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Clinical Patient Care 2023 > General Principles Of Microbiology And Laboratory Methods Of Identification > Flashcards

General Principles Of Microbiology And Laboratory Methods Of Identification Flashcards

1
Q

What should be considered when choosing an ATB

A
  1. Severity or degree of risk
  2. Broad coverage with empiric antibiotics
  3. Timing
  4. Source control
  5. True infection bc colonization
  6. Antimicrobial resistance
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2
Q

How does severity or degree of risk guide us when choosing an ATB

A
  1. Aggressive Vs non aggressive
  2. Emergent vs non-emergent
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3
Q

How does broad coverage with empiric ATBs guide us when choosing an ATB

A
  1. Starting an ATB with board coverage in a timely manner can be lifesaving
    *selecting the wrong dose, improper route, or delay treatment can increase morbidity and mortality
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4
Q

How does timing guide us when choosing an ATB

A
  1. Cultures and specimens should be obtained before ATB, when possible
    *should not be delayed in life-threatening infection
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5
Q

How does source control guide us when choosing an ATB

A
  1. Drain collection of pus when possible
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6
Q

What are the signs of a true infection

A
  1. Almost accompanied by inflammation
  2. Neutrophils present
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7
Q

What are signs of contamination/colonization

A
  1. Large number of epithelial cells
  2. Growth of normal skin flora
    *improper specimen collection
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8
Q

What is MIC

A
  1. Minimal inhibitory concentration
    *lowest concentration of Antimicrobial agent (drug) that will inhibit the growth of the microorganisms
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9
Q

Do you want a low MIC or high MIC

A

Low
*also request a C&S

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10
Q

What does a low MIC mean on a culture

A

There will be a larger zone of inhibition
*small amount of drug goes a long way to kill the organism

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11
Q

What does a high MIC mean on a culture

A

There will be a smaller zone of inhibition
*a lot of a certain drug is needed to kill the organism

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12
Q

What is susceptible

A

Microorganisms is inhibited by a concentration of antibiotic and can be appropriately treated with that drug

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13
Q

What is intermediate Antimicrobial susceptibility

A

The ATB may be effective in high doses

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14
Q

What is a resistant Antimicrobial

A

Microorganisms is not inhibited by the antibiotic
*cant treat with that drug

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15
Q

What are some of the resistant microorganisms

A
  1. MRSA (methicillin resistant staph aureus)
  2. VRE (vancomycin resistant enterococcus)
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16
Q

What are some ways to diagnose infectious diseases

A
  1. Smear and stains
  2. Microscopic examination
  3. Cultures
  4. Tissue biopsy
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17
Q

How are smears and stains prepared

A
  1. By rolling a small amount of specimen across a glass slide
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18
Q

What are the different types of smears and stains

A
  1. Gram stain
  2. Giemsa stain
  3. Wright stain
  4. Acid-fast Bacilli
  5. Tzanck smear
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19
Q

What does the gram and giesma stains tests for

A

Gram: bacteria
Giemsa: microbes in tissue, H.pylori, chlamydia, malaria, histoplasma

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20
Q

What does the wright stain, and Acid-fast bacilli tests for

A

W: differential staining of blood smears, bone marrow, and blood parasites
A: TB and other types of mycobacteria

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21
Q

What does Tzanck smear test for

A

HSV, bulbous diseases

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22
Q

What is a gram stain used for?

A
  1. Bacterial differential stain
    *will differentiate between different types of bacteria based on cell walls
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23
Q

How will gram neg and gram pos stain

A

+ purple
- red (do not retain crystal violet but take up safranin counterstain)

*if there is bacteria from a sterile site that is significant

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24
Q

How does yeast stain?

