DIAGNOSTIC MICROBIOLOGY MAHON AND
LEHMAN KEY CONCEPTS AND PRACTICE
QUESTIONS
◉ What are the four major diagnostic methods in microbiology?
Answer: Morphological, biochemical, DNA, and immunological
diagnostic methods.
◉ What is the difference between direct and indirect fluorescent
antibody techniques?
Answer: Direct uses one antibody to bind the pathogen; indirect
uses two antibodies for stronger fluorescence.
◉ What is selective media?
Answer: Media that inhibit some organisms while allowing others to
grow, e.g., MacConkey Agar for Gram-negative bacteria.
◉ What is differential media?
Answer: Media that distinguish organisms based on their metabolic
processes, e.g., MacConkey Agar differentiates lactose fermenters.
◉ What is a dichotomous key?
, Answer: A tool that identifies organisms using a series of two-choice
questions.
◉ What is the purpose of rapid identification systems in clinical
laboratories?
Answer: To test many biochemical reactions simultaneously for
quick identification of microorganisms.
◉ What does PCR stand for and what is its purpose?
Answer: Polymerase Chain Reaction; it is used to amplify DNA for
identification of microorganisms.
◉ What is the function of FISH in diagnostics?
Answer: Fluorescent In Situ Hybridization; it is used to detect
specific nucleic acid sequences in microorganisms.
◉ How does a Gram stain differentiate bacteria?
Answer: It separates bacteria into Gram-positive (purple) and Gram-
negative (pink) based on cell wall structure.
◉ What are the common shapes of bacteria?
Answer: Cocci (spherical), bacilli (rod-shaped), and spirilla (spiral-
shaped).
LEHMAN KEY CONCEPTS AND PRACTICE
QUESTIONS
◉ What are the four major diagnostic methods in microbiology?
Answer: Morphological, biochemical, DNA, and immunological
diagnostic methods.
◉ What is the difference between direct and indirect fluorescent
antibody techniques?
Answer: Direct uses one antibody to bind the pathogen; indirect
uses two antibodies for stronger fluorescence.
◉ What is selective media?
Answer: Media that inhibit some organisms while allowing others to
grow, e.g., MacConkey Agar for Gram-negative bacteria.
◉ What is differential media?
Answer: Media that distinguish organisms based on their metabolic
processes, e.g., MacConkey Agar differentiates lactose fermenters.
◉ What is a dichotomous key?
, Answer: A tool that identifies organisms using a series of two-choice
questions.
◉ What is the purpose of rapid identification systems in clinical
laboratories?
Answer: To test many biochemical reactions simultaneously for
quick identification of microorganisms.
◉ What does PCR stand for and what is its purpose?
Answer: Polymerase Chain Reaction; it is used to amplify DNA for
identification of microorganisms.
◉ What is the function of FISH in diagnostics?
Answer: Fluorescent In Situ Hybridization; it is used to detect
specific nucleic acid sequences in microorganisms.
◉ How does a Gram stain differentiate bacteria?
Answer: It separates bacteria into Gram-positive (purple) and Gram-
negative (pink) based on cell wall structure.
◉ What are the common shapes of bacteria?
Answer: Cocci (spherical), bacilli (rod-shaped), and spirilla (spiral-
shaped).
