Unit 7 Flashcards
Mannitol Salt Agar is a medium that is both _______ and _______.
selective and differential
Medium that can be used to isolate organisms from the human body because it is enriched with compounds that support the growth of fastidious organisms is _______.
blood agar
Lysis in a biological context means:
A) The replication of cells.
B) The breakdown or destruction of cells.
C) The mutation within cellular DNA.
D) The growth of cells.
B) The breakdown or destruction of cells.
True or False:
TSA-blood agar can be used to assess lactose fermentation.
A) True
B) False
B) False (It’s used to assess hemolysis.)
CNA-blood agar selects for Gram(+) cocci-shaped species and uses _______ and _______ as selective agents.
colistin, nalidixic acid
Which body sites have the largest numbers of resident microbiota?
Fill in the blank: The largest numbers of resident microbiota are found in the __________, __________, __________, __________, and __________.
Throat, skin, large intestine, nose, and vagina.
Mannitol salt agar is selective for which type of bacteria?
A) Gram-negative
B) Gram-positive
C) Bacteria that ferment mannitol
D) B and C
D) B and C
Chocolate Agar gets its name from the color, not because it contains actual chocolate, but due to the presence of _______ sheep red blood cells.
lysed
True or False: Nalidixic acid is effective against both Gram-positive and Gram-negative bacteria.
A) True
B) False
B) False (It’s particularly effective against certain Gram-negative bacteria.)
Which way is the quickest method of isolating bacteria from a mixed culture?
Multiple choice: The quickest method of isolating bacteria from a mixed culture is:
A) Pour plating
B) Streak plating
C) Spread plating
D) Serial dilution
B) Streak plating
The _______ method is a technique used to isolate pure cultures by spreading bacteria over the agar surface to separate individual cells.
streak plate
Gamma hemolysis is characterized by:
A) Growth of bacteria without any lysis or digestion of red blood cells
B) Olive green colonies due to partial digestion of hemoglobin
C) A clear halo around the bacterial growth due to complete lysis of red blood cells
D) Blackening of the medium due to hydrogen sulfide production
A) Growth of bacteria without any lysis or digestion of red blood cells
True or False: If a bacterium produces a white to clear zone on CNA-blood agar, it is indicative of gamma hemolysis.
A) True
B) False
B) False (This is indicative of beta hemolysis.)
Identification of a bacterial species cannot be made on microscopic morphology alone because _______.
many microorganisms have a similar microscopic morphology
What is a characteristic of members of the resident microbiota?
A) They promote the growth of harmful bacteria.
B) They can compete with and limit the growth of harmful bacteria.
C) They have no impact on the growth of other bacteria.
D) They exclusively consist of harmful bacteria.
B) They can compete with and limit the growth of harmful bacteria.
Beta hemolysis is characterized by:
A) Partial lysis of red blood cells without clearing the medium
B) No lysis of red blood cells and no change in the medium
C) Complete lysis of red blood cells resulting in a clear halo around the bacterial growth
D) Greenish discoloration of the medium around the bacterial growth
C) Complete lysis of red blood cells resulting in a clear halo around the bacterial growth
_______ is added to MacConkey agar to differentiate lactose fermenters from non-fermenters.
pH indicator
Colistin is an antibiotic that targets:
A) DNA replication in all cells.
B) Cell walls in fungi.
C) Cell membranes of Gram-negative bacteria.
D) Metabolic pathways in viruses.
C) Cell membranes of Gram-negative bacteria.
In gamma hemolysis, the bacteria grow on the medium showing a _______ coloration on the surface of the red medium, indicating no production of hemolysins.
whitish
In beta hemolysis, the complete lysis of red blood cells results in a _______ halo around the bacterial colony, indicating a high level of hemolysins and potential pathogenicity.
clear
What does MacConkey agar select against?
A) Gram-negative bacteria
B) Gram-positive bacteria
C) Fastidious bacteria
D) Non-fastidious bacteria
B) Gram-positive bacteria
Nalidixic acid selectively blocks _______ in susceptible bacteria, hindering their replication.
DNA replication
Are most bacteria heterotrophs?
True/False: Most bacteria are heterotrophs.
A) True
B) False
A) True
What causes impetigo?
A) Only Streptococcus pyogenes.
B) Only Staphylococcus aureus.
C) Both Streptococcus pyogenes and Staphylococcus aureus.
D) Neither Streptococcus pyogenes nor Staphylococcus aureus.
C) Both Streptococcus pyogenes and Staphylococcus aureus.
MacConkey Agar selects against which type of organisms?
