Question 1

Which statement regarding the Gram stain is False?

Accepted Answer

A)  A Gram stain may give sufficient information to start appropriate antibiotic treatment-for example a Gram-positive diplococcus in sputum is likely to be Streptococcus pneumoniae. 
B)  A Gram stain can sometimes be used to make a diagnosis-for example a Gram-negative diplococcus in WBC from urethral discharge is Neisseria gonorrhoeae. 
C)  Gram staining can be used to differentiate intestinal normal microbiota from pathogens-for example differentiating E. coli from Salmonella enterica. 
D)  In most cases, Gram staining is not sufficient to identify an organism-for example, Gram-positive staphylococci on skin may be either S. aureus or S. epidermidis. 
E)  Medically important bacteria can seldom be identified by Gram staining alone-for example the throat may harbor Streptococcus pyogenes (pathogen) as well as Streptococcus species that are normal microbiota. 
A)  A Gram stain may give sufficient information to start appropriate antibiotic treatment-for example a Gram-positive diplococcus in sputum is likely to be Streptococcus pneumoniae. 
B)  A Gram stain can sometimes be used to make a diagnosis-for example a Gram-negative diplococcus in WBC from urethral discharge is Neisseria gonorrhoeae. 
C)  Gram staining can be used to differentiate intestinal normal microbiota from pathogens-for example differentiating E. coli from Salmonella enterica. 
D)  In most cases, Gram staining is not sufficient to identify an organism-for example, Gram-positive staphylococci on skin may be either S. aureus or S. epidermidis. 
E)  Medically important bacteria can seldom be identified by Gram staining alone-for example the throat may harbor Streptococcus pyogenes (pathogen) as well as Streptococcus species that are normal microbiota.

Question 2

Modern approaches to evolutionary taxonomy often involve

Accepted Answer

A)  biochemical differences. 
B)  comparison of DNA or RNA. 
C)  protein similarities. 
D)  lactose fermentation abilities. 
E)  staining techniques. 
A)  biochemical differences. 
B)  comparison of DNA or RNA. 
C)  protein similarities. 
D)  lactose fermentation abilities. 
E)  staining techniques.

Question 3

Streptococcus pyogenes can be easily distinguished microscopically from other Streptococcus species.

Accepted Answer

A) True 
 B)False

Question 4

A sample must contain many microorganisms in order for them to be seen any using microscopy techniques. Why is this so?

Accepted Answer

A)  The area on a microscope slide is very large compared to the relative size of microbes, and you take a very small amount of your sample to place on the slide surface. Therefore, you must have a large number of microbes initially in the culture to increase the chances that you'll be able to see bacteria on the slide. 
B)  Bacteria are very small. It is only possible to see them if there is a large biofilm of them on the slide. If you don't have a LOT of them, how are you going to see them? 
C)  This statement is misleading. Microscopy allows us to magnify a specimen to the point where we would be able to visualize even just a few microbes on the surface of the slide. Even if there are only a few microbes in a sample, we could easily visualize them with a microscope. 
D)  Microscopes only magnify objects on the slide. If you don't have a lot of microbes on the slide surface, you can't magnify the specimen enough to see them as individual cells. 
E)  When bacteria are placed on a slide, they automatically swarm together into one area of the slide, allowing them to be seen. If there are too few bacteria in the sample, they are unable to swarm effectively and thus cannot be seen, even with staining. 
A)  The area on a microscope slide is very large compared to the relative size of microbes, and you take a very small amount of your sample to place on the slide surface. Therefore, you must have a large number of microbes initially in the culture to increase the chances that you'll be able to see bacteria on the slide. 
B)  Bacteria are very small. It is only possible to see them if there is a large biofilm of them on the slide. If you don't have a LOT of them, how are you going to see them? 
C)  This statement is misleading. Microscopy allows us to magnify a specimen to the point where we would be able to visualize even just a few microbes on the surface of the slide. Even if there are only a few microbes in a sample, we could easily visualize them with a microscope. 
D)  Microscopes only magnify objects on the slide. If you don't have a lot of microbes on the slide surface, you can't magnify the specimen enough to see them as individual cells. 
E)  When bacteria are placed on a slide, they automatically swarm together into one area of the slide, allowing them to be seen. If there are too few bacteria in the sample, they are unable to swarm effectively and thus cannot be seen, even with staining.

