Microbiology review

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1. What does bactericidal mean? Bacteriostatic? Virucidal? Fungistatic?
Bactericidal means something that kill bacteria or bacterial-killing
Bacteriostatic means something that inhibit bacteria or bacteria-inhibiting.
Virucidal means something that kills the virus or virus-killing.
Fungistatic means something that inhibit the fungus or fungus-inhibiting.

2. Why are control cultures necessary in evaluating disinfectants?
Control cultures are necessary in evaluating disinfectants because a control culture is needed to show that the disinfectant itself has not been contaminated. This is important because if the disinfectant is contaminated, then it would not be useful to use it. A control cultures will tell if the disinfectant is good or not.

3. What factors can influence the activity of a disinfectant?
There are a number of factors influencing the activity of the disinfectant. These factors are include:
a. The concentration of the chemical agent.
b. The temperature at which the agent is being used.
c. The kind of microorganisms present.
d. The number of microorganisms present. The more microorganisms present, the harder it is to disinfect.
e. The nature of the material bearing the microorganisms.

4. Why do microorganisms differ in their response to disinfectants?
Microorganisms differ in their response to disinfectants in that microorganisms have unique DNA and characteristics that may be more or less sensitive to the disinfectants. For example, the disinfectants and antiseptics often work slowly on some viruses such as hepatitis viruses, but work strongly for others. The bacteria with an acid fast cell wall such as Mycobacterium tuberculosis are resistant to disinfectants. The bacteria with endospores produced by the genus Baccillus and Clostridium are unreliable for disinfectants

5. What microorganisms are most susceptible to disinfectants?
The most susceptible to disinfectants are the vegetative bacteria, fungi, and enveloped viruses.

6. What is meant by antimicrobial resistance? Susceptibility?
Antimicrobial resistance is the ability of micro-organisms to be resistance to antimicrobial treatments.
Susceptibility means not resistance to the microbes, but easily sensitive to the microbes or other agents.

7. Why are pure cultures used for antimicrobial susceptibility testing?
A pure cultures is used for antimicrobial susceptibility testing because a pure culture will give a more accurate measurement of how far the antibiotic interrupted the susceptibility of the microbes. If the culture is not pure, the contaminates will give a false and incorrect reading.

8. Would it be acceptable to use a mixed culture for this test? Why?
No because previous studies have shown that antibiotic susceptibility of mixed culture will give completely unreliable results. A mixture of both resistant and sensitive species appeared either as "resistant" or "sensitive" depending on the organism and the drug. Reaction of bacterial mixtures are completely unreliable.

9. List three factors that can influence the accuracy of the test.
pH - The pH can determine the effectiveness of the antibiotic against the microbes. If the pH is too low, some antibiotic will be less potent. If the pH is too high, the antibiotic will be more potent.

Moisture- excess surface moisture may influence the susceptibility of the drugs against the microbes.

Media containing thymidine can effect the present of the antibiotic in the media.

10. When performing a broth dilution test, why is it necessary to include a growth control tube?
A sterility control tube?
It is necessary to include a growth control tube to test for contamination of your sample. If no growth occur in the control, then there is no contamination. The same principle applied to the sterility control tube; it is to test for contamination.

11. What does the term IMViC mean?
IMVIc test is used for differentiating the Enteroacteriaceae ( the E. coli and Enterobacter aerogenes, Enterobacter cloacae, and Klebsiella pneumoniae. The IMVic stands for:
Indole production
The methyl red test
The Voges-Proskauer test
And the citrate production

12. Why is the IMViC useful in identifying Enterobacteriaceae? Are further biochemical tests necessary for complete identification?
The IMVIC test is enough to show that the owner not home?
Yes, because the microbes detected are ...