Systems For Detecting Pathogens Flashcards

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1
Q

What is the taxogenic ladder after species?

A

Strain
Type
Isolate

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2
Q

What are the types of pathogens?

A

Commensal non-pathogen
Zoonotic non-pathogen
Commensal opportunist

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3
Q

What is a commensal non-pathogen?

A

Present but not capable of causing disease in the host

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4
Q

What is a zoonotic non-pathogen?

A

Present but only capable of causing disease in another host

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5
Q

What is a commensal opportunist?

A

Present and capable of causing disease in the host in certain circumstances

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6
Q

What is a pathogen?

A

Microbe capable of causing a specific degree of host damage

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7
Q

What is good sample practice?

A

Sterile sites should be free from contamination
Non-sterile sites require decontamination of normal flora
Samples with high volume or low infected pathogen load require concentration

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8
Q

What is direct light microscopy used to detect?

A

Threadworms, entamoeba histolytica, trichomonas vaginalis, schistosoma mansonii

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9
Q

What is direct electron microscopy used for?

A

Viruses

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10
Q

What colour do gram positive bacteria stain?

A

Blue

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11
Q

What colour do gram negative bacteria stain?

A

Pink

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12
Q

Are there bacteria that don’t stain?

A

Yes (TB for example)

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13
Q

What are the types of media?

A

Non-selective
Semi-selective
Selective growth temperatures

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14
Q

What are examples of non-selective media?

A

Blood, agar

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15
Q

What are examples of semi-selective media?

A

DCA, CLED

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16
Q

What are some selective atmospheres?

A

Aerobic
Microaerophilic
Anaerobic

17
Q

What are the different types of test system in bacteriology?

A

Media
Selective atmospheres
Selective temperatures
Specific haemolysis of blood

18
Q

What is a phage?

A

Virus that infect bacteria

19
Q

What is strand displacement amplification?

A

Essentially PCR

20
Q

What does molecular gene targeting aim to do?

A

Detect a gene or gene products that are pathogen specific

21
Q

What genes are suitable targets for PCR?

A
Constitutive 
Virulence
Antibiotic resistance
Pathogenic phenotype 
Repetitive
22
Q

How can you tell if the molecular test for one gene is good enough?

A
Specificity
Reliability 
Sensitivity
Accuracy
Rapidity
23
Q

How do you do bio-signature profiling?

A

Mass spectrometry
Isolate organism
Lyse with crystallising matrix
Ionise and detect time of flight for each particle
Calculate daltons for each protein produced
Compare against an archival database

24
Q

What are the advantages of MALDI-TOF profiling?

A

Rapid and specific identification

25
Q

What are the disadvantages of MALDI-TOF profiling?

A

Requires pure culture
Requires rigorous calibration and protocol standardisation
Will only identify known profiles

26
Q

What are biomarkers of virulence?

A

Looking for selected genes or gene products that drive the disease process

27
Q

What are the advantages of serotyping?

A

Good specificity and sensitivity

Easily automated

28
Q

What are the disadvantages of serotyping?

A

Slow
Can be in response to previous exposure
Some antibodies are cross-reactive
Virulence is only inferred by biomarker presence
Infected into an animal model can prove virulence

29
Q

What are the advantages of molecular detection methods?

A

Rapid
Allows fast, accurate treatment
High sensitivity
Can be automated/ used at point of care

30
Q

What are the disadvantages of molecular detection methods?

A
Expensive
Doesn’t screen for unknown
Needs expertise 
Labour intensive
Possibility of contamination
Complex methods needed