Question 1

A biotechnology lab is preparing equipment for a sterile production process. Which of the following methods is classified as a physical method of sterilization?

Accepted Answer

Autoclaving at $121\ ^\circ\mathrm{C}$ for 15 minutes

Question 2

Which structure allows certain bacteria to survive exposure to heat, chemicals, and UV light, making them highly resistant to disinfectants?

Accepted Answer

Endospores

Question 3

Penicillin targets which part of the bacterial cell, and what is the consequence of this action?

Accepted Answer

The cell wall, causing cell lysis due to osmotic pressure

Question 4

Why is penicillin generally more effective against Gram-positive bacteria than Gram-negative bacteria?

Accepted Answer

Gram-positive bacteria have a thicker peptidoglycan layer that is more accessible to penicillin

Question 5

A patient develops a post-surgical infection with Gram-positive cocci in clusters that are resistant to methicillin. Which species is most likely responsible?

Accepted Answer

Staphylococcus aureus (MRSA)

Question 6

Which of the following best describes the mechanism by which MRSA becomes resistant to methicillin?

Accepted Answer

Alteration of penicillin-binding proteins (PBPs) so methicillin cannot bind

Question 7

Which of the following is NOT true about prions?

Accepted Answer

Prions contain nucleic acids (DNA or RNA)

Question 8

A biotechnologist uses UV radiation to sterilize a work surface. What is the primary mechanism by which UV radiation kills microbes?

Accepted Answer

Formation of thymine dimers in DNA, preventing replication

Question 9

Which of the following antimicrobial drugs acts by inhibiting DNA gyrase, thus blocking DNA replication?

Accepted Answer

Fluoroquinolone (e.g., ciprofloxacin)

Question 10

A 7-year-old boy develops bloody diarrhea and hemolytic uremic syndrome (HUS) after eating an undercooked hamburger. Which bacterial species is most likely responsible?

Accepted Answer

Escherichia coli O157:H7

Question 11

Which of the following statements about aseptic technique is correct?

Accepted Answer

Wearing gloves and sterilizing tools before use is considered aseptic technique

Question 12

Which of the following is a chemical method of microbial control?

Accepted Answer

70% ethanol

Question 13

Which of the following best explains why endospores are resistant to many disinfectants?

Accepted Answer

Endospores have a thick protein coat and dehydrated core

Question 14

Which of the following is the correct formula for calculating the decimal reduction time ($D$ value) in microbial control?

Accepted Answer

$D = \frac{t}{\log_{10}(N_0/N)}$

Question 15

Which of the following is a synthetic antimicrobial drug, made entirely in the laboratory and not based on a natural compound?

Accepted Answer

Ciprofloxacin

Question 16

A patient with a sexually transmitted infection (STI) presents with Gram-negative diplococci in discharge. Which organism is most likely responsible?

Accepted Answer

Neisseria gonorrhoeae

Question 17

Which of the following best describes the action of bacitracin on bacterial cells?

Accepted Answer

Blocks transport of NAG and NAM across the cytoplasmic membrane

Question 18

Which of the following is NOT a potential long-term complication of untreated Neisseria gonorrhoeae infection?

Accepted Answer

Hemolytic uremic syndrome

Question 19

Which of the following statements about viruses is NOT true?

Accepted Answer

Viruses can divide like living cells

Question 20

Which of the following best describes the lytic cycle of a bacteriophage?

Accepted Answer

Host cell bursts, releasing new virus particles

Microbiology Exam #3 Study Guide: Control of Microbial Growth, Antimicrobial Drugs, Infectious Agents, and Case Studies

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