Control of Microbial Growth

All of the following factors contribute to hospital-acquired infections EXCEPT A) some bacteria metabolize disinfectants. B) gram-negative bacteria are often resistant to disinfectants. C) invasive procedures can provide a portal of entry for bacteria. D) bacteria may be present in commercial products such as mouthwash. E) None of the Answers is correct; all of these factors may contribute to hospital-acquired infection.

E) None of the Answers is correct; all of these factors may contribute to hospital-acquired infection.

A suspension of 106 Bacillus cereus endospores was put in a hot-air oven at 170C. Plate counts were used to determine the number of endospores surviving at the time intervals shown. In Figure 7.1, the thermal death point for this culture is A) 15 minutes. B) 50C. C) 30 minutes. D) 170C. E) The Answer cannot be determined based on the information provided

E) The Answer cannot be determined based on the information provided

In Table 7.1, which compound was bactericidal? A) A B) B C) C D) D E) The Answer cannot be determined based on the information provided.

E) The Answer cannot be determined based on the information provided.

In Table 7.1, which compound was the most effective against E. coli? A) A B) B C) C D) D E) The Answer cannot be determined based on the information provided.

E) The Answer cannot be determined based on the information provided.

In Table 7.3, which disinfectant was most effective against Salmonella? A) Doom B) K.O. C) Mortum D) Sterl E) The Answer cannot be determined based on the information provided.

E) The Answer cannot be determined based on the information provided.

Which of the following results in lethal damage to nucleic acids? A) heat B) radiation C) certain chemicals D) heat and radiation E) heat, radiation, and some chemicals

E) heat, radiation, and some chemicals

An iodophor is a(n) A) phenol. B) agent that reduces oxygen. C) quaternary ammonium compound. D) form of formaldehyde. E) iodine mixed with a surfactant.

E) iodine mixed with a surfactant.

Disinfection of water is achieved by all of the following EXCEPT A) ozone. B) UV radiation. C) chlorine. D) copper sulfate. E) peracetic acid.

E) peracetic acid.

If you were preparing nutrient agar at home and did not have an autoclave, what could you use to sterilize the nutrient agar? A) bleach B) boiling for one hour C) hydrogen peroxide D) oven at 121C for one hour E) pressure cooker at 121C for 15 minutes

E) pressure cooker at 121C for 15 minutes

Bone and tendons for transplant are decontaminated by A) ethylene oxide. B) glutaraldehyde. C) peroxygens. D) plasma sterilization. E) supercritical fluids.

E) supercritical fluids.

Which of the following pairs is mismatched? A) ionizing radiation hydroxyl radicals B) ozone takes electrons from substances C) plasma sterilization free radicals D) supercritical fluids CO2 E) ultraviolet radiation desiccation

E) ultraviolet radiation desiccation

T/F: Any process that destroys the non-spore forming contaminants on inanimate objects is sterilization.

False

T/F: Desiccation is a reliable form of sterilization.

False

T/F: Microorganisms placed in high concentrations of salts and sugars undergo lysis.

False

T/F: The pH of the medium has no effect on the activity of the disinfectant being applied.

False

T/F: Ultraviolet light (UV) causes irreversible breaks in DNA strands.

False

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

Four main categories of cellular targets for chemical agents. - Cell wall. - Cell membrane. - Cellular synthesis processes (DNA, RNA). - Proteins. Any dehydrating agents like alchohal will affect bacteria structure

Essay: How is hydrogen peroxide antimicrobial?

Hydrogen peroxide has oxygen as it chemical component which is highly reactive giving it the ability to act as an antimicrobial. Also it is a very strong oxidizing agent enabling to change the chemical structure of many substances. Hydrogen peroxide are able to kill bacteria easily because it is able to oxidized the cell wall of the bacteria leaving them unprotected and eventually die. When hydrogen peroxide is pour on a wound it helps it slow the bleeding in the area by closing off the capillaries and blood vessels. It is also a very affordable and accessible disinfectant which makes it an ideal antimicrobial agent.

T/F: Autoclaving is the most effective method of moist heat sterilization.

True

T/F: Moist heat destroys organisms by denaturing proteins.

True

T/F: Pseudomonas has been found growing in quaternary ammonium compounds (quats).

True

T/F: Some antimicrobial chemicals are considered to be disinfectants and antiseptics.

True

T/F: The thermal death time is the time needed to kill all the bacteria in a particular culture at a certain temperature.

