week 1- clinical samples

Question 1

why are microbiology samples collected and processed

Answer 1

to correctly identify the pathogen, provide a diagnosis and advise on appropriate therapy in time.

Question 2

what is a contaminant

Answer 2

an microorganism that wasn’t present in the original samples, but has got into the sample during collection, transport or during processing

Question 3

what can the isolation of a contaminant lead to

Answer 3

wrong diagnosis and inappropriate treatment

Question 4

how can contamination during collection be avoided

Answer 4

• Cleaning of the collection site, e.g. use of alcohol-based disinfectant on the skin before blood collection.
• Only trained staff collecting samples, e.g. phlebotomist taking blood.
• An appropriate sample being collected, e.g. mid-stream urine (MSU).
• Using only sterile, approved specimen containers

Question 5

why should samples be taken at an appropriate time

Answer 5

to maximise the chance of organism recovery

Question 6

why should samples be taken before anti microbial are taken

Question 7

what can ensure a reliable diagnosis

Answer 7

multiple orthopaedic tissue samples should be taken

Question 8

how can reliable samples be taken

Answer 8

the appropriate type of sample and multiple samples are required. Taking a sufficient quantity of the sample must be collected

Question 9

what should be performed on CSF samples

Answer 9

cell count, gram stain and culture

Question 10

what are the most commonly used specimens containers

Answer 10

sterile universal/pot
faecal or stool specimen pot
general transport swap

Question 11

what is sterile universal/pot used for

Answer 11

collect samples of:
Mid-stream urine
Pus
Sputum
Tissue biopsies
CSF

Question 12

what is purpose of transport medium

Answer 12

contains amines
agar to help maintain organism viability
charcoal to absorb toxins

Question 13

What is the difference between a general transport swab and pernasal swab?

Answer 13

General transport swab:
Has a transport medium
Plastic or wood shaft
Cotton or rayon tip
Used for wounds, throat swabs, high vaginal swab

Pernasal swab:
Also has a transport medium
Has a wire shaft which can bend
Has a fine tip
Swabs the nasopharynx area

Question 14

What is the requirement for specimens?

Answer 14

They must be fully labelled
Maintained at correct temperature
Delivered on time to the lab
Correctly packaged to avoid leakage etc

Question 15

15-17

Question 16

How are specimens transported to the lab?

Answer 16

By porters and couriers - samples are placed in leak proof containers, then in bags, then in boxes

By an air tube system - safe transportation in pneumatic tube systems

Question 17

What are the 2 categories of infectious substances?

Answer 17

A and B

Question 18

What is a category A infectious substance?

Answer 18

An infectious substance that when one is exposed to it, it can cause permanent disability, is a life threatening/fatal disease

Example such as ebola, west nile virus

Question 19

What is a category B infectious substance?

Answer 19

An infectious substance that does not meet the criteria for inclusion in category A.

Examples such as e coli, staph aureus,

Question 20

Why do we culture samples?

Answer 20

To check for organism presence
To check for more than one organism
To identify the pathogen

Question 21

Why do we inoculate media?

Answer 21

To isolate single colonies
To detect mixed cultures,

Question 22

Why do we have more than one agar type?

Answer 22

Because organism have different growth requirements

Question 23

What are the different types of agar?

Answer 23

Selective agars: Contains antibiotics to prevent the growth of some organisms so only specific organisms can grow.

Differential agars: allows the distinction of different organisms based on the biochemical reactions

Question 24

what does enrichment media do

Answer 24

‘impair’ the growth of some organisms, but boost the
growth of target organisms

Question 25

36

Question 26

What is hazard group 1?

Answer 26

A biological agent that is unlikely to cause disease eg soil organism
Handled in an open lab aka containment level 1

Question 27

What is hazard group 2?

Answer 27

A biological agent that can cause human disease, there is a risk of spreading to the community but there is effective treatment available eg e coli, s aureus

Handled in a containment level 2 lab.

Question 28

What is hazard group 3?

Answer 28

A biological agent that can cause severe human disease, is a serious hazard, can spread to the community but there is usually effective treatment. eg TB, monkeypox, salmonella

Handled in containment level 3 lab

Question 29

What is hazard group 4?

Answer 29

A biological agent causing severe harm/disease, a severe hazard to employees, is likely to spread to the community but there is no effective treatment available. eg ebola, Lassa fever, Marburg virus

Handled in containment level 4 labs only containing viruses.

Question 30

What safety features do containment level 3 labs require/

Answer 30

HEPA (high efficiency particulate air) filtration of exhaust air
lab is sealable
microbiological safety cabinet - MSC
authorised personnel only

Question 31

What is a class 1 MSC?

Answer 31

open fronted cabinet where air is drawn at a rate to minimise aerosol escape.
Air is filtered by hepa filter
worker is protected but not the work
used for hazard 2 and most hazard 3 pathogens

Question 32

What is a class 2 MSC?

Answer 32

Open fronted cabinet where working space is flushed down with sterile air = which is hepa filtered
Both worker and work are protected
used for hazard 2 and and for hazard 3 pathogens in some circumstances

Question 33

What is a class 3 MSC?

Answer 33

totally enclosed cabinet where worker is separated from work via gloves attached to the ports
Air is hepa filtered
high degree of protection to work and worker
suitable for hazard group 3 and 4 pathogens