Role Of The Lab

Question 1

What is the process between collection and report

Answer 1

Labelled forms, sterile collection
Register specimen 
microscopy and gram stain
Culture 
Sensitivity 
Final report

Question 2

What can be assumed by specimen site

Answer 2

Type of pathogen likely to be present

Question 3

What determines the urgency of processing

Answer 3

Clinical details

Question 4

What on and when is microscopy done

Answer 4

Day 0

Only on important specimens that have been requested

Question 5

What can be assessed from cultures

Answer 5

type of organism grown significance of growth
Rapid identification tests on same day
Further tests: routine and specialised

Question 6

Why perform antibiotic susceptibility testing

Answer 6

To direct and predict anti microbial chemotherapy
To review and monitor epidemiological trends
Set national and local antibiotic policies
Test activity of new anti microbial agent
Presumptively identity isolates

Question 7

When is susceptibility attained in Vitro meaningful to vivo

Answer 7

If the MIC and MBC can be attained at the site of infection

Question 8

What is MIC

Answer 8

Lowest concentration of an agent that inhibits growth ( prevents development of visible growth) after overnight inoculation

Question 9

What is MBC

Answer 9

Lower at concern traction of an agent able to kill the bacterial strain (decrease in inoculated by a factor of 1000)

Question 10

List five methods to perform antibacterial susceptibility tests

Answer 10

disc susceptibility tests (stokes and BSAC) 
Agar breakpoint method
MIC (tube or e tests)
Automated methods (vitek)
Molecular methods ( PCR)

Question 11

Explain a disc susceptibility test

Answer 11

Inoculate test organising across agar
Apply antibiotics filter paper disc
Incubate
Antibiotics diffuse
zone of inhibition indicates susceptibility

Question 12

How do you measure antibiotic sensitivity qualitatively

Answer 12

Measure zone of inhibition diameter after disc susceptibility
Control with know sensitive strands on same plate ( stokes) of separately ( regression line)

Question 13

What factors effect the zone size in the agar disc diffusion test

Answer 13

Bacterial inoculum and growth rate
Medium composition osmotality and pH
Antibiotic molecule ( size solubility charge)
Antibiotic formulation (esters and pro-drugs may be inactive)
Disc content age condition enzymes secreted by bacteria into medium

Question 14

What is agar breakdown methodology

Answer 14

Used published breakpoint concerntractions
Antibiotic Set to this breakpoint MIC incorporated into agar
Spot test
growth -resistance

Question 15

What is semi-quantitative testing

Answer 15

In agar by break point, series of age plates as different concentrations, the plate at which there is no growth is ‘MIC’

Question 16

What do you quantitatively measure the MIC

And also MBC

Answer 16

Tube, broth dilution, twofold increase in concentration of antibiotic mic read after 24hours

Subculture clear tubes into agar to determine the MBC

Question 17

What are the automated methods of sensitivity testing

Answer 17

Vitek

Ast +/- expert interpretation

Question 18

what are the molecular methods of antibiotic sensitivity testing

Answer 18

Genetic detection by PCR
DNA sequencing
Hybridisation-based techniques

Question 19

What does microarray analysis require

Answer 19

Requires purified DNA

Question 20

Why would you do a serum antibiotic assay

Answer 20

Check compliance
Demonstrate bateau ideal activity in endocarditis
Manage therapy for those AB with narrow TW

Question 21

How do you perform and antibiotic assay

Answer 21

Microbiological assays on large plates

Question 22

Give 7 examples of specimen types

Answer 22

Respiratory ( pulmonary lavage)
Swabs 
Pus and body fluids
CSF
Blood 
Urine
Faeces