Laboratory Diagnosis and Bacterial Identification Flashcards

Question

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

Answer 1

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

Answer 2

Triple Sugar Iron Agar

Answer 3

Change in colony color indicates different colonies Specific and Grow Quick ***Listeria Monocytogenes*** ***Staphylococcus Aureus*** ***Methicillin Resistant vs Methicillin Sensitive***

Answer 4

Chromogenic Agar

Answer 5

**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

Answer 6

Detects presence of Catalase Enzyme Converts Hydrogen Peroxide to Water and Oxygen **Differentiate Gram Positive Bacteria** Anaerobes Less Likely Rapid Under a Minute

Answer 7

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 s**taphylothrombin** which catalyzes the conversion of **fibrinogen** within the medium to i**nsoluble fibrin** **Medium becomes a Gel** **Bound Coagulase** Bound to bacterial cell wall Done on Slide (Few Minutes)

Answer 8

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

Answer 9

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

Answer 10

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***

Answer 11

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

Answer 12

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

Answer 13

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

Answer 14

Dipstick or Strip Format Capillary action brings a dye conjugated antibody antigen complex to a second , immobilizded capture antibody Leaves a Concentration Dot

Answer 15

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

Answer 16

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

Answer 17

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

Answer 18

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