Brucella Agar 50 FAQs and 30 MCQs
Explore a comprehensive guide on Brucella Agar, a selective medium used for isolating Brucella species in clinical and research laboratories. This page provides 50 frequently asked questions (FAQs) covering preparation, composition, uses, and interpretation of Brucella Agar. Additionally, test your knowledge with 30 multiple-choice questions (MCQs) designed for students, microbiologists, and medical lab technicians. Enhance your understanding of bacterial culture techniques with LabTestsGuide.com!
Brucella Agar 50 FAQs:
What is Brucella Agar used for?
It is used for the isolation and cultivation of Brucella species and other fastidious bacteria.
Which bacteria can grow on Brucella Agar?
Brucella melitensis, Brucella suis, Brucella abortus, Campylobacter, Streptococcus pneumoniae, Neisseria meningitidis, Listeria, and Haemophilus influenzae.
Is Brucella Agar selective or differential?
It is a general-purpose medium but can be made selective/differential with additives like dyes or antibiotics.
Why is Brucella Agar considered nutrient-rich?
It contains peptones, yeast extract, dextrose, and other growth-promoting components.
What is the pH of Brucella Agar?
7.0 ± 0.2 at 25°C.
What are the main ingredients of Brucella Agar?
Enzymatic digest of casein (10g/L), animal tissue (10g/L), yeast extract (2g/L), sodium chloride (5g/L), dextrose (1g/L), sodium bisulfite (0.1g/L), and agar (13-15g/L).
Why is yeast extract included in Brucella Agar?
It provides B-complex vitamins essential for fastidious bacteria.
What is the role of sodium bisulfite in Brucella Agar?
Acts as a reducing agent to support microaerophilic bacteria.
How much medium powder is needed per liter?
41-43 grams per liter of distilled water.
How is Brucella Agar prepared?
Suspend powder in water, boil, autoclave (121°C for 15 min), and pour into plates.
Can Brucella Agar be stored after preparation?
Yes, store below 8°C, protected from light.
What is the difference between the two articles’ compositions?
Minor variations in agar content (13g vs. 15g) and additional details in selective/differential modifications.
How is Brucella Selective Agar prepared?
Add bacitracin (500mg), polymyxin B (1mg), cycloheximide (100mg), and ethyl violet (optional)
What is Brucella Differential Agar?
Contains basic fuchsin or thionine acetate to differentiate Brucella species based on dye sensitivity.
How does basic fuchsin help differentiate Brucella species?
Brucella abortus grows on thionine but not on fuchsin, while B. melitensis grows on both.
How is Campylobacter isolation enhanced on Brucella Agar?
Add sodium pyruvate, sodium metabisulfite, ferrous sulfate, and 5-7% sheep blood.
Why is horse blood sometimes added?
Enhances growth of fastidious bacteria like Streptococcus and Haemophilus.
What incubation conditions are best for Brucella Agar?
35 ± 2°C for 24-72 hours in CO₂-enriched atmosphere (for primary isolation).
What do Brucella colonies look like on this agar?
Transparent, convex, smooth, shiny with entire edges.
How is growth scored on Brucella Agar?
Semi-quantitatively based on streaking dilution (confluent vs. isolated colonies).
Which bacteria are inhibited on Brucella Agar?
Staphylococcus aureus and E. coli are typically inhibited.
Why might some strains grow poorly on Brucella Agar?
Due to nutritional variations among strains.
Can Brucella Agar diagnose human brucellosis?
No, it is not for diagnostic use but for cultivation in labs.
Is Brucella Agar used in food testing?
Yes, APHA recommends it for isolating Brucella from food samples.
Can it be used for anaerobic bacteria?
Presumptive anaerobes need confirmatory tests.
What are the limitations of Brucella Agar?
Some strains may grow poorly, and it’s not for human diagnosis.
Is Brucella Agar used for hemolysis studies?
Yes, when supplemented with 5% horse blood.
Why is Brucella Agar hazardous?
Brucella species are highly infective (biosafety level 3 pathogen).
What precautions should be taken when handling Brucella Agar?
Use biosafety cabinets, gloves, and proper disposal methods.
Can Brucella Agar be autoclaved for disposal?
Yes, autoclaving at 121°C for 30 minutes ensures safety.
How does Brucella Agar compare to Blood Agar?
Brucella Agar is more selective for fastidious bacteria.
What is Wundt’s modification in Brucella Agar?
Improved formulation for better Brucella growth (as per Article 2).
Can Thayer-Martin Agar replace Brucella Agar?
