Three major groups of parasitic worms:
Trematodes (flukes), Cestodes (tapeworms), & Nematodes (round worms)
What kinds of bacteria are typically found on the skin?
Micrococcus and Staphylococcus
What is MSA? How is selective or differential?
Mannitol Salt Agar. It is selective because organisms that grow best in high salt concentrations grow here. It is differential for different species of Staphylococcus.
What is MSA made of?
Contains mannitol, 7.5% NaCl, and phenol red.
Which organism will turn MSA yellow?
Staphylococcus aureus. A coagulase test is used to confirm this organism.
What organisms will turn the MSA red?
Staphylococcus epidermis and other Staphylococcus species can turn it red or pink. Micrococcus may also turn it red or pink.
What is a coagulase test?
Looks for the ability of the organisms to produce the enzyme coagulase. This enzyme will form a coagulation of the blood around it, hiding it from host defenses.
Which organism commonly produced coagulase?
Staphylococcus aureus, because it is used to hide from host defenses.
What is a blood agar?
Medium with sheep's blood in it. It a differential medium that is used to tell apart bacteria that produce exotoxins called hemolysins which destroy red blood cells and hemoglobin.
Describe Beta Hemolysis.
complete lysis of blood cells (digestion also) and complete destruction of hemoglobin. Blood agar looks clear (like regular TSA)
Describe Alpha Hemolysis.
incomplete lysis of blood cells. Able to see little pieces of blood cells. Hemoglobin turns into methemoglobin which looks muddy green.
Describe Gamma Hemolysis.
No hemolysis.
What genus of bacteria is found in high numbers in the mouth's of people?
Lactobacillus & other oral streptococci. Usually catalase positive.
How do these bacteria cause tooth-decay?
Lactobacillus produce acid as they ferment glucose. The acid they produce errodes teeth.
What are capnophiles?
They are a type of bacteria that grow in high CO2 levels. We grow them in candle jars because in this jar, the CO2 is increased to 4%
What is a candle jar?
A candle jar is a sealed jar with a lit candle in it. It lowers the oxygen level from 20% (normal air) to 8%. This is a good condition for microaerophiles to grow in. It also increases the carbon dioxide level to 4%, which is good for capnophiles.
What is Snyder's agar?
medium formulated to favor the growth of oral bacteria because it has a low pH (4.8). It tells us if bacteria that cause tooth decay (Lactobacillus) are present. Yellow after 24 hours indicates a high susceptibility to dental cavities. Yellow after 48 hou
Describe MacConkey agar.
Used to differentiate members of the Enterobacteriaceae family. It inhibits Gram positive bacteria (selective medium) and lactose fermenters turn it red/pink (differential)
Describe SF broth.
Selective for Enterococcus bacteria. It contains sodium azide which inhibits the electron transport chain. Acid pH (brown/yellow) indicates Enterococcus growth.
Describe EMB agar.
Inhibits Gram positive bacteria. Used for the isolation of fecal coliforms. Lactose fermenters turn the agar either dark purple or black with metallic green (for high acid production, usually E.coli). Sucrose fermenters retain their normal color.
Describe Tomato Juice agar.
Selective for Lactcobacillus. Grown in anaerobic jar.
Describe TSI slant.
Differential medium because there are three different sugars, sucrose, lactose, and glucose. If it ferments glucose it will turn yellow on the bottom and red/pink on top because there is only a little bit of glucose in the medium and after the organism us
Which types of media are selective?
MacConkey agar, EMB agar, SF broth, and Tomato Juice agar. They are selective because they only allow certain bacteria to grow on them. MacConkey agar and EMB agar inhibit Gram-positive bacteria, SF broth indicates Enterococcus and Tomato Juice agar indic
Be able to interpret a TSI slant.
If the whole tube is yellow then it indicates fermentation of lactose and/or sucrose. If the tube is yellow at the bottom and red/pink on the top then it ferments glucose. If there is black in the tube then there was production of H2S.
What are coliform bacteria?
Coliform bacteria are bacteria that are E. coli or similar to E. coli. MacConkey agar help us identify them because this test is selective for Gram-negative bacteria differential for lactose fermenters. EMB is also selective for Gram-negative and lactose
Describe how enterotubes work.
You get the numbers from each section to make a genetic code then you use the code book to determine the organism. It only works for Enterics (bacteria that live in the GI tract).
Why do we use the "clean catch" to collect urine?
The clean catch technique was used to eliminate bacteria that isn't in the bladder or upper urethra (the external surfaces and lower urethra often have bacteria). We wanted the mid-stream sample because that's from the upper urethra and bladder and becaus
Many people had growth on the blood agar plate, but not on the MacConkey agar. Why?
MacConkey agar is selective for Gram-negative. Gram-negative and Gram-positive can grow on Blood Agar.
Why do we use MacConkey agar for this experiment?
We use MacConkey agar because it is selective for Gram-negative bacteria and differential for lactose fermenters such as E. coli.
How does the UriCheck paddle determine possible UTIs? What are the media found on each side of the paddle? How do these media help? Which organisms will grow on each side?
The UriCheck paddle determines possible UTIs because one side is EMB which tests for E. coli and bacteria that are similar to E. coli and the other side CLED which tests for fermentation of lactose. If there is growth on EMB then you can confirm that it i