Master Analytic Procedures for Mycobacteriology with this expertly curated set of 80 exam-style multiple-choice questions (MCQs) designed for laboratory science students and professionals. These free practice questions are tailored to the latest exam blueprints for ASCP MLS, AMT MLT/MT, AIMS, CSMLS, IBMS, HAAD/DOH, DHA, and MOH certifications. Each question comes with accurate answers, detailed explanations, and trusted references to help you understand core concepts, strengthen analytic skills, and boost exam confidence. Perfect for targeted microbiology revision, improving speed, and closing knowledge gaps.
80 MCQs (1561-1640):
- Which medium is most commonly used for the primary isolation of mycobacteria?
a) Blood agar
b) Lowenstein-Jensen agar
c) MacConkey agar
d) Chocolate agar - What is the function of N-acetyl-L-cysteine in the digestion-decontamination process for mycobacterial culture?
a) Inhibit fungal growth
b) Liquefy mucus
c) Neutralize sodium hydroxide
d) Inhibit bacterial growth - Which staining method is considered the gold standard for detecting acid-fast bacilli?
a) Gram stain
b) Ziehl-Neelsen stain
c) Methylene blue stain
d) Calcofluor white stain - What is the optimal incubation temperature for Mycobacterium marinum?
a) 25°C
b) 30°C
c) 35°C
d) 42°C - Which of the following is a characteristic feature of Mycobacterium tuberculosis?
a) Rapid growth within 24 hours
b) Production of niacin
c) Pigmented colonies
d) Motility at 25°C - Which specimen is considered the most sensitive for the recovery of Mycobacterium tuberculosis in chronic infections?
a) Urine
b) Sputum
c) Blood
d) Bone marrow - What precaution should be taken when processing specimens for mycobacterial culture to prevent laboratory-acquired infections?
a) Use of open bench tops
b) Processing in a biological safety cabinet
c) Incubation at room temperature
d) Centrifugation without a sealed lid - Which of the following organisms is part of the Mycobacterium tuberculosis complex (MTBC)?
a) Mycobacterium avium
b) Mycobacterium kansasii
c) Mycobacterium bovis
d) Mycobacterium fortuitum - What is the primary stain used in the Kinyoun acid-fast staining method?
a) Crystal violet
b) Carbol fuchsin
c) Methylene blue
d) Malachite green - Which of the following is a photochromogen?
a) Mycobacterium tuberculosis
b) Mycobacterium kansasii
c) Mycobacterium avium
d) Mycobacterium fortuitum - Which medium must be refrigerated in the dark to prevent formaldehyde production that could kill mycobacteria?
a) Blood agar
b) Middlebrook 7H10/7H11
c) Chocolate agar
d) Sabouraud dextrose agar - What is the primary purpose of N-acetyl-L-cysteine in sputum processing for mycobacterial culture?
a) Inhibit fungal growth
b) Neutralize alkalinity
c) Liquefy mucus
d) Kill contaminants - A positive niacin test is characteristic of which Mycobacterium species?
a) M. avium
b) M. fortuitum
c) M. tuberculosis
d) M. kansasii - Which specimen type is processed with oxalic acid decontamination for Pseudomonas contamination?
a) Blood
b) Sputum
c) Bone marrow
d) Urine - What safety precaution is mandatory when processing mycobacterial specimens?
a) Open-bench processing
b) Biological safety cabinet
c) UV light exposure only
d) Chemical fume hood - Mycobacterium marinum grows optimally at:
a) 25°C
b) 30°C
c) 37°C
d) 42°C - Scotochromogens produce pigment:
a) Only in light
b) In dark or light
c) Never
d) Only on specific media - Which test confirms Mycobacterium tuberculosis complex in AFB-smear positive respiratory specimens within 24 hours?
a) Culture on LJ medium
b) Niacin accumulation
c) Molecular testing
d) Catalase test - The BCG vaccine strain is derived from:
a) M. tuberculosis
b) M. bovis
c) M. africanum
d) M. microti - Which specimen requires digestion-decontamination for mycobacterial culture?
a) Cerebrospinal fluid
b) Bronchial washing
c) Synovial fluid
d) Pleural fluid
- A branching, partially acid-fast gram-positive rod from a bronchial washing likely belongs to:
a) Actinomyces
b) Nocardia
c) Streptomyces
d) Corynebacterium - Leprosy (Hansen’s disease) is diagnosed by:
a) Culture on LJ medium
b) Urine antigen test
c) Skin biopsy with AFB stain
d) Sputum PCR - Which primary stain is used in Kinyoun’s acid-fast staining?
