Question 1

Which of the following statements correctly distinguishes between Gram-positive and Gram-negative bacteria in terms of their cell wall structure?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer with teichoic acids, while Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane containing lipopolysaccharide.

Question 2

Which of the following best describes the function of bacterial endospores?

Accepted Answer

They enable bacteria to survive harsh environmental conditions such as heat, desiccation, and chemicals.

Question 3

A patient presents with a rapidly progressing skin infection diagnosed as necrotizing fasciitis. Which bacterium is most commonly responsible, and which enzyme does it produce to facilitate tissue invasion?

Accepted Answer

Streptococcus pyogenes; hyaluronidase

Question 4

Which of the following is a correct application of binomial nomenclature?

Accepted Answer

Escherichia coli

Question 5

During a Gram stain, which chemical acts as the mordant, and what is its role?

Accepted Answer

Iodine; it forms a complex with crystal violet to fix the dye in Gram-positive cells.

Question 6

Which of the following best explains why Mycobacterium tuberculosis must be stained using the acid-fast stain rather than the Gram stain?

Accepted Answer

Its cell wall contains mycolic acids that prevent uptake of the Gram stain.

Question 7

A laboratory technician observes a bacterial sample under a microscope using a 40x objective lens and a 10x ocular lens. What is the total magnification?

Accepted Answer

$$40 	imes 10 = 400$$

Question 8

Which of the following is a cardinal sign of inflammation and its physiological basis?

Accepted Answer

Heat, due to increased blood flow to the affected area

Question 9

Which of the following best describes the difference between incidence and prevalence in epidemiology?

Accepted Answer

Incidence is the number of new cases over a period; prevalence is the total number of cases at a given time.

Question 10

Which of the following is a function of the complement system that involves the membrane attack complex (MAC)?

Accepted Answer

Direct lysis of microbial cells by forming pores in their membranes

Question 11

A patient is diagnosed with a urinary tract infection (UTI). Which bacterium is most commonly responsible, and what is one of its key virulence factors?

Accepted Answer

Escherichia coli; fimbriae for attachment to uroepithelial cells

Question 12

Which of the following statements about adaptive immunity is correct?

Accepted Answer

B lymphocytes mediate humoral immunity by producing antibodies, while T lymphocytes mediate cell-mediated immunity.

Question 13

Which of the following best describes the mechanism of action of penicillin?

Accepted Answer

It disrupts the synthesis of peptidoglycan, weakening the bacterial cell wall.

Question 14

Which of the following is a property of an attenuated vaccine?

Accepted Answer

It contains live, weakened pathogens that can replicate in the body.

Question 15

A patient is infected with a virus that acquires its envelope from the host cell membrane. How does this virus typically exit the host cell?

Accepted Answer

By budding from the host cell membrane

Question 16

Which of the following best explains why boiling is not always effective at sterilizing medical instruments?

Accepted Answer

Boiling does not destroy bacterial endospores, which are highly resistant.

Question 17

Which of the following is a correct statement about the difference between an endotoxin and an exotoxin?

Accepted Answer

Exotoxins are secreted proteins, while endotoxins are lipopolysaccharides found in the outer membrane of Gram-negative bacteria.

Question 18

A patient with a history of recent antibiotic use develops severe diarrhea. Laboratory tests reveal the presence of endospores in the stool. Which bacterium is most likely responsible, and what is a recommended treatment for severe cases?

Accepted Answer

Clostridium difficile; fecal microbiota transplantation

Question 19

Which of the following best describes the function of lysozyme and where it is commonly found?

Accepted Answer

It breaks down bacterial cell walls by hydrolyzing peptidoglycan and is found in tears and saliva.

Question 20

Which of the following best explains why herd immunity is important in controlling infectious diseases?

Accepted Answer

It reduces the spread of disease by decreasing the number of susceptible hosts, protecting those who cannot be vaccinated.

Comprehensive Study Guide for General Microbiology (BIO 240)

Study Guide - Practice Questions

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