Bacteria Flashcards
1
Q
What is the minimum requirement for a plasmid to be transferred during conjugation?
A
it must have an oriT
2
Q
What is an R plasmid?
A
one that conveys multiple antibiotic resistance
3
Q
Name the three mechanisms of bacterial conjugation.
A
- F+ conjugation
- Hfr conjugation
- conjugative transposons
4
Q
Antibiotic resistance genes are typically found on what sort of genetic element?
A
transposons
5
Q
What role do resident bacteria populations play in the antibiotic resistance of pathogens?
A
they provide R plasmid reservoirs that can be conveyed to pathogens
6
Q
Long-term use of antibiotics can affect the human gut and increase a person’s risk for what four things?
A
- infection
- obesity
- cancer
- autoimmunity
7
Q
What induces a phage to transition from a lysogenic cycle to a lytic one?
A
DNA damage, which triggers degradation of the phage repressor protein thereby permitting phage genome transcription
8
Q
Name four important components of an F plasmid.
A
- oriT
- oriV
- IS elements
- tra operon
9
Q
What is the tra operon?
A
an operon on F plasmids which encodes the components of the conjugation apparatus and allows for construction of the F pilus as well as nicking, unwinding, transfer of plasmid DNA
10
Q
What is a phage repressor protein?
A
a protein expressed by lysogenic phage to prevent gene transcription and maintain the lysogenic cycle
11
Q
Why don’t Hfr recipients become F+?
A
because transfer is terminated before F factor can be transferred
12
Q
What is a prophage?
A
a bacteria in which lysogenic phage DNA has been incorporated into the genome
13
Q
Where do antibiotic resistance genes typically originate?
A
in the species that makes the antibiotic
14
Q
What happens to the donated DNA at the end of Hfr conjugation?
A
it undergoes exchange with the recipient or is degraded
15
Q
What happens to temperate phage DNA after it first infects a bacterial cell?
A
it circularizes and either enters a lytic cycle or recombines with the bacterial chromosome at the att site
16
Q
What is a temperate phage?
A
one capable of establishing lysogeny
17
Q
What is an oriV?
A
the origin of replication for F plasmids
18
Q
What are integrative conjugative elements?
A
elements within the bacterial genome that are retain the ability to excise and be transferred via conjugation
19
Q
How does R plasmid antibiotic resistance differ from mutation-induced antibiotic resistance?
A
- mutations are more likely to contribute to modification of an antibiotic target such that it is less susceptible
- plasmids are more likely to convey efflux pumps or proteins capable of modifying the antibiotic itself
- furthermore, plasmids are more likely to convey multiple antibiotic resistances rather than just one
20
Q
What is phage conversion?
A
a change in bacterial phenotype due to expression of phage genes during a lysogenic infection
21
Q
What are the three modes of bacterial genetic exchange?
A
- transformation
- transduction
- conjugation
22
Q
What happens to the transferred DNA after generalized transduction?
A
the DNA recombines with chromosomal DNA via homologous recombination
23
Q
What happens to the transferred DNA after specialized transduction?
A
the DNA is inserted at the recipient att site
24
Q
What is a Kirby-Bauer test?
A
an antibiotic resistance test involving disk diffusion
25
Bacteria typically use passive uptake to invade what host cell population?
phagocytic cells
26
Acid-fast stain is used to diagnose what kind of bacteria?
mycobacteria
27
What is CD14?
a membrane bound host receptor that binds LPS-binding protein and signals via a TLR to mediate toxic shock
28
Many AB exotoxins perform what function?
ADP-ribosylation
29
What are type I bacterial pili?
those that adhere to mannose receptors
30
What are type P bacterial pili?
those that adhere to Gal-Gal receptors
31
Describe how blood samples ought to be taken for culture.
- avoiding contamination by skin flora
| - in multiple across 24 hours
32
Name two classes of membrane damaging exotoxins.
- phospholipases
| - pore forming toxins
33
When would you collect a sputum sample?
if you suspected a LRTI
34
How is an ELISA performed?
- antigen or antibody is fixed in place
- sample is applied
- a chromogenic enzyme substrate is applied
- the color change is measured
35
In what cases are next-gen sequencing useful in diagnosing bacterial infections?
low complexity situations like CSF
36
What are pathogenicity islands?
regions of bacterial DNA that encode virulence genes, specifically T3SS
37
What is transcytosis?
a mechanism for cellular invasion that relies on actin polymerization and has no extracellular phase
38
What is latex agglutination?