a) Methylene blue
b) Carbol fuchsin
c) Auramine O
d) Crystal violet - Rapid growers (e.g., M. fortuitum) are defined by visible colonies within:
a) 24 hours
b) 3 days
c) 7 days
d) 14 days - PANTA antibiotic mixture is added to mycobacterial cultures to:
a) Enhance growth
b) Prevent contamination
c) Reduce incubation time
d) Improve staining - Photochromogens require _____ to produce pigment.
a) High CO₂
b) Light exposure
c) Specific nutrients
d) Low temperature - Which characteristic identifies M. tuberculosis colonies?
a) Yellow pigment
b) Smooth texture
c) Rough, buff-colored
d) Mucoid appearance - Auramine-rhodamine staining is preferred over Ziehl-Neelsen for screening because it:
a) Is cheaper
b) Requires no microscope
c) Has higher sensitivity
d) Works on fixed specimens - M. avium-intracellulare complex (MAC) is best differentiated by:
a) Niacin test
b) Growth rate
c) Molecular methods
d) Pigmentation - Decontamination of specimens for mycobacterial culture typically uses:
a) NALC-NaOH
b) HCl-pepsin
c) Potassium permanganate
d) Ethanol - Mycobacteria in liquid media (e.g., MGIT) show growth:
a) Slower than solid media
b) Faster than solid media
c) With different pigmentation
d) Only at 42°C - Which drug is a first-line treatment for tuberculosis?
a) Amphotericin B
b) Vancomycin
c) Rifampin
d) Ciprofloxacin - Non-tuberculous mycobacteria (NTM) are:
a) Always pathogenic
b) Strictly environmental
c) Often opportunistic
d) Only zoonotic - The quantiferon-TB gold test detects:
a) AFB in sputum
b) Antibodies to M. tuberculosis
c) T-cell response to TB antigens
d) Bacterial DNA in CSF - M. kansasii is characterized as a:
a) Scotochromogen
b) Nonchromogen
c) Photochromogen
d) Rapid grower - Acid-fastness in mycobacteria is due to:
a) Peptidoglycan layer
b) Mycolic acids
c) Capsular polysaccharides
d) Porin proteins - Xpert MTB/RIF assay simultaneously detects:
a) TB and HIV
b) TB and rifampin resistance
c) TB and MDR-TB
d) TB and leprosy - Lowenstein-Jensen medium contains:
a) Charcoal and yeast extract
b) Egg base and malachite green
c) Blood and antibiotics
d) Sucrose and agar - For mycobacterial blood cultures, the optimal specimen is:
a) Serum
b) Plasma
c) Whole blood
d) Buffy coat - M. ulcerans causes:
a) Pulmonary TB
b) Buruli ulcer
c) Leprosy
d) Swimming pool granuloma - Which biosafety level is required for culturing Mycobacterium tuberculosis?
a) BSL-1
b) BSL-2
c) BSL-3
d) BSL-4 - Which fluorescent dye combination is commonly used in auramine-rhodamine staining for mycobacteria?
a) Auramine O and rhodamine B
b) Crystal violet and safranin
c) Methylene blue and malachite green
d) Acridine orange and ethidium bromide - The Middlebrook 7H10 and 7H11 media differ primarily in their:
a) Incubation temperature
b) Antibiotic content
c) Nutrient enrichment for recovery of fastidious mycobacteria
d) Malachite green concentration - The role of malachite green in Lowenstein-Jensen medium is to:
a) Enhance pigment production
b) Inhibit growth of contaminants
c) Provide a pH indicator
d) Improve colony morphology - Mycobacterium xenopi grows optimally at which temperature?
a) 25°C
b) 30°C
c) 37°C
d) 42°C - Cord formation in M. tuberculosis cultures is due to:
a) Mycolic acids
b) Niacin accumulation
c) Lipoarabinomannan
d) Sulfatides - Which stain is most sensitive for detecting low numbers of acid-fast bacilli in specimens?
a) Ziehl-Neelsen
b) Kinyoun
c) Auramine-rhodamine
d) Gram stain - Which mycobacterium is associated with “swimming pool granuloma” in humans?
a) M. marinum
b) M. gordonae
c) M. kansasii
d) M. ulcerans - Which gene is most commonly targeted in nucleic acid amplification tests for M. tuberculosis complex?
a) katG
b) rpoB
c) IS6110
d) inhA - The primary purpose of sodium hydroxide in the NALC-NaOH method is to:
a) Liquefy mucus
b) Kill contaminating bacteria
c) Enhance growth of mycobacteria
d) Stain AFB - Mycobacterium gordonae is often referred to as:
a) Tap water bacillus
b) Fish tank bacillus
c) Buruli ulcer bacillus
d) Cow bacillus - Drug susceptibility testing for M. tuberculosis is routinely performed for:
a) Only rifampin
b) First-line drugs
c) Second-line drugs only
d) All antimicrobial agents - Which characteristic differentiates rapid growers from slow growers among mycobacteria?