True

Essay: Why must most milk sold in the U.S. be refrigerated at all times while evaporated canned milk and milk in cardboard containers sold in Europe do not need to be refrigerated until they are opened?

all difference is made by the packaging. The packaging in the UK is aseptic (sterilized) after sterilization of the boxes the milk is transferred into them. So packing of the milk is very important and it differentiates the US refrigerated milk and Europe's non- refrigerated milk.

Essay: What are the advantages of gluteraldehyde compared to formaldehyde?

it is less irritating and more effective than formaldehyde.bactericidal, tuberculocidal, and virucidal in 10 minutes

Essay: 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 20C, and then transferred to growth media without disinfectant. (+ = growth; = no growth) In Table 7.5, which disinfectant is most effective? Against which group of bacteria is Disinfectant A most effective?

A is more effective as it can act at a lower dilution. A is more effective against gram positive bacteria

In Table 7.3, which disinfectant is the most effective at stopping bacterial growth? A) Doom B) K.O. C) Mortum D) Sterl E) The Answer cannot be determined based on the information provided.

A) Doom

Which of the following best describes the pattern of microbial death? A) The cells in a population die at a constant rate. B) All the cells in a culture die at once. C) Not all of the cells in a culture are killed. D) The pattern varies depending on the antimicrobial agent. E) The pattern varies depending on the species.

A) The cells in a population die at a constant rate.

All of the following substances are effective against nonenveloped viruses EXCEPT A) alcohol. B) chlorine. C) ethylene oxide. D) ozone. E) None of the Answers is correct; all of these are equally effective against nonenveloped viruses.

A) alcohol.

Which of the following pairs of terms is mismatched? A) bacteriostatic kills vegetative bacterial cells B) germicide kills microbes C) virucide inactivates viruses D) sterilant destroys all living microorganisms E) fungicide kills yeasts and molds

A) bacteriostatic kills vegetative bacterial cells

All of the following substances are used to preserve foods EXCEPT A) biguanides. B) nisin. C) potassium sorbate. D) sodium nitrite. E) calcium propionate.

A) biguanides.

All of the following are effective for destroying prions EXCEPT A) boiling. B) incineration. C) NaOH + autoclaving at 134C. D) proteases. E) None of the Answers are correct; each of these will destroy prions.

A) boiling.

An agent used to reduce the number of bacteria on a toilet would most accurately be called a(n) A) disinfectant. B) antiseptic. C) aseptic. D) fungicide. E) virucide.

A) disinfectant.

Which one of the following is most resistant to chemical biocides? A) gram-negative bacteria B) gram-positive bacteria C) mycobacteria D) protozoan cysts E) viruses with lipid envelopes

A) gram-negative bacteria

Essay: 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

A) hepa vacuuming, ultraviolet germicidal radiation, light enzyme most to kill remaining colonies. B) Put it in the autoclave C)it's disposable one time use so just throw it away. Use ethylene oxide if u must sterilize them first(which seems a bit unnecessary considering they have special bins for bio waste D) Gamma irradiation and gas sterilization with ethylene oxide can be used to sterilize human tissue taken from patients. the gas penetrates the tissue.

The antimicrobial activity of chlorine is due to which of the following? A) the formation of hypochlorous acid B) the formation of hydrochloric acid C) the formation of ozone D) the formation of a hypochlorite ion E) disruption of the plasma membrane

A) the formation of hypochlorous acid

In Figure 7.1, the decimal reduction time (D value) for the culture, which is defined as the time to reduce a population by one log, is approximately A) 0 minutes. B) 10 minutes. C) 30 minutes. D) 40 minutes. E) 60 minutes.

B) 10 minutes.

A suspension of 106 Bacillus cereus endospores was put in a hot-air oven at 170C. 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? A) 150C B) 60 minutes C) 120 minutes D) 100C E) The Answer cannot be determined based on the information provided.

B) 60 minutes

Which concentration of ethanol is the most effective bactericide? A) 100 percent B) 70 percent C) 50 percent D) 40 percent E) 30 percent

B) 70 percent

Which of the following pairs is mismatched? A) Ag wound dressings B) alcohols open wounds C) CuSO4 algicide D) H2O2 open wounds E) organic acids food preservation

B) alcohols open wounds

Assume 109 E. coli cells/ml are in a flask. Which graph in Figure 7.2 best depicts the effect of placing the culture in an autoclave for 15 minutes at time x? A) a B) b C) c D) d E) e

B) b

Which of the following could be used to sterilize plastic Petri plates in a plastic wrapper? A) autoclave B) gamma radiation C) microwaves D) sunlight E) ultraviolet radiation

B) gamma radiation

Oxidizing agents include all of the following EXCEPT A) chlorine. B) glutaraldehyde. C) hydrogen peroxide. D) iodine. E) ozone.

B) glutaraldehyde.

Which of the following does NOT achieve sterilization? A) dry heat B) pasteurization C) autoclave D) supercritical fluids E) ethylene oxide

B) pasteurization

In Table 7.2, which preservative is most effective? A) potassium sorbate B) sodium benzoate C) potassium sorbate + sodium benzoate D) no preservative

B) sodium benzoate

In Table 7.3, which disinfectant was bactericidal? A) Doom B) K.O. C) Mortum D) Sterl E) The Answer cannot be determined based on the information provided.

C) Mortum

Which of the following disinfectants acts by disrupting the plasma membrane? A) soaps B) aldehydes C) bisphenols D) halogens E) heavy metals

C) bisphenols

A disk-diffusion test using Staphylococcus gave the following results: Disinfectant Zone of inhibition (mm) A0 B2.5 C10 D5 In Table 7.1, which compound was the most effective against Staphylococcus? A) A B) B C) C D) D E) The Answer cannot be determine based on the information provided.

C) c

Which of the following substances is used for surgical hand scrubs? A) phenol B) chlorine bleach C) chlorhexidine D) soap E) glutaraldehyde

C) chlorhexidine

The preservation of beef jerky from microbial growth relies on which method of microbial control? A) filtration B) lyophilization C) desiccation D) ionizing radiation E) supercritical CO2

C) desiccation

Which of the following chemical agents is used for sterilization? A) alcohol B) phenolics C) ethylene oxide D) chlorine E) soap

C) ethylene oxide

Which of the following methods is used to preserve food by slowing the metabolic processes of foodborne microbes? A) lyophilization B) nonionizing radiation C) freezing D) ionizing radiation E) pasteurization

C) freezing

Which of the following is the best method to sterilize heat-labile solutions? A) dry heat B) autoclave C) membrane filtration D) pasteurization E) freezing

C) membrane filtration

The following is true of quarternary ammonium compounds EXCEPT A) they are non-toxic at lower concentrations. B) they are tasteless. C) they are effective when combined with soaps. D) they are stable. E) they may be an ingredient in mouthwash.

C) they are effective when combined with soaps.

Which of the following is a limitation of the autoclave? A) It requires an excessively long time to achieve sterilization. B) It cannot inactivate viruses. C) It cannot kill endospores. D) It cannot be used with heat-labile materials. E) It cannot be used with glassware.

D) It cannot be used with heat-labile materials.

Which of the following treatments is the most effective for controlling microbial growth? A) 63C for 30 minutes B) 72C for 15 seconds C) 140C for 4 seconds D) They are equivalent treatments. E) None of the Answers is correct.

D) They are equivalent treatments.

Which graph in Figure 7.2 best depicts the effect of placing the culture at 7C at time x? A) a B) b C) c D) d E) e

D) d

Application of heat to living cells can result in all of the following EXCEPT A) breaking of hydrogen bonds. B) alteration of membrane permeability. C) denaturation of enzymes. D) decreased thermal death time. E) damage to nucleic acids.

D) decreased thermal death time.

34) Ethylene oxide A) is a good antiseptic. B) is not sporicidal. C) requires high heat to be effective. D) is a sterilizing agent. E) is the active chemical in household bleach.

D) is a sterilizing agent.

All of the following are methods of food preservation EXCEPT A) desiccation. B) high pressure. C) ionizing radiation. D) microwaves. E) osmotic pressure.

D) microwaves.

Which of the following regarding antimicrobial control agents is FALSE? A) Contaminating organic debris such as blood or sputum will decrease effectiveness. B) Some agents kill by denaturing microbial cell proteins. C) Some agents affect microbial cell membranes by dissolving lipids. D) Some agents are utilized as both an antiseptic and a disinfectant. E) A true antimicrobial control agent is equally effective against both bacteria and viruses.

E) A true antimicrobial control agent is equally effective against both bacteria and viruses.

Which of the following regarding antimicrobial control agents is FALSE? A) Contaminating organic debris such as blood or sputum decrease effectiveness. B) Some agents kill by denaturing microbial cell proteins. C) Some agents affect microbial cell membranes by dissolving lipids. D) Silver is used for treating antibiotic-resistant bacteria. E) Alcohols effectively inactivate nonenveloped viruses by attacking lipids.

E) Alcohols effectively inactivate nonenveloped viruses by attacking lipids.