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Physical and Chemical Agents Questions and Answers

Answer: A

Sterilization is absolute: nothing viable is left, spores and all. Disinfection destroys pathogens and many other organisms but is not required to eliminate spores, and sanitization only lowers numbers to an agreed safe level, so the three terms are not interchangeable.

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Answer: B

Disinfection kills pathogens and many other organisms by heat or chemicals, but unlike sterilization it carries no requirement to destroy bacterial spores. That is why a disinfected instrument is not a sterile one, however clean it looks.

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3.

An agent that prevents or arrests the growth of microorganisms on living tissue is

Answer: C

Antiseptics are formulated for skin and mucous membranes, so they must be active yet tolerable to tissue. Disinfectants are for inanimate surfaces and are often too irritant for skin, which is why the same chemical may appear at different strengths under both names.

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Answer: D

Sanitization is a numbers game rather than an absolute: the count is brought down to an accepted threshold, which is the standard applied to eating utensils and dairy equipment. It neither sterilizes nor guarantees the removal of any particular pathogen.

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Answer: A

The suffix -cide marks killing, so a germicide destroys organisms; bactericide, virucide, fungicide and sporicide name the target more narrowly. An agent that merely halts division is described with the suffix -static instead.

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Answer: B

A static agent holds the population in check, and growth can resume once it is removed or diluted. That distinction matters clinically, because a bacteriostatic drug depends on the host's own defences to clear the organisms it has merely suspended.

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Answer: C

Killing spores at adequate concentration and contact time is the defining capability, which is why high-level disinfection is accepted for semicritical items such as endoscopes. Given long enough, such agents approach sterilization.

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8.

An intermediate-level disinfectant destroys vegetative bacteria including tubercle bacilli, but not

Answer: D

Correct answer: bacterial spores

Spores are the most resistant form of microbial life, and killing them is exactly what separates sterilisation from disinfection. An intermediate-level disinfectant handles vegetative bacteria including mycobacteria, most viruses and fungi, but leaves spores viable. Only a high-level disinfectant, given prolonged contact, approaches sporicidal activity.

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Answer: A

Mycobacteria have a waxy cell wall that resists many chemicals, so the ability to kill them is used as the benchmark for the intermediate level. A low-level agent handles ordinary vegetative bacteria but not the tubercle bacillus.

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Answer: B

Risk of infection drives the requirement: a critical item such as a surgical instrument or an intravascular catheter bypasses every host barrier, so nothing short of sterilization will do. Semicritical items touch mucous membranes and noncritical items only intact skin.

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