On a Thursday evening, a clinic in Al Ain collects midstream urines for culture from two outpatients with dysuria. Urine 1 is put into a boric acid tube filled to the marked line and kept at room temperature (about 24 °C). Urine 2 is put into a plain sterile container and kept in the clinic refrigerator at 4 °C. Because of a public holiday, the courier delivers both specimens 30 hours after collection. Both are correctly labeled, neither has leaked, and the request forms are complete. The laboratory applies the standard holding limits for urine culture. What should the laboratory do?

Culture urine 1 and reject urine 2

Culture urine 2 and reject urine 1

Reject both, as each is over 24 hours old

Culture both specimens with a delay comment

A swab of a leg ulcer from a 60-year-old man is sent in a plain sterile tube with no transport medium. It arrives 5 hours later, completely dry. What is the best action?

Request a new specimen, as many organisms die when dried

Place it in thioglycolate broth for enrichment

Moisten it with sterile saline and then culture it as usual

Culture it and report only the organisms that grow

A sputum container for culture reaches the laboratory with specimen leaking down the outside. What is the best action?

Reject it and request a new specimen

Process it and add a leakage comment

Wipe the outside clean and process it

Pour it into a new sterile container

Viral transport medium contains antibiotics and an antifungal agent in order to:

Stop bacteria and fungi overgrowing the specimen

Inactivate the virus for safe transport

Make the virus grow faster in cell culture

Prevent the viral nucleic acid from degrading in transit

A urine for culture is labeled with the patient's name and a medical record number that differs from the number on the electronic request. What is the correct action?

