Studied by 55 people
What is enriched media? Give examples
contains the nutrients required to support the growth of a wide variety of organisms; blood agar, mannitol salt agar
what is differential media? Give examples
contains compounds that allow groups of microorganism to be visually distinguished by the appearance of the colony or surrounding media; blood agar
what is selective media? Give examples
contain chemical substances that inhibit growth of one group or species of bacteria while encouraging another group or species to grow; mannitol salt agar
What kind of bacteria only grow on blood agar?
gram positive bacteria
Describe the characteristics of Staphylococci
gram positive spheres that are found in clusters.
Where are Staphylococci normally found on our bodies?
Commonly found on the skin and in the nose
Where is S. epidermidis normally found? Does it cause and diseases? If so, what?
present is the normal microflora of the body but are generally not pathogenic
Where is S. saprophyticus normally found? Does it cause any diseases? If so, what?
present in the normal microflora of the body but are generally not pathogenic
Where is S. aureus normally found? Does it cause any disease? If so, waht?
found in the environment and is also found in the nose and on the skin: can cause conditions as food poisoning, toxic shock, cellulitis, boils, and impetigo
hemolysins
a substance in the blood that destroys red blood cells and liberates hemoglobin
coagulase
a bacterial enzyme which brings about the coagulation of blood or plasma and is produced by disease-causing forms of staphylococcus
leukocidin
kill immune cells; a type of cytotoxin created by some types of bacteria; pore-forming toxin
hyaluronidase
an enzyme that breaks down a substance in the body called hyaluronic acid
staphylokinase
promotes the establishment of Staphylococcus aureus skin infections while decreasing disease severity
enterotoxin
harmful to the digestive system; causes symptoms such as cramps, nausea/vomiting, or diarrhea; enters stomach and intestines if you drink contaminated water
what staph species produce enterotoxin?
Staphylococcus aureus
What does Mannitol Salt Agar (MSA) select for? What ingredient is present in MSA that causes it to be selective?
selects for staph species and inhibits the growth of all others; 7.5% sodium chloride;
How is MSA differential? What does it differentiate between? What ingredients are present in MSA that cause it to be differential?
it can distinguish mannitol fermenters from non-fermenters; carbohydrate mannitol and phenol red
Why are “hospital” strains of Staph a particular problem?
because of the many sick people and weakened immune systems
List several members of the normal flora of the respiratory system
streptococci, staphylococci
Which parts of the respiratory system normally have microbes present
the upper respiratory tract
What defenses help protect the respiratory system from microbial invasion?
ciliated cells and mucous secreting cells
Describe the members of the genus Streptococcus
they are facultative anaerobic organisms or obligate anaerobes that are spherical or oviod and found in pairs or chains
What does fastidious mean?
microorganisms that are difficult to grow in the laboratory because they have complex or restricted nutritional and/or environmental requirements
What type of media do strep need to grow on?
blood agar
Substances that destroy red blood cells are called
hemolytic anemia
alpha hemolytic strep
partial destruction of red blood cells, with no use of the hemoglobin, characterized by the production of green color in the medium
beta hemolytic strep
complete destruction of red blood cells and hemoglobin molecules, characterized by complete clearance of the medium around a bacterial colony(medium will change from opaque to transparent)
gamma strep
a lack of hemolysis. Characterized by growth without a clearing or a discoloration of the media surrounding the bacterial colony
What groups do normal flora belong to?
eucaryotic fungi and protists
Do any of the normal flora cause disease? How?
many can produce disease in humans. Anaerobes in the intestinal tract are the primary agents of intra-abdominal abscesses and peritonitis
Which group causes disease? List several of the diseases that are caused by a member of this group.
streptococcus pneumoniae, staphylococcus aureus
A second way strep can be classified is by the type of carbohydrate antigens present in their cell wall. What is an antigen?
a toxin or foreign substance which induces an immune response in the body, especially the production of antibodies
How are these strep named?
by culture morphology and biochemical characteristics such as hemolytic reactions and a negative catalase reaction (serological grouping system called the Lancefield classification)
Human pathogens belong to which group?
virus, bacteria, prion or fungus
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