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Immuno mikro eng > First Pass Miss - Micro Exam 2 > Flashcards

First Pass Miss - Micro Exam 2 Flashcards

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1
Q

What are the symptoms of the toxic shock syndrome exerted by LPS, and what induces similar physiologic responses?

A

Hypotension, fever, and disseminated intravascular coagulation (blood clotting / thromboses) mostly mediated via IL-1 / TNFalpha

Staphylococcal / streptococcal superantigens have a similar effect

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2
Q

What are three types of cis-acting regulatory regions?

A
  1. Promoter - DNA sequence recognized via RNA polymerase
  2. Operator - near promotor, binds repressor protein and reduces transcription when bound (i.e. lac repressor)
  3. Activator - near promotor, binds activator protein to increase transcription (i.e. CRP protein)
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3
Q

What is an attenuator?

A

mRNA secondary structure which modulates transcription (i.e. hairpin loop)

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4
Q

Would lacI be cis-acting or trans-acting?

A

Trans-acting since it creates the protein which binds the cis-acting lacO

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5
Q

What is an R factor and their two subunits?

A

R(esistance) factor is a conjugative episome which encodes for Abx resistance

  1. RTF - resistance transfer factor, coding autonomous replication and conjugal transfer
  2. Resistance determinant - composed of 1+ transposons, which carries the antibiotic resistance gene
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6
Q

What is the inducer of the lac operon?

A

Allolactose (indicates lactose presence), binds lac repressor to inactivate it, increasing transcription

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7
Q

What is lysogenic conversion, and what are some examples?

A

Change in bacterial phenotype after phage infection (bacterial virulence factors carried by specialized transduction)

Examples:
Diphtheria toxin, botulinum toxin, cholera toxin, exotoxin A (S. pyogenes), Shigatoxin

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8
Q

What penicillin class has the highest chance of kidney damage, and what symptoms are associated?

A

an be seen with all penicillins, but methicillin most common. Cause:
Acute interstitial nephritis

Triad: Fever, Rash, Eosinophilia which can lead to renal failure

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9
Q

What is the first line empiric treatment for bacterial meningitis?

A

3rd generation cephalosporins like ceftriaxone and ceftazidime which penetrate the BBB well, then if it’s like listeria you can switch to ampicillin

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10
Q

Why do we worry about SPICE organisms when treatment with 3rd generation cephalosporins? What should we do instead?

A

All have a beta lactamase which can be selected for during therapy, so against these it is best to use cefepime or carbapenems for invasive / critically ill infections

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11
Q

What does Avibactam do?

A

It is a non-betalactam b-lactamase inhibitor which can restore ceftazidime activity against organisms which produce b-lactamases and carbapenemases

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12
Q

What is the only monobactam and what is its claim to fame?

A

Aztreonam (beta-lactam with no side chain)

Used for empiric nosocomial gram negative coverage in patient with penicillin allergy (zero cross-reactivity)

Covers P. aeruginosa but NO ESBL (not quite carbapenem)

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13
Q

What are the only Beta-lactams which are not renally cleared and thus you don’t have to think about dosing?

A
  1. Ceftriaxone
  2. Penicillinase-resistant penicillins - i.e. Nafcillin

Have a major contribution of biliary secretion

Explains why ceftriaxone can’t be used in infants / neonates - biliary sludging

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14
Q

What is changed about the gram + and gram - activity of 3rd gen cephalosporins?

A

Gram + - Enhanced S. pneumoniae activity (good against Community-acquired pneumonia and bacterial meningitis), but worse MSSA activity (use first class)

Gram - - Good against nosocomial gram negative (PEK), but no Pseudomonas coverage

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15
Q

What is Streptolysin O analogous to in S. aureus?

A

It is a cytolysin which forms pores in RBCs, analogous to alpha toxin of S. aureus

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16
Q

What is TSST analogous to in S. pyogenes?

A

SpeA-E, inducing fever, rash, and hypotension. They are Streptococcal pyrogenic exotoxins

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17
Q

What do hydrolytic enzymes like streptokinase cause?

A

They dissolve fibrin to facilitate spread of bacteria, and are responsible for runny, thin pus. (pyoderma / streptococcal impetigo)

Can be used therapeutically to dissolve blood clots

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18
Q

When does erysipelas occur and what does it progress to? What are the associated symptoms?

A

Occurs on face, especially following strept throat. Can rapidly spread infection to deeper layers and cause necrosis + septicemia.

Associated with edema, fever, and lymphadenopathy

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19
Q

What limits the spread of tinea infections? What do chronic infections mean?

A

Rapid shedding of keratinized layers due to advanced skin growth which is induced by infection.

Cell mediated immunity is important and delayed-type (Type 4) hypersensitivity will result

Chronic infections: impaired T cell and lack of DTH reaction

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20
Q

What is the purpose of M protein? What is it responsible for?