A) Gram-positive
B) Gram-negative
C) Non-lactose fermenters
D) Lactose fermenters
A) Gram-positive
When lactose is fermented on MacConkey Agar, the acid waste products change the pH indicator to a _______ color.
fuchsia
CNA-blood agar contains which two selective agents?
A) Lactose and sucrose
B) Crystal violet and bile salts
C) Colistin and nalidixic acid
D) Mannitol and salt
C) Colistin and nalidixic acid
Enterococcus faecalis is known for being one of the leading causes of _______.
hospital-acquired infections
True or False: MacConkey Agar can differentiate bacteria based on their ability to ferment lactose, with non-fermenters potentially being pathogens.
A) True
B) False
A) True
_______ agar is a type of supportive medium containing sheep blood cells where the RBCs have been lysed to support the growth of more fastidious bacteria.
Chocolate
Alpha hemolysis is characterized by:
A) No change in the color of the medium around the bacterial growth
B) Complete lysis of red blood cells and a clear halo around the colony
C) Partial digestion of hemoglobin in red blood cells, turning the medium olive green
D) Greenish discoloration due to the production of hydrogen sulfide
C) Partial digestion of hemoglobin in red blood cells, turning the medium olive green
The process of _______ can be caused by various factors, including toxins, immune responses, or mechanical damage.
lysis
Colistin disrupts the _______ of Gram-negative bacteria, leading to their death.
cell membranes
Which body sites are gram positive cocci predominant?
True/False: Gram-positive cocci are predominantly found in the skin, mouth, throat, and nose.
A) True
B) False
A) True
Hemolysis refers to:
A) The breakdown of hemoglobin only.
B) The lysis of white blood cells.
C) The breakdown of red blood cells.
D) The production of hemoglobin.
C) The breakdown of red blood cells.
True or False: TSA-blood medium can differentiate bacteria by their ability to hemolyze sheep red blood cells and is used to identify potential pathogens.
A) True
B) False
A) True
What does Chocolate Agar contain that supports the growth of fastidious bacteria?
A) Actual chocolate
B) Lysed sheep red blood cells
C) Live sheep red blood cells
D) Hemolysins
B) Lysed sheep red blood cells
Which gram-positive cocci are frequently found as resident microbiota in humans?
Multiple choice: The gram-positive cocci frequently found as resident microbiota in humans are:
A) Escherichia coli
B) Pseudomonas aeruginosa
C) Streptococcus, Staphylococcus, and Enterococcus.
D) Clostridium difficile
C) Streptococcus, Staphylococcus, and Enterococcus.
True or False: MacConkey’s agar is both selective and differential.
A) True
B) False
A) True
Streptococcus pyogenes causes bacterial pharyngitis, also known as _______.
strep throat
True or False: Gamma hemolysis indicates that bacteria do not produce hemolysins and are not considered pathogenic.
A) True
B) False
A) True
A spectrophotometer is used to _______.
measure culture turbidity to determine bacterial cell numbers
True or False: Lactose fermenters on MacConkey agar turn the medium a bright fuchsia color.
A) True
B) False
A) True
Blood agar is considered an _______ and _______ medium.
Enriched and differential
Reliable source of info regarding tests that can be used to identify a particular bacterial isolate is _______.
The Bergey’s Manual
The release of hemoglobin from red blood cells due to their destruction is known as _______.
hemolysis
On CNA-blood agar, Gram-positive cocci that can grow indicate they are resistant to _______ and _______.
colistin, nalidixic acid
In TSA-blood medium, bacteria that completely digest the blood, clearing the medium underneath, are exhibiting _______ hemolysis.
beta
Alpha-hemolysis is characterized by a “halo” or partial clearing around the bacteria in blood agar, while Beta-hemolysis shows a clear zone with blood completely digested. Gamma-hemolysis shows _______.
no change at all in the blood around the bacteria
Hemolysins are _______.
Toxins that can break down red blood cells
True or False: Chocolate Agar is named for its color and contains no actual chocolate; it’s supportive for fastidious species like Aggregatibacter aphrophilus.
A) True
B) False
A) True
Growth on mannitol salt agar indicating a pathogenic organism produces acid, making the agar _______.
yellow
Enterobius vermicularis are transmitted via the _______ route.
fecal-oral
Fastidious organisms are those that require _______.
unusual or complex nutrient mixtures to grow
Which strain of E. coli bacteria can cause severe gastrointestinal illness and/or hemolytic uremic syndrome?
EHEC
Which media is used to isolate and differentiate enteric bacteria based on lactose fermentation?