- antibody or antigen is fixed to latex beads
- sample is applied
- a positive test will results in visible clumping of the beads
39
What are the three components of LPS?
- O antigen
- core polysaccharide
- lipid A
40
Which part of LPS is responsible for its toxicity?
lipid A
41
What is a quantitative diffusion E test?
a form of disk diffusion that uses a strip infused with varying concentration of antibiotic
42
What advantage does a bacterial capsule offer?
it can mask or prevent complement binding, thereby preventing opsonification
43
List Koch's molecular postulates.
- gene or its products should be associated with the organism
- the gene should be isolated via cloning
- inactivation should lead to loss of pathogenicity
- reactivation should restore pathogenicity
44
How is acid-fast staining performed?
- heat fix the specimen
- stain with carbolfuchsin
- promote uptake with heat
- decolorize (acid-fast will resist this)
- counterstain with methylene blue
45
What are southern and northern blots?
diagnostic techniques that utilize hybridization of nucleic acid probes against DNA or RNA, respectively
46
What is a catalase test?
a diagnostic technique that tests the ability of a bacteria to form gas
47
Encapsulated bacteria pose a greater problem for hosts with what kind of immune deficiency?
those with depressed cell-mediated immunity
48
List four types of exotoxins.
- membrane damaging
- enzymes that act on ECM
- AB
- superantigens
49
What group of virulence factors are largely responsible for the tissue tropism of a pathogen?
the adhesins it expresses
50
What are the steps of PCR?
- heat to denature RNA
- cool to allow annealing of primers
- allow polymerase to amplify
- repeat
51
How is pulse-field gel electrophoresis performed?
- digest DNA with a rare cutter
| - separate these fragments by gel electrophoresis with a switching electric field
52
What are alpha, beta, and gamma hemolysis?
- alpha is partial and has a geen color
- beta is complete hemolysis
- gamma is no hemolysis
53
What is wright-giemsa stain?
a stain used to diagnose chlamydia
54
Where on the anaerobe-anaerobic spectrum do mycobacteria fall?
they are obligate aerobes
55
Name the two important tuberculous mycobacteria.
- M. tuberculosis
| - M. bovus
56
Why is M. bovus important?
it is the basis for the BCG vaccine against tuberculosis
57
Name the two important non-tuberculous mycobacteria.
- M. kansasii
| - M. avium-intracellulare
58
List seven risk factors for tuberculosis.
- young or old age
- immunocompromised state
- exposure to persons with disease
- chronic pulmonary disease
- homelessness
- alcohol or elicit drug use
- incarceration
59
Mycobacteria have cell walls with a high __ content.
lipid
60
What is arabinogalactan?
the other significant component of the mycobacteria cell wall apart from mycolic acids and lipids
61
Which bacteria have mycolic acids and lipids in their cell wall?
mycobacteria
62
What is lipoarabinomannan?
an adhesin expressed by mycobacteria that binds the mannose receptor of macrophages
63
How does M.tb survive intracellularly in macrophages?
it prevents fusion of the phagosome and lysosome
64
A PPD is a example of what kind of hypersensitivity reaction?
a delayed type IV
65
What is cord factor?
a virulent protein expressed by M.tb which disrupts mitochondrial membranes and is cytotoxic for PMNs
66
Describe the histology of a M.tb tubercle.
a large granuloma containing bacilli, epithelioid histiocytes, and Langhans cells, surrounded by T cells and macrophages and encapsulated with collagen
67
Epithelioid histiocytes have what cell origin?
macrophage
68
Define Ghon focus, Ghon complex, and Ranke complex.
- Ghon focus: a primary M.tb tubercle
- Ghon complex: a goon focus that also involves the adjacent lymphatics and hilar lymph nodes
- Ranke complex: a fibrous, calcified Ghon complex
69
How does pulmonary TB present?
- night sweats
- weight loss
- initially unproductive cough that begins to produce a blood sputum
70
What is primary TB?
clinically apparent TB within two years of infection
71
In which two populations do we most often see primary TB rather than secondary TB?
- children
| - the immunocompromised
72
What is miliary TB?
widespread, hematogenous dissemination of M.tb
73
What is scrofula?
another name for mycobacterial cervical lymphadenitis
74
How is active TB diagnosed?
- clinically
| - and confirmed by skin test and radiology
75
Where in the lungs are TB lesions most common?
the most oxygenated
76
A PPD will not be positive until how long after the initial infection?
