Commercial-grade hydrogen peroxide is an effective disinfectant at room temperature after how many ...

(Answer to Q. 1)  ANS: B
Commercially available 3 solutions of hydrogen peroxide are effective disinfectants of bacteria (including Mycobacteria sp.), fungi, and viruses and are active within 10 minutes at room tem-perature.

(Answer to Q. 2)  ANS: B
Because the process of autoclaving depends on several factors, heat-sensitive tape and biologic indicators are routinely used to ensure quality control during the process. Heat-sensitive tape that is used for packaging materials for autoclaving changes color when it is exposed to a given tem-perature for a prescribed amount of time. The most common biologic indicators for autoclaving are strips of paper that are impregnated with Bacillus stearothermophilus spores. These strips should be used weekly (at a minimum) to ensure that the autoclave is working properly. Biologic indicators are also used for ethylene oxide sterilization.

(Answer to Q. 3)  ANS: D
Because water boils at a lower temperature at high altitudes, exposure time must be prolonged during this form of sterilization at high elevations.

(Answer to Q. 4)  ANS: C
Dry heat is another effective method of heat sterilization. Its use is limited to items that are not heat-sensitive. Temperatures must be maintained between 160 C and 180 C for 1 to 2 hours for sterilization.

(Answer to Q. 5)  ANS: D
Air is evacuated, moisture is added (100 humidity), and the pressure inside the autoclave is raised to 15 to 20 lb-force per square inch gauge (psig). Air is evacuated from the chamber be-cause residual air prolongs the penetration time of steam, thus increasing the total autoclave cycle time. Pressure is used to raise the temperature of the steam, which is critical because the amount of time required to achieve sterilization depends on the temperature inside of the autoclave. Dry heat is not used during autoclaving.

(Answer to Q. 6)  ANS: B
Pseudomonas aeruginosa is killed by 1.25 acetic acid or one part 5 white household vinegar and three parts water. Pseudomonas aeruginosa transmission is through indirect contact via fom-ites, such as those on clothing, surgical bandages, and especially equipment. It is the most com-mon respiratory pathogen in patients with cystic fibrosis and is encountered in patients with chronic obstructive pulmonary disease.

(Answer to Q. 7)  ANS: C
Carbolic acid is the prototype 6-carbon aromatic compound. It was first used as a germicide by Lister in his pioneering work on antiseptic surgery.

(Answer to Q. 8)  ANS: C
Peracetic acid is an excellent disinfectant with sterilization capabilities. It kills microbes by de-naturing proteins, disrupting cell wall permeability, and oxidizing cellular metabolites. Its short-coming is that it can corrode brass, iron, copper, and steel.

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