Question 5

Organisms that grow very slowly, cannot be cultured, are present in very small numbers, or are mixed with a number of other bacteria may still be identified using

Accepted Answer

A)  Southern blotting. 
B)  replica plating. 
C)  PCR. 
D)  the Ames test. 
E)  positive selection. 
A)  Southern blotting. 
B)  replica plating. 
C)  PCR. 
D)  the Ames test. 
E)  positive selection.

Question 6

Media that change color as a result of the biochemical activity of growing bacteria

Accepted Answer

A)  usually contain a pH indicator. 
B)  usually contain blood. 
C)  usually require the addition of various reagents before the color is evident. 
D)  contain a colorless reagent that breaks down. 
E)  are always selective media. 
A)  usually contain a pH indicator. 
B)  usually contain blood. 
C)  usually require the addition of various reagents before the color is evident. 
D)  contain a colorless reagent that breaks down. 
E)  are always selective media.

Question 7

Which technique(s) is/are used to help identify and classify bacteria?

Accepted Answer

A)  Microscopic examination 
B)  Culture characteristics 
C)  Biochemical tests 
D)  Nucleic acid analysis 
E)  All of the choices are correct. 
A)  Microscopic examination 
B)  Culture characteristics 
C)  Biochemical tests 
D)  Nucleic acid analysis 
E)  All of the choices are correct.

Question 8

Your patient asks what other types of tests are available for identifying N. gonorrhoeae. You tell him that the organism is fastidious, oxidizes only glucose as a carbohydrate source, breaks down H₂O₂, exhibits cytochrome c oxidase activity, is resistant to the antibiotic colistin, and produces at least four different colony types. Based on this, which of the following would you NOT use for characterization of this pathogen?

Accepted Answer

A)  Colony morphology 
B)  Oxidase test 
C)  Ability to utilize different carbohydrates 
D)  Catalase test 
E)  Growth on selective medium 
A)  Colony morphology 
B)  Oxidase test 
C)  Ability to utilize different carbohydrates 
D)  Catalase test 
E)  Growth on selective medium

Question 9

Why might it be easier to identify the bacterium that caused pneumonia than one that caused a wound infection?

Accepted Answer

A)  There are very few microorganisms that can cause pneumonia, while there are many that can cause wound infections, including normal microbiota and a variety of environmental organisms. 
B)  Bacteria that cause pneumonia can be identified with few tests because the lungs have no normal microbiota. Many bacteria are normally found on the skin however; these may be in the wound, complicating identification. 
C)  We have much better tests for bacteria in the lungs than we do for bacteria on the skin which may be the causative agents of wounds infection. 
D)  The techniques of 16S rRNA sequencing are easier to perform on a sample taken from the lungs than a sample taken from a wound, because it is easier to get a sputum sample than it is a wound sample. 
E)  Very few people actually get pneumonia, so tests are quick and easy to carry out; on the other hand, many people get very serious wound infections, so the tests are more complicated. 
A)  There are very few microorganisms that can cause pneumonia, while there are many that can cause wound infections, including normal microbiota and a variety of environmental organisms. 
B)  Bacteria that cause pneumonia can be identified with few tests because the lungs have no normal microbiota. Many bacteria are normally found on the skin however; these may be in the wound, complicating identification. 
C)  We have much better tests for bacteria in the lungs than we do for bacteria on the skin which may be the causative agents of wounds infection. 
D)  The techniques of 16S rRNA sequencing are easier to perform on a sample taken from the lungs than a sample taken from a wound, because it is easier to get a sputum sample than it is a wound sample. 
E)  Very few people actually get pneumonia, so tests are quick and easy to carry out; on the other hand, many people get very serious wound infections, so the tests are more complicated.

Question 10

Wisconsin state health authorities alerted the CDC about an E. coli O157:H7 outbreak. Soon thereafter, officials from two other states reported that they also had cases of illness associated with this pathogen. Within days, the CDC determined that the E. coli strains from all three states were the same, and the likely source of the outbreak was a particular brand of pre-packaged fresh spinach. The CDC then issued a press release advising people not to eat bagged fresh spinach. 
-You have identified the causative organism of the outbreak as E. coli. In an effort to characterize the strain of the organism involved, you do different tests. The results are as follows:
Gram stain-Gram-negative rods
Oxidase test-negative
Lactose fermentation-positive
Serological testing-O157:H7
Colony morphology-smooth
Creamy colonies
RFLPs-E. coli O157:H7
Antibiogram-resistant to ampicillin.
Which test(s) confirm the identity of the organism at the strain level?

