Unit 5: Control of Microorganisms - Practice Quiz

1 Which physical agent is commonly used to sterilize culture media?

2 Pasteurization is mainly used to:

3 Filtration controls microorganisms by:

4 Filtration is especially useful for sterilizing:

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

6 Ionizing radiation can control microorganisms by damaging their:

7 Desiccation inhibits many microorganisms by removing:

8 High concentrations of salt or sugar inhibit microbial growth mainly by:

9 A disinfectant is a chemical agent used on:

10 An antiseptic is designed for use on:

11 Preservatives are added to products mainly to:

12 Which chemical is commonly used as an antiseptic on skin?

13 Antibiotics are chemicals used to treat infections caused by:

14 Which drug is an example of an antibiotic?

15 Antifungal agents are used to treat infections caused by:

16 Antiviral agents are used to control infections caused by:

17 An endospore is best described as a:

18 Which bacterial genera are well known for producing endospores?

19 During sporulation, the bacterial DNA is first enclosed by a developing:

20 What happens when an endospore germinates?

21 A bacterial culture contains vegetative cells but no endospores. Which treatment would most reliably achieve sterilization?

22 Why is moist heat generally more effective than dry heat at the same temperature?

23 A heat-sensitive antibiotic solution must be sterilized before use. Which method is most appropriate?

24 A filter with a pore diameter of 0.22 micrometers is commonly used to sterilize liquids because it can remove most

25 Which application best demonstrates the use of ionizing radiation for microbial control?

26 Ultraviolet radiation is less effective for sterilizing the inside of a wrapped instrument mainly because it

27 A culture exposed to drying shows a large decrease in viable cells but is not completely sterile. Which explanation is most accurate?

28 A bacterium placed in a highly concentrated salt solution loses water and stops growing. This effect is primarily due to

29 A disinfectant is applied to a visibly dirty surface and performs poorly. Which factor most likely reduced its effectiveness?

30 Which statement best distinguishes a disinfectant from an antiseptic?

31 Before inserting an intravenous catheter, a healthcare worker applies an alcohol-based preparation to the skin. This treatment is classified as

32 A food manufacturer adds a chemical that inhibits mold growth without sterilizing the product. The chemical functions primarily as a

33 A patient stops taking an antibiotic as soon as symptoms improve, and the infection returns with resistant bacteria. Which principle is illustrated?

34 A bacterial isolate is resistant to penicillin because it produces an enzyme that breaks the drug's beta-lactam ring. This resistance mechanism is called

35 Why can a drug that targets fungal ergosterol be selectively toxic to fungi?

36 A patient receiving a broad-spectrum antifungal develops toxicity because the drug also affects a similar molecule in human cells. This illustrates the importance of

37 An antiviral drug prevents a viral polymerase from copying the viral genome. Which stage of viral multiplication is directly inhibited?

38 A bacterial endospore is located near one end of the cell and causes a noticeable swelling. This arrangement is described as

39 A bacterium forms an endospore approximately in the middle of its cell without causing obvious swelling. Which description is correct?

40 During bacterial sporulation, the DNA becomes concentrated in an axial filament before a septum divides the cell. What is the significance of this event?

41 A bacterial suspension is heated at a constant temperature. After 6 minutes, viable cells decrease from 10^6 to 10^3 CFU/mL, and the survivor curve is linear on a semilogarithmic plot. What is the decimal reduction time (D-value) under these conditions?

42 An autoclave reaches 121°C, but the biological indicator containing bacterial endospores remains positive. Which explanation is most likely if the chamber temperature was recorded accurately?

43 A heat-sensitive serum is passed through a membrane filter with a nominal pore size of 0.22 micrometers. Which contaminant is most likely to pass through under typical conditions?

44 A sterilizing-grade membrane filter removes bacteria from a solution, but the filtrate still transmits bacteriophages. Which conclusion is best supported?

45 Ultraviolet radiation effectively reduces bacteria on an exposed countertop but fails to sterilize a shaded surface. Which property best explains this result?

46 Two bacterial populations receive the same ionizing-radiation dose. Population X has efficient DNA double-strand-break repair, whereas population Y lacks this repair capacity. Which outcome is most likely?

47 A culture of Neisseria cells rapidly loses viability when dried, while a culture of Staphylococcus cells remains recoverable for days. Which interpretation is most appropriate?

48 A halotolerant bacterium grows in a high-salt food even though the surrounding medium has lower water activity than its cytoplasm. Which mechanism most directly supports its survival?

49 A hospital disinfectant produces rapid killing of vegetative bacteria but does not reliably destroy bacterial endospores. Which classification best fits this agent?

50 An alcohol-based antiseptic is applied to visibly soiled hands and performs poorly. Which factor most plausibly caused the reduced effectiveness?

51 A preservative prevents growth in a food at pH 4.0 but is much less effective in the same food at pH 6.5. Which explanation is most likely for a weak-acid preservative?

52 A patient receiving a bacteriostatic antibiotic improves clinically, but cultures remain positive during treatment and become negative after immune recovery. Which interpretation is most consistent?

53 A mutation alters a bacterial porin and reduces entry of a beta-lactam antibiotic. The organism remains susceptible to an antibiotic that enters through a different route. What resistance mechanism is illustrated?

54 A patient with a mixed infection receives an antibiotic that blocks bacterial 70S ribosomes but has no effect on human 80S ribosomes. Which principle is most directly demonstrated?

55 A fungal infection is treated with a drug that binds ergosterol and forms membrane pores. Why can this drug damage fungi more selectively than human cells?

56 A fungal isolate becomes resistant to an azole drug while remaining susceptible to a drug that targets the fungal cell wall. Which change most plausibly explains the azole resistance?

57 A nucleoside analog reduces viral replication only after phosphorylation by a virus-associated enzyme. Which selective advantage does this activation provide?

58 Microscopy shows a terminal, spherical endospore that markedly distends the bacterial cell. Which identification is most consistent with this morphology?

59 During bacterial sporulation, a forespore becomes surrounded by a second membrane before cortex deposition. Which stage is occurring?

60 A sporulating cell has completed cortex and coat synthesis, but the mature endospore remains inside the mother cell. Which event must occur next for the spore to become free?