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Clin Lab Med II > CLM 2 infectious dz > Flashcards

CLM 2 infectious dz Flashcards

1
Q

What are the five basic lab techniques

A
  1. Direct Visualization
  2. Detection of Microbial antigens
  3. Examination of Host immune of inflammatory response
  4. Detection of Microbial Nucleotide Sequences (don’t worry about)
  5. Isolation of Organism in culture
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2
Q

How do you visualize an organism

A
  1. Gram stain
  2. KOH prep
  3. Tzanck Prep
  4. India ink prep
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3
Q

What is a gram stain of buffy coat and what can it help visualize

A

*The Buffy coat is the little white layer in bw the RBC that are the bottom and the serum at the top after blood is centrifuged

(Can show pair of G- intracellular diplococci consistent with suspected meningococcemia)

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4
Q

Gram neg is what color. What about gram positive?

A

Neg – red, pink

Positive – purple/blue

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5
Q

What is KOH prep

A

Skin scraping, oral or vaginal secretions on slide with drop of KOH, heated briefly with flame then examined on low power microscope
KOH dissolves host cells and bacteria, sparing fungi and elastin fibers

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6
Q

What would a Tzanck Smear be used for

A

Herpes virus multinucleated giant cells

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7
Q

What would India ink prep be used for and how is it done

A

Cryptoccoci large capsules which exclude the ink

Drop of centrifuged CSF placed on microscope slide next to drop of artist’s india ink, coverslip placed over drops

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8
Q

What are the different ways to detec microbial antigens/ specific etiologic agents in infectious dz

A 
Latex agglutination
Immunofluorescence
Enzyme immunoassay
Radioimmunoassay
*note we did not focus much on this
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9
Q

Histopathologic exam of host tissue revealing PMN infiltration vs. Lymphocytic vs Granulomas suggest..

A

PMN infiltration: ACUTE bacterial process
Lymphocytic infiltration suggest more CHRONIC process: viral, fungal, TB
Granulomas suggest mycobacterial or fungal process

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10
Q

What are PPD or Cocci skin tests? Use? Negative tests?

A

Host cell mediated immune response skin test for delayed type hypersensitivity PPD for TB
Negative tests can occur if pt has depression of cell mediated immunity (anergy); consider applying control skin test to check for anergy (candida and/or mumps skin tests as control bc always +)

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11
Q

What is detection of microbial nucleotide sequence used for

A

Genetic molecular dz technique that can provide rapid ID of certain pathogens
Can also id genetic markers of antimicrobial resistance which can help guide tx
Identify species: M tuberculosis vs other mycobacterium
Dx infection: detect herpes simplex, CMV, syphilis in CSF
Detect markers of antimicrobial resistance: may help in HIV to determine if there is resistance to certain tx regimens

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12
Q

How is culture used in infectious disease process

A

One of the most common ways to identify organisms responsible for infection
Specimen sent to lab or planted on culture medium at bedside
Specific culture media needed for certain organisms (medium that selects for growth of suspected organism ie Neisseria gonorrhea)

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13
Q

What is an important component to using culture isolation for identifying organisms

A

must interpret results using information about clinical setting and method to obtain specimen
fever, cough, sob expectorated sputum
cotton swab in pus vs aspirated pus from closed abscess
“sterile” pus from brain abscess cultured on aerobic media (can be misleading if trying to grow anaerobic organisms)
Lots of room for error and confusing results (inadequate specimen, contamination, wrong medium, wrong transport medium)
*bring specimens PROMPTLY to lab

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14
Q

How do you determine sensitivity of organism to an antibiotic

A

C&S MIC (minimum inhibitory concentration)
ABX serum levels need to be over the MIC for a sig period of time in order to effectively kill bacteria
MIC determined by serially diluting abx into liquid media containing FIXED concentration of bacteria (automated)

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15
Q

What is the MBC and how is it determined

A

MBC = lowest concentration of abx that blocks growth of bacteria (no colonies)
Determined by inoculating tube with inhibited growth onto solid media plates, plates are then incubated
MIC is used more, but MBC takes things to the next level
The lower the MIC or MBC, the more effective the antibiotic

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16
Q

How is successful tx of infectious organisms obtained

A

Adequate antibiotic serum levels OVER TIME
Ratio of area under the curve to MIC is a parameter
The time above the MIC is another parameter
*want more area under the curve and longer time above MIC

17
Q

How can antimicrobials be classified by pharmacodynamics

A

Concentration vs time dependent killing (concentration - aminoglycosides, FQ, azithromycin)

18
Q

What is Sensitivity? How is it reported?

