INTRO TO DIAGNOSTICS IN MICROBIOLOGY

Question 1

What are the 6 roles of microbiological lab?

Answer 1

• Diagnoses of infectious disease
• Clinical interface with clinicians
• Surveillance
• Infection control and antimicrobial stewardship
• Research
• Teaching and training

Question 2

Non-culture based diagnostics determine the organism by determining its?_________

Answer 2

• Genetic material
• Antigen
• Antibody reaction to antigens

Question 2

What are the 7 diagnostic functions of microbiological lab?

Answer 2

• Clinical microbiology
• Clinical Virology
• Clinical haematology
• Clinical Chemistry
• Genetics
• Forensic pathology
• Anatomical Pathology

Question 3

What organisms are detected using the ‘triumphant trio’ (MC&S)?

Answer 3

• Bacteria
• Fungi

*Only microscopy for parasites
*Viruses only use molecular based methods

Question 4

Name 5 types of agar plates used for microbial culture

Answer 4

• 5% blood agar plate (for dertemining type of haemolysis)
• Chocolate agar plate ( Used to cultivate fastidious organism)
• Mac Conkey agar (selective and differential- used for cultivating gram negative bacilli)> used to differentiate the lactose fementers from non fermenters
• Mueller Hinton agar plate (non-selective and non-differential- used for antibiotic susceptibility testing)

Question 5

After culture you need to identify an organism to genus and species level. Which techniques do we use for microbial identification?

Answer 5

• Array of biochemical tests:
  -Manual: API
  -automated: Vintek
• Molecular: PCR
• Mass Spectrometry: MALDI-TOF

Question 6

How long does it take to culturally grow myobacterim and fungi?

Answer 6

• up to 6 weeks

*normal bacteria be taking 24-48 hours

Question 7

What constituents are used to make a medium (the thing in an agar disc)?

Answer 7

• Mixture of digested proteins
• Inorganic salts
• Additional 1.5% agar (making the culture media solid hard)

Question 8

Methods used to carry out antimicrobial susceptibility testing include:

Answer 8

• Diffusion disks
• Antibiotic gradient strips
• Broth microdilution

Question 9

When are ‘blood culture bottles used’ in the micro lab?

Answer 9

• When sepsis from bacterial infection is suspected

Question 10

List the 5 antigen-antibody detection methods.

Answer 10

• Agluttination:
  -used in testing for anti-streptolysin O antigens
• Focculation:
  -employed in the RPR (Rapid Plasma Reagin test) for syphilis
• Haemaglutttination:
  -method employed in the Treponema Pallidum Haemagluttination assay (TPHA)
• ELISA:
  -the detection method is employed in HIV Elisa test, and HBV surface antigen detection)
• Lateral flow assay:
  -employed on cryptococcal and malaria antigen test