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Define contamination The action or state of making or being impure with unwanted/ accidental introduction of microbes.
Why do you think the enriched media plate was incubated at 37 C? Because the bacteria was collected on the human body, which is 37 C; so in order for that bacteria to keep growing, it needs to be kept at the same temperature as the body.
Hopefully you realize now that the microorganisms are in the air, dust, you, etc. What is one procedure that we follow at the beginning and end of each laboratory to cut down on the numbers of contaminating microbes? Washing your hands and benches.
What are some ways that the numbers of microorganisms might be decreased in a hospital setting? Changing the type of cleaner used to prevent unintentional selection of resistant bacteria, and making people wash their hands before entering into common areas, such as the food court.
What information should be included in labeling your lab work? Name, date, specimen, section # (and type of plate or test if applicable).
Describe two example tragedies that could result from inadequately labeled lab work in a hospital. You could grab the wrong plate and the plate could potentially be lost. Or you could not know what object/specimen that was swabbed/inoculated on that plate and you wouldn't be able to get any results from that plate.
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Results and Conclusions are two different things in science. Results refer to the actual data that you collect, like the number of colonies we obtained after washing our hands a certain way. Our Conclusions are the logical judgement or analysis we make from our Results, like "This way of handwashing is more effective than that one." What Conclusions can you make from your experiment? Did your experiment support your hypothesis or refute it? Hand sanitizer was more effective than hand washing with soap and water, which refutes our original hypothesis that using soap and water would be more effective.
this) to let the normal flora replenish itself. Swab your hand again, and inoculate the second half of the plate. Incubate for 24 hours, then compare the two halves. If there are any flora that is on the first half but isn't on the second half, is transient flora.
Define nosocomial infection and describe how handwashing can help decrease the probability of these infections. Nosocomial infections are infections that were acquired in the hospital (AKA the patient did not come into the hospital with this infection). Hand washing can decrease this because a lot of microbes inevitably collect on our hands because we use them for just about everything. So by washing your hands frequently, the potential infection-causing microbes can be removed/killed before spreading the microbes to another person (by shaking their hand for example).
The particular locations shown in Figure 2.1 usually contain the highest numbers of microorganisms. Why do you think that might be true? Fingernails- because dirt and microbes get stuck under them and are not often cleaned out. Under Jewelry- because it gets hot and moist (ideal growing conditions for bacteria) and doesn't often get cleaned under. Between Fingers- because it gets hot and moist (ideal growing conditions for bacteria). Wrist- because the wrist doesn't get cleaned as well or is neglected during hand washing.
What is the total magnification of the microscope when you are using the oil immersion lens? 10x (ocular) X 100x (objective) = 1000x
Simple microscope A microscope with a single magnifying lens.
Compound microscope A microscope with two magnifying lens: ocular and objective.
Parfocal When one lens is in focus, all the others are as well.
Refraction The fact or phenomenon of light, radio waves, etc., being deflected between one medium and another through a medium of varying density.
How often should you clean the lens of your microscope? Before you use it, a couple times while you're using it, and after you use it.
If you had a letter "p" right side up on a slide, draw below how the letter would appear through the microscope. d
Which objective lens should you use first for viewing a slide and why? The scanning lens because you can see the widest range of the slide. Since the microscope lenses are parfocal, you can change the lens to the next/higher magnification lens and it will be focused, but with a smaller visual range. So you need to start off on the lens with the widest range so you can find the organism faster/easier.
Which is more important in the quality of the a microscope lens, it's magnification or its resolving power? Why?
A microscopic single-celled organism that has neither a distinct nucleus with a membrane nor other specialized organelles.
Vibrio cholerae is a vibrantly motile bacterium and is the etiologic agent for cholera. What type of microscope would be most useful in observing the motility of this microbe? A darkfield microscope.
What type of microscope would be most helpful in studying the 3- D fine structure of the surface of microvilli from the intestine? A scanning electron microscope.
Pure culture A medium growing one, and only one, intended species of microorganism.
Transport medium Is used to transport microbes from one place to another and supports survival without allowing overgrowth.
Sterile Completely devoid of life.
Colony A cluster of identical cells on the surface of a medium derived from a single parent cell.
Aerosol A suspension or dispersion of fine particles (bacteria) in a gas.
Describe three medical procedures that demonstrate the two goals of aseptic technique. (e.g., When giving an injection, the
needle should be sterile to avoid infecting the patient. After the injection, the needle should be disposed of properly to avoid transmitting a patient's disease to others.)
When handling surgery equipment/tools, the equipment and tools need to be sterile (as well as the doctor's hands/gloves) to avoid infecting the patient. After the tools are used they should be properly cleaned/disposed of.
