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Semester 3 > Laboratory Diagnosis and Bacterial Identification > Flashcards

Laboratory Diagnosis and Bacterial Identification Flashcards

1
Q

What are Characteristics of Light Microscopy?

A

Most Common Type

Resolution = 0.2um

Microbes larger then virus

Wet Mounts to Study Live Microbes

  1. ) Fluids (Urine ,CSF or Feces)
  2. ) Larger Cells ( Parasites , eggs and protazoa)
  3. ) Fungi from Skin (KOH)
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2
Q

What are the Stained Preparations of Light Microscopy?

A

Gram Stain

Acid Fast Stain ( Kinyoun , Ziehl Neelsen)

Capsule Stain ( India Ink)

Spore Stains

Giemsa or Giemsa Wright

Silver Stains

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3
Q

What is the Principle of Darkfield Microscopy?

A

The light microscope is adapted by modifying the condenser to prevent transmitted light from directly illumintating the unstained species

Light Passes around (reflected) rather then through

Spirochetes appear bright (thin)

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4
Q

What is the Principle of Phase Contrast Microscopy?

A

Unstained sample

Uses light refraction to give 3D image

Better visualization of Internal Structures

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5
Q

What is the Principle of Fluorescence Microscopy?

A

Fluorescent Compounds

Absorb Energy at One Wavelength and Emit

Staining uses Calcofluor White (Fungi) or Auramine O Rhodamine (Myobacteria)

Targeted Fluorophores are conjugated to Antibody

Direct (AB to Antigen)

Indirect ( Secondary AB to AB to Antigen)

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6
Q

What is the Principle of Electron Microscopy?

A

Can visualize smaller particles

Virus and Organelles

Scanning EM gives a surface image

Transmission EM uses stain to provide internal image

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7
Q

What is a Blood Agar Media (BAP)?

A

General Purpose and Differential Medium

Sheep Blood

Growth Factors for Fastidous Organisms ( Complex Requirement)

Pattern of Hemolysis can aid in Identification

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8
Q

What type of Media is Shown in the Image

A

Blood Agar

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9
Q

What is the characteristics of a Choclate Agar (CAP) and Thayer Martin Agar?

A

Contains blood that has been heated to lyse red blood cells and release intracellular nutrients

Organisms with difficult nutritional requirements that cannot lyse themselves

Haemophilus and Neisseria

Thayer Martin has antibiotic added for isolation of Neisseria Gonorrhoeae

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10
Q

What type of Media is Shown in this Image?

A

Choclate Agar or Thayer Martin Agar

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11
Q

What are the Characteristics of a Mannitol Salt Agar(MSA)?

A

High Salt Concentration inhibits all but osmotolerant organisms

Fermentation of Mannitol results in acid production , causing a drop in pH and turning pH indicator from red to yellow

Staphylcocci

Differentiating Staph Aureus (Ferments Mannitol) form Coagulase negative Staph

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12
Q

What type of Media is Shown in the Image?

A

Mannitol Salt Agar (MSA)

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13
Q

What are the characteristics of the MacConkey and Sorbitol MacConkey Agar?

A

Contains Bile Salts and Crystal Violet to inhibit growth of Gram Positive Organisms and some Gram Negative

Selective for Gram Negative Bacteria

Lactose and Neutral Red pH Indicator

If Organism ferments lactose , colonies appears pink (Low pH) (E Coli)

If Organism is non lactose , colonies appear beige (Salmonella)

Can use Sorbitol as Well

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14
Q

What type of media is shown in the image?

A

MacConkey Agar (MAC)

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15
Q

What are the Characteristics of Eosin Methylene Blue Agar?

A

Use Eosin and Methylene Blue to inhibit Gram Positive

Lactose Fermenters appear Blue/Black

Non Fermenters are Clear

E Coli has a shiny green

Similar to MAC

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16
Q

What type of Media is Shown in the Image?

A

Eosine Methylene Blue Agar

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17
Q

What is the characteristics of a Bile Esculin Agar (BEA)?

A

Bile Salts Inhibit the growth of Gram Positive Organisms and most Streptococci except Group D Streptococcus and Enterococcus

Esculin cany by hydrolyzed by Group D to Esculitin which interacts with iron to form a black precipitate or ferrous sulfate

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18
Q

What type of media/tube is shown in the Image?

A

Bile Esculin Agar (BEA)

19
Q

What is a Hektoen Enteric Agar (HE)?

A

Bile Salts and Indicator to Inhibit Gram Positive Organisms

Use Lactose , Sucrose and Salicin

Fermenters apper Yellow Orange

Non Fermenters Appear Green or Transparent

Hydrogen Sulfide (H2S) producers will form Black Precipitate

Salmonella

20
Q

What type of Media is shown in the image?

A

Hektoen Enteric Agar (HE)

21
Q

What are the Characteristics of a Cetrimide Agar?

A

Isolation of Pseudomonas Aeruginosa

Detergent that Inhibits most bacteria

Contain magnesium and potassium which promote the produciton of the pigments pyocyanin (Blue Green)

Fluorescein ( Yellow Green)

22
Q

What type of media is shown in this Image?

A

Cetrimide

23
Q

What are the Characteristics of Tellurite Agar? (Cystine Tellurite Agar)

A

For isolation of Corynebacterium Diphtheriae

Potassium Tellurite inhibits Gram Negative Organisms and most Upper Respiratory Flora

Colonies appear gray or black (tellurite reductase activity) with a brown halo (cysteinase activity)

24
Q

What type of media is shown in this image?

A

Tellurite Agar

25
Q

What are the Characteristics of a Triple Sugar (TSI Agar)?