A

Antiphagocytic, does molecular mimicry with antigen variation via N terminus (>80 serotypes)

Mediates binding to epidermis

Responsible for post-streptococcal sequelae, including acute glomerulonephritis, rheumatic heart disease

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21
Q

What are complications of roseola?

A

High fever, aseptic meningitis, hepatitis, mononucleosis-like syndrome

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22
Q

What is the structure of papillomaviruses?

A

Non-enveloped icosahedral

Circular dsDNA with 8-10 genes

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23
Q

What is the structure of Picornaviruses and what is one example?

A

Small, non-enveloped viruses with ssRNA (+) genomes

example: Coxsackieviruses (especially A)

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24
Q

What are two diseases caused by picornaviruses?

A
  1. Hand, Foot, and Mouth Disease - blisters / ulcers on all these areas, typical in Asia
  2. Herpangina - includes only the mouth lesions
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25
What is one difference between HFM disease and when the lesions clear vs Roseola?
Typically, Roseola lesions do not actually appear until the fever is actually gone. HFM lesions appear immediately and are gone in 1-5 days
26
What are levofloxacin and moxifloxacin also called and why?
Respiratory fluoroquinones -> good against all streptococcus, and all CAP organisms Should not be relied on vs Staph / Enterococcus due to easy mutation
27
What is B. fragilis and what fluoroquinone is good against it?
An anaerobe commonly targeted in therapies Only moxifloxacin Unfortunately, it lacks anti-pseudomonal activity, also it's not good versus UTI's because it's not renally cleared
28
What are the common fluoroquinolone side effects?
CNS toxicity - headaches, seizures, neuropathies Tendon ruptures due to cartilage damage Dysglycemia Cardiac arrythmias / prolonged QT, especially moxifloxacin
29
What are daptomycin's issues and when is it absolutely contraindicated?
Causes CPK elevations and rhabdomyolysis (muscle breakdown) Irreversibly binds pulmonary surfactant, avoid in pneumonia
30
What is the clinical application of Linezolids?
VRE infections - but keep in mind it's only static | MRSA - pneumonia (when vanco-resistant, dapto can't be used)
31
What are VRE and what is the most common species for it? How is it typically treated?
Vancomycin-resistant enterococcus Common in Enterococcus faecium Treated via Linezolid / Daptomycin usually
32
What are the macrolides mostly active against?
Respiratory pathogens, including pneumococcus, Hemophilus, mycobacterium Also: Chlamydia / gonorrhea Mycobacterium avium complex seen in HIV
33
What is Azithromycin used for? Why is it chosen most often?
Chlymadia, gonorrhea, non-TB mycobacteria, and 1st line for CAP It has a long half life, allowing for shorter drug course, has fewest CYP3A4 interactions, causes diarrhea least in class
34
What are doxycycline / minocycline typically used for?
Respiratory tract infections, including CAP Skin infections, especially when CA-MRSA is a concern Good against animal bites / lyme disease
35
What is minocycline emerging as good for?
Carbapenem-resistant A. baumannii | treated with Sulbactam or Imipenem/doripenem/meropenem before with little else
36
What are the two big problems with tigecycline?
1. Highly lipophilic - poor for treating blood, lung, and urine infections 2. Causes nausea/vomiting in 20% of patients
37
What is the spectrum of tigecycline activity? When is it used clinically?
Very broad in both gram positive and negative, just misses PP = pseudomonas and proteus Used as last line for resistant gram-negative like Acetinobacter and Klebsiella Used often in POLYMICROBIAL WOUNDS including MRSA or VRE TPP = tigecycline misses pseudomonas and proteus
38
What should be done if something is found to be erythromycin resistant but clindamycin susceptible?
Special "D test", since resistance may be latent and inducible - bacteria likely has the erm gene
39
What is the major clinical role for TMP/SMX?
Outpatient UTIs, good against MRSA but poor for Strept (not good for skin infections) Also PJP pneumonia and S. maltophilia pneumonia
40
What can Trimethoprim cause? Sulfa?
Hyperkalemia -> blocks K+ excretion, so beware with K+ sparing diuretics Also anemia, leukopenia, and granulocytopenia Increased bleeding when given with warfarin Sulfa: Hypersensitivity mostly, + rise in plasma creatinine although just by blocking secretion (unlike daptomycin which causes muscle breakdown and increased CPK)
41
What are three main uses of metronidazole?
1. Empiric anaerobic coverage for intra-abdominal infections 2. Drug of choice for mild-moderate C. difficile 3. Trichomonas vaginalis coverage
42
What is the major side effect of metronidazole?
Peripheral neuropathy if given cumulatively Also warfarin reaction (increase) + disulfiram-like reaction with alcohol consumption
