Pre-Lab Quiz 10

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