When inserting a catheter, the catheter and the doctor's hands/ gloves should be sterile to avoid infecting the patient. When it is removed the doctor's hands should be washed and the gloves and catheter should be properly disposed of to avoid infecting the patient or transmitting their disease.
When inserting an IV, the needle should be sterile to avoid infecting the patient and it should stay covered when it is in use. When it is removed, the needle should be properly disposed of to avoid transmission of the patient's disease to others.
Demonstrate your understanding of the term synthetic medium by briefly describing an experiment that would require this type of culture. If you were trying to learn about what type of sugars a new microbe needed to survive, you would use a synthetic medium. You would make a couple different types of synthetic mediums, each one with a different type of sugar, in order to see which one(s) the microbe needs to survive.
In the transfer technique procedure why is it important to cool the loop before obtaining an inoculation of bacteria? If the loop is too hot, it could burn and kill all of the bacteria and the transfer would not be successful, and it could cause aerosolization of the bacteria releasing it into the air where you could breathe it in and become infected.
lab, Walther Hesse, got the idea from his wife to use agar. From your own experience with gelatin (Jello), list two advantages agar has over gelatin for microbiological media.
Agar melts at above body temperature, whereas gelatin melts below body temp., so growing bacteria at body temp. would be impossible on gelatin.
Gelatin can be digested by microbes, whereas agar cannot.
List one purpose for the streak plate and two for the pour plate technique. Streak plate: to isolate colonies
Pour plate: to count bacteria by isolating colonies, and by creating a 'lawn' of bacteria
In the dilute pour plate for Micrococcus, what difference did you notice between colonies growing within the agar and those growing on the surface? The colonies on the surface seemed larger and wider/more flat, while the colonies within the agar seemed smaller and more spherical in shape.
Why are all the Petri plates incubated upside down (i.e., agar side up)? So the condensation on the lid doesn't fall into the agar and mess up the bacteria's growth.
Which species showed the fastest average generation time in our experiment? Serratia marcescens
Was our experimental hypothesis supported? Why or why not?
No, because the bacteria that had the quickest generation time was S. marcescens and not E. coli.
What can be done by health care workers to decrease the chance of cystitis during catheterization? They can insert the catheters using aseptic technique.
What does TNTC stand for? Too Numerous To Count
Write 1/100,000 in powers of ten. 10^-
Write 5,646,004 in scientific notation. 5.6 x 10^
Using scientific notation calculate how many bacteria per milliliter there would be in the sample Figure 8.4. Show your work. Number of CFU/( Volume plated (mL) * Total dilution plated)
36 CFU/(0.1mL * 10^-3) = 36 x 10^4 = 3.6 x 10^5 CFU/mL
Suppose a broth has 436 million bacteria per milliliter. A serial dilution is made using three bottles of 99 milliliters each. 1 mL is transferred from the sample to the first bottle; 1 mL is transferred from the first bottle to the second; and then 1 mL is transferred from the second bottle to the third. From the third bottle 0.1 mL is transferred to a pour plate. How many colonies would you expect to find on this plate? Bottle 1: 10^- Bottle 2: 10^- Bottle 3: 10^- Pour plate: 10^-
Strep Throat - streptococcus Vaginal Candidiasis - oval-shaped Cholera - vibrios (comma-shaped)
Based on the information you learned today, how could a person diagnose the disease thrush, an oral yeast infection? (i.e., How could you differentiate it from a bacterial infection?) Based on their size and shape, yeast is a Eukaryote, so it will be much larger in size compared to a bacterial infection.
Define mordant. It causes a stain to become more tightly bound to the cell.
In a Gram stain if a person used too little alcohol or none and all, what color would a Gram-negative bacterium like Escherichia coli turn out? Why? The crystal violet would stain the Gram-negative E. coli purple unless the alcohol was used because it rinses it off. If no alcohol is used, the Gram-negative would look like a Gram-positive because the purple color wasn't rinsed off.
What effect would an old culture have on the results of a Gram stain? Explain your answer in terms of the permeability theory. The permeability states that as the cell ages, some cells begin to die and their cell walls break down. The broken down cell wall is no longer able to prevent the alcohol from leaching out the crystal violet.
Make a pair of detailed drawings showing the differences and similarities between Gram-positive and Gram-negative cell walls. Gram Positive: Outside the cell
///////////\
//Peptidoglycan// ///////////\
Cell Membrane
Inside of the cell
Gram Negative: Outside of the cell
Cell Membrane
//Peptidoglycan//\
Cell Membrane
Mark the appropriate column in Table 10.1, to indicate whether Gram-positive or Gram-negative correspond to each of the characteristics or diseases. Sensitivity to Penicillin - Positive Sensitivity to Lysozyme - Positive Lipid A Endotoxin - Negative Gonorrhea - Negative Strep Throat - Positive Cholera - Negative Typhoid Fever - Negative Tetanus - Positive Diphtheria - Positive
How could you differentiate between bacterial pneumonia and viral pneumonia using the Gram stain? Viruses cannot be seen with a Gram stain. So if you perform a Gram stain and could see the bacteria, it would be bacterial
which uses UV light to treat skin conditions such as Psoriasis and eczema.