Accepted Answer

A)  Gram stain AND antibiogram 
B)  Serological testing AND colony morphology 
C)  RFLPs AND serological testing 
D)  Oxidase test AND RFLPs 
E)  Lactose fermentation AND oxidase test 
A)  Gram stain AND antibiogram 
B)  Serological testing AND colony morphology 
C)  RFLPs AND serological testing 
D)  Oxidase test AND RFLPs 
E)  Lactose fermentation AND oxidase test

Question 11

Please select the False statement regarding taxonomic hierarchy.

Accepted Answer

A)  A species is a group of closely related strains or an organism; it is the basic unit of taxonomy. 
B)  A genus is a collection of related species. 
C)  A phylum is a collection of similar classes; it may also be called a division. 
D)  A domain is a collection of similar kingdoms; there are three domains: Bacteria, Archaea, and Animalia. 
E)  A kingdom is a group of several phyla or divisions; a collection of similar kingdoms makes up a domain. 
A)  A species is a group of closely related strains or an organism; it is the basic unit of taxonomy. 
B)  A genus is a collection of related species. 
C)  A phylum is a collection of similar classes; it may also be called a division. 
D)  A domain is a collection of similar kingdoms; there are three domains: Bacteria, Archaea, and Animalia. 
E)  A kingdom is a group of several phyla or divisions; a collection of similar kingdoms makes up a domain.

Question 12

E. coli 0157:H7 produces clear colonies on MacConkey agar, while common strains of the organism produce pink colonies on this medium. The organism stains pink in the Gram stain. Select the True statement, given this information.

Accepted Answer

A)  E. coli 0157:H7 is Gram-positive AND is a normal constituent of the intestinal tract. 
B)  E. coli 0157:H7 is a normal constituent of the intestinal tract AND does not ferment sorbitol. 
C)  E. coli 0157:H7 does not ferment sorbitol AND is Gram negative. 
D)  E. coli 0157:H7 does not ferment sorbitol AND is Gram-positive. 
E)  E. coli 0157:H7 produces a toxin AND is a normal constituent of the intestinal tract. 
A)  E. coli 0157:H7 is Gram-positive AND is a normal constituent of the intestinal tract. 
B)  E. coli 0157:H7 is a normal constituent of the intestinal tract AND does not ferment sorbitol. 
C)  E. coli 0157:H7 does not ferment sorbitol AND is Gram negative. 
D)  E. coli 0157:H7 does not ferment sorbitol AND is Gram-positive. 
E)  E. coli 0157:H7 produces a toxin AND is a normal constituent of the intestinal tract.

Question 13

Mycobacterium tuberculosis is one of the few species of bacteria that

Accepted Answer

A)  is encapsulated. 
B)  is acid-fast. 
C)  stains Gram-negative. 
D)  stains Gram-positive. 
E)  lacks a peptidoglycan cell wall. 
A)  is encapsulated. 
B)  is acid-fast. 
C)  stains Gram-negative. 
D)  stains Gram-positive. 
E)  lacks a peptidoglycan cell wall.

Question 14

To study the phylogeny of eukaryotes,

Accepted Answer

A)  16S rRNA is used. 
B)  18S rRNA is used. 
C)  40S rRNA is used. 
D)  80S rRNA is used. 
E)  70S rRNA is used. 
A)  16S rRNA is used. 
B)  18S rRNA is used. 
C)  40S rRNA is used. 
D)  80S rRNA is used. 
E)  70S rRNA is used.

Question 15

An early attempt by Cohn at bacterial classification grouped bacteria according to their

Accepted Answer

A)  biochemistry. 
B)  Gram stain. 
C)  shape. 
D)  arrangement. 
E)  size. 
A)  biochemistry. 
B)  Gram stain. 
C)  shape. 
D)  arrangement. 
E)  size.

Question 16

Please select the False statement regarding phenotypic approaches to identifying microorganisms.