No, Thayer-Martin is for Neisseria gonorrhoeae, while Brucella Agar supports broader fastidious bacteria.
What if Brucella Agar doesn’t solidify?
Check agar concentration (should be 13-15g/L) and pH.
Why is there no growth after incubation?
Possible CO₂ requirement, incorrect incubation, or poor sample quality.
What if contaminants overgrow Brucella colonies?
Use selective supplements (bacitracin, polymyxin, cycloheximide).
Who recommends Brucella Agar for food testing?
APHA (American Public Health Association).
Which WHO references support Brucella Agar use?
WHO Technical Report Series (1951-1964) on brucellosis.
What is the ATCC reference for Brucella abortus?
ATCC 4315.
What is the ATCC reference for Brucella melitensis?
ATCC 4309.
How is sodium pyruvate beneficial for Campylobacter?
Acts as an antioxidant, enhancing microaerophilic growth.
Why is ferrous sulfate added for Campylobacter?
Helps detect H₂S production in some species.
Can Brucella Agar be used for antibiotic susceptibility testing?
Not standard; requires Mueller-Hinton Agar with supplements.
How should dehydrated Brucella Agar powder be stored?
In tightly sealed containers at 2-25°C.
How long can prepared Brucella Agar plates be stored?
Up to 4 weeks at 2-8°C if sealed properly.
Can Brucella Agar be used for environmental samples?
Yes, but selective agents may be needed to suppress contaminants.
Is Brucella Agar used in veterinary diagnostics?
Yes, for detecting Brucella in animal samples.
What is the role of dextrose in Brucella Agar?
Serves as an energy source for bacterial growth.
Why is CO₂ needed for primary isolation?
Many pathogens (e.g., Brucella, Campylobacter) are capnophilic.
Can Brucella Agar detect hemolysis?
Only when 5% blood is added (e.g., horse or sheep blood).
Brucella Agar 30 MCQs :
- What is the primary purpose of Brucella Agar?
a) Cultivating fungi
b) Isolating Brucella and other fastidious bacteria
c) Growing viruses
d) Detecting parasites - Which ingredient in Brucella Agar acts as a reducing agent?
a) Sodium chloride
b) Sodium bisulfite
c) Dextrose
d) Agar - What is the final pH of Brucella Agar?
a) 6.0 ± 0.2
b) 7.0 ± 0.2
c) 8.0 ± 0.2
d) 5.5 ± 0.2 - How much agar is typically used per liter in Brucella Agar?
a) 5 g
b) 10 g
c) 13-15 g
d) 20 g - What is the autoclaving condition for Brucella Agar?
a) 100°C for 5 minutes
b) 121°C for 15 minutes
c) 80°C for 30 minutes
d) 115°C for 10 minutes
- Which additive makes Brucella Agar selective for Brucella?
a) Bacitracin + Polymyxin B
b) Lactose
c) Phenol red
d) Sodium citrate - What dye is used in Brucella Differential Agar to distinguish Brucella abortus?
a) Methylene blue
b) Basic fuchsin
c) Crystal violet
d) Safranin - Which Brucella species grows on thionine but not on basic fuchsin?
a) Brucella melitensis
b) Brucella suis
c) Brucella abortus
d) Brucella ovis - What is added to Brucella Agar for isolating Campylobacter?
a) Sodium pyruvate + Sheep blood
b) Potassium tellurite
c) MacConkey agar
d) Xylose lysine dextrose - Why is cycloheximide added to selective Brucella Agar?
a) To inhibit fungi
b) To enhance bacterial growth
c) To change agar color
d) To detect hemolysis
- What is the optimal incubation temperature for Brucella Agar?
a) 25°C
b) 30°C
c) 35 ± 2°C
d) 42°C - How long should Brucella Agar plates be incubated?
a) 6-12 hours
b) 24-72 hours
c) 1 week
d) 10 minutes - Which bacterium shows inhibited growth on Brucella Agar?
a) Brucella melitensis
b) Escherichia coli
c) Streptococcus pneumoniae
d) Haemophilus influenzae - What is the colony morphology of Brucella suis?
a) Rough and dry
b) Transparent, convex, shiny
c) Greenish metallic sheen
d) Mucoid and pink - Why is CO₂ required for primary isolation of Brucella?
a) To prevent contamination
b) Because Brucella is capnophilic
c) To solidify the agar
d) To enhance pigment production
- Brucella Agar is NOT recommended for:
a) Cultivating Neisseria meningitidis
b) Diagnosing human brucellosis
c) Isolating Campylobacter
d) Growing Listeria - Which organization recommends Brucella Agar for food testing?
