Unit 5 - Diagnosis of infectious diseases

Question 1

If the lab promptly and accurately identifies infectious agents, what does this do (3)?

Answer 1

1. Provides patient with appropriate and effective therapy
2. Avoids delay in providing therapy
3. Helps reduce risk of further spread

Question 2

When are most mistakes likely made in the diagnosis of infectious disease, in the post-analytic phase or the pre-analytic phase?

Answer 2

Pre-analytic phase

Question 3

What is involved in the pre-analytic phase?

Answer 3

• order placed
• order transmitted to lab
• identifying information entered
• specimen obtained

Question 4

What is involved in the post-analytic phase?

Answer 4

• report generated
• result conveyed to clinician
• data interpreted
• clinical response to result

Question 5

What is a major decisive factor for successful identification of disease-causing agents?

Answer 5

Specimen collection

Question 6

Who is responsible for collecting specimens (5)?

Answer 6

• RNs
• LPNs
• Physicians
• Registered medical lab technologists
• med lab assistants

Question 7

What are the five major steps of “I’s” for the identification of an infectious specimen?

Answer 7

1. Inoculation
2. Incubation
3. Isolation
4. Inspection
5. Identification

Question 8

True or False:

A nurse is likely to be the first health care worker to be aware of s/s of an infection in a patient

Answer 8

True

Question 9

True or False:
One of the general principles of proper specimen collection and handling is … Taking the RIGHT specimen from the RIGHT patient

Answer 9

True

- check the physician’s orders and the patient’s ID

Question 10

True or False:
One of the general principles of proper specimen collection and handling is … Taking the specimen first thing in the AM

Answer 10

False

• Collect the specimen at the APPROPRIATE time
• Ex: during the acute phase or the convalescent phase

Question 11

Describe what serology (paired sera) is

Answer 11

Paired sera collected from a patient to detect a significant rise in ANTIBODY TITRE

Question 12

True or False:

A paired sera serology measures the difference in level of infectious agent between one time and another

Answer 12

False

• measure the levels of antibodies present in the body
• minimum 4 fold increase

Question 13

True or False:
One of the general principles of proper specimen collection and handling is …Collecting a specimen after the patient has started antimicrobials

Answer 13

False

- collect the specimen BEFORE patient receives antimicrobials

Question 14

True or False:
One of the general principles of proper specimen collection and handling is … Using clean technique when collecting a specimen

Answer 14

False

- use ASEPTIC technique

Question 15

True or False:
One of the general principles of proper specimen collection and handling is … Using the appropriate, sterile container and collection tools for the required specimen

Answer 15

True

Question 16

True or False:
One of the general principles of proper specimen collection and handling is …Collecting an adequate amount of specimen (for various tests)

Answer 16

True

Question 17

Why is it necessary to use the appropriate transport media when transporting a collected specimen?

Answer 17

To ensure the survival of the delicate disease-causing agents in the specimen during transport

Question 18

Why is it important that the collected specimen has the appropriate label on it?

Answer 18

Ensures that the correct diagnosis goes to the CORRECT patient

Question 19

Why is it important to communicate with the lab regarding special requires and possible etiology?

Answer 19

Because it gives the lab time to prepare

• in the event of a lot of samples coming to the lab
• ex. adequate staffing of lab

Question 20

True or False:
One of the general principles of proper specimen collection and handling is … Transporting the specimens to the lab promptly

Answer 20

True

- different time limits may be applied to different specimens

Question 21

What is the main role and responsibility of the clinical microbiology lab?

Answer 21

To accurately identify the disease-causing agent in a timely fashion

Question 22

What are the two major approaches that the clinical microbiology lab uses to identify disease-causing agents?

Answer 22

1. Identify the pathogen and/or its products (through phenotypic, genotypic and immunological methods)
2. Detect and often quantify antibodies made by the patient to the pathogen

Question 23

What are two other roles and responsibilities of the clinical microbiology lab?

