Quiz 3 Flashcards
What is the importance of bacterial plate counts?
We can use this to test the quality of food, milk, and water
Why are dilutions important for bacterial cultures?
because our original sample is too concentrated. In order to reduce concentration, we will dilute the specimen (aliquot) with a diluent.
What is the valid range for bacterial plate counts?
30-300
What is CFU?
Colony forming units: a unit used to estimate the number of viable bacteria in a sample.
What is a diluent?
the fluid we use to dilute a sample
What is an aliquot?
the smaller volume we obtain from the concentrated sample
What is dilution factor?
A ratio from the initial sample to the diluted sample
What is hypertonic?
When the outside concentration is greater than the inside (cell shrivels up because water leaves)
What is hypotonic?
When the outside concentration is less than the inside
cell swells up because water enters
What is isotonic?
When the outside concentration is equal to the inside concentration of the cell
what affects bacterial growth
- osmotic pressure
- oxygen
- pH
- temperature
what is a strict aerobe?
An organism that relies on oxygen to live and grow
What is a strict anaerobe?
An organism that cannot live with oxygen (it is toxic to them)
What is a facultative anaerobe?
An organism that can live with or without oxygen (doesn’t affect them)
What is an aerotolerant anaerobe?
An organism that does not need oxygen but can use it to grow
What is a microaerophile?
An organism that can grow with low oxygen levels and higher carbon dioxide
How does thioglycollate medium work?
This medium is a differntial media that allows us to detect qnd determine an organisms ability to use oxygen. We can add resazurin which is an agent that turns pink in the presence of oxygen
What are examples of strict aerobes?
Bacillus subtilis, Mycobacterium tuberculosis, Mycobacterium leprae.
What are examples of facultative anaerobes?
Staphylococcus, Corynebacterium, Klebsiella, and Bacillus anthracis
What is an example of aerotolerant aerobes?
Clostridium sporogenes.
What is an example of a strict anaerobe?
Clostridium perfringens
What is a soluble pigment?
A pigment that diffuses into the media/agar
What is an insoluble pigment?
A pigment that is only in the bacteria
Why is it important to perform other tests (besides gram stain)?
Because since bacteria can have similar morphology, we have to find a way to classify them
What is the material used for citrate?
simmons citrate slant
What is the citrate results?
+: green to blue
-: stays green
What is the material used for carbohydrate fermentation?
BCP broth tubes
What are the results for carbohydrate fermentation?
+: yellow
-: purple
What media do we use for H2S?
PIA stab
What is the results of H2S?
+: black
-: yellow
What media do we use for indole?
tryptone broth tube
What is the results for indole?
+: red ring
-: yellow ring
What is the media used for methyl red?
MRVP tubes
What is the results for methyl red?
+: red
-: yellow
What is the media for motility?
semi solid agar tubes
What is the results for motility?
+: if agar is red
-: if only stab is red
What is the media used for urease?
Urea slants
What is the results for urease?
+: bright pink
-: no color change
why do we need loose caps on media?
Because it maintains the environment under aerobic conditions
What is an antiseptic?
An agent that reduces the growth of bacteria and can be used on living people
What is a disinfectant?
An agent that kills bacteria and is used on inanimate objects
What is a bacteriostatic agent?
If an agent temporarily slows down microorganisms, it is a bacteriostatic agent
What is a bactericidal agent?
If an agent (disinfectant or antiseptic) kills microorganisms, it is a bactericidal agent.
What is the zone of inhibition?
the area around the antibiotic (if it was effective against the bacteria)
Why is antibiotic sensitivity testing used in medical microbiology?
We use this to make sure that we are choosing an appropriate antibiotic for the infection
How is the disk diffusion method is used to test the quality and spectrum of antibiotics?
By comparing the zone of inhibition, we will be able to determine the effectiveness of the antibiotic. The greater the ZOI, the more effective the antibiotic is
What is the minimum inhibition concentration (MIC)?
the minimum concentration of an antibiotic needed, that will visibly inhibit bacterial growth.
Why is it important to perform different tests when studying unknown organisms?
Performing the tests on bacteria will lead us to the identification of an organism which can lead to a diagnosis of a disease/infection
What did doctors believe Addie was infected with initially? What were her symptoms?
They thought she had MRSA or staph and her symptoms were hip pain, pneumonia, septic shock
Addie had a ‘community-acquired’ resistant staph (as opposed to hospital-acquired). How did Addy likely become infected initially?
Community-acquired staph means that she most likely obtained the infection by coming into contact with others.
They presume that she obtained the infection through a scab
What secondary infection did Addie acquire in the hospital? How did she acquire it?
Stenotrophonomas was acquired from the ECMO machine which basically helped function like lungs
It can live inside breathing tubes and it is a very resistant bacteria.
What does pan-resistant mean?
Resistant to everything
What have been the lasting effects of Addie’s infections?
She eventually received a lung transplant and she has to take a handful of pills every day. There is a constant worry about her obtaining another infection and has had bacterial pneumonia 5 times after her infection.
How was David Ricci injured in India?
He was dragged and ran over by a train, he was then rushed to a local hospital
Ricci was infected with CRE (carbapenem-resistant Enterobacteriaceae). What gene invokes this type of resistance?
NDM-1 is a resistance gene that can turn bacteria to “superbugs” and can be passed onto other bacteria.
Are bacteria with the NDM-1 gene found in the environment?
Yes, it was found in places where water and sanitation were poor, the spread of resistance can be spread.
If a spreading infection cannot be cured, what has to happen?
Since NDM1 was brought to the US, the person carrying the infection had to be quarantined so that it will not spread resistance to others.
