4. A particular disinfectant takes 2 min. of contact time to kill 90% of all mic

Question

4. A particular disinfectant takes 2 min. of contact time to kill 90% of all microorganisms on a particular surface. How would the following situations affect the time normally needed to kill 90% of all microorganisms? (1.5 pts.)

   a. Microorganisms are in a dirt matrix (i.e. someone falls outside and scraps their knee).

   b. Microorganisms are in a working refrigerator (a culture of Salmonella is spilled in a refrigerator).

   c. The surface was swabbed down with ethanol 2 hours previously.

5. Entamoeba histolytica and Giardia lamblia were isolated from the stool sample of a 45 year old man, and Shigella sonnei was isolated from the stool sample of an 18 year old woman. Both patients experienced diarrhea and severe abdominal cramps, and prior to onset of digestive symptoms, both had been treated by the same chiropractor. The chiropractor had administered colonic irrigations (enemas) to these patients. The device used for this treatment was a gravity-dependent apparatus using 12 liters of tap water. There were no check valves to prevent backflow, so all parts of the apparatus could have become contaminated with feces during each colonic treatment. The chiropractor provided colonic treatment to four or five patients per day. Between patients, the adaptor piece that is inserted into the rectum was placed in a “hot-water sterilizer.” Tap water does not contain pathogens. (2 pt.)

What 2 errors were made by the chiropractor?

6. Name two desirable properties of an antimicrobial. Tell me why each is important in selecting an antimicrobial for a particular infection. (2 pts.)

7. A child comes down with a moderately high fever and a very sore throat that is red with white patches. Initial diagnosis from the quick strep test is strep throat. Strep throat is caused by Streptococcus pyogenes (also known as Group A strep or GAS). Although the acute disease (while painful) is seldom fatal and despite concerns about producing antibiotic resistant strains of bacteria, most doctors prescribe antibiotics to treat this disease. Why do they choose to use antibiotics?

Explanation / Answer

6) An Antimicrobial can function

1 by competitively inhibiting enzymes and

2 by being wrongly incorporated into important molecules such as nucleic acids.  Such actions are called molecular mimicry where they mimic the normal molecule, preventing a reaction from occurring or causing it to go wrong.

Competitive Inhibition In this, an antimicrobial compound binds to an enzyme’s active site, so that the enzyme cannot react with its true substrate.  To bind to the active site, the antimicrobial compound must be similar in structure to the true substrate.  

For example, drug sulfanilamide is very similar to the compound para-aminobenzoic acid (PABA).  Sulfanilamide competitively inhibits an enzyme that acts on PABA.  Many bacteria require PABA to make folic acid, which is used in synthesizing nucleic acids and other compounds.  So, when sulfanilamide is bound to the enzyme, a bacterium cannot make folic acid. Hence, its action gets disrupted.

Nucleic Acid Incorporation Antimicrobial compounds like idoxuridine and vidarabine are incorrectly incorporated into nucleic acids.  These molecules are very similar in structure to the nitrogen bases.  When incorporated into a nucleic acid, they mix up the information that it encodes because they cannot form the correct base pairs during replication and transcription. These compounds can harm the microorganisms as well as host cells. These agents are most useful in treating viral infections.

7) Patients are treated with antibiotics because a throat culture tested positive for strep may be healthy carriers. Antibiotics are given to kill the bacteria and shorten the time of contagiousness. Antibiotics also prevent spreading of bacteria to other parts of the body. It checks the infection from triggering the immune system to attack itself and cause serious conditions such as rheumatic fever.

Related Questions

Navigate

• Browse (All)
• Browse 4
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.