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Questions and Answers
What is the correct purpose of barcoding in specimen collection?
Which preservative is specifically recommended for accurate colony counts in urine?
Which statement regarding refrigeration and freezing of specimens is accurate?
What is the role of anticoagulants in sample collection?
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In labeling specimens, which information is NOT required?
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Which of the following organisms is classified as fragile?
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What is a key characteristic of formalin as a preservative?
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Why is it critical for laboratory staff to be informed about specimen collection in advance?
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What characteristic distinguishes Mycobacterium from Gram-positive bacteria?
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Which Bacillus species is primarily known for causing anthrax?
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What is the main function of Bacillus stearothermophilus spores in laboratory settings?
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Which of the following pairs of Bacillus species are considered laboratory contaminants?
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What physical characteristics do Bacillus species typically exhibit?
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Which of the following groups of Bacillus species produce spores that do not distend the sporangium?
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Which Bacillus species is utilized in genetically modified crops for pest resistance?
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What is a unique feature of Bacillus endospores?
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Which Gram staining characteristic is associated with Corynebacterium species?
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What is the significance of Loeffler’s methylene blue in identifying Corynebacterium?
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What type of hemolysis is observed in some Corynebacterium species on sheep blood agar?
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Which of the following tests is NOT one of the four preliminary tests for identifying Corynebacterium species?
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What distinguishes C.pseudotuberculosis biovar equi from biovar ovis in nitrate reduction?
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Which containment level is recommended for handling C.diphtheriae and C.ulcerans?
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What is the main effect of untreated TB disease?
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What must be considered when performing laboratory procedures that can generate infectious aerosols?
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Which of the following statements accurately describes Bacillus anthracis?
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What is a notable characteristic that differentiates Bacillus anthracis from other Bacillus species?
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What kind of spores do Bacillus species typically produce?
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Which Bacillus species is incorrectly categorized based on its haemolytic properties?
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At what temperature does Bacillus anthracis grow optimally?
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What statement about the spore formation of Bacillus anthracis is true?
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Which genus has had a taxonomic development including Bacillus species?
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Bacillus species that are described as oxidase positive can lead to confusion with which other bacteria?
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What is the primary reason for performing the catalase test on colonies from TSA instead of BAP?
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Which specimen type is NOT suitable for culturing meningococci?
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In which Gram-positive genus are spores located toward the end of the cells?
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Which group of bacteria is primarily associated with anaerobic cultivation?
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What is the least common specimen type to be tested for enterics and Vibrio?
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Which of the following organisms is NOT included in the Gram-negative coccobacilli grouping?
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What is a characteristic feature of spirochetes that makes them difficult to Gram-stain?
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Which Gram-negative bacilli group includes organisms associated with foodborne illnesses?
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Study Notes
Specimen Collection and Transport
- Bacteriology Laboratory must be informed prior to specimen collection for preparation of necessary materials and instructions for MLS/MT.
Labelling Protocol
- Critical that patients provide their full name; if unable, guards must state the name.
- Include essential details: age, sex (Male/Female), in-patient/out-patient status, and date of collection.
- Barcoding is employed to ensure accurate identification of specimens; bar codes placed on containers—not caps—to prevent mix-ups.
- Bar codes linked to bacteriology worksheets upon specimen processing to maintain traceability.
Use of Preservatives
- Boric acid utilized for reliable colony counts in urine samples.
- Phosphate buffered saline preserves fecal samples to prevent bacterial death (e.g., Shigella).
- Formalin, polyvinyl alcohol, and Schaudinn's fluid used to maintain viability of trophozoites and cysts in stool specimens.
Anticoagulants in Specimen Collection
- Anticoagulants prevent blood clotting while preserving microorganisms.
- Sodium polyanethol sulfonate (0.025% w/v) is preferred for blood specimens.
- Heparin inhibits Gram-positive bacteria; alternatives include citrate and EDTA.
Refrigeration vs. Freezing of Specimens
- Refrigeration is favored as it slows microorganism growth, whereas freezing can be lethal to bacteria.
Organism Classification
- Fragile Organisms: Examples include Streptococcus pneumoniae, Neisseria species, and anaerobes.
- Bacillus Characteristics: Notable for their endospore formation and Gram-positive rod structure.
- Gram-Negative Organisms: Diverse group including enterics (e.g., Escherichia, Salmonella) and vibrio.
Bacillus Species Overview
- Genera includes 268 species, medically significant ones being Bacillus anthracis (causes anthrax) and Bacillus cereus (causes foodborne illness).
- Bacillus subtilis is a common lab contaminant; B. thuringiensis is used in GMO crops.
Characteristics of Bacillus
- Endospores typical of Bacillus are resistant to harsh conditions.
- Division based on spore morphology: Group 1 (smooth spores), Group 2 (variable spores), Group 3 (swollen sporangia).
- Many species exhibit hemolytic activity, whereas B. anthracis is non-hemolytic.
Anthrax Detection
- B. anthracis is sensitive to penicillin and requires direct referral to reference labs if suspected.
- Characteristic colonies on BAP appear gray/white with a “bee’s eye” look and irregular, tacky edges.
Corynebacterium Species Insights
- C. diphtheriae and related species categorized as Hazard Group 2, necessitating safety precautions in labs.
- Identification methods include nitrate and urease testing, with hemolysis on different media affecting test outcomes.
- Diphtheria antitoxin available for treatment of clinical cases, with strict controls around handling specimens.
Mycobacterium Overview
- Mycobacterium tuberculosis is the causative agent of Tuberculosis (TB), impacting lungs and other body parts.
- Distinction between latent TB infection (LTBI) and TB disease essential for treatment considerations.
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