Unit 4: Control of microorganisms - Practice Quiz

1 The process of destroying all microbial life, including endospores, is called:

2 The use of chemical agents on living tissue to reduce microbes is known as:

3 The term used for killing microorganisms is:

4 A bacteriostatic agent is one that:

5 Which factor generally increases the rate of microbial killing by an agent?

6 The presence of organic matter such as blood or feces typically:

7 Which microbial form is generally the most resistant to control methods?

8 Longer exposure time of microbes to an antimicrobial agent usually results in:

9 An ideal antimicrobial agent should be:

10 Which is a desirable property of an ideal disinfectant?

11 The instrument that uses pressurized steam for sterilization is the:

12 Standard autoclave conditions for sterilization are approximately:

13 Pasteurization is mainly used to:

14 Which type of radiation is commonly used to disinfect surfaces and air?

15 Which chemical agent is widely used as a skin antiseptic?

16 Who discovered penicillin in 1928?

17 Penicillin is naturally produced by which type of organism?

18 The term selective toxicity means an antimicrobial drug:

19 Penicillin kills bacteria mainly by inhibiting the synthesis of the:

20 A major cause of the rise in antibiotic resistance is:

21 A hospital wants to completely eliminate all forms of microbial life, including bacterial endospores, from surgical instruments. Which term best describes this process?

22 A chemical applied to living tissue to reduce the number of microorganisms is best classified as which of the following?

23 If a disinfectant reduces a bacterial population by 90% every 5 minutes, what fraction of the original population remains after 15 minutes, assuming logarithmic death?

24 Why does the presence of organic matter such as blood or feces reduce the effectiveness of many chemical disinfectants?

25 A technician increases the temperature while using a chemical disinfectant. What is the most likely effect on antimicrobial activity?

26 Which factor explains why a longer exposure time is often required to achieve sterilization when the initial microbial load is very high?

27 Which property is LEAST desirable in an ideal chemical disinfectant intended for household use?

28 An ideal antimicrobial chemotherapeutic drug should exhibit selective toxicity. What does this mean in practice?

29 Why is chemical stability considered an important characteristic of an ideal antimicrobial agent?

30 An autoclave sterilizes at 121°C under 15 psi pressure. Why is pressurized steam more effective than boiling water at 100°C?

31 Ultraviolet (UV) light is used to control microbes on exposed surfaces. What is its primary limitation?

32 Filtration is chosen to sterilize a heat-sensitive antibiotic solution. What is the main mechanism by which it controls microorganisms?

33 Which chemical agent controls microbes primarily by denaturing proteins and disrupting membranes, and is most effective at a 60–70% concentration in water?

34 Alexander Fleming's 1928 observation that led to penicillin involved which key finding?

35 Paul Ehrlich's concept of a "magic bullet" and his development of Salvarsan (arsphenamine) is historically significant because it was?

36 The sulfa drugs (sulfonamides) introduced in the 1930s were important because they were?

37 Penicillin selectively harms bacteria with little toxicity to human cells because it targets?

38 An antibiotic binds the bacterial 30S ribosomal subunit and blocks protein synthesis. Which mechanism of action does this represent?

39 A drug is described as "bacteriostatic." What does this indicate about its action?

40 A bacterial strain acquires resistance to penicillin by producing an enzyme that cleaves the drug's β-lactam ring. This enzyme is known as?

41 A suspension contains CFU/mL of a bacterial species with a decimal reduction time (-value) of minutes at a given temperature. Assuming first-order (logarithmic) death kinetics, how long must the treatment continue to reach a theoretical survivor level of CFU/mL?

42 Two sterilization processes both achieve a -log reduction of Clostridium botulinum spores, but Process A uses higher temperature for shorter time and Process B uses lower temperature for longer time. If both yield the same value, which conclusion is most accurate?

43 A hospital finds that a phenolic disinfectant that worked in the lab fails on ward floors soiled with blood and pus. Which factor most directly explains this reduced efficacy?

44 For most chemical disinfectants, increasing temperature by can roughly double the killing rate. If a disinfectant kills a population in minutes at and has a temperature coefficient () of , what is the approximate kill time at ?

45 When evaluating whether a new surface disinfectant approaches the 'ideal' profile, which trade-off represents the most fundamental inherent conflict among desired properties?

46 A disinfectant has excellent broad-spectrum activity but leaves a toxic residue and rapidly loses potency once diluted. According to the criteria for an ideal antimicrobial agent, which set of properties is deficient?

47 Why does moist heat (autoclaving at ) kill microbes far more efficiently than dry heat at the same temperature?

48 A researcher must sterilize a heat-labile enzyme solution and a batch of glass pipettes. Which pairing of methods is most appropriate?

49 Ultraviolet radiation at is strongly germicidal. What limits its use as a general sterilizing agent despite this?

50 Ethylene oxide gas is used to sterilize heat- and moisture-sensitive medical devices. Which combination best explains both its utility and its major operational hazard?

51 Paul Ehrlich's development of Salvarsan (arsphenamine) is historically significant primarily because it demonstrated which concept?

52 Fleming observed penicillin in 1928, yet penicillin did not become a usable drug until the 1940s. Which pair of scientists is credited with the purification and demonstration of its therapeutic value that enabled clinical use?

53 The discovery of streptomycin by Waksman and Schatz was historically distinct from penicillin because it primarily addressed which unmet need?

54 Penicillin and vancomycin both target the bacterial cell wall but by different mechanisms. Which statement correctly distinguishes them?

55 A drug selectively inhibits the bacterial ribosome without affecting the host ribosome. This is the clearest example of which principle underlying antimicrobial drug design?

56 Sulfonamides are effective against many bacteria but not against humans consuming the same nutrient sources. What is the mechanistic basis for this selectivity?

57 For an antibiotic, the therapeutic index is defined as the ratio of the toxic dose to the therapeutic (effective) dose. If Drug X has and , while Drug Y has and , which drug is safer and what is its index?

58 A strain of Staphylococcus aureus becomes resistant to methicillin. Which mechanism best explains MRSA resistance to -lactams generally?

59 Why does using a single antibiotic to treat active tuberculosis frequently lead to treatment failure, whereas multidrug regimens succeed?

60 R-plasmids can spread multidrug resistance rapidly through a bacterial population. Which feature of this mechanism makes it especially dangerous compared to chromosomal mutation?