3-6 weeks
77
What are four limitations of the PPD?
- anergy in immunocompromised patients
- 3-6 weeks delay until positive
- prior immunization may generate a false positive
- there is some cross-reactivity with other mycobacteria
78
For which populations does a 5mm induration indicate a positive PPD?
- close contact with someone TB+
- someone with known HIV
- someone with a history of IV drug use
79
For which populations is a 10mm induration a positive PPD?
- foreign-born individuals
- children under 4
- HIV negative individuals with history of IV drug use
- low income
- residential facility occupants
80
How is an interferon-gamma release assay performed?
- M.tb antigens added to whole blood
- antigens activate TH1 cells to produce interferon
- that production is measured with an ELISA
81
What population of T helper cells mediates M.tb reactions?
TH1
82
Why isn't culture used to diagnose M.tb?
it is definitive but very slow
83
List the five first-line therapies for treatment of TB.
- isoniazid
- ethambutol
- rifampin
- streptomycin
- pyrazinamide
84
What is XDR-TB?
TB resistant to isoniazid, rifampin, quinolone, and at least one second line drug
85
What is MDR-TB resistant to?
- isoniazid
| - rifampin
86
Who is a candidate for TB prophylaxis?
someone with a positive skin test and some other risk factor
87
Name four actions that have been taken to control TB.
- pasteurization of milk
- antibiotic prophylaxis for HIV
- development of the BCG vaccine
- better surveillance and treatment programs
88
What is the BCG vaccine?
a live, attenuated M. bovis vaccine
89
Why is the BCG vaccine not used in the US?
- unreliable efficacy
| - most US citizens are at low risk
90
HIV patients have what risk of TB?
7-10 percent annual risk
91
How is M. leprae transmitted?
close contact or aerosols
92
M. leprae targets which human cell population?
schwann cells
93
Armadillos are a reservoir for what pathogen?
M. leprae
94
How does tuberculoid leprosy differ from lepromatous leprosy?
- tuberculoid is mediated by TH1 cells and there are few bacteria in lesions
- lepromatous is mediated by TH2 humoral immunity and there are many bacteria found in lesions
95
Name three diagnostic tests for leprosy.
- lepromin skin test
- serology for PGL-1
- acid fast stain of tissues
96
What is the two drug combination preferred for treatment of leprosy?
- rifampin
| - dapsone
97
Dapsone is contraindicated for which group of people?
those with a G6PDH deficiency
98
What is the mechanism of action of dapsone?
it inhibits folic acid synthesis
99
Which disease presents with a hypo pigmented, anesthetic skin patch and complaints of an electric-current-like sensation?
leprosy
100
Which non-tuberculous mycobacteria is ubiquitous in water?
M. avium-intracellulare
101
What are Runyon classifications?
a method for classifying mycobacteria based on the pigment produced in their colonies
102
M. avium-intracellulare is resistant to which antibiotics?
clarithromycin and ethambutol
103
How does M. kansasii manifest?
as a TB-like disease
104
How does M. marinum manifest?
subcutaneous abscesses and skin ulcers
105
Which mycobacteria-like pathogen has a hyphae form and also forms white-to-orange colonies?
nocardia
106
Where is nocardia found?
in the soil and decaying organic matter
107
How does nocardia evade phagocytic killing once inside macrophages?
by secreting catalase and SOD
108
Nocardia causes what two diseases?
- bronchopulmonary disease
| - cutaneous nocardiosis
109
What is nocardia bronchopulmonary disease?
- a localized disease in immunocompetent patients with pre-existing pulmonary conditions
- spreads into pleura and then into CNS and skin
110
Who is at risk for nocardia bronchopulmonary disease?
- immunocompetent patients with a pre-existing pulmonary condition
- patients with a T cell deficiency
111
Cutaneous nocardiosis comes in what two forms?
- actinomycotic mycetoma
| - lymphocutaneous disease
112
How does actinomycotic mycetoma present?
- painless, firm subcutaneous nodules
- erythema and sinus tract formation
- caused by nocardia
113
How does lymphocutaneous disease present?
- nodules along lymphatics
| - caused by nocardia
114
How is nocardia treated?
- TMP-SMX for six weeks
| - possible surgical intervention
115
CD14 signals through which TLR?
TLR4
116
How do we subtype members of the same bacterial species?
based on their pattern of antigens, toxins, or bacteriophage sensitivity
117
How is gram staining performed?