A

Purple
*will be a long pseudohyphae

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25
Q

What organism can stain neg or pos

A

Gardnerella vaginalis

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26
Q

What bacteria’s do not stain

A
  1. Mycobacterium tuberculosis
    *waxy coating (use acid fast)
  2. Chlamydia trachomatis
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27
Q

How is bacteria classified

A
  1. Scientific name
  2. Stain
  3. Shape
  4. Need for O2
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28
Q

How will the stained bacteria be described

A

To their morphology
1. Coccus (spherical or oval)
2. Bacillus (rod-shaped)
3. Spiral or helical (twisted)
By arrangement
1. Chains
2. Clusters

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29
Q

What are common spherical bacteria (+ cocci)

A
  1. Staphylococcus species
    *grapelike clusters
  2. Streptococcus species
    *spherical and arranged in chains or pairs
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30
Q

What are common spherical bacteria (- cocci)

A
  1. Neisseria species (pairs)
    *N. Gonorrhea
    *N. Meningitides
  2. Moraxella catarrhalis
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31
Q

What are the three main species of staphylococcal

A

S. Aureus
S. Epidermidis
S. Saprphyticus

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32
Q

How are the staphylococcus species differentiated from each other

A

By coagulation test (and morphology)

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33
Q

When conducing the coagulation test how will the different staphylococcus species turn out

A
  1. S. Aureus in clumps
    *enzyme is present
  2. S. Epidermis and S. Saprophyticus does not clump
    *enzyme is absent
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34
Q

How does streptococcus pneumonia stain?

A

Gram + (purple-ish) diplococci
*diplococci are oval with somewhat pointed ends

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35
Q

What are the gram negative coccobacilli

A
  1. Haemophilus species
  2. Bordetella
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36
Q

What are the gram + bacillus bacteria

A
  1. Clostridium botulinum
  2. Clostridium difficile
  3. Clostridium tetani (tetanus)
  4. Clostridium perfringes (gas gangrene)
  5. Listeria
  6. Corynebacterium
  7. Bacillus anthracis
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37
Q

What are the gram - bacillus bacteria

A
  1. Escherichia coli (E. coli)
  2. Pseudomonas aeruginosa
  3. Salmonella species
  4. Klebsiella pneumonia
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38
Q

What spirochetes are difficult to gram stain?

A
  1. Treponema pallidum
  2. Borrelia burgdorferi (Lyme disease)
  3. Leptospira (Leptospirosis)
    *difficult to stain bc of shape
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39
Q

What are the gram negative spiral bacteria

A
  1. Campylobacter jejuni
  2. Helicobacter pylori
  3. Vibrio cholera
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40
Q

A patient presents with penile discharge and you suspect Neisseria gonorrhea, what findings on the gram stain would support your diagnosis?

A

Gram neg diplo cocci

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41
Q

A patient presents with burning, frequency, and urgency. Urine culture reveals a gram negative bacillus (rods). What is the most likely etiology?

A

E. Coli

42
Q

Patient presents with fever and chills, culture results reveal gram positive cocci in clusters what is the most likely etiology?

A

Staphylococcus

43
Q

Patient presents with fever, cough, and shortness of breath. CXR reveals and right lower lobe infiltrate and gram stain results demonstrate a Gram positive diplococci. What organism do you need to cover for when choosing your ATB?

A

Strep pneumonia

44
Q

What type of bacteria does a Giemsa stain look for?

A
  1. Chlamydia
  2. Plasmodium (malaria)
  3. Other parasites
45
Q

What is a wright stain use for?

A
  1. Used to differentiate blood cell types
    *Erythrocytes stain pink to buff
    *Platelets exhibit a light pale pink
    *Leukocyte stain magenta purple
    *Monocytes stains ground glass blue
    *Lymphocytes stain clear sky blue
46
Q

What is Acid-Fast Bacilli used for?

A

Suspect mycobacterium species infection
*mycobacterium tuberculosis
*monitor TB

47
Q

When should you consider the AFB test?

A
  1. Immunocompromised systems
  2. travel
  3. Confinement (prison)
  4. Recent exposure tuberculosis
48
Q

What is the AFB smear performed on?

A

Sputum
*takes about 24 hours
*AFB red rod shaped against light blue background

49
Q

What is required with a AFB smear?

