Medical Microbiology Notes
The field of study in which medicine and microbiology intersect is known as medical microbiology.
Which of the following is a characteristic of members of the resident microbiota? Resident microbiota
can compete with and limit growth of harmful bacteria.
Which body sites normally have large numbers of resident microbiota? Vagina, skin, throat, large
intestine, nose.
Which of the following may provide opportunities for members of the resident microbiota to cause
disease? A break in the skin or mucous membrane barriers, antibiotic usage which changes the
balance of normal microbiota, poorly functioning immune system.
Which of the following are genera of gram-positive cocci frequently found as resident microbiota in
humans? Enterococcus, streptococcus, staphylococcus
Which of the following infections are frequently caused by Staphylococcus species as well as
Streptococcus species? Pneumonia, endocarditis, abscess, urinary tract infection.
In which body sites are gram positive cocci predominant members of the resident microbiota? Nose,
skin, mouth and throat
Impetigo, a type of inflammatory skin infection, is caused by staphylococcus aureus and streptococcus
pyogenes.
Before attempting to identify an unknown bacterial species, the organism must be isolated in a pure
culture.
Quickest way to isolate bacteria from a mixed culture? Streak Plating
A specific example of a 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.
Which of the following is an example of a morphological characteristic that could be used in the bacterial
identification process? Cell shape
Gram positive cocci in chains = Streptococcus
Gram positive cocci in clusters = Staphylococcus
Gram positive cocci in pairs = Diplococcus
Identification of a bacterial species cannot be made on a microscopic morphology alone because many
microorganisms have a similar microscopic morphology.
The most reliable source of information regarding the tests that can be used to identify a particular
bacterial isolate and the expected results is Bergey’s Manual.
When choosing a biochemical test to run on an unknown, you should consider which of the following?
Choose an easy, rapid test that is standard for its main group of bacteria.
, A dichotomous key is a flowchart that can be used to identify an organism by making a series of choices
until you arrive at one possibility.
What test is most useful for distinguishing between streptococcus pyogenes and streptococcus
pneumoniae? Hemolysis on blood agar.
Which of the following types of media might be particularly helpful in the isolation of a bacterial species
from a mixed bacterial culture? Selective, differential
What type of medium is enriched with a complex organic substance, allowing for the growth of
fastidious organisms from the human body? Blood agar.
The Gram stain is an example of a test that can be used to determine the morphological characteristics
of a bacterium.
What correctly describes the streptococci? Purple after gram stain, cells arranged in chains, spherical
cells
How do you determine the species of an unknown bacterium? You use standard tests and pre-existing
knowledge to classify the bacterium.
FALSE: The Same tests are used on streptococci and staphylococci to determine the exact species
identity of an unknown gram-positive coccus.
Circle around it =
sensitive No circle =
resistant Triangle = Camp
positive
No triangle = Camp
negative Square looking =
gamma
U looking = beta
Which biochemical tests involve streaking bacteria onto a plate, applying a small disc, and after
incubation, examining for a zone of inhibited growth? Novobiocin sensitivity, optochin sensitivity,
bacitracin sensitivity.
Which biochemical test requires rabbit plasma as a reagent and its results are determined by
observation of thickening of the medium? Coagulate test
Which biochemical tests are used fot the identification of species within the staphylococcus genus?
Mannitol fermentation, coagulate test, novobiocin susceptibility, catalase test
Staphylococcus aureus = coagulase positive
Streptococcus pyogenes = beta hemolytic, bacitracin sensitive
Streptococcus pneumoniae = alpha-hemolytic, optochin sensitive
Staphylococcus saprophyticus = novobiocin resistant
The field of study in which medicine and microbiology intersect is known as medical microbiology.
Which of the following is a characteristic of members of the resident microbiota? Resident microbiota
can compete with and limit growth of harmful bacteria.
Which body sites normally have large numbers of resident microbiota? Vagina, skin, throat, large
intestine, nose.
Which of the following may provide opportunities for members of the resident microbiota to cause
disease? A break in the skin or mucous membrane barriers, antibiotic usage which changes the
balance of normal microbiota, poorly functioning immune system.
Which of the following are genera of gram-positive cocci frequently found as resident microbiota in
humans? Enterococcus, streptococcus, staphylococcus
Which of the following infections are frequently caused by Staphylococcus species as well as
Streptococcus species? Pneumonia, endocarditis, abscess, urinary tract infection.
In which body sites are gram positive cocci predominant members of the resident microbiota? Nose,
skin, mouth and throat
Impetigo, a type of inflammatory skin infection, is caused by staphylococcus aureus and streptococcus
pyogenes.
Before attempting to identify an unknown bacterial species, the organism must be isolated in a pure
culture.
Quickest way to isolate bacteria from a mixed culture? Streak Plating
A specific example of a 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.
Which of the following is an example of a morphological characteristic that could be used in the bacterial
identification process? Cell shape
Gram positive cocci in chains = Streptococcus
Gram positive cocci in clusters = Staphylococcus
Gram positive cocci in pairs = Diplococcus
Identification of a bacterial species cannot be made on a microscopic morphology alone because many
microorganisms have a similar microscopic morphology.
The most reliable source of information regarding the tests that can be used to identify a particular
bacterial isolate and the expected results is Bergey’s Manual.
When choosing a biochemical test to run on an unknown, you should consider which of the following?
Choose an easy, rapid test that is standard for its main group of bacteria.
, A dichotomous key is a flowchart that can be used to identify an organism by making a series of choices
until you arrive at one possibility.
What test is most useful for distinguishing between streptococcus pyogenes and streptococcus
pneumoniae? Hemolysis on blood agar.
Which of the following types of media might be particularly helpful in the isolation of a bacterial species
from a mixed bacterial culture? Selective, differential
What type of medium is enriched with a complex organic substance, allowing for the growth of
fastidious organisms from the human body? Blood agar.
The Gram stain is an example of a test that can be used to determine the morphological characteristics
of a bacterium.
What correctly describes the streptococci? Purple after gram stain, cells arranged in chains, spherical
cells
How do you determine the species of an unknown bacterium? You use standard tests and pre-existing
knowledge to classify the bacterium.
FALSE: The Same tests are used on streptococci and staphylococci to determine the exact species
identity of an unknown gram-positive coccus.
Circle around it =
sensitive No circle =
resistant Triangle = Camp
positive
No triangle = Camp
negative Square looking =
gamma
U looking = beta
Which biochemical tests involve streaking bacteria onto a plate, applying a small disc, and after
incubation, examining for a zone of inhibited growth? Novobiocin sensitivity, optochin sensitivity,
bacitracin sensitivity.
Which biochemical test requires rabbit plasma as a reagent and its results are determined by
observation of thickening of the medium? Coagulate test
Which biochemical tests are used fot the identification of species within the staphylococcus genus?
Mannitol fermentation, coagulate test, novobiocin susceptibility, catalase test
Staphylococcus aureus = coagulase positive
Streptococcus pyogenes = beta hemolytic, bacitracin sensitive
Streptococcus pneumoniae = alpha-hemolytic, optochin sensitive
Staphylococcus saprophyticus = novobiocin resistant
