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Bacteria > Lecture 2 > Flashcards

Lecture 2 Flashcards

1
Q

Why utilize a dx lab? (3)

A
  1. To determine if an infectious agent is present at clinically significant levels
  2. To obtain an etiological dx
  3. To guide antimicrobial therapy
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2
Q

What are the other functions of a dx lab? (3)

A
  1. Disease surveillance - trend/outbreak identification & antimicrobial resistance
  2. Regulatory - test for reportable diseases
  3. Research
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3
Q

Colony forming unit

A

The single organism which gave rise to a clonal pop colony

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4
Q

Why is a colony forming unit of interest?

A

Provides info on the number of bacteria present

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5
Q

Why is it important to determine the number of bacteria present?

A
  1. Establish clinical significance
  2. To help identify contaminants
  3. Standardize lab tests
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6
Q

What is an isolate?

A

A pure culture derived from a single colony

Genetically homogenous

Suitable for additional characterization

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7
Q

How do you determine your culture media?

A

Based on the target organism

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8
Q

What is selective media?

A

Used to preferentially isolate particular taxa or organisms possessing a particular phenotype

Contains chemicals to inhibit the growth of non-target organisms

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9
Q

List the selective media from least to most selective (3)

A

CNA

MacConkey

Campy-BAP

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10
Q

What is differential media?

A

Exploits unique physiology of particular taxa to produce unique colony morphologies

Differential means that the organism has the ability to breakdown the different ingredient & produce a characteristic change of hemolysis, colour change, black dots etc.

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11
Q

What are 3 differential media?

A

MacConkey

XLD

CHROMagar

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12
Q

What does CHROMagar ESBL select for? & what does it look like?

A

3rd generation cephalosporin resistance

Pink colonies = Escherichia coli

Blue colonies = non- Escherichia coli Enterobacteriaceae

White colonies = pseudomonas

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13
Q

What does CHROMagar MRSA select for? & what does it look like?

A

Selects for methicillin resistance

Pink colonies = MRSA

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14
Q

What does Mannitol Salt Agar select for? & what does it look like?

A

Selects for NaCl tolerant organisms

Yellow = Staphylococcus aureus

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15
Q

What does Eosin Methylene Blue select for? & what does it look like? - OT

A

Selects for gram negatives

Metallic green = Escherichia coli

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16
Q

What does Mannitol Salt Agar media differentiate?

A

Mannitol fermentation

Breaks down mannitol becoming more acidic & causes a pH change

17
Q

What does Eosin Methylene Blue differentiate? - OT

A

lactose fermentors

18
Q

When is liquid media used?

A

When testing large samples which aren’t playable on media & occasionally used for pure culture

19
Q

How do we identify bacteria?

A

biochemical tests

Matrix-assisted laser depolarization/ionization (MALDI-TOF)

20
Q

What are the biochemical tests used to identify bacteria? (3)

A

Colour change

Agglutination

Change in consistency of media

21
Q

What are biocontainment levels for?

A

Considers the lab procedures which are required to handle the organism safely

22
Q

What is biocontainment level 1?

A

Could be safely handed in basic, well functioning lab (organism won’t cause issues)

23
Q

What is biocontainment level 2?

A

Requires personal protective equipment

Pathogens with ingestion & inoculation with primary route of exposure

24
Q

What is biocontainment level 3?

A

Organisms which may be transmitted by airborne route

Requires additional primary & secondary barriers

25
Q

What is biocontainment level 4?

A

Max precautions, complete isolation of facility from the rest of structure, decontamination of all lab effluents, positive pressure “space suits”

26
Q

What do bio risk gaps consider?

A

Pathogenicity

Ifnectious dose

Mode of transmission

Host range

Availability of preventative measures (ex: vaccines)

Availability of effective tx (ex: a/bs)

27
Q

What is the biological risk grp 1?

A

Low individual & low community risk

Organisms are unlikely to cause disease in healthy indices, maybe in immunosuppressed or compromised animals (opportunistic pathogens)

28
Q

What is the biological risk grp 2?

A

Moderate individual & low community risk

Majorty of pathogens that we encounter on a day to day basis

29
Q

What is the biological risk grp 3?

A

High indiv & low community risk

Includes some zoonotic pathogens & some fungi causing systemic mycoses

30
Q

What is the biological risk grp 4?

A

High indiv, high community risk

Scariest pathogens

Does NOT include bacteria or fungi (mostly viruses)

Bacteria (16 decks)

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