Practice Test Geeks(CLT) Clinical Laboratory Technologist Certification Practice Test
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CLT Microbiology & Urinalysis Flashcards

6 cards from real CLT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. Which culture medium is selective for gram-negative enteric bacteria and inhibits gram-positive organisms?

    Answer: MacConkey agar

    MacConkey agar contains bile salts and crystal violet that inhibit gram-positive bacteria, making it selective for gram-negative enteric organisms.

  2. A urine culture grows >100,000 CFU/mL of a single organism. How should this result be interpreted?

    Answer: Significant bacteriuria consistent with urinary tract infection

    A colony count of ≥100,000 CFU/mL (10^5) of a single organism in a clean-catch midstream urine specimen is the classic threshold for significant bacteriuria indicating a UTI.

  3. In the Gram stain procedure, what is the purpose of the decolorization step using acetone-alcohol?

    Answer: To remove the crystal violet-iodine complex from gram-negative cells

    Acetone-alcohol decolorizes gram-negative bacteria by dissolving their thin peptidoglycan layer and outer lipid membrane, releasing the crystal violet-iodine complex.

  4. Which organism is the most common causative agent of urinary tract infections in otherwise healthy women?

    Answer: Escherichia coli

    Escherichia coli accounts for approximately 80–85% of uncomplicated UTIs in women due to its ability to adhere to uroepithelial cells.

  5. What does a positive catalase test result (bubbling with hydrogen peroxide) indicate about a gram-positive coccus?

    Answer: It is a Staphylococcus species

    Staphylococci are catalase-positive, while Streptococci are catalase-negative; this is a key initial test to differentiate these two genera of gram-positive cocci.

  6. Which component of a routine urinalysis evaluates the kidney's ability to concentrate urine?

    Answer: Specific gravity

    Specific gravity (normal 1.003–1.030) measures urine concentration and reflects the kidney's ability to dilute or concentrate urine based on hydration status.