a) Pigment production
b) Growth within 7 days on solid media
c) Resistance to rifampin
d) Ability to grow without oxygen - The MGIT (Mycobacteria Growth Indicator Tube) system detects growth by:
a) Turbidity measurement
b) CO₂ production
c) Oxygen depletion and fluorescence quenching
d) pH change - The niacin test is positive for:
a) M. kansasii
b) M. tuberculosis
c) M. fortuitum
d) M. avium - Which is the most common cause of false-negative AFB smear results?
a) Poor staining technique
b) Low bacterial load in the sample
c) Excessive heat during staining
d) Use of auramine stain - The term “scotochromogen” refers to mycobacteria that produce pigment:
a) Only in the presence of light
b) In the absence and presence of light
c) Never
d) Only at low temperature - Which mycobacterium causes “Buruli ulcer”?
a) M. avium
b) M. marinum
c) M. ulcerans
d) M. fortuitum - Which biosafety cabinet type is used for processing mycobacterial specimens?
a) Class I
b) Class II
c) Class III
d) Class IV - Mycobacterium haemophilum requires which supplement for growth?
a) Mycobactin J
b) Hemin
c) Iron salts
d) Egg yolk - AFB smears are reported as “scanty” when:
a) 1–9 AFB per 100 fields are seen
b) 10–99 AFB per field are seen
c) >100 AFB per field are seen
d) No AFB seen - Which method can provide rifampin resistance results within hours?
a) Culture on LJ medium
b) Xpert MTB/RIF assay
c) Niacin accumulation test
d) Catalase test - The catalase test in mycobacteriology is often used to detect:
a) Drug resistance
b) Heat-labile catalase in isoniazid-resistant strains
c) Presence of pigment
d) Growth rate - Which mycobacterium is the most frequent cause of cervical lymphadenitis in children?
a) M. kansasii
b) M. scrofulaceum
c) M. marinum
d) M. xenopi - Mycobacterium leprae is best detected by:
a) Ziehl-Neelsen stain of nasal smears
b) Culture on Middlebrook medium
c) PCR from urine
d) MGIT - In liquid culture, contamination is most effectively prevented by adding:
a) Malachite green
b) PANTA antibiotic mixture
c) Rifampin
d) NaOH - Which feature is typical of M. avium complex colonies?
a) Rapid growth
b) Smooth, non-pigmented
c) Rough, pigmented
d) Mucoid, yellow - Which chemical fixative can destroy acid-fastness?
a) Methanol
b) Formalin
c) Acetone
d) Ethanol - Which mycobacterium is known for its association with AIDS patients causing disseminated infection?
a) M. tuberculosis
b) M. kansasii
c) M. avium complex
d) M. gordonae - The term “runyon classification” is based on:
a) Growth rate and pigment production
b) Drug susceptibility
c) Colony morphology
d) Antigenic structure - Which pigment is produced by photochromogens upon exposure to light?
a) Red
b) Yellow
c) Blue
d) Green - Mycobacterium bovis BCG strain is used for:
a) Leprosy treatment
b) TB vaccination
c) MAC infection prevention
d) MDR-TB therapy - Which gene mutation is most associated with isoniazid resistance in M. tuberculosis?
a) katG
b) rpoB
c) gyrA
d) inhA - In Ziehl-Neelsen staining, acid-alcohol acts as:
a) Primary stain
b) Counterstain
c) Decolorizer
d) Mordant - Which specimen is least likely to require digestion-decontamination before culture?
a) Sputum
b) Urine
c) CSF
d) Bronchial lavage - Mycobacterium szulgai is classified as a:
a) Scotochromogen
b) Nonchromogen
c) Photochromogen
d) Rapid grower - Which component of the mycobacterial cell wall is responsible for acid-fastness?
a) Peptidoglycan
b) Mycolic acids
c) Arabinogalactan
d) Lipoarabinomannan - Which mycobacterium can grow at both 30°C and 37°C and produce yellow pigment in the light?
a) M. kansasii
b) M. marinum
c) M. scrofulaceum
d) M. gordonae - In MGIT tubes, growth is detected when:
a) Fluorescence increases due to oxygen depletion
b) pH decreases
c) CO₂ levels rise
d) Turbidity exceeds threshold - Which staining method uses phenol to aid dye penetration into mycobacteria?
