PCR and Ag Detection Procedures

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Questions and Answers

What is the recommended storage temperature for viruses being transported for more than 48 hours?

-70 degrees

During an outbreak, how many stool samples should ideally be collected from patients?

10-20 patients

What type of container should be used for collecting stool samples to ensure sterility?

Clean and sterile container

What is the appropriate method for stool sample collection for PCR analysis?

Fresh stool unmixed with urine in a clean, dry, and sterile container Signup and view all the answers

What medium is recommended for the transport of bacterial samples for antigen detection?

Cary-Blair medium Signup and view all the answers

How should stool samples be stored if testing is expected to occur within 48 hours?

Store at 4 degrees Signup and view all the answers

What timing consideration should be taken into account when collecting stool samples for detecting viruses?

Collect within 48 hours of onset Signup and view all the answers

What key safety practice must be followed during the collection of samples to ensure aseptic conditions?

Use aseptic techniques Signup and view all the answers

What is the required temperature for storing PCR samples related to antigen detection?

-15 degrees Celsius Signup and view all the answers

When should stool samples for parasite detection be collected?

As soon as possible after onset. Signup and view all the answers

What is the appropriate ratio of stool to preservative when mixing for parasite sample handling?

3:1 ratio of stool to preservative. Signup and view all the answers

What condition should water for bacteriology be treated with before sampling?

Add sodium thiosulphate. Signup and view all the answers

What samples require transport at ambient temperature within 24 hours?

Post-mortem microbiological specimens. Signup and view all the answers

How should nasopharyngeal aspirates be collected?

Using a silicon catheter, gently aspirate secretion from each nostril. Signup and view all the answers

What handling technique should be used when collecting rectal swabs from small children?

Adapt the swab for reduced material availability. Signup and view all the answers

What transport conditions are recommended for bacterial samples taken from respiratory sources?

Transport under ambient temperature for up to 24 hours. Signup and view all the answers

What should be avoided when instructing a patient to collect sputum?

Avoid saliva or postnasal discharge. Signup and view all the answers

What is the minimum volume of sputum that should be collected for testing?

1ml minimum. Signup and view all the answers

What materials are required when labeling collected samples for microbiological testing?

Clearly label all samples with relevant patient and sample information. Signup and view all the answers

What preservation method is used for post-mortem samples?

Placed in formalin or in transport medium. Signup and view all the answers

What is the necessary transport temperature for water sources collected from a reservoir?

Transport at 4-8 degrees Celsius. Signup and view all the answers

How should solid food samples be handled during collection?

Cut 100-200g from the center using a sterile knife. Signup and view all the answers

What are the specific requirements for blood culture collection to reduce contamination?

The skin must be cleaned, the collector should wear gloves, and aseptic techniques should be followed. Signup and view all the answers

Describe the ideal conditions for transporting blood samples to ensure cell integrity.

Blood samples should be transported upright with cushioning to prevent hemolysis and kept at ambient temperature. Signup and view all the answers

What is the purpose of using Cary Blair medium in stool sample transportation?

Cary Blair medium preserves clinical specimens, primarily faecal and rectal samples, for testing by maintaining the viability of organisms. Signup and view all the answers

What process is followed when collecting cerebrospinal fluid (CSF)?

CSF is collected via a lumbar puncture under aseptic conditions by a trained professional. Signup and view all the answers

What is the purpose of a blood smear and how should it be prepared?

A blood smear provides information about the number and shape of blood cells and is prepared by spreading a drop of blood across a slide, followed by fixation with methanol. Signup and view all the answers

What are the critical steps in the collection of blood serum?

Blood serum is collected from venous blood into sterile glass tubes, allowed to clot, then centrifuged. Signup and view all the answers

How long should blood culture samples be collected after fever onset for accurate results?

Blood culture samples should be collected within 10 minutes of fever onset. Signup and view all the answers

What type of conditions must be maintained when transporting blood samples for laboratory analysis?

Blood samples should be transported at ambient temperature and kept upright to avoid hemolysis. Signup and view all the answers

What is the significance of using sterile techniques in specimen collection?

Sterile techniques minimize contamination and ensure accurate testing results. Signup and view all the answers

What is the role of transport mediums in microbiological sampling?

Transport mediums help preserve the viability of pathogens and contaminants for accurate testing. Signup and view all the answers

Identify the main considerations when collecting stool samples for analysis.

Consider adequate documentation, timely collection, and the use of proper transport media. Signup and view all the answers

What is the recommended procedure for handling blood culture bottles post-collection?

