Exam III (Lab Testing)

Question 1

What are two common staining techniques?

Answer 1

Gram stain and acid fast stain

(others include lactophenol cotton blue stain, trichrome stain, and auramine O stain)

Question 2

What are the 3 different microbial detection methods?

Answer 2

A. Staining
B. Antigen-antibody PCR
C. Cultures

Question 3

The gram stain is only used for ______.

Answer 3

Bacteria

Question 4

A gram + bacteria stains ________.

Answer 4

Purple

Question 5

A gram - bacteria stains ________.

Answer 5

Pink/red

Question 6

What is the first step in determining the identity of a pathogen and guides the initial antibiotic selection?

Answer 6

The gram stain

Question 7

What is the information that is obtained from a gram-stain?

Answer 7

Cell wall form (+/-), shape, configuration (pairs/clusters), quantity of bacteria, and other cells in sample like RBCs, WBCs, eosinophils, and more.

Question 8

What is the goal of an acid-fast stain?

Answer 8

The differentiate bacteria into acid fast group or non-acid fast group. It is mainly used to detect mycobacterium and nocardia species due to the large presence of mycolic acid in the cell wall.

Question 9

Acid-fast positive cultures will turn the color _____.

Answer 9

Red

Question 10

T or F: Acid-fast bacterial cells are resistant to decolorization and retain carbol fuchsin stain red color because of their lipoidal cell wall.

Answer 10

True. Acid-fast negative bacteria lack the lipoidal material in the cell wall and are decolorized and counterstained with methylene blue.

Question 11

What two bacteria are commonly identified with an acid-fast stain?

Answer 11

Mycobacterium and Nocardia species

Question 12

What are the 3 automated processors that help with organism identification?

Answer 12

Vitek, Microscan, and Sensititre

Question 13

What is the machine that uses mass spectrometry to identify pathogens?

Answer 13

MALDI-TOF

Question 14

What are the advantages of the MALDI-TOF over traditional methods for pathogen identification?

Answer 14

Identification can be completed in less than 1 hour

Question 15

What are three ways in which antimicrobial susceptibility testing can be done?

Answer 15

A. Kirby-Bauer disk diffusion
B. Microbroth Dilution method
C. Epsilometer test

Question 15

What are the advantages and disadvantages of the Kirby-Bauer disk diffusion test for antimicrobial susceptibility?

Answer 15

It is rapid and inexpensive but it is qualitative and does not provide an MIC

Question 16

What is the microbroth dilution method?

Answer 16

It is an antimicrobial susceptibility test that is quantitative and gives an MIC.

Question 17

What is an MIC?

Answer 17

MIC is the minimum inhibitory concentration which is the lowest concentration of antibiotic that inhibits visible growth of a pathogen.

Question 18

What are the different MIC breakpoint concentrations?

Answer 18

4 or less= susceptible
8= intermediate
16 or more= resistant

Question 19

What is the epsilometer test?

Answer 19

This is a quantitative antimicrobial susceptibility test that gives the MIC.

Question 20

What are the overall limitations of antimicrobial susceptibility testing?

Answer 20

It does not take into account patient specific factors, including their immune system, the site of infection, and inoculum size. It also does not detect all resistance mechanisms.

Question 21

The MIC is a relationship between what two things?

Answer 21

Pathogen and antibiotic

Question 22

What is the MIC of pseudomonas aeruginosa?

Answer 22

It does not gave an MIC typically.

Question 23

The relationship between a pathogen’s MIC and an antibiotic fits into the ______________ category.

Answer 23

Pharmacodynamic

Question 24

What is the MIC90?

Answer 24

This is the lowest concentration of an antibiotic that inhibits visible growth of 90% of tested isolates

Question 25

T or F: Definitive antimicrobial therapy is based on patient specific MIC values.

Answer 25

True

Question 26

In what disease states should procalcitonin be monitored?

Answer 26

Lower respiratory tract infections like pneumonia and sepsis

Question 27

When should procalcitonin levels be checked?

Answer 27

Initially at symptom onset and then every 24-48 hours. (ideally would be daily for 7 days)

Question 28

What are the 3 things that daily procalcitonin monitoring has shown in those with pneumonia or sepsis?

Answer 28

Decreased antibiotic use duration, decreased length of stay, and cost savings.

Question 29

What is peptide nucleic acid fluorescence in-situ hybridization (PNA-FISH)?

Answer 29

This is rapid nucleic acid amplification that is being used to detect staph aureus, enterococcus faecalis, and candida albicans in about 2 hours

Question 30

What is the VERIGENE system?

Answer 30

This is a fast culture nucleic acid test that tests for gram + bacteria in the blood. There other system can identify gram - organisms.

Question 31

What is BioFire?

Answer 31

This is a PCR technique that amplifies nucleic acids of multiple targets including respiratory, blood, GI, and brain bugs.

Question 32

What are the advantages of using BioFire?

Answer 32

No need to sample and culture the pathogen so quicker results and less contamination. Can detect the presence of pathogen in a few hours and can identify resistance genes.