A) Blood agar
B) MacConkey agar
C) Mannitol salt agar
D) Chocolate agar
B) MacConkey agar
True or False: If the colonies on MacConkey Agar are pink, it indicates lactose fermentation and the bacteria are likely non-pathogenic coliforms.
A) True
B) False
A) True
True or False: CNA-blood agar uses antibiotics to inhibit the growth of Gram-negative bacteria, making it selective for Gram-positive organisms.
A) True
B) False
A) True
Before attempting to identify an unknown bacterial species, the organism must be isolated in _______.
a pure culture
The Gram stain is an example of a test that can be used to determine the _________ characteristics of a bacterium.
morphological
What type of hemolysis is characterized by complete digestion of the blood under the bacterial growth on CNA-blood agar?
A) Alpha hemolysis
B) Beta hemolysis
C) Gamma hemolysis
D) Delta hemolysis
B) Beta hemolysis
True or False: In alpha hemolysis, the bacteria produce some hemolysins and the species is likely a pathogen, indicated by olive green colonies or halos.
A) True
B) False
A) True
TSA-blood medium differentiates bacteria based on what enzyme production?
A) Lactase
B) Hemolysin
C) Catalase
D) Oxidase
B) Hemolysin
Which infections are frequently caused by Staphylococcus and Streptococcus species?
Select all that apply:
A) Abscess
B) Pneumonia
C) Endocarditis
D) Urinary tract infections
E) Common cold
A) Abscess
B) Pneumonia
C) Endocarditis
D) Urinary tract infections
True or False: Beta hemolysis indicates that the bacteria produce a high level of hemolysins and are likely pathogenic, resulting in the complete removal of the red color from the medium underneath the bacterial growth.
A) True
B) False
A) True
Blood agar is considered a(n) _______ medium because it can differentiate bacteria based on hemolytic patterns.
A) Supportive
B) Selective
C) Differential
D) Enrichment
C) Differential
True or False: Hemolysis is exclusively a pathological condition and cannot occur naturally.
A) True
B) False
B) False (Hemolysis can be both a natural and pathological process.)
Nalidixic acid is an antibacterial that inhibits:
A) Protein synthesis in eukaryotic cells.
B) Cell wall synthesis in Gram-positive bacteria.
C) DNA gyrase in susceptible bacteria.
D) Membrane function in archaea.
C) DNA gyrase in susceptible bacteria.
A flowchart that can be used to identify an organism by making a series of choices until you arrive at one possibility is called a _______.
dichotomous key
The differential agent in TSA-blood allows the growth of most bacteria and distinguishes species based on their ability to produce the enzyme _______.
hemolysin
True or False: The streak plate method can be used with both selective and differential media.
A) True
B) False
A) True
What is the role of crystal violet and bile salts in MacConkey Agar?
A) Support growth of Gram-negative bacteria
B) Inhibit growth of Gram-positive bacteria
C) Differentiate lactose fermenters
D) Act as a pH indicator
B) Inhibit growth of Gram-positive bacteria
True or False: CNA-blood agar uses colistin and nalidixic acid to selectively inhibit the growth of Gram-negative bacteria.
A) True
B) False
A) True
Chocolate agar is heated to lyse red blood cells, making it enriched for the growth of _______ bacteria.
fastidious
What is the primary purpose of supportive media in microbiology?
A) Inhibit the growth of certain bacteria
B) Support the growth of more fastidious bacteria
C) Differentiate between bacterial species
D) Select for the growth of Gram-negative bacteria
B) Support the growth of more fastidious bacteria
Which of the following is an example of a differential medium?
A) T-soy agar
B) TSA-blood
C) MacConkey’s agar
D) Both B and C
D) Both B and C
MacConkey Agar contains a pH indicator called _______ which turns fuchsia if the pH is acidic.
neutral red
Inflammatory disease that can be caused by strep throat is _______.
Rheumatic fever
CNA-blood agar differentiates bacteria based on their ability to produce the enzyme _______.
hemolysin
Alpha hemolysis results in the reduction of red hemoglobin to _______ methemoglobin, leading to olive green colonies and sometimes an olive green halo around and under the colonies.
green
Are streptococci pink or purple after the Gram stain?
True/False: Streptococci are purple after the Gram stain.
A) True
B) False
A) True
True or False: All differential media are also selective media.
A) True
B) False
B) False (Differential media can differentiate between organisms based on certain biochemical characteristics, but not all are designed to selectively inhibit or promote the growth of specific groups of microbes.)
