Infectious disease molecular by Dr. Davis

Question 1

list reasons for performing molecular microbiology testing in place of traditional microbiology cultures.

Answer 1

1. Microorganisms not easily cultured (legionella)
2. Slow growing microorganisms (M. tuberculosis)
3. low volume tests added little to the lab budget or workload
4. tests that make money and save money? (outpatient)
5. high/low volume tests

Question 2

List mycobacterial species identified by DNA probe technology- Gen-probe Accuprobes.

Answer 2

Mycobacterium tuberculosis complex (tuberculosis, bovis, africanum);
mycobacterium avium complex (avium and intracellulare);
mycobacterium gordonae and kanasaii.

Question 3

List the mycobacterial species identified by DNA probe technology- Cepheid (GenExpert)

Answer 3

M. tuberculosis and Rifampin susceptibility

Question 4

Indicate the color of fluorescence of the Candida species - albicans, tropicalis, glabrata when detected by PNA-FISH

Answer 4

C. albicans - green
C. trophicalis- Yellow
C. glabrata/krusei- red

Question 5

For the BD GeneOhm MRSA assay, indicate which part of the staphylococcal chromosome must be detected to definitely identify MRSA.

Answer 5

DNA detection of the SCCmec-orfX junction found only in MRSA provides definitive identification of MRSA.

Question 6

This method requires isolated colonies or high bacterial concentrations, and does identification only. Instrument is expensive and reagents can be cheap.

Answer 6

MALDI-TOF/MS

Question 7

This method does direct Identification from patient specimens and detection of resistance genes. cheap instrument/expensive reagents.

Answer 7

Molecular methods

Question 8

explain why enrichment broth is required for optimal screening for maternal colonization by streptococcus agalactiae.

Answer 8

Allows organism to grow overnight with enough copies of the organism

Question 9

List sexually transmitted diseases commonly detected by molecular methods.

Answer 9

GC, CT, TV, and HPV

Question 10

explain how HIV-1 viral load predicts clinical course in HIV/AIDS

Answer 10

the viral load levels as low as possible for as long as possible decreases the complications of HIV disease, slows the progression from HIV infection to AIDS, and prolongs life. So, increase in viral load in HIV-1 leads to AIDS. CD4 <200 = AIDS + HIV

Question 11

Discuss the importance of HIV-1 genotyping in patient management.

Answer 11

Examine the HIV genome for resistance associated mutations in the PR and RT regions; because the virus multiplies too fast

Question 12

Enzyme used in Transcription mediated amplification (TMA)

Answer 12

RT and RNA polymerase.

Question 13

Temperature of reaction in TMA

Answer 13

Isothermal reaction (no thermocycler), room temperature

Question 14

Indicate which analytes are most commonly detected by the TMA method in the U.S.

Answer 14

Neisseria gonorrhoeae and Chlamydia trachomatis (also detects TV and HPV high risk)

Question 15

List the types of clinical specimens useful for molecular detection of GC, CT, TV and HPV.

Answer 15

Urine, urethral/cervical swab, and Pap smear sample

Question 16

List several different methods for identifying bacteria and yeast directly in blood cultures.

Answer 16

AccuProbe, PNA FISH< QuickFISH, real time PCR (cepheid and BD), and Multiplex PCR (biofire, Verigene)