Reject it and ask for a new, correctly labeled specimen

Process it and add a comment about the labeling

Phone the ward and correct the label by hand

Relabel it from the request and then process it

Microbiology specimen collection, transport and rejection

18 DOH Abu Dhabi (HAAD) lab licensing practice questions on Microbiology specimen collection, transport and rejection, part of Microbiology. The first 18 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Hard
On a Thursday evening, a clinic in Al Ain collects midstream urines for culture from two outpatients with dysuria. Urine 1 is put into a boric acid tube filled to the marked line and kept at room temperature (about 24 °C). Urine 2 is put into a plain sterile container and kept in the clinic refrigerator at 4 °C. Because of a public holiday, the courier delivers both specimens 30 hours after collection. Both are correctly labeled, neither has leaked, and the request forms are complete. The laboratory applies the standard holding limits for urine culture. What should the laboratory do?
1. ACulture urine 2 and reject urine 1
2. BCulture urine 1 and reject urine 2
3. CReject both, as each is over 24 hours old
4. DCulture both specimens with a delay comment
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Answer: B · Culture urine 1 and reject urine 2
Unpreserved urine must be plated within 2 hours or refrigerated, and refrigerated urine is acceptable for up to 24 hours. Boric acid holds the colony count steady for up to 48 hours at room temperature, provided the tube is filled to the line so that the preservative is at the right concentration. Urine 1 is within its 48-hour limit, but urine 2 has been held past its 24-hour limit, so its colony count may no longer reflect the bladder. Culturing it with a comment still risks a misleading result, and rejecting both would waste a valid specimen. The clinic should be asked for a fresh specimen from patient 2.
- A: This reverses the limits: the refrigerated urine is the one past its 24-hour limit.
- C: Boric acid keeps urine stable at room temperature for up to 48 hours, so urine 1 is acceptable.
- D: Culturing a specimen held past its limit, even with a comment, can give a misleading count.
Question 2 · Medium
A swab of a leg ulcer from a 60-year-old man is sent in a plain sterile tube with no transport medium. It arrives 5 hours later, completely dry. What is the best action?
1. ARequest a new specimen, as many organisms die when dried
2. BPlace it in thioglycolate broth for enrichment
3. CMoisten it with sterile saline and then culture it as usual
4. DCulture it and report only the organisms that grow
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Answer: A · Request a new specimen, as many organisms die when dried
Drying kills many bacteria, especially fastidious organisms and anaerobes, while hardy skin flora such as staphylococci may survive. A culture of a dry swab can therefore be falsely negative or misleading. The specimen is rejected, the reason documented and a new one requested, ideally tissue or an aspirate, or at least a swab in transport medium. Swabs should go into transport medium immediately after collection.
- B: Enrichment cannot recover organisms that are already dead.
- C: Moistening does not revive organisms that died while the swab dried.
- D: Growth from a dry swab may show the survivors, not the true pathogen.
Question 3 · Easy
A sputum container for culture reaches the laboratory with specimen leaking down the outside. What is the best action?
1. AProcess it and add a leakage comment
2. BReject it and request a new specimen
3. CWipe the outside clean and process it
4. DPour it into a new sterile container
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Answer: B · Reject it and request a new specimen
A leaking container exposes staff to infectious material, and the specimen inside may have been contaminated from outside. Sputum is easy to recollect, so it is rejected, the requester is told and the reason is documented. A leaking irreplaceable specimen, such as CSF or tissue, is opened in a biological safety cabinet and processed with a comment after discussion with the requester. Containers should have screw caps and travel upright in sealed bags.
- A: A comment does not make a contaminated, replaceable specimen acceptable.
- C: Wiping does not undo contamination of the specimen through the leak.
- D: Transferring a leaking specimen adds exposure and does not remove contamination.
Question 4 · Easy
Viral transport medium contains antibiotics and an antifungal agent in order to:
1. AInactivate the virus for safe transport
2. BMake the virus grow faster in cell culture
3. CPrevent the viral nucleic acid from degrading in transit
4. DStop bacteria and fungi overgrowing the specimen
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Answer: D · Stop bacteria and fungi overgrowing the specimen
Respiratory and other swabs carry normal flora that would multiply in a protein-containing medium and spoil cell cultures or the specimen. Antibiotics and an antifungal such as amphotericin B suppress this growth. A buffered salt solution with protein, such as albumin or gelatin, keeps the virus stable. The medium keeps viruses viable, so specimens must still be handled as infectious.
- A: Viral transport medium keeps viruses viable; inactivating media are a different product.
- B: Antibiotics do not speed viral growth; they only remove competing microbes.
- C: Antibiotics do not protect nucleic acid; cold storage and stabilizers do that.
Question 5 · Medium
A urine for culture is labeled with the patient's name and a medical record number that differs from the number on the electronic request. What is the correct action?
1. AReject it and ask for a new, correctly labeled specimen
2. BProcess it and add a comment about the labeling
3. CPhone the ward and correct the label by hand
4. DRelabel it from the request and then process it
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Answer: A · Reject it and ask for a new, correctly labeled specimen
Two identifiers on the container must match the request, and a mismatch means the specimen may belong to another patient. Urine is easy to recollect, so the specimen is rejected, the requester informed and the event recorded as a nonconformity. The laboratory must not relabel specimens itself, because doing so can hide a misidentification. Irreplaceable specimens, such as CSF or tissue, follow a written procedure in which the collector confirms the identity and signs for it.
- B: A comment does not resolve a possible misidentification.
- C: A phone call does not prove whose specimen it is; urine can be recollected.
- D: Relabeling by the laboratory can hide a specimen that belongs to someone else.
Question 6 · Hard
A woman has dysuria. Her urine for culture arrives in a boric acid tube marked with a 3 mL fill line, but it holds only 0.5 mL. Urinalysis on a second, plain specimen shows positive nitrite and leukocyte esterase. The culture grows nothing at 24 hours. What is the most likely explanation?
1. AShe has sterile pyuria from a non-bacterial cause
2. BRoutine urine plates need 72 hours of incubation
3. CToo little urine was left for the calibrated loop
4. DToo much boric acid for the volume inhibited bacteria
Answer and explanation in LearnFree account
Question 7 · Medium
Early-morning gastric aspirates from a 4-year-old child are sent for mycobacterial culture. If processing cannot start promptly, how should the specimen be treated?
1. AFrozen at -20 °C until it is processed
2. BMixed with an equal volume of 10% formalin
3. CNeutralized with sodium carbonate
4. DAcidified with dilute hydrochloric acid
Answer and explanation in LearnFree account
Question 8 · Easy
A lymph node biopsy for bacterial culture arrives in 10% formalin. What should the laboratory do?
1. ACulture it only in an enrichment broth
2. BCulture it with an extended incubation
3. CReject it for culture and notify the requester
4. DRinse it well in sterile saline, then culture it
Answer and explanation in LearnFree account
Question 9 · Medium
Endocervical specimens for gonococcal culture are collected at a clinic 3 hours away from the laboratory. Which transport system gives the best recovery?
1. ADry swab in a sterile tube at room temperature
2. BSwab in viral transport medium, kept on ice
3. CSelective agar in a JEMBEC pack with a CO2 tablet
4. DSwab in Cary-Blair medium, kept in the refrigerator
Answer and explanation in LearnFree account
Question 10 · Medium
A patient admitted 6 days ago develops diarrhea on the ward, and a stool culture for Salmonella, Shigella and Campylobacter is ordered. Why do many laboratories reject this request?
1. AInpatient stool is usually too contaminated with skin flora
2. BHospital antibiotics make every inpatient stool culture negative
3. CThese pathogens are only sought in children under 5 years
4. DDiarrhea that starts after 3 days in hospital is rarely due to them
Answer and explanation in LearnFree account
Question 11 · Easy
A stool for ova and parasites is collected from a patient the day after a barium meal. What should the laboratory do?
1. AExamine it with a longer concentration step
2. BExamine only the permanent stained smear
3. CAdd formalin and examine it at once
4. DAsk for a new stool once the barium has cleared
Answer and explanation in LearnFree account
Question 12 · Hard
Four specimens arrive in the laboratory at 10:00 on the same morning. Which one should be rejected?
1. AStool in Cary-Blair from last night, kept refrigerated
2. BUrine in a filled boric acid tube, collected at 06:00
3. CCSF for bacterial culture, 1 hour old, at room temperature
4. DSputum for mycobacterial culture pooled over 24 hours
Answer and explanation in LearnFree account
Question 13 · Hard
During a cholera alert, rice-water stools are sent in buffered glycerol saline and reach the laboratory 18 hours later. TCBS agar shows no growth, although a rapid antigen test on a fresh stool from one patient was positive for Vibrio cholerae O1. What is the most likely cause of the negative cultures?
1. ABuffered glycerol saline does not keep vibrios alive
2. BThe plates should have been incubated at 42 °C
3. CThe stools should have been refrigerated in transit
4. DTCBS agar inhibits Vibrio cholerae O1
Answer and explanation in LearnFree account
Question 14 · Medium
A traveler returning to Abu Dhabi has had fever for 5 days, and enteric fever is suspected. Which culture is most likely to grow Salmonella Typhi at this stage?
1. ACulture of rose spots
2. BBlood culture
3. CStool culture
4. DUrine culture
Answer and explanation in LearnFree account
Question 15 · Easy
Charcoal is added to some swab transport media, such as Amies with charcoal, mainly to:
1. AKeep the pH of the medium acidic
2. BSupply nutrients so the bacteria multiply in transit
3. CAbsorb substances toxic to fastidious bacteria
4. DStop normal flora from overgrowing the pathogen
Answer and explanation in LearnFree account
Question 16 · Easy
For the serologic diagnosis of a recent infection, paired serum samples should be collected:
1. AOnly after the symptoms have fully resolved
2. BIn the acute phase and again 2 to 4 weeks later
3. COn two consecutive days in the acute phase
4. DBefore and 24 hours after the first antibiotic dose
Answer and explanation in LearnFree account
Question 17 · Easy
Which swab type is preferred for most bacterial culture and nucleic acid tests because it collects and releases the most specimen?
1. AFlocked nylon swab
2. BCalcium alginate swab
3. CCotton swab on a wooden shaft
4. DPolyester swab on a wooden shaft
Answer and explanation in LearnFree account
Question 18 · Medium
A 12-year-old boy from an area endemic for urinary schistosomiasis has blood in his urine. Urine for Schistosoma haematobium eggs is best collected as:
1. AThe first urine passed on waking
2. BA midstream urine passed at bedtime
3. CA terminal urine passed around midday
4. DA first-catch urine kept refrigerated
Answer and explanation in LearnFree account

