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10 Cards in this Set
- Front
- Back
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Describe how the D-value for a particular disinfectant is calculated. |
A known concentration of test culture is exposed to a disinfectant for increasing times, at which point samples are withdrawn, neutralised, and plated to determine the residual infectivity. The microbial population size (on a log scale) at different time points is plotted and the time taken to decrease the population size from 1000 to 100 (on a log scale) is the D-value. |
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Which of the following statements regarding chlorine is CORRECT? A Chlorine-releasing compounds are highly active against both vegetative and spore-forming bacteria. B It's efficiency is not decreased by the presence of soils. C A major advantage of chlorine as a disinfectant is that it has a long shelf-life. D A major disadvantage of chlorine is that it can be corrosive to metal surface at high concentrations. |
D A major disadvantage of chlorine is that it can be corrosive to metal surface at high concentrations. |
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Which of the following statements regarding iodine is INCORRECT? A It has a broad spectrum of antimicrobial activity, including sporicidal activity at high concentrations. B Aqueous iodine is active over a wide range of pH values but iodophors are only active at acidic pH values. C A major disadvantage of iodine is that is causes brown staining on surfaces including skin and clothing. D Iodine compounds can be toxic at high concentrations. |
B Aqueous iodine is active over a wide range of pH values but iodophors are only active at acidic pH values. |
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Which of the following statement regarding formaldehyde is CORRECT? A It is active against vegetative bacteria, and mycobacteria. but not against fungi and most viruses. B Its activity does not change in the presence of soil. C It can be used in aqueous or gaseous forms. D Formalin is an aqueous solution of ~37% formaldehyde put 20-30% methanol. |
C It can be used in aqueous or gaseous forms. |
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Which of the following statements regarding glutaraldehyde is INCORRECT? A 2% solutions are active against bacteria, fungi and viruses in less than 10 minutes. B It is not suitable for medical devices as it is corrosive to metal surfaces. C Its activity is decreased in the presence of soils. D It is highly irritating to the skin and mucous membranes. |
B It is not suitable for medical devices as it is corrosive to metal surfaces. |
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Which of the following is NOT a similarity between hydrogen peroxide and peracetic acid? A They both break down into non-toxic by-products. B They both are effective against bacteria, mycobacteria, viruses, fungi and spores. C High concentrations can act as irritants to skin. D They are bot used in the food industry due to the non-toxic nature of their by-products. |
D They are bot used in the food industry due to the non-toxic nature of their by-products. |
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What alcohol(s) are most commonly used as disinfectants? A Ethanol B Isopropanol C Methanol D A and B only E All of the above |
D A and B only |
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Which of the following is NOT a disadvantage regarding the use of alcohols as a disinfectant? A They are inactivated by the presence of soils. B They are flammable and cannot be used near naked flames. C They requires long contact times (minutes to hours) to be effective. D They have little sporicidal activity. |
C They requires long contact times (minutes to hours) to be effective. |
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Which of the following is NOT an example of a phenolic? A Phenol B Cresol C Xylenol D None of the above |
D None of the above |
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Which of the following is an advantage of phenols as a disinfectant? A They are generally active in the presence of soils. B They are not corrosive to plastic and rubber surfaces. C They are very effective against spores. D They are not irritants to the skin and mucous membranes. |
A They are generally active in the presence of soils. |