43
What is Rifampin's spectrum of activity?
Good against all gram +, including MRSA, but not used as a monotherapy Ineffective against gram negative unless in combination Excellent against TB
44
Give two reasons why Rifampin is not typically used
1. Hepatotoxicity 2. Induces multiple Cytochrome P450 enzymes, including CYP3A4. Contraindicated in many HIV meds because it causes subtherapeutic levels of the drugs (quicker metabolism)
45
How does Polymyxin B work and why did it stop being used?
Cationic detergent which destroys outer cell membrane LPS by displacing divalent cations Stopped being used due to nephrotoxicity, only works against gram negative but works great
46
Why is polymyxin used clinically?
Last line treatment against multi-drug resistant gram negative: P. aeruginosa, A. baumanii, K. pneumoniae, E. coli
47
What is nitrofurantoin used for, and its main contraindication?
Urinary tract organisms (gram negative, narrow spectrum) Contraindicated if GFR < 60 mL/min (compromised kidney function) Can be used in place of TMP/SMX or Keflex or Cipro
48
What is the mechanism of action of dapsone and when is it used?
antagonist of PABA Used in prevention and treatment of pneumocystic pneumonia when patient has sulfa allergy (can't used TMP/SMX) causes Hemolysis worse with G6PDH deficiency
49
What is the primary virulence factor of Group D Streptococcus / Enterococcus?
Multiple, high-level resistances to a wide variety of antibiotics Includes VRE
50
What is used for malaria prophylaxis?
Atovaquone / Proguanil = Malarone
51
How is Aspergillus identified in culture?
Branched, septate hyphae (mold form). Blood cultures will be negative, biopsy of infected tissue is necessary (unlike Candida).
52
What are the symptoms of babesiosis? How does it resolve?
Fever, not periodic Myalgia, anemia, hepatosplenomegaly, renal dysfunction Resolves spontaneously within a few week, but very dangerous in asplenic individuals
53
What is one major CNS complication of IE? One more? hehe
Mycotic aneurysm formation in arterial wall (abscess formation of vasovasorum) Will be silent until rupture occurs causing subarachnoid hemorrhage Also fibrin plates can break off and cause cerebral emboli
54
What are three main causes of osteomyelitis?
Recent trauma (hematologic spread) - common in young people Surgery (local spread) Diabetes - poor vasculature / insufficiency / necrosis
55
What time scale defines chronic osteomyelitis, and what is the main difference from acute?
>3 months duration, often following acute OM Main difference: chronic can be polymicrobial (acute is usually monomicrobial)
56
What are the major risk factors for septic arthritis?
Poor health indicators (low SES, diabetes, IDU) rheumatoid arthritis joint prostheses / history of steroid injections to joints
57
What joints are commonly affected in septic arthritis vs reactive arthritis? What disease processes do they follow?
Septic arthritis - usually monoarticular of knees or ankles, follows UTI Reactive arthritis - usually four or fewer joints, asymmetrical, of back or lower limb, follows UG or GI infection
58
What are some extra-articular manifestions of reactive arthritis?
Anterior uveitis, conjunctivitis, keratoderm blennorrhagicum (psoriasis-like, often on feet)
59
What are involucrum and sequestrum?
Sequestrum - necrotic bone in osteomyelitis | Involucrum - ectopic bone overgrowth
60
What is the first line treatment for aspergillus? What azole is not active against it?
Voriconazole Only fluconazole is not active against it
61
What is the clinical application of itraconazole?
Non-life threatening cases of endemic mycoses
62
What are posaconazole / isuvaconazole used for?
Mucormycoses, with isuvaconazole's niche to be determined
63
What organisms are echinocandins good against?
All candida species, considered first line for all, except maybe C. parapsilosis Aspergillus - used in combination therapy if patient is intolerant to voriconazole or amphotericin
64
When would you know to use echinocandins vs fluconazole for yeast infection?
If patient is not critically ill and this is new, use fluconazole If recent azole exposure, known colonizer with C. glabrata, or critically ill, use echinocandins
65
What is the spectrum for cidofovir and when is it used?
HSV, VZV, CMV Used for CMV when CMV is resistant to ganciclovir / foscarnet
66
When is foscarnet used and what are its big side effects?
Only for CMV when ganciclovir is not available Side effects: Nephrotoxicity, CNS effects, potential chelator of divalent cations in blood (hypokalemia - bananas, hypocalcemia - milk, hypomagnesia - magnets)
67
What are the major neuraminidase inhibitors and what is one side effect?
Zanamivir (IV), oseltamivir (PO) Zanamivir can exacerbate COPD if inhaled
68
What are the side effects of flucytosine?
Dose-dependent bone marrow suppression
69