- apply crystal violet stain
- apply gram's iodine
- decolorize
- counterstain with safranin red
118
List four methods for phylogenetic classification of bacteria.
- GC content
- sequencing
- comparing conserved genes (70%)
- comparing 16S rRNA (97%)
119
Bacteria use which ribosome for translation?
70S
120
All bacteria have what kind of genome?
a dsDNA genome
121
Where in bacterial cells is the ETC and ATP synthesis machinery?
on the inner membrane
122
How does the composition of the phospholipid bilayer of bacterial cells differ from that of humans?
it lacks sterols
123
What component of tears and saliva destroy bacterial cell walls?
lysozyme
124
Describe the basic subunit of peptidoglycan.
NAG-NAM-peptide chain
125
What is leptoteichoic acid?
a component of the gram+ cell wall, which serves as an endotoxin
126
Describe gram- cell walls.
- a thin peptidoglycan layer
| - an outer, asymmetric layer of phospholipids and LPS
127
Gram- porins allow passage of what kind of molecules?
small, hydrophilic molecules
128
List the cell wall types in order of most to least permeable.
- acid-fast
- gram-
- gram+
- mycoplasma
129
What powers flagella?
membrane potential
130
Which group of bacteria express T3SS and T4SS?
gram- bacteria
131
Which bacteria are capable of forming spores?
gram+
132
List three endotoxins.
- LPS
- teichoic acids
- PG fragments
133
What is the difference between facultative and aerotolerant anaerobes?
facultative will use oxygen if it is present, but aerotolerant will only endure it
134
Why is oxygen toxic to obligate anaerobes?
often because they are unable to deal with the ROS that will form
135
What is superoxide dismutase?
enzyme that converts O^-2 to water
136
What is catalase?
an enzyme that converts hydrogen peroxide to water
137
What three mechanisms drive active transport across bacterial cell membranes?
- ATP
- the proton motive force
- group translocation
138
B-lactams are an analog for what?
the D-ala, D-ala terminal of peptidoglycan chains
139
What is cabapenemase?
a beta-lactamase capable of degrading all beta-lactams
140
What change mediates vancomycin resistance?
modification fo the terminal D-ala of peptidoglycan to prevent vancomycin binding
141
Which topoisomerases are involved in bacterial DNA replication?
II: removes supercoils ahead of fork
IV: resolves interlocked plasmids
142
Why is folic acid important for cellular processes?
it is needed for 1 carbon transfers in reactions used for nucleotide and amino acid synthesis
143
Why aren't human cells susceptible to sulfonamides?
they block synthesis of dihydrogolic acid, something we obtain from diet
144
What is mcr-1?
a gene that modifies LPS to convey resistance to colistin (a polymixin)
145
Define antiseptic.
a chemical agent used to reduce the concentration of microbes in tissue
146
Define disinfectant.
an agent used to kill microorganisms but doesn't meet the standard of sterilization
147
List five sterilization methods.
- radiation
- chemical
- gas vapors
- heat
- filtration
148
What chemical agent is used to disinfect surgical instruments?
chlorine
149
What are genomic islands?
patches of unusual sequence or GC content acquired through horizontal gene transfer
150
How is plasmid replication related to genome replication?
both processes use the same machinery
151
What is oriC?
the origin of replication for bacterial chromosomes
152
What role does DnaA play in bacterial chromosome replication?
it recognizes the oriC, unwinds the DNA, and recruits the necessary enzymes
153
What is the Rep protein?
a protein that initiates plasmid replication at oriT or oriV
154
What is a polycistronic transcript?
one that encodes multiple genes, usually from the same operon
155
What is dyad symmetry?
inverted repeats found at the end of bacterial transcripts which form hairpins and trigger termination
156
Expression of most operons is controlled via regulation of what step?
transcription initiation
157
What is a co-repressor?
a small molecule that binds a transcription repressor and alters its activity
158
How is the Lac operon negatively regulated?
allolactose, the inducer, binds the repressor and inactivates it so it can no longer bind the operator sequence
159
How is the Lac operon positively regulated?
falling glucose levels, increase cAMP, which binds the cAMP binding protein, which binds the DNA to serve as an activator
160
Under what conditions is the Trp operon expressed?
low levels of tryptophan
161
Describe trp attenuations.
when trp levels are low, transcription is stalled and avoids termination
162
What are the parts of a two-component system?
