Week 3 - Microbial Diagnosis

Question 1

What is the most important first step in diagnosis of microbial infection?

Answer 1

An accurate clinical history and physical exam is the important first step in diagnosis

Question 2

Ways to test?

Answer 2

Question 3

Lab Tests

Microscopic Examination of clnical specimans

Answer 3

Direct microscopic examination of clinical specimens, ex. Sputum, CSF, etc.
Gram and acid-fast stain
India ink (CSF for Cryptococcus neoformans)
KOH treatment for fungal forms
Fluorescent antibodies

Question 4

Most common microscopies

Answer 4

Usually light microscopy or electron microscopy

Question 5

Gram stain and acid fast

Answer 5

Most comon

Question 6

Flourescent Microscopy

Answer 6

Uses proteins on microorganism as targets of antibodies.. then label the antibody with flourescent tag it will light up

Question 7

Indirect vs direct flourescent microscopy tests

Answer 7

Look at picture.

In order to prove it attacts use antibody to the antybody which will light up..

THes are used to diagnose SPECIFIC microbial diseases…

Question 8

Growing bacteria, fungi, and viruses

Answer 8

Growing bacteria, fungi and viruses
Use of enriched and selective media (bacteria & fungus) or appropriate cell types (viruses) for cultivation of clinical specimens

Question 9

Virus grown in culture then antibodies added to see which is there..

Answer 9

Question 10

Tests for enzymes and metabolic pathways

Answer 10

Catalase, oxidase, lactose fermentation, etc

Question 11

Specific antiserum detection of microbial antigens

Answer 11

Quelling reaction
Slide agglutination
Virus neutralization

Question 12

Hemophilius influenza visualiztion..

Answer 12

Question 13

Identification of serum antibodies

Answer 13

No antibodies in body untill about 2 weeks after infection*

So if find antibodies in blood, cant tell if is past or present infection.

Only way to tell is that there are types of antigens, IgM (the first to appear, so that infection had just occured)

No antibody early in infection
Does not differentiate between past and present infection
Need accurate and convalescent sample to confirm active infection

Tests include:
Complement fixation
Hemagglutination and hemagglutination inhibition
Latex agglutination
Enzyme-linked immunosorbent assays (ELISA)
Western blots

Question 14

Read

Answer 14

Question 15

Read

Answer 15

Question 16

Western Blot

Answer 16

Important in identifying HIV

The blot will show specific HIV proteins that you can identify HIV from…

Question 17

Detection of microbial proteins and nucleic acids

Answer 17

• Western blots and ELISAs - microbial proteins
• Southern blots - microbial DNA
• Northern blots – microbial RNA

Question 18

ELISA Test

Answer 18

Plates have a antibody in well

Pts serum is incubated in well.. any antigen in serum is then bound to antibody in cell wall..

so looking to see if some specific antigen of virus is present in blood..

The specific antigen will react with certain antibody which contains an antibody that contains an enzyme

Usually the enzyme is peroxidase so it causes a black type of rxn.

See if this SPECIFIC antibody reacted to a SPECIFIC antigen in pts blood.

Question 19

Detection of microbial genes

Answer 19

Known gene probes which are single-stranded and labeled are hybridized with clinical samples
Frequently need a polymerase chain reaction (PCR) to amplify DNA sequences in clinical specimens ex. Nested PCR

Question 20

Polymerase Chaine Reaction PCR

Answer 20

Going to look for genetic information in an infectious agent in CSF..

Thinking it might be herpies simplex virus (HSV)