Amies Transport Medium 50 FAQs and 30 MCQs
Amies Transport Medium is a critical solution for preserving clinical specimens during transit. This article covers its formulation, applications, protocols, FAQs, and MCQs to enhance lab accuracy and support medical education.
Introduction to Amies Transport Medium
Amies Transport Medium, developed by Stuart Amies in 1967, is a semi-solid agar gel designed to maintain bacterial viability in clinical samples (e.g., swabs). It prevents overgrowth of fastidious organisms and ensures reliable diagnostics.
Key Components & Mechanism
- Base Solution: Sodium thioglycollate (reducing agent) and phosphate buffer (pH stabilization).
- Charcoal: Neutralizes toxins and absorbs fatty acids.
- Calcium Chloride: Enhances survival of Neisseria species.
- Semi-Solid Agar: Minimizes oxygen exposure for anaerobes.
Mechanism: Maintains viability without replication for 24–48 hours at room temperature.
Best Practices for Sample Handling
- Collection: Swab lesions firmly; avoid contamination.
- Transport:
- Insert swab into Amies medium immediately.
- Store at 2–8°C if delayed >4 hours.
- Process within 48 hours.
- Avoid: Freezing, direct sunlight, or excess air in tubes.
Applications in Clinical Labs
- Ideal for:
- Throat/nasal swabs (detecting Streptococcus, Corynebacterium).
- Wound cultures.
- STI screening (Neisseria gonorrhoeae).
- Not recommended for viral or fecal samples.
Amies Transport Medium 50 FAQs
What is Amies Transport Medium?
It is a semisolid transport medium containing charcoal to prolong the viability of pathogenic organisms.
How does Amies Transport Medium differ from Stuart’s Transport Medium?
It replaces glycerophosphate with an inorganic phosphate buffer and adds charcoal.
Why is charcoal added to Amies Transport Medium?
To neutralize toxic materials that may harm sensitive pathogens like Neisseria gonorrhoeae.
What is the pH of Amies Transport Medium?
7.2 ± 0.2 at 25°C.
Is Amies Transport Medium liquid or solid?
It is a semisolid medium due to the presence of agar.
What is the purpose of sodium thioglycollate in Amies medium?
It provides a reduced environment, helping maintain anaerobic conditions.
Which salts are present in Amies Transport Medium?
Sodium chloride, potassium chloride, calcium chloride, magnesium chloride, monopotassium phosphate, and disodium phosphate.
What is the role of phosphates in Amies medium?
They act as buffers to maintain pH stability.
What is the concentration of agar in Amies Transport Medium?
4.0 g/L.
How much charcoal is added to Amies Transport Medium?
10.0 g/L.
How do you prepare Amies Transport Medium?
Suspend 20g in 1L distilled water, boil to dissolve agar, distribute into bottles, autoclave (121°C for 15 min), and cool while inverting.
Why should the medium be stirred while distributing into bottles?
To keep the charcoal evenly suspended.
Why should bottles be completely filled before autoclaving?
To minimize air exposure, maintaining anaerobic conditions.
Why are bottles inverted while cooling?
To ensure uniform distribution of charcoal.
How should swabs be placed in Amies medium?
Push the swab one-third into the medium, cut the stick, and screw the cap tightly to submerge the swab.
How should Amies medium be stored before use?
In a cool place (not frozen).
Can old Amies medium be reused?
It should be freshly steamed and charcoal resuspended before reuse.
What specimens can be transported in Amies medium?
Throat, vaginal, wound, and other swab specimens.
Which pathogens survive well in Amies Transport Medium?
Neisseria gonorrhoeae, Haemophilus influenzae, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, etc.
Is Amies medium suitable for anaerobic bacteria?
Yes, it helps preserve anaerobes like Bacteroides fragilis.
Can Amies medium be used for viral transport?
No, it is designed for bacterial specimens.
How long can specimens survive in Amies medium?
Most bacteria survive 6-12 hours, but fastidious organisms like gonococci may decline after 24 hours.
Is Amies medium suitable for stool samples?
No, it is primarily for swab specimens.
Can Amies medium be used for blood cultures?
No, it is not designed for liquid specimens like blood.
Why is Amies medium preferred for Neisseria gonorrhoeae?
