11. Finding the right treatment

Question 1

Colony forming units: Quantification

Answer 1

Need to quantify and qualify.
Best example = urine
Normal flora overgrowth
Machine quantify quickly
Mixed culture: Can extract probable microbe

Question 2

Latex agglutination - Definition

Answer 2

Exploring antibody-antigen interaction for rapid diagnosis

Question 3

Latex agglutination - Results

Answer 3

Confirms isolate identity

Identify known pathogen-associated antigens in specimen where isolation fails: serum, blood, urine, CSF, not faeces

Question 4

Latex agglutination - Method

Answer 4

Latex beads poke with specific antibody raised to surface antigen from bacteria
Add beads to serum
Antigen binds to antibodies and produce agglutination effect

Question 5

Stereotyping

Answer 5

Determines subtype of organism.
Knowing which serotype allows effective treatment.
Usually correlated with antibiotic resistance patterns.

Question 6

Serotyping

Answer 6

Concerns antibody only.
Latex agglutination.
Only relevant antigens bond by specific antibody

Question 7

Biochemical assays - Examples

Answer 7

Oxidases: Pseudomonas spp. (Positive), E.coli (Negative)
Latalases: Gram positive bacteria
Ureases: Heliobacteria pylori

Question 8

Biochemical assays - Positives

Answer 8

Rapid and accurate

Question 9

Real time PCR

Answer 9

RT = Sees copies as they are being produced
SYBR green = Cyanine dye - binds dsDNA - Absorbs blue light and emits green.
FRET probes = Fluorescent resonance energy transfer

Question 10

Real time PCR - Meningitis

Answer 10

Neisseria meningitidis
Pre-emptive treatment before CSF collect
Even without treatment: CFU in CSF very low
RT-PCR gave 56% positive diagnosis
Important for rapid diagnosis

Question 11

Real time PCR - Whooping cough

Answer 11

Bordella pertusis
Very slow culture growth: 3-12 days
RT-PCR diagnosis in hour
Important for correct treatment and prophylaxis of contents

Question 12

Main antibiotic action: Bacteriostatic

Answer 12

Stops population increasing

Question 13

Main antibiotic action: Bacteriocidal

Answer 13

Kill bacterial cells that can divide

Question 14

Main antibiotic action: Bacteriolytic

Answer 14

Lyses cells