- sensor kinase with autophosphorylation ability
| - response regulator which gets phosphorylated
163
Why do bacterial populations express rare mutations more than humans?
- they are haploid
| - they have a rapid growth rate
164
What is the most common form of DNA mutation?
base substitution
165
What causes DNA breaks?
x-ray and gamma radiation
166
What is the largest group of chemical DNA mutagens?
alkylating agents
167
Through what mechanism do alkylating agents cause DNA mutation?
they interfere with proper hydrogen bonding of bases
168
Name the two most significant base analog chemical mutagens.
2-aminopurine and 5-bromouracil
169
What are intercalating agents?
DNA mutagens that insert themselves between adjacent bases and cause a frameshift mutation
170
What is a common intercalating agent?
ethydium bromide
171
How are ROS DNA mutagenic?
they oxidize DNA and cause mispairing
172
Through what repair mechanism is UV damage resolved?
direct repair
173
What DNA mutations are fixed via excision repair?
bulky adducts
174
Where does the sequence come from for recombinational DNA repair?
the sister chromosome
175
DNA polymerases have what proofreading mechanism?
3'-5' exonuclease activity
176
What are two non-mutagenic mechanisms for repairing thymine dimers?
- light repair (aka photo reactivation)
| - dark repair (nucleotide excision)
177
What are LexA and RecA?
- LexA is a repressor protein which inhibits SOS repair proteins
- RecA cleaves it in response to DNA damage
178
Which polymerase mediates SOS repair?
DNA polymerase V
179
DNA damage has what three effects on bacteria?
- mutation
- induces phages
- induces transposition
180
Describe Griffith's transformation experiment.
- rough S. pneumoniae didn't kill mice but smooth did
- heat-killed smooth + active rough did kill mice
- able to isolate live smooth from mice
181
What is a competent bacteria?
one in the late log/early stationary phase, capable of transformation
182
List two unique about transformation among gram+ species.
- they require a competence factor (from quorum sensing)
| - dsDNA is bound to the cell but only ssDNA is translocated
183
List three unique things about transformation among gram- species.
- only uptake DNA from closely related species
- bind DNA via a transformasome that recognizes a specific sequence
- only ssDNA is translocated
184
What is an ampicillin rash?
an adverse effect of PCNs seen mostly in patients with mono
185
Most inhibitors of protein synthesis target what bacterial component?
the 50S ribosome
186
What is the main mechanism bacteria use to become amino glycoside resistant?
increased bacterial metabolism
187
Describe the folate pathway.
- PABA is converted to dihydrofolic acid
| - dihydrofolic acid is converted to tetrahydrofolic acid
188
List four things that make anti-mycobacterial therapy so difficult?
- resistance develops quickly
- pathogen has long periods without growth
- pathogen is largely intracellular
- therapy has to be long-term
189
How did S. pneumonia develop penicillin resistance?
- point mutations in PBPs provide resistance in nonpathogenic organisms
- mosaic PBPs are formed via transformation with low beta-lactam affinity
190
What kind of protease is the HIV protease?
aspartyl
191
Which group of drugs are often given with cobistat and ritonavir?
HIV protease inhibitors
192
What is the primary ART option during pregnancy?
atazanavir or darunavir + ritonavir
193
Which HIV treatments induce and which inhibit CYP3A4?
- induce: efavirenz, nevirapine, amprenavir
| - inhibit: PIs, efavirenz, delavirdine
194
Why is protein synthesis not a common target of anti-virals?
because viruses typically use host machinery
195
Under what circumstances does B. anthracis form spores?
in rich media under aerobic conditions
196
Human B. anthracis infections are ___ and not ___.
incidental and not contageous
197
From what animals does B. anthracis originate?
from herbivores
198
List the three ways B. anthracis enters the human body.
- cutaneous via contact with infected material
- inhalation of spores
- ingestion of contaminated meat
199
What are the symptoms of inhalation anthrax?
- flu-like symptoms without runny nose
- non-productive cough
- radiographic evidence of mediastinal widening
200
What is the incubation period of anthrax?
1-7 days usually, but can be up to 60
201
When must anthrax be treated to prevent mortality?
in the first 48 hours after exposure
202
Why does mediastinal widening occur in inhalation anthrax?
- alveolar macrophages phagocytize the spores
- transport them to mediastinal lymph nodes
- spores germinate and multiple
203
What are the two forms of gastrointestinal anthrax?