a) Ziehl-Neelsen
b) Gram stain
c) Acridine orange
d) Wright-Giemsa
Answer Key
Answer Key:
- b) Lowenstein-Jensen agar
- b) Liquefy mucus
- b) Ziehl-Neelsen stain
- b) 30°C
- b) Production of niacin
- b) Sputum
- b) Processing in a biological safety cabinet
- c) Mycobacterium bovis
- b) Carbol fuchsin
- b) Mycobacterium kansasii
- b) Nocardia
- c) Skin biopsy with AFB stain
- b) Carbol fuchsin
- c) 7 days
- b) Prevent contamination
- b) Light exposure
- c) Rough, buff-colored
- c) Has higher sensitivity
- c) Molecular methods
- a) NALC-NaOH
- c) BSL-3
- a) Auramine O and rhodamine B
- c) Nutrient enrichment for recovery of fastidious mycobacteria
- b) Inhibit growth of contaminants
- d) 42°C
- a) Mycolic acids
- c) Auramine-rhodamine
- a) M. marinum
- c) IS6110
- b) Kill contaminating bacteria
- a) 1–9 AFB per 100 fields are seen
- b) Xpert MTB/RIF assay
- b) Heat-labile catalase in isoniazid-resistant strains
- b) M. scrofulaceum
- a) Ziehl-Neelsen stain of nasal smears
- b) PANTA antibiotic mixture
- b) Smooth, non-pigmented
- b) Formalin
- c) M. avium complex
- a) Growth rate and pigment production
- b) Middlebrook 7H10/7H11
- c) Liquefy mucus
- c) M. tuberculosis
- b) Sputum
- b) Biological safety cabinet
- b) 30°C
- b) In dark or light
- c) Molecular testing
- b) M. bovis
- b) Bronchial washing
- b) Faster than solid media
- c) Rifampin
- c) Often opportunistic
- c) T-cell response to TB antigens
- c) Photochromogen
- b) Mycolic acids
- b) TB and rifampin resistance
- b) Egg base and malachite green
- d) Buffy coat
- b) Buruli ulcer
- a) Tap water bacillus
- b) First-line drugs
- b) Growth within 7 days on solid media
- c) Oxygen depletion and fluorescence quenching
- b) M. tuberculosis
- b) Low bacterial load in the sample
- b) In the absence and presence of light
- c) M. ulcerans
- b) Class II
- b) Hemin
- b) Yellow
- b) TB vaccination
- a) katG
- c) Decolorizer
- c) CSF
- a) Scotochromogen
- b) Mycolic acids
- a) M. kansasii
- a) Fluorescence increases due to oxygen depletion
- a) Ziehl-Neelsen
Top 8 Medical Laboratory Scientist (MLS) Exams:
Top 8 Medical Laboratory Scientist (MLS) Exams that are recognized globally and can help professionals validate their credentials and enhance their career opportunities:
1. ASCP – American Society for Clinical Pathology (USA)
- Exam Name: MLS(ASCP)
- Eligibility: Bachelor’s degree with clinical laboratory experience.
- Global Recognition: High
- Purpose: Certifies Medical Laboratory Scientists in the United States and internationally.
2. AMT – American Medical Technologists (USA)
- Exam Name: MLT(AMT) or MT(AMT)
- Eligibility: Academic and/or work experience in medical laboratory technology.
- Global Recognition: Moderate
- Purpose: Credentialing for medical technologists and technicians.
3. AIMS – Australian Institute of Medical and Clinical Scientists
- Exam Name: AIMS Certification Exam
- Eligibility: Assessment of qualifications and work experience.
- Recognition: Required for practice in Australia.
- Purpose: Certification and registration in Australia.
4. CSMLS – Canadian Society for Medical Laboratory Science
- Exam Name: CSMLS General or Subject-specific Exams
- Eligibility: Graduation from a CSMLS-accredited program or equivalent.
- Recognition: Canada
- Purpose: Entry-to-practice certification in Canada.
5. IBMS – Institute of Biomedical Science (UK)
- Exam Name: Registration and Specialist Portfolio Assessment
- Eligibility: Accredited degree and lab experience.
- Recognition: UK and some Commonwealth countries.
- Purpose: Biomedical Scientist registration with the HCPC (UK).
6. HAAD / DOH – Department of Health, Abu Dhabi (UAE)
- Exam Name: DOH/HAAD License Exam
- Eligibility: Degree in medical laboratory science and experience.
- Recognition: UAE (Abu Dhabi)
- Purpose: Licensure for medical laboratory practice in Abu Dhabi.
7. DHA – Dubai Health Authority (UAE)
- Exam Name: DHA License Exam for Medical Laboratory Technologists
- Eligibility: Relevant degree and experience.
- Recognition: Dubai, UAE
- Purpose: Professional license for clinical laboratory practice in Dubai.
8. MOH – Ministry of Health (Gulf Countries like UAE, Saudi Arabia, Kuwait)
- Exam Name: MOH License Exam
- Eligibility: BSc/Diploma in Medical Laboratory + experience.
- Recognition: Varies by country.
- Purpose: Required for practicing in public and private sector labs.
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