A

Culture required
*2-6 weeks

50
Q

When is Tzanck smear used?

A

to diagnose herpes virus infections
*HSV
*Herpes zoster
*Varicella

51
Q

What will be on the Tzanck Smear?

A

Multinucleated giant cells
*will be diagnostic for herpes virus
*epithelial cells infected with HSV
*culture is required to identify specific virus

52
Q

What is a wet prep (saline wet prep) used for?

A
  1. Microscopic exam of vaginal discharge
  2. For suspect Trichomonas infections or bacterial vaginosis
  3. Can also indicate hyphae (yeast)
53
Q

What are abnormal results of a wet prep?

A
  1. Flagellated protozoan vaginalis infection
  2. “Clue cells” grainy appearance
    *epithelial cells surrounded by bacteria
    *suggest BV
  3. Stick like projections are hyphae (yeast)
54
Q

What are affirm wet preps?

A
  1. Used for vaginal discharge are often combined with KOH test which allows you to test for
    *BV
    *trich
    *yeast
    *all from the same swab
55
Q

What is aptima used for?

A
  1. A separate culture swab is needed for gonorrhea and chlamydia
56
Q

What is a viral culture used for?

A
  1. Needed for herpes if it is visualized
57
Q

When is a KOH prep used for?

A

Diagnosis of fungal infections
*tinea
*candidiasis
*will be a direct examination of skin, hair, nails, vaginal discharge, sputum

58
Q

How do KOH prep work for fungal infections

A
  1. KOH destroys epithelial cells and debris other than fungus
  2. Identifies hyphae, mycelia and budding yeast cells
59
Q

How do KOH prep work for vaginitis

A

KOH is added after saline wet prep
1. Will yield a positive whiff test (get a fishy odor)
*AKA amine odor test (suggest BV)

60
Q

What is the Amstel criteria for BV

A
  1. Homogenous vaginal discharge
  2. pH >4.5
  3. Presence of clue cells in gram stain
  4. Positive whiff test
    *need 3/4 for diagnostic
61
Q

When is India ink prep used for?

A

Used to identify fungal organisms
*especially cryptococcus
*opportunistic yeast

62
Q

How does an India ink prep work?

A
  1. The polysaccharide capsule present in yeast will exclude the paricles of India ink
    *there will be a halo around the organism
63
Q

When is Darkfield microscopy used?

A

To detect primary syphilis (treponema pallidum)
*a drop of exudate from chancre lesion is placed on the slide
*can also use rapid plasma reagin (RPR) to test for syphilis

64
Q

When is scotch tape test used?

A

For diagnosis of pinworm infection enterobius vermicularis

65
Q

How to conduct the scotch tape test?

A
  1. Nighttime collection while sleeping I
66
Q

What are cultures used for

A

Laboratory controlled growth of microorganisms on special media to determine the cause of an infection

67
Q

What is the incubation period time frame?

A

24-48 hours

68
Q

How should and when should cultures be obtained?

A
  1. Obtained under sterile environments
  2. Before starting ATB
69
Q

When are aerobic cultures used

A

For more superficial wounds since
*bc bacteria needs O2

70
Q

When are anaerobic cultures used

A

For abscess or deep wound, tissue, or normally sterile body fluids

71
Q

What do cultures confirm?

A

The identification of the organism

72
Q

Why is susceptibility testing used (bacterial cultures)

A

To determine the organisms sensitive or Resistance to various ATB
*will show the MIC

73
Q

What are the different types of viral cultures?

A
  1. Throat
  2. Nasopharyngeal
  3. Rectal
  4. CSF
  5. Vesicles
    **slow growing takes at least 3-5 days
74
Q

How fast do fungal cultures grow?

A

Slow growing
*1 week or months
*need a specialized culture media

75
Q

When are blood cultures used?