- oropharyngeal
| - intestinal
204
How does oropharyngeal anthrax present?
local ulcerations leading to tonsillitis
205
How does intestinal anthrax present?
an ulcer followed by bloody diarrhea or sepsis
206
How does cutaneous anthrax present?
a painless papule that develops into a black necrotic ulcer with edema
207
Describe the anthrax capsule.
it is an unusual poly-D-glutamic acid
208
Describe the anthrax exotoxin.
an AB exotoxin
- protective antigen (B) binds the anthrax toxin receptor and is cleaved to form PA63-ATR, which forms a hepatmeric complex
- 2 active subunits, edema factor and lethal factor
209
What does anthrax lethal protein cause?
it inactivates MAPKK
210
Anthrax toxin binds what two host cell receptors?
tumor endothelial marker 8 and capillary morphogenesis protein 2
211
How is anthrax diagnosed?
- the plating and appearance of non-motile, non-hemolytic mucoid colonies on sheep's blood agar
- confirmed by gamma phage susceptibility
212
What is the drug of choice for anthrax?
ciprofloxacin
213
Describe the human anthrax vaccine.
a cell-free attenuated strain containing the protective antigen of anthrax toxin
214
What are the primary sources of B. cereus?
- contaminated food
- trauma
- IV injections
215
Describe the course of B. cereus emetic gastroenteritis.
- usually from contaminated rice
- with a less than 6 hour incubation
- vomiting, nausea, and abdominal cramps
216
What causes B. cereus emetic gastroenteritis? What causes the diarrheal form?
a heat-stable enterotoxin causes emetic, a heat-liable enterotoxin causes the diarrheal form
217
How does B. cereus emetic gastroenteritis differ from the diarrheal form?
- diarrheal is usually from meat or vegetables
- diarrheal has a more than 6 hour incubation
- diarrheal induces diarrhea rather than vomiting
218
B. cereus ocular infections are usually associated with what other factor?
contact-lenses
219
What is panophthamitis?
a massive vitro retinal destruction within 48 hours of ocular surgery due to B. cereus toxins
220
Why is B. cereus not diagnosed via stool samples?
because most GI tracts are colonized already
221
How is B. cereus diagnosed?
culture and gram staining of contaminated food or infected specimen
222
How is B. cereus treated?
vancomycin or clindamycin
223
What is the hemolytic activity of B. cereus?
beta-hemolytic
224
What bacteria has a "tumbling motility" at room temperature?
Listeria
225
For which bacteria is refrigeration not sufficient to protect against food contamination?
listeria because it grows at 4 degrees celsius
226
Listeria is classically a contaminant of what food products?
dairy products
227
Which populations are most at risk for listeria infection?
- primarily pregnant women
| - neonates
228
What is granulomatosis infanticeptica?
an in utero presentation of listeria with disseminated abscesses and granulomas
229
How does late-onset neonate infection of listeria present?
soon after birth with meningitis, meningoencephalitis, and septicemia
230
Where does a listeria infection typically begin in the human body?
enterocytes or M cells of Peyer's patches
231
What are internalins?
listeria virulence factors that mediate entry into non-phagocytic cells
232
What is listeriolysin O?
a listeria virulence factor encoding a pore-forming hemolysin activated by acidic pH
233
Which bacteria relies heavily on transcytosis?
listeria
234
What is the function of actin-binding protein in listeria?
it is localized to the surface of a new pole, binds actin, and mediates polymerization to facilitate transcytosis
235
What part of the immune system is critical for fighting listeria?
cell-mediated immunity
236
Which bacteria has a tumbling motility and umbrella-like growth?
listeria
237
What is the preferred treatment for listeria?
ampicillin
238
Which bacteria is said to have form "chinese characters" due to it's V- and L-shaped arrangements?
diphtheriae
239
What is the action of diphtheria toxin?
it shuts down protein synthesis via ADP-ribosylation of elongation factor
240
Vaccines against diphtheria include what antigen?
toxoids formed from diphtheria toxin
241
Diphtheria toxin targets what three things?
- URT
- heart
- nerve cells
242
What is pseudomembranous pharyngitis?
- aka respiratory diphtheria
- it has a one week incubation period followed by sudden onset pharyngitis due to toxin secretion
- see a grayish pseudomembrane difficult to dislodge which may cause stridor or asphyxiation
243
What is tellurite chocolate agar?
a media for diagnosing diphtheria which the organism reduces to form a black pigment
244
How is diphtheria treated?