Accepted Answer

A)  Most of these methods do not require sophisticated equipment and can easily be done anywhere in the world. 
B)  Size, shape, and staining characteristics can give suggestive information about the identity of an organism but additional testing is usually required. 
C)  MALDI-TOF MS separates and sorts an organism's carbohydrates by mass, generating a profile that provides a fast way to identify an organism grown in culture. 
D)  A set of biochemical tests that examine the metabolic capabilities of a microorganism can be used to identify it. 
E)  Colony morphology can give initial clues to the identity of an organism but additional testing is required for absolute identification. 
A)  Most of these methods do not require sophisticated equipment and can easily be done anywhere in the world. 
B)  Size, shape, and staining characteristics can give suggestive information about the identity of an organism but additional testing is usually required. 
C)  MALDI-TOF MS separates and sorts an organism's carbohydrates by mass, generating a profile that provides a fast way to identify an organism grown in culture. 
D)  A set of biochemical tests that examine the metabolic capabilities of a microorganism can be used to identify it. 
E)  Colony morphology can give initial clues to the identity of an organism but additional testing is required for absolute identification.

Question 17

If each of two bacteria have a GC content of 50%, they are both definitely closely related.

Accepted Answer

A) True 
 B)False

Question 18

Disagreements between conclusions obtained from rRNA data and other techniques may be explained by

Accepted Answer

A)  horizontal DNA transfer. 
B)  vertical DNA transfer. 
C)  the difference in translation machinery. 
D)  vertical RNA transfer. 
E)  differences in post-replication modification. 
A)  horizontal DNA transfer. 
B)  vertical DNA transfer. 
C)  the difference in translation machinery. 
D)  vertical RNA transfer. 
E)  differences in post-replication modification.

Question 19

Very often clinically relevant information may be obtained by examining

Accepted Answer

A)  a wet mount. 
B)  the size and shape of the organism. 
C)  the sequence of proteins. 
D)  the transformation ability. 
E)  a wet mount AND the size and shape of the organism. 
A)  a wet mount. 
B)  the size and shape of the organism. 
C)  the sequence of proteins. 
D)  the transformation ability. 
E)  a wet mount AND the size and shape of the organism.

Question 20

Despite the fact that you are certain that your patient has gonorrhea based on the Gram stain results, it is essential to confirm your diagnosis by 16S rRNA sequencing.

Accepted Answer

A) True 
 B)False

Exam 10: Identifying and Classifying Microorganisms

Which statement regarding the Gram stain is False?

Modern approaches to evolutionary taxonomy often involve

Streptococcus pyogenes can be easily distinguished microscopically from other Streptococcus species.

A sample must contain many microorganisms in order for them to be seen any using microscopy techniques. Why is this so?

Organisms that grow very slowly, cannot be cultured, are present in very small numbers, or are mixed with a number of other bacteria may still be identified using

Media that change color as a result of the biochemical activity of growing bacteria

Which technique(s) is/are used to help identify and classify bacteria?

Why might it be easier to identify the bacterium that caused pneumonia than one that caused a wound infection?

Please select the False statement regarding taxonomic hierarchy.

E. coli 0157:H7 produces clear colonies on MacConkey agar, while common strains of the organism produce pink colonies on this medium. The organism stains pink in the Gram stain. Select the True statement, given this information.

Mycobacterium tuberculosis is one of the few species of bacteria that

To study the phylogeny of eukaryotes,

An early attempt by Cohn at bacterial classification grouped bacteria according to their

Please select the False statement regarding phenotypic approaches to identifying microorganisms.

If each of two bacteria have a GC content of 50%, they are both definitely closely related.

Disagreements between conclusions obtained from rRNA data and other techniques may be explained by

Very often clinically relevant information may be obtained by examining

Despite the fact that you are certain that your patient has gonorrhea based on the Gram stain results, it is essential to confirm your diagnosis by 16S rRNA sequencing.

Humans and the Microbial World

The Molecules of Life

Microscopy and Cell Structure

Dynamics of Microbial Growth

Control of Microbial Growth

Microbial Metabolism: Fueling Cell Growth

The Blueprint of Life, from DNA to Protein

Bacterial Genetics

Biotechnology

The Diversity of Bacteria and Archaea

The Eukaryotic Members of the Microbial World

Viruses, Viroids, and Prions

The Innate Immune Response

The Adaptive Immune Response

Host-Microbe Interactions

Immunological Disorders

Applications of Immune Responses

Epidemiology

Antimicrobial Medications

Respiratory System Infections

Skin Infections

Wound Infections

Digestive System Infections

Blood and Lymphatic Infections

Nervous System Infections

Genitourinary Tract Infections

Microbial Ecology

Environmental Microbiology: Treatment of Water, Wastes, and Polluted Habitats

Food Microbiology

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