A

When there is suspected septicemia or bacteremia

76
Q

What is the collection protocol for blood cultures

A

Adult: 2
Peds: 1
*peripheral blood draw from 2 different sites

77
Q

What will a negative blood culture show

A
  1. No growth for # of days
    *consider the timing of collection visual ATB administration
78
Q

What will a + blood culture show

A

Common blood pathogens reported
1. Staphlocccocus aureus
2. Streptococcus pneumonia
3. Haemophilus influenza
4. Enterococcus
5. Pseudomonas

79
Q

What could be a contaminant of a + blood culture

A
  1. Staphylococcus epidermidis
80
Q

When should cultures be performed/

A

Before ATB started
*if already started try to take sample before the second ATB dose

81
Q

When is a urine culture done?

A

For a suspected UTI
*common pathogens e.coli, enterococcus, Proteus sp., Klebsiella

82
Q

What is the collection technique for urine culture

A
  1. Midstream, clean catch sample
    *can be contaminated by patient
  2. Catheterized
    *best sample to culture
    *less risk of contamination
    *urine is sterile
83
Q

What is an insignificant and a significant result for a clean catch specimen

A

Insignificant: <10,000 CFU
Significant: >100,000 CFU (infection)

84
Q

What is significant result for a catheter specimen catch

A

Any # of CFU is concern for infection
*if more than >3 organisms grow, it is a likely contaminant

85
Q

When is a nasopharyngeal culture done?

A

When there is suspected active bacterial or viral infection or carrier state

86
Q

How is nasopharyngeal collection done

A
  1. Swab deep in nasopharynx
  2. Don’t let swab touch skin
  3. Rotate swab and rest briefly
  4. Place swab in tube
87
Q

What can lead to rapid viral identification of a nasopharyngeal swab

A

Immunofluorescence of nasal secretion
*PCR assay and antigen detection is more reliable

88
Q

When is a throat culture used?

A

To differentiate viral from bacterial pharyngitis and identify carriers

89
Q

What is the most common pathogen detected on a throat culture?

A

Group A beta hemolytic strep (GABHS)
*streptococcus pyogenes
*takes 24-48 hours to culture

90
Q

What is the gold standard for diagnosis of acute pharyngitis due to GABHS

A

Throat culture
*if the rapid strep is + no need to perform culture

91
Q

How can true streptococcal infection be confirmed?

A

By measurement of antistreptococcal antibody titers
*antistreptolysin O (ASO) titers (for complicating factors)

92
Q

When is a sputum culture used

A

For suspicion of pneumonia or TB

93
Q

Is salvia the same thing as a sputum collection

A

No
*the sputum most come from the lungs

94
Q

What would be a poor sample of a sputum culture

A

> 25 squamous epithelial cells/hpf

95
Q

What is cerebrospinal fluid culture indicated for

A

Suspected meningitis (bacterial or viral)
*collection from lumbar puncture for CSF (Sterile)

96
Q

What are the + results (CSF)

A

Adults:
1. strep pneumonia
2. H. Influenza
3. neisseria meningitides
Peds
1. Enteroviruses (Coxsackie, Echovirus)
2. Group B Strep
3. E. coli
4. S.pneumonia
5. N. meningitis

97
Q

What are the most common pathogens on a wound culture

A

Staphylococcus aureus
*MSSA (methicillin sensitive)
*MRSA (methicillin resistant)

98
Q

When is a stool culture collected

A

When there is suspicion of infectious diarrhea
*most collect a series of fecal samples

99
Q

What are the most common pathogens collected on a stool culture?

A

SSYCE
1. Salmonella
2. Shigella
3. Yersinia
4. Campylobacter
5. E.coli
*specifically request the bacteria (include ova and parasites)

100
Q

When is a rectal culture done

A

When there is a suspected viral infection

101
Q

When are Cervical and urethral cultures done?

A
  1. For genital lesions, abnormal discharge or itching
  2. Suspected STD, PID, urethritis (gonrrohea/chlamydia)
102
Q

What is considered the gold standard for many disease processes

A

Tissue biopsy
*ultimate determination of etiology

Clinical Patient Care 2023 (33 decks)

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