- immediate administration of antitoxin
- erythromycin
- immunization (because infection doesn't generate protective antibodies)
245
How is Staph differentiated from Strep?
staph has a positive catalase test
246
___ is the bacterial genus most responsible for orthopedic infection.
Staph
247
Staph is the number one cause of what three bacterial infections?
- orthopedic infection
- endocarditis
- nosocomial bloodstream infections
248
How is S. aureus spread?
via direct contact, so wash hands
249
What is VRSA?
vancomycin-resistant staph aureus (also methicillin-resistant)
250
Describe the changing epidemiology of S. areus.
- no new genes but it overproduces virulence factors
| - no longer just an opportunistic infection
251
What is USA300?
the most common strain of MRSA in the US
252
Is MRSA usually community or hospital acquired?
nowadays it is usually CA
253
S. aureus is common in what food products?
meats, pastries, and milk products left at room temperature
254
Describe the course of food-borne S. aureus infection.
rapid onset, short-lived nausea, diarrhea, stomach cramps
255
What causes the pathology associated with food-borne S. aureus infections?
a heat stable enterotoxin
256
What is the best drug used in the treatment of toxins?
clindamycin
257
S. aureus uses what sort of exotoxin?
a superantigen
258
What is Protein A?
a S. aureus adhesin that binds the Fc region of antibodies
259
What skin and soft tissues diseases are caused by S. aureus?
- impetigo
- folliculitis
- cellulitis
- abscesses
260
Describe S. aureus cellulitis.
warm, red, swollen soft tissue that is tender to touch
261
What skin disease is characterized by "honey crusting"?
impetigo
262
Cellulitis is most commonly associated with which two pathogens?
MSSA or GAS
263
Where are most S. aureus abscesses located?
in association with the base of hair follicles
264
What is scalded skin syndrome? What causes it?
an exfoliative dermatitis with fever and blistering caused by S. aureus toxins ETA and ETB
265
Who is most often affected by scalded skin syndrome?
children under the age of 5
266
What is TSST-1?
a superantigen produced by S. aureus capable of triggering toxic shock syndrome
267
Describe the pathogenesis of TSST-1 mediated toxic shock syndrome.
- non-specifically activates T cells
- causes a massive cytokine storm
- causes endothelial damage
- causes leakage
268
A child presents with sudden onset of pain over the knees, fever, redness, and a refusal to bear weight. What is the likely diagnosis?
S. aureus osteomyelitis
269
What species is the most common cause of acute bacterial endocarditis?
S. aureus
270
What are the three primary symptoms of bacteremia?
- high fever
- shaking chills
- hypotension
271
CAP most commonly follows what other infection?
influenza
272
List three respiratory tract disease associated with S. aureus.
- pneumonia
- empyema
- cystic fibrosis
273
S. aureus infection often precedes a ___ infection in CF patients.
pseudomonas
274
What are the two major host defenses against S. aureus?
- neutrophils
| - C3b
275
Name three immune problems that are risk factors for S. aureus infection.
- neutropenia
- complement deficiency
- reduced radial production
- lazy leukocytes
276
What is the preferred treatment for S. aureus?
- topical: bacitracin
- MSSA: cephalosporin or amoxicillin
- MRSA: clindamycin, bactrim, doxycycline
277
What mechanism is in place to make S. aureus VISA?
thickened cell wall
278
What mechanism is in place to make S. aureus VRSA?
a resistance plasmid
279
How are VRSA and VISA treated?
- linezolid
| - daptomycin
280
Why is Staph saprophyticus clinically relevant?
it causes many UTIs in sexually active young women
281
How does S. aureus differ diagnostically from S. epidermidis?
- epidermidis is coagulase negative
| - aureus is beta hemolytic and performs mannitol fermentation
282
Strep are normal flora where in the human body?
skin and mouth
283
How are Strep species grouped?
- by their hemolytic character (alpha, beta, gamma)
| - then surface antigens (A, B, etc.)
284
What is Strep pyogenes?
a GAS that causes strep throat
285
What is Strep agalactiae?
a GBS that causes neonatal infections and bacteremia
286
What is Strep mutans?
an alpha-hemolytic strep known to cause dental caries and endocarditis
287
What is S. enteroccocus?
the most relevant species of gamma-hemolytic strep
288
How is S. pyogenes spread?
very efficiently via direct contact and respiratory droplets
289
How does strep throat present?