What is the mainstay of therapy for animal bites?
Beta-lactam / beta-lactamase inhibitors which hit both gram positive and gram negative infections -> i.e. augmentin Can still use doxycycline / ceftriaxone though
70
What drug of the cephalosporin class is good against S. pneumoniae?
1st generation cephalosporins are not good against it (all other streptococci they are fine against) ceftriaxone is the drug of choice for CAP because of this coverage
71
What is a common saying for Clindamycin / Metronidazole?
Clindamycin above the diaphragm, metronidazole below Clindamycin is good at treating Bacteriodetes and anaerobic species from mouth anaerobes leading to aspiration pneumonia Metronidazole is good at treating anaerobic species in the gut and pelvis (C. difficile, Trichomonas)
72
What is the drug of choice for enterococccal endocarditis?
Ampicillin 4 weeks, gentamacin can be added If amp-resistant, 6 weeks Vanco Do at least 8 weeks if VRE (use daptomycin)
73
What is the empiric therapy for infected diabetic foot ulcers?
Initially IV therapy with vancomycin +/- ceftriaxone to cover gram negative in case of deep tissue infiltration DONT WAIT FOR ULCER TO FULLY HEAL TO STOP
74
What are three major virulence factors of S. pneumoniae?
1. Polysaccharide capsule - primary, avoids complement-mediated phagocytosis and lysis 2. Pneumolysin, a membrane-damaging cytolysin related to SLO of S. pyogenes 3. Cell wall teichoic acid / peptidoglycan promote inflammation
75
What are two other names for S. pneumoniae?
Pneumococcus or diplococcus (gram positive diplococci) Same morphology as group B strep
76
What are the three primary virulence factors of P. aeruginosa?
1. Exotoxin A 2. Elastase 3. Adhesin
77
What does elastase do? How does it relate to eye pathology?
Cleaves elastin and human Igs, collagen, and complement It is the primary cause of corneal perforation in eye infection
78
What is the Quellung reaction?
One of the biochemical tests (other than capsular serotyping and P disk susceptibility testing) to test for P. pneumoniae It checks if there is capsular swelling on addition of anti-capsule antibodies
79
What biochemical test is diagnosis of P. aeruginosa?
High levels of cytochrome oxidase -> positive oxidase test
80
What are the two stages of Chlamydia trachomatis?
1. Elementary body - infectious, expresses adhesins | 2. Reticulate body - replicative, intracellular
81
What is inclusion conjunctivitis?
Chlamydia eye infection of the neonate from direct contact with cervical secretions during delivery. (perinatal) Marked by acute, mucopurulent discharge ~7 days post-partum
82
What is chronic follicular conjuncitivitis also called and who does it typically affect?
Trachoma - typically chronically infects people in the developing world of lower SES Can cause blindness if complicated by trichiasis
83
What is seen on retinoscopy for Candida enophthalmitis?
Following injury, a white cotton ball expanding on retina or floating in vitreous humor
84
How are humans typically infected via histoplasma?
Inhalation of infectious conidia while handling bird (i.e.. chicken) or bat droppings
85
What are the two forms of Acanthamoeba species?
1. Trophozoites - free-living and tissue-invading | 2. Cysts - infectious stage, often get in following mild corneal trauma and improper contact lens sterilization
86
What is the primary virulence factor of GBS and how does it work? How does it create pneumonia?
Polysaccharide capsule with sialic acid moiety on terminal sugar, limiting C3b deposition and decreasing phagocytosis Has a beta-hemolysin as well which injures lung epithelial cells and helps it penetrate BBB (E. coli K1 uses invasins)
87
How is E. coli K1 meningitis contracted?
Via low BW and pre-term babies (GBS meningitis contracted via same group + in moms with no IgG against GBS capsule)
88
What will Listeria most likely cause if contracted perinatally?
Septicemia + meningitis (third leading cause as a neonate) Treat with IV Ampicillin
89
What do infants born with T. gondii often show? (if not aborted or stillbirthed)
Microcephaly, hydrocephaly, psychomotor disturbances, and convulsions (CNS involvement)
90
What forms are the Hep A and Hep B vaccines?
Hep A - inactivated, given around 12 months | Hep B - given to all high risk adults as recombinant surface antigen (subcellular)
91
What is Pneumovax? Prevnar13?
Pneumococcal vaccine, conjugated vaccine covering 23 pneumococcal capsular types Recommended in adults >65 yo and high risk individuals >2 yo Prevnar13: 13 types, recommended in all children <5
92
What does Rotavirus cause? When should you get the vaccine?
Severe acute gastroenteritis Recommended between ages 2-6 months
93
What is the meningococcal vaccine?
Vaccine with capsular polysaccharides A, C, Y, and W-135. B was not immunized previously (due to sialic acid autoimmune risk) but is now

Immuno mikro eng (56 decks)

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