PORTAGE LEARNING
16/May/2026 — 9:32 AM
Module 4 Exam - Requires Respondus LockDown Browser + Webcam
Due No due date Points 100 Questions 31 Time Limit 120 Minutes Requires Respondus LockDown Browser
Instructions
Please read the following before beginning the exam:
You must TYPE your work for calculations or give an explanation for short answer questions in order to receive credit.
You may only use the methods and explanations provided by this course for your answers. The use of a method or
explanation that was not taught in this course is a violation of the Academic Integrity Policy.
You MUST only use the exam resource bank that is provided within the exam.
Any equation or constant used on an exam that is not from the exam resource bank and is different from the method
taught in this course will be considered an outside source and a violation of the Academic Integrity Policy.
During module exams you may not use any outside source of information such as the module, problem sets, notes,
Internet, tutor, etc.
The only items you are allowed to have in front of you are your computer, 1-2 pieces of blank scratch paper, a
calculator (non-cell phone), and a pen/pencil.
Your desk should be free of all other items and clutter.
Attempt History
Attempt Time Score
LATEST
Question 1 pts
Resource Bank
Scientific Calculator
A clinical microbiologist receives a blood culture bottle flagged positive by the automated system. In your own words,
explain why obtaining a pure culture is essential before performing biochemical identification or antibiotic susceptibility
testing, and describe two consequences of attempting these tests on a mixed culture.
Answer: A pure culture ensures that all subsequent tests reflect the characteristics of a single species. Mixed cultures
yield ambiguous biochemical results because different organisms produce conflicting reactions. Antibiotic susceptibility
testing on mixed cultures may miss true pathogens entirely or report false resistance/susceptibility patterns, leading to
inappropriate antibiotic selection and treatment failure.
Correct!
Question 2 pts
, Resource Bank
Scientific Calculator
The streak plate method is used to __________ bacterial cells across the surface of an agar plate so that individual cells grow
into isolated colonies.
Answer: dilute (or spread / separate)
Correct!
Question 3 pts
Resource Bank
Scientific Calculator
Match the type of culture media to its primary purpose:
Media Type Primary Purpose
1. Selective media a) Distinguishes between different groups of bacteria based on metabolic differences
2. Differential media b) Provides additional nutrients for fastidious organisms
3. Enriched media c) Inhibits growth of unwanted organisms while allowing desired organisms to grow
4. General purpose media d) Supports growth of most non-fastidious organisms
Answer: 1-c, 2-a, 3-b, 4-d
Correct!
Question 4 pts
Resource Bank
Scientific Calculator
Which of the following best describes the function of Columbia CNA agar?
a) Selects for Gram-negative bacteria by inhibiting Gram-positive growth
b) Differentiates lactose-fermenting from non-lactose-fermenting Gram-negative bacteria
c) Selects for Gram-positive bacteria by suppressing Gram-negative growth with colistin and nalidixic acid
d) Identifies Staphylococcus aureus by mannitol fermentation
Correct!
Question 5 pts
Resource Bank
16/May/2026 — 9:32 AM
Module 4 Exam - Requires Respondus LockDown Browser + Webcam
Due No due date Points 100 Questions 31 Time Limit 120 Minutes Requires Respondus LockDown Browser
Instructions
Please read the following before beginning the exam:
You must TYPE your work for calculations or give an explanation for short answer questions in order to receive credit.
You may only use the methods and explanations provided by this course for your answers. The use of a method or
explanation that was not taught in this course is a violation of the Academic Integrity Policy.
You MUST only use the exam resource bank that is provided within the exam.
Any equation or constant used on an exam that is not from the exam resource bank and is different from the method
taught in this course will be considered an outside source and a violation of the Academic Integrity Policy.
During module exams you may not use any outside source of information such as the module, problem sets, notes,
Internet, tutor, etc.
The only items you are allowed to have in front of you are your computer, 1-2 pieces of blank scratch paper, a
calculator (non-cell phone), and a pen/pencil.
Your desk should be free of all other items and clutter.
Attempt History
Attempt Time Score
LATEST
Question 1 pts
Resource Bank
Scientific Calculator
A clinical microbiologist receives a blood culture bottle flagged positive by the automated system. In your own words,
explain why obtaining a pure culture is essential before performing biochemical identification or antibiotic susceptibility
testing, and describe two consequences of attempting these tests on a mixed culture.
Answer: A pure culture ensures that all subsequent tests reflect the characteristics of a single species. Mixed cultures
yield ambiguous biochemical results because different organisms produce conflicting reactions. Antibiotic susceptibility
testing on mixed cultures may miss true pathogens entirely or report false resistance/susceptibility patterns, leading to
inappropriate antibiotic selection and treatment failure.
Correct!
Question 2 pts
, Resource Bank
Scientific Calculator
The streak plate method is used to __________ bacterial cells across the surface of an agar plate so that individual cells grow
into isolated colonies.
Answer: dilute (or spread / separate)
Correct!
Question 3 pts
Resource Bank
Scientific Calculator
Match the type of culture media to its primary purpose:
Media Type Primary Purpose
1. Selective media a) Distinguishes between different groups of bacteria based on metabolic differences
2. Differential media b) Provides additional nutrients for fastidious organisms
3. Enriched media c) Inhibits growth of unwanted organisms while allowing desired organisms to grow
4. General purpose media d) Supports growth of most non-fastidious organisms
Answer: 1-c, 2-a, 3-b, 4-d
Correct!
Question 4 pts
Resource Bank
Scientific Calculator
Which of the following best describes the function of Columbia CNA agar?
a) Selects for Gram-negative bacteria by inhibiting Gram-positive growth
b) Differentiates lactose-fermenting from non-lactose-fermenting Gram-negative bacteria
c) Selects for Gram-positive bacteria by suppressing Gram-negative growth with colistin and nalidixic acid
d) Identifies Staphylococcus aureus by mannitol fermentation
Correct!
Question 5 pts
Resource Bank