Microbiology specimen collection, transport and rejection

A swab of a leg ulcer from a 60-year-old man is sent in a plain sterile tube with no transport medium. It arrives 5 hours later, completely dry. What is the best action?

A sputum container for culture reaches the laboratory with specimen leaking down the outside. What is the best action?

Viral transport medium contains antibiotics and an antifungal agent in order to:

A urine for culture is labeled with the patient's name and a medical record number that differs from the number on the electronic request. What is the correct action?

A woman has dysuria. Her urine for culture arrives in a boric acid tube marked with a 3 mL fill line, but it holds only 0.5 mL. Urinalysis on a second, plain specimen shows positive nitrite and leukocyte esterase. The culture grows nothing at 24 hours. What is the most likely explanation?

Early-morning gastric aspirates from a 4-year-old child are sent for mycobacterial culture. If processing cannot start promptly, how should the specimen be treated?

A lymph node biopsy for bacterial culture arrives in 10% formalin. What should the laboratory do?

Endocervical specimens for gonococcal culture are collected at a clinic 3 hours away from the laboratory. Which transport system gives the best recovery?

A patient admitted 6 days ago develops diarrhea on the ward, and a stool culture for Salmonella, Shigella and Campylobacter is ordered. Why do many laboratories reject this request?

A stool for ova and parasites is collected from a patient the day after a barium meal. What should the laboratory do?

Four specimens arrive in the laboratory at 10:00 on the same morning. Which one should be rejected?

A traveler returning to Abu Dhabi has had fever for 5 days, and enteric fever is suspected. Which culture is most likely to grow Salmonella Typhi at this stage?

Charcoal is added to some swab transport media, such as Amies with charcoal, mainly to:

For the serologic diagnosis of a recent infection, paired serum samples should be collected:

Which swab type is preferred for most bacterial culture and nucleic acid tests because it collects and releases the most specimen?

A 12-year-old boy from an area endemic for urinary schistosomiasis has blood in his urine. Urine for Schistosoma haematobium eggs is best collected as: