Exam 7: The Control of Microbial Growth

The following is true of quarternary ammonium compounds EXCEPT

Bone and tendons for transplant are decontaminated by

Autoclaving is the most effective method of moist heat sterilization.

Which of the following regarding antimicrobial control agents is FALSE?

Table 7.5 The following results were obtained from a use-dilution test of two disinfectants. Cultures were inoculated into tubes containing varying concentrations of the disinfectants, incubated for 10 min. at 20°C, and then transferred to growth media without disinfectant. (+ = growth; - = no growth) $\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\text { Disinfectant A }$ Concentration Gram-positive bacteria Gram-negative bacteria 1:10 - - 1:20-70 - + 1:80 + + 1:90 + + 1:100 + + 1:110-500 + + $\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\text { Disinfectant B }$ Concentration Gram-positive bacteria Gram-negative bacteria 1:10 - - 1:20-70 + + 1:80 + + 1:90 + + 1:100 + + 1:110-500 + + In Table 7.5, which disinfectant is most effective? Against which group of bacteria is Disinfectant A most effective?

Which of the following chemical agents is used for sterilization?

All of the following substances are effective against nonenveloped viruses EXCEPT

List the microbial targets of disinfecting chemicals and provide one example of a chemical agent that affects that structure.

Table 7.3 The following data were obtained by incubating gram -positive bacteria in nutrient medium + disinfectant for 24 hr, then transferring one loopful to nutrient medium (subculturing). (+ = growth; - = no growth) $\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\text { Doom }$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\text { K.O. }$ Dilution Initial Subculture Initial Subculture 1:16 - + + + 1:32 - + + + 1:64 - + + + 1:128 + + + + $\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\text { Mortum }$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\text { Sterl }$ Dilution Initial Subculture Initial Subculture 1:16 - - - + 1:32 - + + + 1:64 + + + + 1:128 + + + + -In Table 7.3, which disinfectant was most effective against Salmonella?

Which of the following treatments is the most effective for controlling microbial growth?

Table 7.3 The following data were obtained by incubating gram -positive bacteria in nutrient medium + disinfectant for 24 hr, then transferring one loopful to nutrient medium (subculturing). (+ = growth; - = no growth) $\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\text { Doom }$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\text { K.O. }$ Dilution Initial Subculture Initial Subculture 1:16 - + + + 1:32 - + + + 1:64 - + + + 1:128 + + + + $\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\text { Mortum }$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\text { Sterl }$ Dilution Initial Subculture Initial Subculture 1:16 - - - + 1:32 - + + + 1:64 + + + + 1:128 + + + + -In Table 7.3, which disinfectant was bactericidal?

Table 7.4 The results below were obtained from a use-dilution test of two disinfectants. Cultures were inoculated into tubes with varying concentrations of disinfectants and incubated for 24 hr at 20°C, then subcultured in nutrient media without disinfectants.(+ = growth; - = no growth) $\quad\quad\quad\quad\quad\quad\quad\quad\text { Disinfectant } 1$$\quad\quad\quad\quad\quad\text { Disinfectant } 2$ Concentration Initial Subculture Initial Subculture 1:10 - + - - 1:90 + + - - 1:900 + + - - 1:90,000 + + - - 1:900,000 + + - + 1:9,000,000 + + - + In Table 7.4, what is the minimal bacteriostatic concentration of each disinfectant? Which compound is bactericidal? At what concentration?

Which of the following does NOT achieve sterilization?

Ethylene oxide

Assume that you are responsible for decontaminating materials in a large hospital. How would you sterilize each of the following? Briefly justify your answers. a. a mattress used by a patient with bubonic plague b. intravenous glucose-saline solutions c. used disposable syringes d. tissues taken from patients

An agent used to reduce the number of bacteria on a toilet would most accurately be called a(n)

Which of the following disinfectants acts by disrupting the plasma membrane?

All of the following substances are used to preserve foods EXCEPT

Microorganisms placed in high concentrations of salts and sugars undergo lysis.

Figure 7.1 A suspension of 106 Bacillus cereus endospores was put in a hot-air oven at 170°C. Plate counts were used to determine the number of endospores surviving at the time intervals shown. -In Figure 7.1, what is the thermal death time?