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Microbiology > Detection Of Food Bourne Illness > Flashcards

Detection Of Food Bourne Illness Flashcards

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Biology 101 flashcards
1
Q

What is the main advantage of ATP-bioluminescence?

A

Portable, low cost, rapid estimation of residual bacterial contamination

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2
Q

What is a disadvantage of ATP-bioluminescence?

A

Does not indicate the type of bacteria detected

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3
Q

What does Polymerase Chain Reaction (PCR) amplify?

A

Specific ID genes/portions in the genome of target microorganisms

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4
Q

What are the three steps of Polymerase Chain Reaction (PCR)?

A
  • Denaturation
  • Annealing
  • Elongation
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5
Q

What temperature is used for the denaturation step in PCR?

A

95°C

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6
Q

What is the purpose of the annealing step in PCR?

A

Primers bind to the target DNA

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7
Q

What enzyme is used during the elongation step of PCR?

A

Taq polymerase

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8
Q

What is the limit of detection for conventional PCR?

A

10² - 10³ cells/gr tested food

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9
Q

What is the main difference between simplex PCR and multiplex PCR?

A

Simplex PCR detects one target sequence, while multiplex PCR detects multiple target sequences

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10
Q

What are the advantages of multiplex PCR?

A
  • Detection of several different pathogenic bacteria
  • Improved identification of closely related pathogenic bacteria
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11
Q

What is the principle of Real-Time Quantitative PCR (qPCR)?

A

Specific detection and amplification of specific genes with online acquisition of results

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12
Q

What type of method is Reverse Passive Latex Agglutination (RPLA)?

A

Immunological method used for detecting bacterial toxins in food

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13
Q

What does ELISA stand for?

A

Enzyme-linked immunosorbent assay

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14
Q

What is a key feature of ELISA?

A

Detection based on colorimetric reaction rather than visible clumping

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15
Q

What is the limit of detection for ELISA in terms of bacteria?

A

10³ - 10⁴ CFU/ml

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16
Q

What is the primary function of reverse transcription in RT-PCR?

A

Conversion of RNA into complementary DNA (cDNA)

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17
Q

What are some foodborne pathogens that are RNA viruses?

A
  • Human Norovirus
  • Hepatitis A virus
  • Hepatitis E virus
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18
Q

Fill in the blank: PCR requires two _______ molecules.

A

single strand (SS)

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19
Q

True or False: Multiplex PCR is less sensitive than conventional PCR.

A

True

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20
Q

What is the incubation time typically required for RPLA?

A

< 60 minutes

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21
Q

What is the role of antibodies in ELISA?

A

Bind to the target antigen to form antigen-antibody complexes

22
Q

What type of result does ATP-bioluminescence provide?

A

Semi-enumeration of bacteria

23
Q

What is the temperature range for the annealing step in PCR?

A

50-62°C

24
Q

What are the components of the PCR reaction mixture?

A
  • DNA extracted from the sample
  • Two primers
  • dNTPs
  • Taq polymerase
25
Q

What is the detection method used in qPCR?

A

Fluorescence emitted by newly synthesized DNA copies

26
Q

What are the disadvantages of traditional culture methods?

A
  • Enrichment may be required
  • Results take several days
  • Viable, infectious organisms may not be detected
27
Q

What is the primary target for immuno-based detection methods?

A

Specific biomarkers/proteins

28
Q

What is the primary advantage of ELISA over agglutination methods?

A

More sensitive and permits direct detection of toxins and bacteria

29
Q

What is the role of Taq polymerase in Real time quantitative PCR (qPCR)?

A

Assemble the DNA components in the two ss DNA molecules

30
Q

What happens during the denaturation/melting phase of qPCR?

A

Heating samples at 95ºC to separate DNA into single strands

31
Q

What is the purpose of fluorescent components in qPCR?

A

Bind to the melted DNA and emit fluorescence to be measured

32
Q

During which phase do primers bind to single-stranded DNA in qPCR?

A

Annealing

33
Q

What does the release of dyes during elongation in qPCR indicate?

A

Emission of fluorescence proportional to DNA copies synthesized

34
Q

How is the enumeration of microorganisms calculated in qPCR?

A

Based on the number of PCR cycles required to produce detectable fluorescence

35
Q

What is the limit of detection (LOD) in qPCR for microorganisms?

A

~100 microorganisms

36
Q

What are some advantages of Real time quantitative PCR (qPCR)?

A
  • Quicker results (≤ 3 hours) * Accurate enumeration of microorganisms * More sensitive than conventional PCR
37
Q

What are some disadvantages of qPCR compared to conventional PCR?

A
  • More expensive * Requires specialized equipment * Needs trained personnel
38
Q

List the steps involved in conventional food microbiology.

A
  • Aseptic collection of samples * Homogenization on Stomacher * Selective enrichment * Selective culture on Agar plates * Incubation * Enumeration of Colony Forming Unit (CFU) * Identification of isolates
39
Q

What is the total time required for conventional food microbiology methods?

A

Up to 6-7 days

40
Q

What are some selective and differential media used for detecting Bacillus cereus?

A
  • Polymyxin * Egg Yolk Mannitol Bromothymol Blue (PEMBA)
41
Q

What are good practices for food safety in the food chain?

A
  • Good Operating Practices * Good Manufacturing Practices * HACCP
42
Q

What percentage of food safety issues are caused by bacteria?

A

> 60%

43
Q

What is the main focus of modern food microbiology?

A

Detection of foodborne microorganisms

44
Q

What technology measures ATP for rapid detection of bacterial contamination?

A

ATP-luminescence technology

45
Q

What is the significance of minimally processed food (MPF) in modern food microbiology?

A

MPF are perishable with a shelf life generally ≤ 10 days

46
Q

What is the selective agent in Brilliance Listeria agar?

A

Lithium chloride, polymyxin B, and nalidixic acid

47
Q

What does MacConkey agar differentiate based on?

A

Lactose fermentation

48
Q

What are the main features required for quick acquisition of results in food microbiology?

A
  • Quick results (1-2 working days) * Sensitive detection of pathogens * Semi-automated processes to reduce costs and errors
49
Q

What is the role of bile salts in Deoxycholate agar?

A

Prevent growth of non-enteric bacteria

50
Q

Fill in the blank: The EU Reg 178/2002 requires an integrated approach _______.

A

[from farm to fork]

Microbiology (15 decks)

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