Charcoal neutralizes toxins, and the reduced environment enhances survival.
What are the limitations of Amies Transport Medium?
Not ideal for fastidious organisms, may allow contaminant growth, and has a limited survival window.
How does temperature affect specimen viability in Amies medium?
Extreme temperatures reduce survival, especially for gonococci.
Why might Neisseria gonorrhoeae not survive beyond 24 hours?
Numbers decrease significantly, making recovery difficult if initially low.
Can contaminants grow in Amies medium during transport?
Yes, prolonged transport may allow contaminant growth.
How soon should specimens be cultured after transport?
As soon as possible (within 6-12 hours for best results).
Is Amies medium suitable for long-term storage of specimens?
No, it is for short-term transport only.
What happens if the medium dries out?
Bacteria may die due to desiccation.
Why should the cap be screwed tightly?
To prevent drying and maintain anaerobic conditions.
Which organisms show good recovery in Amies medium?
E. coli, Klebsiella, Pseudomonas, Salmonella, Staphylococcus, Streptococcus, Vibrio cholerae, etc.
Does Amies medium support bacterial growth?
No, it is non-nutritive and only preserves viability.
Why is Amies medium semisolid rather than liquid?
To prevent swab drying while avoiding excessive bacterial multiplication.
Can fungi survive in Amies Transport Medium?
It is not optimized for fungi; specialized media are better.
How does Amies medium compare to Stuart’s medium in recovery rates?
Amies gives higher positive results due to charcoal and buffer improvements.
Is Amies medium suitable for Haemophilus ducreyi?
Yes, it helps preserve this fastidious organism.
Can Amies medium be used for Mycobacterium tuberculosis?
No, specialized transport media (e.g., Middlebrook) are needed.
What is the alternative if Amies medium is unavailable?
Stuart’s Transport Medium, but with lower efficacy for fastidious organisms.
Can Amies medium be used for urine samples?
No, it is designed for swab specimens only.
Is refrigeration required during transport?
Cool conditions (not frozen) are recommended, especially for gonococci.
Can multiple swabs be stored in one Amies medium bottle?
No, one swab per bottle is recommended to avoid cross-contamination.
What should be done if the charcoal settles unevenly?
Re-mix by inverting the bottle before use.
Why might some organisms not survive in Amies medium?
Fastidious organisms may decline if transport is delayed beyond 12-24 hours.
Can expired Amies medium be used?
No, freshly prepared or properly stored medium should be used.
How can contamination be minimized during specimen collection?
Use sterile swabs and avoid touching non-target surfaces.
What is the maximum recommended transport time?
Within 24 hours, but ideally 6-12 hours for fastidious bacteria.
Can Amies medium be used for environmental swabs?
Yes, but clinical specimens are its primary use.
Amies Transport Medium 30 MCQs
- What is the primary purpose of Amies Transport Medium?
a) To enhance bacterial growth
b) To transport and preserve clinical swab specimens✔
c) To sterilize specimens
d) To provide nutrients for fastidious bacteria - Amies Transport Medium is a modification of which medium?
a) Blood agar
b) MacConkey agar
c) Stuart’s Transport Medium✔
d) Thioglycollate broth - Which component in Amies medium neutralizes toxic substances for pathogens like Neisseria gonorrhoeae?
a) Sodium chloride
b) Charcoal✔
c) Agar
d) Thioglycollate - What is the pH of Amies Transport Medium?
a) 6.0 ± 0.2
b) 7.2 ± 0.2✔
c) 8.0 ± 0.2
d) 5.4 ± 0.2 - Amies medium is best described as:
a) Liquid medium
b) Solid medium
c) Semisolid medium✔
d) Gaseous medium
- Which ingredient provides a reduced environment in Amies medium?
a) Sodium chloride
b) Sodium thioglycollate✔
c) Charcoal
d) Magnesium chloride - What is the concentration of agar in Amies Transport Medium?
a) 1.0 g/L
b) 4.0 g/L✔
c) 10.0 g/L
d) 20.0 g/L - Which salts help control bacterial cell permeability in Amies medium?
a) Calcium, magnesium, potassium, and sodium salts✔
b) Only sodium chloride
c) Only potassium chloride
d) None of the above - Why is charcoal added to Amies medium?