- erythematous posterior pharynx with purulent exudate
- lasting 1-4 weeks without treatment
- caused by S. pyogenes
290
What is the preferred treatment for GAS?
penicillin
291
What causes scarlet fever?
SpeA and SpeC (aka strep pyrogenic exotoxin) producing GAS
292
What are the three major symptoms of scarlet fever?
- "sand paper" rash on chest
- "strawberry" tongue
- circumoral pallor
293
What are the two major complications of scarlet fever?
- rheumatic fever
| - glomerulonephritis
294
Which species of strep commonly causes skin infections like impetigo and cellulitis?
GAS S. pyogenes
295
What is erysipelas? What pathogen causes it?
a GAS skin infection characterized by raised bright-red plaques with sharply defined borders
296
List three adhesins used by GAS and what each binds.
- M protein
- Protein F
- lipoteichoic acid
297
What kind of capsule do GAS produce?
a hyaluronic acid one that mimics host antigens
298
What is streptomycin O? What pathogen produces it?
a pore forming toxin secreted by GAS
299
What is Spe?
- streptococcus pyrogenic exotoxin
| - superantigen that produces scarlet fever or toxic shock
300
What is streptokinase?
a GAS virulence factor that activates plasminogen to dissolve clots
301
How is strep throat treated?
amoxicillin
302
How is strep toxic shock syndrome treated?
penicillin and clindamycin
303
How is strep throat diagnosed?
- rapid antigen detection test for group A capsule antigen
| - confirmed by a culture
304
GBS are normal flora where in the body?
GI and GU tracts
305
What are four risk factors for GBS infection in adults?
- diabetes
- kidney disease
- increasing age
- cancer
306
GBS is a major cause of what two disease in pregnant women?
- UTIs
| - puerperal sepsis
307
Pregnant women must get a screening for what vaginal flora?
GBS
308
What are four risk factors for GBS disease in neonates?
- mother had UTI during pregnancy
- prolonged labor
- premature rupture of membranes
- maternal colonization
309
GBS causes what three disease in neonates?
- sepsis
- meningitis
- pneumonia
310
What is C5a peptidase? Which organisms utilize it?
a GBS virulence factor that inhibits neutrophil recruitment
311
What is CAMP factor? Which pathogen produces it?
a phospholipase produced only by GBS which lysis erythrocytes
312
List four
- beta-hemolyin
- CAMP factor
- C5a peptidase
- capsule
313
How is neonatal GBS infection treated?
ampicillin and gentamicin
314
How is GBS endocarditis treated?
penicillin G and gentamicin
315
What are viridans streptococci?
those that are alpha hemolytic
316
Why are viridans streptococci so likely to cause endocarditis?
they can bind fibrin-platelet aggregates at damaged heart valves
317
What is the most common cause of CAP?
strep pneumoniae
318
Name four disease commonly caused by S. pneumoniae in adults and children.
```
In adults...
- CAP
in children...
- meningitis
- otitis media
- sinusitis
```
319
Describe S. pneumoniae pneumonia.
- abrupt onset fever and shaking
- pleurisy
- productive, blood tinged cough
320
What are the three major causes of atypical pneumonia?
- mycoplasma
- chlamydia
- legionella
321
How does atypical pneumonia compare to typical?
slower onset, more moderate fever, non-productive cough
322
What pathogen accounts for most middle ear infections in children?
S. pneumoniae
323
What is C polysaccharide? What pathogen produces it?
a capsular antigen of S. pneumoniae
324
What is pneumolysin? What pathogen produces it?
a toxin secreted by S. pneumoniae which targets bronchial epithelial cells
325
Why does S. pneumonia produce autolysin?
to promote release of pneumolysin and endotoxins
326
What is quelling?
a swelling reaction to antisera that helps visualize S. pneumoniae capsules
327
How is S. pneumoniae treated?
fluroquinolones
328
Why are enterococci more antibiotic resistant than other species of Strep?
they have a modified peptidoglycan cell wall
329
Enterococcus most often spreads from the intestines to cause what?
endocarditis
330
Which species of Streptococci are very resilient and hardy?
enterococci
331
What is cytolysin?
a virulence factor produced by enterococci
332
What is aggregation substance?
an adhesin secreted by enterococci to promote conjugation and adherence to intestinal epithelial cells
333
What is enterococcal surface protein?
an adhesin that promotes colonization of the urinary tract
334
How are enterococci infections diagnosed?
they can be cultured in high salts