Blood culture bottles should be inoculated with a new needle, transported upright, and cushioned to prevent hemolysis. Signup and view all the answers

What is the purpose of using non-nutritive transport mediums?

Non-nutritive transport mediums do not promote the growth of organisms, allowing for the sample's stability during transport. Signup and view all the answers

What steps are taken to prepare a blood smear for microscopic analysis?

A drop of blood is spread across a slide and fixed with methanol, then must be transported within 24 hours. Signup and view all the answers

What factors influence the type of clinical samples needed for testing?

Considerations include the suspected differential diagnosis and consultation among healthcare professionals. Signup and view all the answers

Study Notes

Sample Storage and Transport

Antigen (Ag) detection and PCR samples should be stored at -15 degrees Celsius.
For short-term storage, keep samples at 4 degrees Celsius, avoiding freezing. Use dry ice for transport of Ag and PCR samples.
For parasites, collect 3 samples of 5-10ml fresh stool from patients as soon as possible after symptom onset; mix with a 10% formalin or polyvinyl chloride preservative in a 3:1 stool to preservative ratio.
Unpreserved samples are preferred for Ag detection and PCR.

Collection Methods

Rectal Swabs: Adapted for small children; require less material and do not allow macroscopic assessment; not suitable for viral testing.
Throat Swabs: Use a tongue depressor to hold the tongue away; target areas of inflammation without contacting the tongue.
Nasopharyngeal Swabs: Insert a flexible polyester swab into the nostril towards the nasopharynx, rotate, and withdraw after a few seconds.
Nasopharyngeal Aspirates: Tilt the head back, use sterile saline or VTM in one nostril, and gently aspirate secretions.
Sputum Collection: Instruct patients to cough into a sterile container while avoiding saliva and postnasal discharge. Minimum volume is 1ml.

Respiratory and Special Sample Transport

Transport all respiratory samples (except sputum) in appropriate media: non-nutritive for bacteria, VTM for viruses.
For transit periods up to 24 hours, maintain ambient temperature for bacteria and 4-8 degrees for viruses.
Post-Mortem Samples: Handle in formalin for histopathology, transport microbiological specimens in transport media within 24 hours at ambient temperature.

Water and Food Sample Collection

Bacteriology in chlorinated water requires sodium thiosulphate addition; collect samples deep (20cm) in wells or waterways without touching containers to well sides.
For solid food, cut samples from the center with a sterile knife; refrigerate raw meat in sterile containers.
Liquids should be mixed and stored in sterile tubes.

Specimen Labeling and Transport Guidelines

Ensure transport media is pre-warmed to 25-37 degrees for inoculation; maintain ambient temperature for bacteria sensitive to cold.
For viruses, use 4-8 degrees transport within 48 hours; if longer, store at -70 degrees.

Stool and Bacterial Sample Collection

Use freshly passed stool samples, avoiding bedpan collections, in sterile or clean containers. During outbreaks, collect from 10-20 patients.
For viral testing, collect samples within 48 hours of onset using 5-10ml from patients.
Bacterial specimens should be collected during the active phase of the infection.

Epidemiology Terms

Holoendemic: Disease affects most children in a population, leading to adult immunity.
Epidemic: Rapid spread of disease affecting many individuals simultaneously.
Pandemic: Global spread of a new disease.
Incidence: Rate of new cases developing in a specific time period.
Prevalence: Total number of cases at a given time.

Successful Lab Investigation Practices

Thorough planning before specimen collection ensures adequate and appropriate samples.
Sufficient documentation, bio-safety, and decontamination are crucial.
Choose labs capable of performing necessary tests accurately.

Types of Transport Media

Nutritive Media: Supports survival and growth of pathogens, important for testing growth capabilities.
Non-Nutritive Media: Prevents organism proliferation; survival matter isn't crucial.
Cary-Blair Medium: Preserves bacterial specimens, particularly fecal and rectal samples.
Virus Transport Media (VTM): Preserves viral specimens post-collection for future analysis.

Blood Collection and Transport

Blood Smear: Spread a drop of blood on a slide; fix with methanol, transport within 24 hours without refrigeration.
Blood Cultures: Essential for suspected sepsis; requires precise aseptic technique during collection, ideally within 10 minutes of fever onset.
Blood Serum: Collected from venous blood in sterile tubes, allowed to clot, and spun to separate serum for testing.
Cerebrospinal Fluid (CSF): Collected via lumbar puncture under aseptic conditions for diagnostic purposes.

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Description

This quiz focuses on the proper procedures for antigen detection and PCR storage, including temperature guidelines for transportation and sample collection timing for parasite testing. Understand the importance of handling samples correctly to ensure accurate results.