The minimum sterilizing conditions in a steam autoclave are
160°C for 2 hours.
71.6°C for 15 seconds.
100°C at 10 psi for 30 minutes.
63°C at 5 psi for 30 minutes.
121°C at 15 psi for 15 to 30 minutes.
The Correct Answer is E
A. 160°C for 2 hours: This temperature and duration correspond to dry heat sterilization rather than steam sterilization in an autoclave. Dry heat sterilization is commonly performed in hot air ovens for glassware or metal instruments that cannot tolerate moisture. Autoclaves rely on moist heat under pressure, which allows sterilization at lower temperatures compared with dry heat.
B. 71.6°C for 15 seconds: This condition corresponds to high-temperature short-time (HTST) pasteurization, commonly used in the dairy industry to reduce microbial load in milk. Pasteurization reduces pathogenic microorganisms but does not destroy all microbes or bacterial spores. Therefore, it does not achieve sterilization.
C. 100°C at 10 psi for 30 minutes: Boiling water reaches 100°C at atmospheric pressure and can kill many vegetative bacteria and viruses. However, many bacterial endospores, such as those produced by Bacillus and Clostridium species, can survive this temperature. True sterilization requires higher temperatures achieved through pressurized steam.
D. 63°C at 5 psi for 30 minutes: This temperature corresponds to low-temperature long-time (LTLT) pasteurization, also known as batch pasteurization. Like other pasteurization methods, it reduces microbial numbers but does not eliminate all microorganisms or spores. As a result, it cannot achieve sterilization.
E. 121°C at 15 psi for 15 to 30 minutes: These are the standard minimum conditions for steam sterilization in an autoclave. Pressurized steam at 121°C effectively denatures proteins, destroys cellular structures, and kills all forms of microbial life, including highly resistant bacterial endospores. This method is widely used for sterilizing laboratory media, surgical instruments, and medical equipment.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. Enveloped: Enveloped viruses acquire their lipid membrane from the host cell during the budding process. This allows the virus to exit the host cell without immediately lysing it. The envelope contains viral glycoproteins essential for attachment and entry into new host cells, and the budding process helps maintain host cell viability temporarily.
B. Non-enveloped: Non-enveloped viruses lack a lipid membrane and typically exit host cells through lysis, which destroys the cell. Because they do not have an envelope, they cannot bud and must rely on cell rupture to release progeny virions.
C. Noninfectious: Viruses that are noninfectious are incapable of establishing infection in host cells. Budding does not determine infectivity; enveloped viruses released via budding are usually fully infectious and able to infect subsequent cells.
Correct Answer is A
Explanation
A. Infectious dose: The infectious dose (ID) refers to the minimum number of microorganisms required to establish an infection in a host. Different pathogens have varying IDs depending on their virulence, host susceptibility, and route of entry. A lower infectious dose indicates higher virulence, while a higher dose may be required for less virulent organisms.
B. Mutation rate: Mutation rate describes how frequently changes occur in the genetic material of an organism. While mutations can affect virulence, antibiotic resistance, or adaptability, mutation rate does not define the number of microbes required to initiate infection.
C. Growth rate: Growth rate refers to how quickly microorganisms replicate under optimal conditions. Although rapid growth can contribute to the severity of an infection, it does not determine the minimum number of organisms necessary to cause disease. The infectious dose specifically quantifies that threshold.
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