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Questions and Answers
Which scientist developed the Gram staining technique?
What is the purpose of the alcohol or acetone in Gram staining?
What is the primary stain used in Gram staining?
What can cause Gram-positive bacteria to appear Gram-negative?
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What happens if the decolorization step is skipped during Gram staining?
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Which bacteria appear as Gram-negative kidney bean shaped diplococci?
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Which step in the Gram staining process is key to differentiating between Gram-positive and Gram-negative bacteria?
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What is the role of safranin in the Gram staining procedure?
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Which bacteria is characterized as Gram-negative and has a curved, comma-shaped form?
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Which of the following bacteria is described as Gram-negative and has a curved, thin rod shape?
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Which organism exhibits Gram-negative rods with bipolar staining, often described as resembling a 'closed safety pin'?
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Which of the following statements regarding the bacterial cell wall is false?
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What factor can result in a Gram-negative organism appearing Gram-positive?
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Which media is primarily used in general bacteriology to support the growth of most bacteria, with specific exceptions?
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Which stain is primarily used as a counterstain in Kinyoun staining?
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What is the primary stain used in endospore staining procedures?
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Which media is used for the cultivation or isolation of fastidious bacteria like Neisseria spp and Haemophilus spp?
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Which medium contains cysteine and iron supplementation necessary to support the growth of Legionella spp?
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Which media contain bile salts and crystal violet that inhibit the growth of gram-positive bacteria?
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To which bacteria do bile salts that inhibit gram-positive bacteria and alkaline pH enhance growth?
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Which media is resistant to cephalexin, preventing the growth of Bordetella spp?
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Which media are Neisseria spp resistant to when recovering from nonsterile sites?
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What is the primary factor contributing to the localized nature of Staphylococcus aureus lesions?
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Which statement about S. aureus food poisoning is incorrect?
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Which of the following is NOT a primary mode of transmission for Brucella abortus bacteria?
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What color does Mycobacterium tuberculosis appear in the Ziehl-Neelsen stain?
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Which test is specifically used to identify Streptococcus pneumoniae?
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What is the ONPG test primarily used for?
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Which test would you perform to differentiate between two beta-hemolytic bacteria?
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For which bacteria is the CAMP test used?
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What is the indicator used in the candle jar method for creating anaerobic conditions?
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Which bacterial strain is associated with the characteristic 'double zone' hemolysis on blood agar?
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What is the primary mechanism by which Staphylococcus epidermidis colonizes prosthetic devices?
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Given a urine specimen culture result with >100,000 col/mL of gram-positive cocci resembling staphylococci and resistant to novobiocin, what is the most likely isolate?
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Which staining sequence is appropriate for staining a sputum sample from a patient who works in construction and presents with fever and hemoptysis?
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What does a positive HCV antibody test and negative HCV RNA testing imply about the patient's infection status?
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At what temperature is complement inactivated in human serum?
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Which organization is responsible for accrediting medical laboratories in Saudi Arabia?
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What is the appropriate action if a CSF sample was stained and later reported incorrectly?
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What is the typical diagnosis method for Neisseria gonorrhoeae in males?
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Study Notes
Gram Staining Technique
- Developed by Hans Christian Gram for differentiating bacterial species.
- Uses crystal violet as the primary stain.
- Alcohol or acetone is crucial for decolorization.
- Over-staining or using old cultures can lead to misinterpretation of Gram results.
Bacterial Morphology
- Gram-negative bacteria appear as kidney bean-shaped diplococci; notable examples include Neisseria spp.
- Curved, comma-shaped, short rods are characteristic of Campylobacter and Vibrio cholerae.
- Thin, curved rods with a "seagull" shape are indicative of Campylobacter spp.
Gram Staining Results
- Skipping decolorization can result in false positive results for Gram-positive bacteria.
- Bipolar staining resembling a "closed safety pin" is a sign of Yersinia pestis.
- Teichoic acid is present in Gram-positive cell walls but absent in Gram-negative.
Acid-Base Staining and Media
- The zinc stain uses 3% hydrochloric acid for decolorization.
- Malachite green is the primary stain for endospore staining, with a concentration of 0.5%.
- Schaeffer-Fulton method is specific for endospore detection.
Culture Media in Microbiology
- Chocolate agar supports growth of fastidious organisms like Neisseria and Haemophilus.
- Buffered charcoal yeast extract (BCYE) agar is essential for cultivating Legionella spp.
- Thayer Martin agar selectively isolates Neisseria spp by incorporating antimicrobials.
Pathogenic Bacteria and Their Properties
- Staphylococcus saprophyticus is catalase positive, coagulase negative, and resistant to novobiocin.
- Streptococcus pneumoniae identification involves the optochin sensitivity test and produces alpha-hemolysis.
Disease Associations
- Mycobacterium tuberculosis appears red in the Ziehl-Neelsen stain.
- Brucella abortus transmission occurs through contact with infected animal products and inhalation of airborne agents.
- Infants and immunocompromised individuals are particularly at risk for meningitis caused by Streptococcus pneumoniae.
Quality and Laboratory Protocols
- In Saudi Arabia, CBAHI is responsible for accrediting medical laboratories.
- Errors in laboratory results must be communicated to patients with sincerity and transparency.
Specialty Tests
- The ONPG test differentiates between lactose fermenters and non-fermenters.
- The CAMP test is specifically used for Streptococcus agalactiae identification.
Microbial Growth Conditions
- The candle jar method uses methylene blue as an indicator for anaerobic conditions.
- Some bacteria, like Chlamydia and Treponema pallidum, do not grow in traditional culture media.
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Description
This quiz explores the Gram staining technique developed by Hans Christian Gram for differentiating bacterial species. It covers bacterial morphology, results of Gram staining, and related acid-base staining methods, emphasizing the significance of decolorization and interpretation of results.