a) To enhance bacterial growth
b) To neutralize toxic substances✔
c) To provide nutrients
d) To increase agar solidification - What is the role of phosphates in Amies medium?
a) To act as a buffer✔
b) To provide energy for bacteria
c) To solidify the medium
d) To inhibit contaminants
- How is Amies Transport Medium sterilized?
a) By filtration
b) By autoclaving at 121°C for 15 minutes✔
c) By boiling for 5 minutes
d) By UV radiation - Why should bottles be inverted while cooling after autoclaving?
a) To prevent agar solidification
b) To distribute charcoal evenly✔
c) To enhance bacterial growth
d) To reduce pH - How should a swab be placed in Amies medium?
a) Fully submerged at the bottom
b) Left outside the medium
c) Placed one-third into the medium✔
d) Floating on top - What is the correct storage condition for Amies medium before use?
a) Frozen at -20°C
b) Kept at room temperature
c) Stored in a cool place (not frozen)✔
d) Exposed to sunlight - Why should the cap be screwed tightly after placing the swab?
a) To prevent drying and maintain anaerobic conditions✔
b) To speed up bacterial growth
c) To increase pH
d) To kill contaminants
- Which pathogen survives poorly in Amies medium after 24 hours?
a) Escherichia coli
b) Neisseria gonorrhoeae✔
c) Staphylococcus aureus
d) Pseudomonas aeruginosa - Amies medium is NOT suitable for:
a) Throat swabs
b) Vaginal swabs
c) Blood cultures✔
d) Wound swabs - What is the maximum recommended transport time for optimal recovery of gonococci?
a) 2-4 hours
b) 6-12 hours✔
c) 24-48 hours
d) 1 week - Which of the following is a limitation of Amies Transport Medium?
a) Supports fungal growth
b) May allow contaminant growth during prolonged transport✔
c) Enhances viral survival
d) Cannot be autoclaved - For which type of specimens is Amies medium primarily designed?
a) Liquid specimens (e.g., urine, blood)
b) Swab specimens (e.g., throat, vaginal)✔
c) Stool samples
d) Sputum samples
- Which component is present in Amies medium but absent in Stuart’s medium?
a) Sodium chloride
b) Charcoal✔
c) Agar
d) Magnesium chloride - Why does Amies medium give a higher recovery rate than Stuart’s medium?
a) Due to added nutrients
b) Because of charcoal and phosphate buffer✔
c) Due to lower pH
d) Because it is liquid - Which organism is most likely to survive poorly in Amies medium after 24 hours?
a) E. coli
b) Staphylococcus aureus
c) Neisseria gonorrhoeae✔
d) Pseudomonas aeruginosa - What should be done if old Amies medium is to be reused?
a) Discard it
b) Re-autoclave it
c) Freshly steam and resuspend charcoal✔
d) Add extra agar - Which of the following is NOT a recommended use of Amies medium?
a) Transport of wound swabs
b) Preservation of stool samples✔
c) Throat swab transport
d) Vaginal swab transport
- What happens if Amies medium dries out during transport?
a) Bacteria multiply rapidly
b) Bacteria may die due to desiccation✔
c) pH increases
d) Charcoal loses function - How can contamination be minimized during specimen collection?
a) Using non-sterile swabs
b) Using sterile swabs and avoiding non-target surfaces✔
c) Leaving the cap open
d) Storing at high temperatures - What is the best practice after transporting a specimen in Amies medium?
a) Store it for a week before culturing
b) Inoculate it into culture medium as soon as possible✔
c) Freeze it
d) Discard it after transport - Why is Amies medium not suitable for fastidious organisms beyond 24 hours?
a) They overgrow contaminants
b) Their numbers decrease significantly✔
c) The medium becomes toxic
d) pH drops drastically - Which factor does NOT affect the viability of bacteria in Amies medium?
a) Temperature extremes
b) Prolonged transport time
c) Tightly screwed cap✔
d) Exposure to sunlight
Amies Transport Medium remains indispensable for accurate bacteriology. Adherence to protocols—timely transport, correct storage, and avoiding misuse—ensures diagnostic reliability. Continual education through FAQs and MCQs empowers labs and students to uphold specimen integrity.
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