Define and diagram a thymine dimer. In a DNA molecule, the pyrimidine bases (such as thymine) can absorb the UV energy and form an abnormal bond with an adjacent pyrimidine (i.e., thymine to thymine bond).
G A T=T A G | | | | | | C T A A T C
When the bonds occur between two thymine, it's called a thymine dimer.
When you receive your copy of the tabulated class results, use this space to ionterpret those results. Compare the effectiveness of the various disinfectants and compare the resistance of the two species of bacteria. Lysol, Alcohol, Mouthwash, Bleach and 70% Alcohol were the best disinfectants, killing most bacteria in 30 seconds. Hydrogen Peroxide and Betadine were the least effective by still having growth at 3 minutes. In a majority of the results, E. coli died first meaning that B. megaterium was more resistant to the disinfectants.
List one virus and three genera of bacteria that are highly resistant troublesome forms. HIV Mycobacterium (M. tuberculosis) Staphylococcus (S. aureus - MRSA) Pseudomonas (Ps. aeruginosa)
Why is it important to clean fomites before disinfecting them? Washing/cleaning will remove 90-95% of pathogens present. The disinfectant will remove the rest, but not all disinfectants kill all pathogens/bacteria. This is why it is best to clan away as many pathogens as you can first.
Disinfectant Are chemical agents that kill vegetative, pathogenic microorganisms.
Sterilize Destruction or removal of all organisms from an object or from a particular environment.
Iodophor A complex iodine and a surfactant that releases free iodine in solution, used as antiseptic disinfectant.
Tincture of iodine Is an antiseptic; usually 2-7% elemental iodine, along with potassium iodine or sodium iodine, dissolved in a mixture of ethanol and water.
Bactericidal Kills bacteria (many possible mechanisms).
Fungistatic Capable of inhibiting the growth of fungi without killing them.
Were there differences in the sensitivities of the two bacteria in this exercise? If yes, how can you explain these differences? If not, why not?
What year was methicillin introduced to treat penicillin resistant Staphylococcus? 1960
How long did it take before MRSA (Methicillin Resistant Staphylococcus aureus) was reported? 2 years
The most dangerous MRSA is now resistant to every antimicrobial drug drug except vancomycin. In recent years in the cases of VRSA ( Vancomycin Resistant Staphylococcus aureus) have been reported. Describe how the process of natural selection applies to the increase in VRSA. The bacteria is only being exposed to one antibiotic (Vancomycin), so when the bacteria randomly gets a DNA mutation, it could make the bacteria survive better. This random mutation could become resistant to Vancomycin, so it will survive and produce more daughter cells that will also be resistant.
What recommendations would you use to prevent or at least postpone the development of VRSA? By being prudent when using Vancomycin, and not using it if possible. Reporting Vancomycin resistance promptly and immediately implementing appropriate infection-control measures to prevent person-to-person transmission of the resistant bacteria.
Is blood agar an enriched medium or a differential medium? Explain. It is enriched because it contains added nutrients to enhance the growth of particular bacteria, and it is differential because it can
differentiate between Streptococcus based on the reaction produced.
Is mannitol salt agar differential or selective medium? Explain. Selective because of the high salt concentration will favor the growth of some bacteria over others. It is differential because it will change colors if mannitol is fermented.
Do your results from the bile esculin agar and salt test support placing Enterococcus faecalis into group D? and into enterococci? Explain. Both the bile esculin agar and salt test were positive, meaning it is in group D and is streptococci, not enterococci. Group D can only grow on the bile esculin agar, and only streptococcus can grow in the salt test.
Define coagulase. Is an enzyme produced by S. aureus that will cause plasma to clot.
Name three potentially dangerous species of Streptococcus other than S. pyogenes and the diseases caused by them. Streptococcus Viridans - infective endocarditis Streptococcus pneumoniae - pneumonia Enterococcus faecalis - nosocomial infections
Explain how dietary sucrose, Streptococcus mutans, and other bacteria work together to cause dental caries. S. mutans ferments fructose to create lactic acid, if there's a lot of sucrose in the diet and plaque isn't removed regularly, the lactic acid can dissolve the calcium of the tooth creating cavities or caries, called dental caries.
