Lab 2 - Normal Flora and Pathogenicity Flashcards
What are the different bacteria that can be found on human skin?
Propionibacterium, Micrococcus, and Staphylococcus
How can the bacteria on our skin be classified?
Micrococcus = aerobes Staph = facultative Propioni = anaerobes
Where can the anaerobes in our skin be found? What are they called?
Propionibacterium
Hair canals
Forehead and armpit too????
What is RCAF?
Reinforced Clostridial Medium with Furoxone
Why did we use it in our lab?
Because we could use it so that only different species of Propionibacterium could grow on it.
How did RCAF prevent growth of some things?
The GasPak was used to create anaerobic conditions, thus inhibiting growth of micrococcus.
Furaxone allowed the inhibition of Staphylococcus.
Can you differentiate with what has grown on the RCAF plates?
Yes.
Different propionibacterium species can be differentiated by the colour of the colonies and texture.
Where can Staphylococcus aureus and epidermis be found?
On the skin and nasal passages
What kinds of pathogenic infections can they cause?
Boils, carbuncles, impetigo, meningitis, urinary tract infections, and food poisoning
What is a “staph carrier?”
A person who carries pathogenic staph normally.
What type of staphylococcus is more dangerous?
Staph epidermidis is less invasive. But if it does cause disease, lesions are usually restricted to small abcesses.
How can Staph aureus be distinguished from epidermidis?
Staph aureus ferments mannitol and produces coagulase
What does coagulase do?
It causes fibrin in the blood plasma to clot
What type of medium was used in this part of the lab?
Mannitol salt agar plate
How does MSA select for staph?
It contains a high concentration of salt, which is inhibitory to most other bacteria
How does MSA differentiate between Staphs?
Staph aureus can ferment mannitol, so it lowers the pH.
This causes the phenol red indicator to go from red to yellow.
Yellow colonies with yellow zones around them are staph aureus.
What is the Snyder test for?
Determining susceptibility to dental carries
What is dental carries?
Tooth decay/cavity, caused by bacterial infection that causes the demineralization of the enamel of teeth
What types of bacteria are thought to be the cause of dental caries?
Streptococcus mutans and several Lactobacillus species
How do bacteria cause dental carries?
They ferment dietary carbohydrates to produce lactic acid, which demineralizes tooth enamel.
What is the basis of the Snyder test?
See if there are any bacteria in your saliva that can produce lactic acid from glucose
How does the formation of plaques increase your likelihood of getting dental caries?
Plaque supplies an anaerobic environment for some bacteria, allowing them to ferment carbohydrates, thereby producing lactic acid.
What does the Snyder test agar contain?
2% glucose and bromcresol green indicator. pH is 4.8
What does the Snyder test select for?
Bacteria that can grow at a pH of 4.8 (ie. Lactobacilli and streptococci)
What are the results of Snyder test?
<72 hours = Low
