Question 1

What is the primary purpose of performing a White Blood Cell (WBC) count in a clinical laboratory setting?

Accepted Answer

To assess the number and types of white blood cells present, which helps diagnose infections, inflammation, and immune disorders

Question 2

Which term describes an increase in the number of neutrophils in the blood, often seen during bacterial infections?

Accepted Answer

Neutrophilic leukocytosis

Question 3

A patient’s blood smear shows an abnormally high number of lymphocytes. What is this condition called?

Accepted Answer

Lymphocytosis

Question 4

Refer to the first image provided. What laboratory technique is being set up in this image?

Accepted Answer

ELISA (Enzyme-Linked Immunosorbent Assay)

Question 5

Which of the following correctly lists the order of binding events in a positive well of an ELISA test?

Accepted Answer

Antigen binds to well, primary antibody binds to antigen, enzyme-linked secondary antibody binds to primary antibody, substrate is added and color change occurs

Question 6

Which ingredient in a PCR reaction is responsible for providing the building blocks for new DNA synthesis?

Accepted Answer

dNTPs (deoxynucleotide triphosphates)

Question 7

What is the correct sequence of steps in a standard PCR cycle?

Accepted Answer

Denaturation, annealing, extension

Question 8

Which of the following best defines the 'zone of inhibition' in antimicrobial susceptibility testing?

Accepted Answer

The clear region around an antibiotic disk where bacterial growth is prevented

Question 9

Refer to the second image provided. In a Kirby-Bauer test, which disk would you interpret as the most effective antibiotic against the bacteria?

Accepted Answer

Disk B, because it has the largest zone of inhibition

Question 10

A Mueller-Hinton agar plate is inoculated with E. coli and antibiotic disks are placed on the surface. After incubation, which result indicates resistance to an antibiotic?

Accepted Answer

Bacterial growth up to the edge of the disk

Question 11

Which of the following best describes a selective medium?

Accepted Answer

A medium that contains substances that inhibit the growth of some organisms while allowing others to grow

Question 12

What result would you expect from a positive catalase test?

Accepted Answer

Production of bubbles due to the breakdown of hydrogen peroxide

Question 13

Which of the following is a correct interpretation of a positive oxidase test?

Accepted Answer

The reagent turns purple within 10-30 seconds

Question 14

Which medium would you use to test for the ability of bacteria to hydrolyze starch, and what indicates a positive result?

Accepted Answer

Starch plate; a clear zone around the growth after adding iodine

Question 15

A bacterium is inoculated into a phenol red broth tube containing glucose. After incubation, the broth turns yellow and a gas bubble is present in the Durham tube. What does this indicate?

Accepted Answer

The bacterium fermented glucose and produced acid and gas

Question 16

Which test would you use to determine if a bacterium can reduce nitrate to nitrite, and what is a positive result?

Accepted Answer

Nitrate reduction broth; red color after adding reagents

Question 17

A patient’s blood test shows a total WBC count of 2,000 cells/μL (normal: 4,000–11,000 cells/μL). What is this condition called, and what might it indicate?

Accepted Answer

Leukopenia; possible viral infection or bone marrow suppression

Question 18

Which of the following best describes the function of primers in a PCR reaction?

Accepted Answer

They are short sequences that provide a starting point for DNA polymerase

Question 19

Which of the following is a differential medium and what does it differentiate?

Accepted Answer

MacConkey agar; differentiates lactose fermenters from non-fermenters

Question 20

A clinical laboratory uses PCR to detect the presence of a specific pathogen in a patient sample. What is the main advantage of using PCR in this scenario?

Accepted Answer

It allows for rapid and specific detection of even small amounts of pathogen DNA

Microbiology Lab Final Exam Review – Step-by-Step Guidance

Study Guide - Practice Questions

Study Guide - Flashcards