Ex. 16

Question 1

Which statement is true regarding wavelengths of light?

Answer 1

UV rays are a longer wavelength than gamma rays;

Shorter wavelengths contain more energy. UV rays are longer than either gamma or X-rays. UV rays also are the primary cause of pyrimidine dimers, and also can cause denaturaion of DNA and protein (as can gamma and X rays).

Question 2

Which types of radiation are capable of denaturing DNA and proteins?

Answer 2

Gamma rays
X-rays
UV rays

Question 3

Which of these is NOT true of UV radiation?

1. Can penetrate deep into water.
2. Can cause pyrimidine dimers
3. Is longer wavelength than gamma rays
4. Won’t penetrate endospores

Answer 3

1. Can penetrate deep into water

Question 4

We are using two species for this experiment. Serratia marcescens is a Gram-negative, red-pigmented bacillus. Bacillus subtilis is a Gram-positive, non-pigmented endospore-forming bacillus. Which of these two would be least likely to be affected by UV light?

Answer 4

Bacillus subtilis because it forms endospores

Question 5

Which of these statements is NOT correct?

1. Antiseptics are used mostly on inanimate objects.
2. An agent of microbial control could possibly be used as both an antiseptic and a disinfectant.
3. A sterilant kills more microorganisms than a disinfectant.
4. Bleach is an example of a disinfectant.

Answer 5

1. Antiseptics are used mostly on inanimate objects;

Skin, living tissue

Question 6

Name one example of an agent that could be both an antiseptic and a disinfectant

Answer 6

Hydrogen peroxide
Alcohol
Iodine

Ethyl alcohol or certain forms of iodine (such as Betadine)

Question 8

The larger the zone of inhibition, the more ______ the bacterium is to that antiseptic

Answer 8

sensitive, susceptible

Question 9

Which definition BEST describes a chemotherapeutic agent?

1. It is always used internally.
2. It is always used topically
3. It is used to prevent disease.
4. It is used to treat disease.

Answer 9

4. It is used to treat disease;

There are some chemotherapeutic agents (such as antibiotic salve) that are only used topically. And, while some people use them to prevent disease, they really are intended for treatment of disease.

Question 10

Using the table on page 122 in your lab exercise, determine the correct interpretation of a zone of 22 mm for tetracycline.

Answer 10

Susceptible

Question 11

Using the table on page 122 in your lab exercise, determine the correct interpretation of a zone of 1.4 cm for vancomycin

Answer 11

Susceptible;

Note the units! 1.4 cm = 14 mm, so this is susceptible.

Question 12

A particular microorganism is tested for its susceptibility to Neomycin, Vancomycin and Erythromycin. When students measure the zone of inhibition, they arrive at a diameter of 13 mm for all three antibiotics. What should be their conclusion?

Answer 12

The best antibiotic of the three would be vancomycin;

Even though all 3 have the same diameter zone, the meaning (according to the table) is different. Thus, the only one that is in the susceptible range is vancomycin.