic of:
Erythema nodosum
176
Viridans streptococci - what type of hemolysis
Alpha
177
Viridans streptococci is normal flora of:
Oral cavity
178
True or false: viridans streptococci is classifiable by the Lancefield system
False
179
S.mutans is a part of the ____ streptococci group
Viridans streptococci
180
Viridans streptococci - associated diseases
- caries
- subacute bacterial endocarditis (especially in patients with existing heart damage)
181
Mitral valve vegetations can occur as a result of:
Viridans strep - subacute bacterial endocarditis
182
In almost all cases of viridans strep, what occurs?
Heart murmurs
183
According to AHA recommendations, what must be given to patients with history of heart valve therapy prior to dental therapy?
Prophylactic antibiotics
(pre-med)
184
What medical history would indicate the need for pre-meds before dental therapy?
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
Viridans strep can be found in what area of the teeth?
Towards the roots
186
Dental procedures that involve ______ pose significant risks of bacteremia with viridans strep
Gingiva, periapical region of the teeth, perforation of oral mucosa
187
What does not require antibiotic prophy for viridans strep? (5)
- 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
What is the antibiotics prophylaxis regimen?
Single dose of **amoxicillin** taken orally 30-60 minutes before procedure
- Adults - 2 gm
- Children - 50mg/kg
189
Streptococcus pneumoniae is gram ____ ____ and ____ hemolytic
Gram positive diplococcus;
Alpha
190
True or false: S. pneumoniae cannot be classified using the Lancefield system
True
191
_____ can be lysed by bile
S. pneumoniae
192
Most of S. pneumoniae is _____-sensitive
Optochin
193
Streptococcus mitis is unaffected by:
optochin
194
S. pneumoniae virulence factors
1. polysaccharide capsule (**antiphagocytic**)
2. IgA protease (cleaves IgA on mucosal surfaces to **help bacteria stick to membranes and colonize**)
195
Smooth-edge colonies indicated presence of:
S. pneumoniae (S strain capsule = smooth strains)
196
Capsule serotype tests (2)
| regarding S. pneumoniae
1. Immunofluorescence (test of choice)
2. Quellung test (capsular swelling)
| regarding S. pneumoniae
197
Most common cause of bacterial pneumonia, meningitis, ear infection
S. pneumoniae
198
S. pneumonia primarily affects what age groups?
Immunocompromised old/young people
199
S. pneumoniae infects you via:
Auto inoculation (infecting yourself)
200
Common cause of U.S. vaccine-preventable death
S. pneumoniae
201
Predisposing factors to getting pneumonia from S. pneumoniae
Sickle cell disease (splenic insufficiency), impaired immunity, HIV
202
47% of all meningitis cases in the U.S. are caused by:
S. pneumoniae (leading cause)
203
Pneumonia caused by S. pneumoniae is usually localized to:
Lower lobes of the lungs --> lobar pneumonia
204
Generalized bronchopneumonia may occur in ____ people due to this bacteria:____
Very young/old people; S. pneumoniae
205
Meningitis definition
Infection of the meninges covering the brain and spinal cord
206
Encephalitis definition
Infection of the brain
207
Meningoencephalitis infects:
Meninges and the brain
208
Symptoms of meningitis
In adults
- Fever
- headache
- stiff neck
- Photophobia
- Altered mental status/seizures
- Nausea and vomiting
209
What is the fatality rate of meningitis caused by S. pneumoniae?
30%, up to 80% in elderly
210
Bacterial meningitis is ____ and presentation includes ____
Purulent; acute, **rapid** onset, **life threatening**
211
Characteristics of CSF in bacterial meningitis (WBC count, cell type, glucose and protein levels?)
WBC = 0 - 60,000
Cell type = neutrophil
Glucose = very low (bacteria is using it all up)
Protein = high (increased antibodies and bacterial proteins)
212
What does CSF look like if someone has bacterial meningitis?
Appears turbid/cloudy (high number of neutrophils)
213
What does bacterial meningitis look like on histology?
Leptomeninges is infiltrated with neutrophils
214
True or false: susceptibility testing is needed to treat S. pneumoniae meningitis due to prevalence of multidrug-resistance strains
True
215
According to the American Academy of Pediatrics, what is the recommended DOC for bacterial meningitis?
**Vancomycin and cephalosporin** for initial diagnosis until organism is identified
| Vancomycin used for highly resistant strains of S. pneumoniae
216
S. pneumoniae is resistant to many drugs due to:
Transposons jumping onto R plasmid
217
True or false: Vaccines are not available for S. pneumoniae
False
| Polyvalent (23) vaccine; Conjugate (13) vaccine
218
Which S. pneumoniae vaccine is given to people older than 2 years?
Polyvalent (23)
219
Polyvalent vaccine (S. pneumoniae) is T-_______
**independent** (B cells produce antibodies without stimulation from T cells)
220
True or false: Polyvalent vaccine for S. pneumoniae is efficient and has good memory
False - inefficient, poor memory
221
Which S. pneumoniae vaccine is given to people younger than 2 years?
Conjugate polyvalent (13)
- polysaccharide and diphtheria toxin
222
Conjugate polyvalent vaccine (S. pneumoniae) is T-_______
Dependent
(Efficient and good memory)
223
How does conjugate polyvalent vaccine induce T cell response?
- 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
Streptococcus agalactiae is classified as ____ in Lancefield
Group B Strep
225
If Group B strep is present, positive ____ will occur
Agglutination
226
Most common infectious cause ofneonatal morbidity and mortality/neonatal meningitis
S. agalactiae
227
A thin rim of beta hemolysis on blood agar may indicate presence of:
S. agalactiae
| weakly hemolytic
228
At what age does S. agalactiae affect the most?
Less than one month old
229
Streptococcus dysgalactiae is classified as:
Group L Strep (also found in Group D --> subspecies have similarities between group C, G, L antigens)
230
S. dysgalactiae causes _____ like S. pyogenes
pharyngitis
231
Enterococcus Faecalis is classified as Group ____ Strep
Group D strep
232
Enterococcus faecalis is a major cause of:
Nosocomial/healthcare facilities infection
- UTI most common
233
Vancomycin resistance is common in which bacteria?
Enterococcus faecalis