a) CDC
b) APHA
c) WHO
d) FDA - What is a major limitation of Brucella Agar?
a) Too expensive
b) Some Brucella strains grow poorly
c) Only supports viral growth
d) Cannot be autoclaved - Which bacterium is NOT typically cultured on Brucella Agar?
a) Brucella abortus
b) Staphylococcus aureus
c) Streptococcus pyogenes
d) Salmonella typhi - What supplement is added to study hemolysis on Brucella Agar?
a) 5% horse blood
b) 10% NaCl
c) 0.1% methylene blue
d) 20% sucrose
- What biosafety level is required for handling Brucella?
a) BSL-1
b) BSL-2
c) BSL-3
d) BSL-4 - How should used Brucella Agar plates be disposed of?
a) Autoclave at 121°C for 30 minutes
b) Throw in regular trash
c) Freeze at -20°C
d) Wash down the sink - What could cause poor growth on Brucella Agar?
a) Incorrect pH
b) Lack of CO₂
c) Old culture medium
d) All of the above - Which component prevents contamination in selective Brucella Agar?
a) Bacitracin
b) Dextrose
c) Yeast extract
d) Agar - Why should Brucella Agar be stored below 8°C?
a) To prevent melting
b) To maintain nutrient stability
c) To inhibit bacterial growth
d) To enhance color changes
- Which reference strain is used for Brucella melitensis?
a) ATCC 25922
b) ATCC 4309
c) ATCC 4315
d) ATCC 11775 - Who modified Brucella Agar for improved growth?
a) Robert Koch
b) Louis Pasteur
c) Wundt
d) Joseph Lister - What is the role of dextrose in Brucella Agar?
a) Energy source
b) Solidifying agent
c) pH indicator
d) Selective inhibitor - Which Brucella species does NOT grow on basic fuchsin?
a) Brucella melitensis
b) Brucella suis
c) Brucella abortus
d) Brucella ovis - What is the purpose of sodium chloride in Brucella Agar?
a) Maintain osmotic balance
b) Act as a carbon source
c) Inhibit Gram-positive bacteria
d) Change agar color
Brucella Agar: A Key Medium for Fastidious Pathogens
Brucella agar is an enriched medium primarily used to cultivate Brucella species, fastidious bacteria responsible for brucellosis in humans and animals. This medium is also essential for isolating other anaerobic and microaerophilic organisms, such as Clostridium perfringens, when supplemented with hemin and vitamin K1. The composition of Brucella agar typically includes peptones, yeast extract, and dextrose, providing essential nutrients for bacterial growth. Variations like Remel Brucella agar, BBL Brucella agar, and Brucella blood agar (with 5% horse blood) enhance the recovery of fastidious pathogens. Unlike blood agar, which supports a broader range of bacteria, Brucella agar is more selective, often producing black colonies due to hydrogen sulfide production by certain species.
For diagnostic purposes, Brucella agar plates are incubated under anaerobic conditions, particularly when testing for Brucella abortus or other anaerobic pathogens. Laboratories may also use chocolate agar (heated blood agar) for Brucella cultivation, as it provides additional growth factors. The Brucella microagglutination test (BMAT) and urease test are common confirmatory assays following culture. Additionally, Brucella agar MCQs and mock tests are useful for training microbiologists on its applications, while Brucella agar FAQs address common issues like contamination or slow growth.
Chocolate Agar vs. Brucella Agar: Uses and Differences
Chocolate agar (heated blood agar) is another enriched medium used for cultivating fastidious bacteria, including Neisseria gonorrhoeae and Haemophilus influenzae. Unlike Brucella agar, which is often used anaerobically (anaerobic Brucella blood agar), chocolate agar is typically incubated aerobically or in CO₂-enriched environments. The composition of chocolate agar includes lysed red blood cells, releasing essential growth factors like Factor V (NAD) and Factor X (hemin). While Brucella species can grow on both media, Brucella does not grow on MacConkey agar, helping differentiate it from other Gram-negative bacteria.
For specialized applications, Brucella agar with hemin and vitamin K1 supports the growth of anaerobic bacteria, whereas chocolate agar is preferred for pathogens requiring additional nutrients. Laboratories may use BD Brucella agar, Oxoid Brucella blood agar, or HiMedia Brucella agar base, depending on availability. Educational resources such as Brucella agar mock tests and FAQs help clarify its role in clinical microbiology, ensuring accurate identification of Brucella and related pathogens. Whether for diagnostic or research purposes, both Brucella and chocolate agar remain vital tools in microbiology.
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