Answer 23

1. To quantify the disease-causing agent

2. To determine the susceptibility of the pathogen

Question 24

What does a culture and sensitivity test determine?

Answer 24

Whether the test organism is sensitive (susceptible) to antibiotics

Question 25

What are 3 common lab identification methods used to identify disease-causing agents?

Answer 25

1. Phenotypic methods 2. Genotypic methods 3. Immunological methods

Question 26

True or False: | A phenotypic method usually involves a microscopic and macroscopic examination

Answer 26

True

Question 27

What are 3 examples of microscopic examinations in phenotypic testing?

Answer 27

Gram stain Acid-fast stain Electron microscopy

Question 28

True or False: | During macroscopic examination, the characteristics of bacterial colonies are examined

Answer 28

True | - such as growth patterns, texture, color, shape

Question 29

True or False: | Isolating the disease-causing specimen is often required using phenotypic methods

Answer 29

True

Question 30

Following isolation, what is required next during phenotypic methods of identification of disease-causing specimens?

Answer 30

Culturing (growing) of the microbes to sufficient numbers

Question 31

During phenotypic methods, selective media are used to grow/culture the microbes - what does selective media suppress and what does it promote?

Answer 31

``` Suppress = growth of gram-positive and some fastidious bacteria Promotes = growth of gram-negative bacteria ```

Question 32

What is an example of a selective OR differential media?

Answer 32

Mac Conkey agar

Question 33

What is used in enriched media to culture fastidious bacteria?

Answer 33

Blood or chocolate agars

Question 34

True or False: When using phenotypic methods to identify a disease-causing microbe, a combination of phenotypic methods can be used to identify the agent

Answer 34

True - you can't do just ONE test to find out what the agent is - you have to narrow it down, step by step - IT TAKES TIME!

Question 35

What does the biochemical method of phenotypic identification do?

Answer 35

Detects enzymes and/or metabolic products in a bacterial isolate

Question 36

True or False: | Using biochemical methods of identification, the tests comes out either positive or negative

Answer 36

True | - usually quite a few substrates are tested at the same time

Question 37

What is considered a definitive microbiological diagnosis of an infectious disease?

Answer 37

Culture and sensitivity

Question 38

What is a routine test for many bacterial and fungal infections?

Answer 38

Culture and sensitivity

Question 39

True or False: | Culture and sensitivity usually involves identifying the pathogens in culture

Answer 39

True | - they are isolated and grown in artificial media

Question 40

What is a classic qualitative approach for testing microbial susceptibility to antibiotics?

Answer 40

Culture and sensitivity

Question 41

What does the diameter around the antibiotic disk where no microbial growth is observed, tell us about the agent?

Answer 41

Whether the test organism is sensitive or susceptible or resistant to a particular antibiotic

Question 42

True or False: | The less space around an antibiotic disc, the more effective the antibiotic is

Answer 42

False | - more space = more effective

Question 43

What does it mean if an infectious agent is between the range of susceptible and resistant?

Answer 43

Means that the organism is on its way to becoming susceptible OR resistant

Question 44

What is a broth dilution test?

Answer 44

Tubes containing serial dilutions of an antibiotic inoculated with the test organism - tubes incubated and then observed for the presence of growth

Question 45

What is minimum inhibitory concentration?

Answer 45

Smallest concentration of an antibiotic required to prevent microbial growth

Question 46

What is minimum bactericial concentration?

Answer 46

Lowest concentration of an antibiotic required to kill 100% of the microbes

Question 47

What is genotypic methods based on?

Answer 47

Identification of unique microbial DNA or RNA segments extracted from a patient's clinical specimen

Question 48

What happens during genotyping of an infectious agent?

Answer 48

Gene probe binds to the complementary target sequence(s) detactable by color change, fluorescence or radioactivity

Question 49

True or False: | During genotyping, there is no need to culture the microbe

Answer 49

True | - therefore, it saves time

Question 50

What are some characteristics of genotyping?

Answer 50

- sensitive (only small amount needed) - specific to the organism - quick - unaffected by the prior presence of antimicrobials