A

Contain Lactose , Sucrose , Glucose , Protein Digest , Sodium Thiosulfate , Ferrous Iron and a pH indicator

Pink to Yellow Color Change Indicates:

A.) No Yellow , No Sugar Utilization

B.) Entire Tube Pink , Multiple Sugars

c.) Glucose Fermentation , Pink on Top with Black (H2S)

D.) H2S Produciton of a Black Precipitate

26
Q

What type of tube test is shown in the Image?

A

Triple Sugar Iron Agar

27
Q

What are the Characteristics of a Chromogenic Agars?

A

Change in colony color indicates different colonies

Specific and Grow Quick

Listeria Monocytogenes

Staphylococcus Aureus

Methicillin Resistant vs Methicillin Sensitive

28
Q

What type of Media is shown in this Image?

A

Chromogenic Agar

29
Q

What are the three types of Hemolysis Reactions on a Blood Agar plate?

A

Alpha Hemolysis

Partial Lysis of the RBCs

Organsims produce Hydrogen Peroxide

Oxidation of Hemoglobin to Green Methemglobinperoxide

Beta Hemolysis

Complete clearing of the RBC

Organsims produce Hemolysin which Lyses

Gamma Hemolysis

Bacteria have no Effect on the RBCs

30
Q

What is a Catalase Test?

A

Detects presence of Catalase Enzyme

Converts Hydrogen Peroxide to Water and Oxygen

Differentiate Gram Positive Bacteria

Anaerobes Less Likely

Rapid Under a Minute

31
Q

What is a Coagulase Examination?

A

Detects Bacteria which convert fibrinogen to fibrin

Staphylococcus Aureus

Yersinia Pestis

Free Coagulase (Overnight)

Secreted bacterial coagulase reacts with prothrombin in the liquid test tube medium to form staphylothrombin which catalyzes the conversion of fibrinogen within the medium to insoluble fibrin

Medium becomes a Gel

Bound Coagulase

Bound to bacterial cell wall

Done on Slide (Few Minutes)

32
Q

What is a Fermentation Test?

A

pH indicator in media reflects the production of acid from metabolism of a sugar in a medium

Differentiate gas productions vs none

Home/Hetro Fermentation

Happens Overnight

33
Q

What is an Oxidase Test?

A

Detect the Presence of Cytochrome C Oxidase

Indicator turn Purple

Some bacteria with ETC have a different molecule and will test negative

Helps Differentiate Gram Negative Bacteria

Rapid

34
Q

What is an Urease Test?

A

Detects the presence of the urease enzyme

Breaks down Amides which produces ammonia

Result in a Color change to pink

Can be agar slant or broth

Helicobacter , Proteus , Ureaplasma , Nocardia and Cryptococcus

35
Q

What is a Thioglycollate Test?

A

Thioglycolates Remove Oxygen

Bacteria places in semi solid test tube allowing oxygen to diffuse through the top

Creates and Oxygen Gradient:

  1. ) Obligate Aerobes at the Top
  2. ) Aerotolerant Anaerobes throughout the tube
  3. ) Strict Anaerobes in the Bottome

Overnight

36
Q

What is a Direct Assay? (Latex Agglutination Test)

A

Determine the presence of Antigens

Inert latex beads conjugated to specific antibodies are mixed with a specimen

Results in a Visible Clumping Reaction

IgM antibodies work the same way

Results within Minutes

Non Specific Binding and Low Sensitivity

Qualitative

37
Q

What is a Sandwhich Enzyme-Linked Immunosorbent Assay (ELISA and EIA)?

A

Use of Enzymatic Detection mechanism or Fluorophore can amplify the signal , providing high levels of Sensitivity

The amount of signal is proportional to the amount of detection present , which is proportional to the analyte

Compare to a Standard Curve

38
Q

What is a Chromotographic Immunoassay (CIA)?

A

Dipstick or Strip Format

Capillary action brings a dye conjugated antibody antigen complex to a second , immobilizded capture antibody

Leaves a Concentration Dot

39
Q

What are Nucleic Acid Based Tests?

A

Detection of Specific Nucleic Acid Signatures via Hybridization to complementary nucleic acid sequences

Use PCR or Branched DNA Assay to Amplify

Reverse Transcriptase PCR

Starts from RNA , RT enzyme converts the RNA into complementary DNA (cDNA) , then normal PCR used

Can be Real Time as Well (Fluorescence)

Used for RNA Viruses

Real Time PCR

Incorporates visualization of the product via fluoroscence as amplification occurs

40
Q

What is Branched DNA Assays?

A

Amplifies the Signal not the Nucleic Acid itself

Single Stranded DNA probe is generated that incorporates a portion that is complementary to the targeted sequence and a portion that will bind an engineered branched DNA Structure

Conjugated to Enzymes that will create a signal when mixed with a substrate

Single Nucleic Acid Signal will produce a highly amplified signal , and the amount is proportional to the number of copies of the specific nucleic acid target

41
Q

What are some Advantages and Disadvantages to Serologic Tests?

A

IgM Indicates an early active Infection

IgG takes several weeks (Active or Previous Infection)

Advantage

Usually Very Sensitive

Acute Infection

Disadvantage

IgM antibodies can only be detected early in infection

IgG Antibodies appear 2-4 weeks after

42
Q

What is Indirect ELISA?

A

Test kit contain antigen from the organism of interest

Patient serum is applied and wells/slides are washed

If antigen specific antibodies are present they will bind and will not wash off

ELISA is enzyme linked while IFA is Fluorophore

Second Antibody will bind them and will remain through a wash step

Label permits detection

Subject to Lab Techs Experiance

43
Q

What is a Western Blot?

A

Semester 3 (6 decks)

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