MLPAO Microbiology and Parasitology Fundamentals Flashcards
6 cards from real MLPAO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 MLPAO Microbiology and Parasitology Fundamentals flashcards as text
What is the CAMP test used to identify?
Answer: Group B Streptococcus (Streptococcus agalactiae)
The CAMP test identifies Group B Streptococcus (S. agalactiae) by demonstrating enhanced hemolysis in the shape of an arrowhead where the CAMP factor of GBS intersects with the beta-hemolysin of Staphylococcus aureus on a blood agar plate. GBS is a critical pathogen in neonatal sepsis and meningitis.
Which organism causes pseudomembranous colitis, and how is it typically diagnosed?
Answer: Clostridioides difficile; toxin detection (EIA or PCR for toxin genes)
Clostridioides difficile (formerly Clostridium difficile) causes antibiotic-associated pseudomembranous colitis through production of toxins A and B. Diagnosis involves detection of C. difficile toxin by enzyme immunoassay (EIA), PCR for toxin B gene (tcdB), or a multi-step algorithm combining GDH screening with toxin confirmation.
What is the purpose of an anaerobic culture and which specimen types should NOT be cultured anaerobically?
Answer: To isolate oxygen-sensitive bacteria; specimens from sites with normal anaerobic flora (stool, vaginal)
Anaerobic cultures isolate bacteria that cannot survive in oxygen. Specimens from sites with normal anaerobic flora (stool, vaginal, oral) should not be cultured anaerobically because normal flora will overgrow pathogens. Appropriate specimens include normally sterile body fluids, deep tissue, and aspirates from closed abscesses.
Which blood culture system is most commonly used in Canadian clinical laboratories?
Answer: Automated continuous-monitoring blood culture systems (BacT/ALERT or BACTEC)
Automated continuous-monitoring blood culture systems (such as bioMérieux BacT/ALERT and Becton Dickinson BACTEC) are the standard in Canadian laboratories. These systems continuously monitor bottles for CO2 production or pH changes indicating microbial growth, providing rapid detection (average 12-36 hours for common pathogens).
What is the indole test used for, and which organism is characteristically indole-positive?
Answer: Detecting tryptophan degradation; Escherichia coli
The indole test detects the ability of bacteria to produce indole from tryptophan via the enzyme tryptophanase. Escherichia coli is characteristically indole-positive, which helps differentiate it from other Enterobacterales. Indole is detected by adding Kovac's or Ehrlich's reagent, producing a red colour.
Which specimen processing step is critical for recovery of Mycobacterium tuberculosis from sputum?
Answer: Digestion and decontamination with NALC-NaOH
Sputum specimens for mycobacterial culture require digestion and decontamination with N-acetyl-L-cysteine (NALC) as a mucolytic agent and sodium hydroxide (NaOH) to kill contaminating bacteria. This step is critical because mycobacteria grow slowly (2-8 weeks) and would be overgrown by faster-growing normal flora.