A

Sensitivity is the S of C&S indicates the abx an organism is sensitive to
Reported as MIC (mcg/mL) and MIC interpretation (R, I or S for resistant, intermediate, or sensitive)
*Report may also indicate usual adult dose or average cost/day
*As clinicians we should be away of geographic sensitivity/resistance

19
Q

Ex: how would we make an antibiotic selection for MRSA

A

Senstivity report can help, but can also be misleading (clinical experience may show certain drugs not effective even if report says they are – in vitro vs in vivo)
Can antibiotic get to infected site? Ie if there is a CNS infection, must select an abx that can cross the BBB

20
Q

What is a bacteriostatic agent and examples

A

STATIC = When MBC/MIC ≥16 for pathogen isolated
Macrolides, tetracyclines, sulfonamides, clindamycin. Linezolid, chloramphenicol
CIDAL = when MBC/MIC ≤ 4
Beta lactams, aminoglycosides, cancomycin, FQ, daptomycin, metro

21
Q

What strategies can help select abx tx

A
  1. Decide if it is a bacterial infection
  2. Try to reasonably guess that pathogen
  3. Be aware of susceptibility patterns in hospital and community
  4. Take into account previous abx tx of pt
  5. Take into consideration host factors (ie is pt immunocompromised, allergies)
  6. Less is best
  7. Switch to narrow spectrum w/in 3 days after empiric tx (prevent resistance)
  8. When all things are equal, choose the cheapest drug
22
Q

Pt has elevated WBC, Increased neutrophils and/or bands and serious illness…

A

BACTERIAL INFECTION!

23
Q

How do you go about making a statistical guess at causative agent

A

Depends on anatomic site of primary infection (pulmonary, GU, GI, Skin)
Community vs. institutional setting (resistant organism or not)

24
Q

What causes acute bacterial sinustitis

A

S pneumo, H flu, M catarrhalis

25
Q

CAP, what causes it usually and what abx are they susceptible to

A

S penumo, H flu, M catarrhalis

Susceptible to Macrolide, FQ, doxycycline

26
Q

What abx is good for community acquired MRSA

A

Bactrim often used first, then clindamycin

*other: vanco, minocycline, doxycycline, Linezolid, daptomycin

27
Q

What are hospitalized pt likely to be colonized with

A

Resistant flora; be aware of what they have been treated with before and consider likelihood of resistant organisms to that antibiotic

28
Q

What aspects should we be assessing when considering host factors

A 
Site of infection (CNS, BBB etc)
White count  neutropenia?
Age and underlying diseases  renal or hepatic dysfunction, DM, CA?
Duration of hospitalization
Severity of pt illness
29
Q

Why should we use the fewest drugs possible

A

Multiple drugs increase risk of adverse reactions, cost, and risks of resistant organisms
Some drugs are antagonistic rather than synergistic

30
Q

What happens in the inflammatory response

A
  1. Bacteria/trauma/shock
  2. Activate complement system, coagulation, serum proteins
  3. Pro inflam cytokines and chemokines, ROS production, enzyme release
  4. Increase vascular perm, bacterial killin, DIC, Tachypnea, fever, leukocytosis, tachycardia, increased TPR
  5. Edema, tissue damage, organ failure, keukocytopenia
31
Q

What is Bacteremia

A

Presence of organisms that can be cultred from blood

32
Q

What is septicemia

A

Bacteremia with greater severity of s/sx: FEVER/hypothermia, tachycardia, Tachypnea, leukocytosis/leucopenia

33
Q

What is sepsis syndrome. s/sx?

A

Even more severe than septicemia, impaired organ perfusion resulting in hypoxemia, oliguria, AMS
Severe sepsis, septic shock and refractory septic shock are even more advanced degrees of organ failure, usually accompanied by HYPOTN which may be unresponsive to fluids and/or vasopressors
s/sx: fever, chills, hyperventilation, hypothermia, AMS, hypotn, leucopenia/thrombocytopenia, END ORGAN FAILRUE (lung, kidney, liver, heart, DIC)

34
Q

Outline the natural history of sepsis

A

Pathogenic micro organism local inflam response/local infection SIRS/sepsis SIRS + inadequate organ perfusion/sepsis syndrome Cardiovascular insuff/septic shock, respiratory insufficiency/ARDS MOSF death

35
Q

What organisms commonly cause sepsis and how do you treat

A

Staph, strep, E. coli, enterobacter, pseudomonas
Tx:
PROMPT dx, ICU monitoring,
ABX (empirical coverage of G+ and G- until cultures available),
Judicioius fluid admin, O2, vasopressors

Clin Lab Med II (3 decks)

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