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CHAPTER 7 1) 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 Answer: C 2 2) 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. Answer: A 3 3) Which of the following chemical agents is used for sterilization? A) alcohol B) phenolics C) ethylene oxide D) chlorine E) soap Answer: C 4 4) Which of the following substances is used for surgical hand scrubs? A) phenol B) chlorine bleach C) chlorhexidine D) soap

E) glutaraldehyde Answer: C 5 5) 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 Answer: A 6 6) 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 Answer: A 7 7) 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. Answer: E 8 8) Which of the following does NOT achieve sterilization? A) dry heat B) pasteurization C) autoclave D) supercritical fluids

E) ethylene oxide Answer: B 9 9) 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. Answer: D 10 10) 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. Answer: A 11 11) 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. Answer: D 12 12) Which of the following disinfectants acts by disrupting the plasma membrane? A) soaps B) aldehydes C) bisphenols D) halogens

E) heavy metals Answer: C 13 13) Oxidizing agents include all of the following EXCEPT A) chlorine. B) glutaraldehyde. C) hydrogen peroxide. D) iodine. E) ozone. Answer: B 14 14) Disinfection of water is achieved by all of the following EXCEPT A) ozone. B) UV radiation. C) chlorine. D) copper sulfate. E) peracetic acid. Answer: E 15 15) 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. Answer: A 16 16) 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 Answer: C 17 17) Which concentration of ethanol is the most effective bactericide? A) 100 percent B) 70 percent C) 50 percent D) 40 percent E) 30 percent Answer: B 18 18) 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. Answer: E 19 19) Which of the following treatments is the most effective for controlling microbial growth? A) 63°C for 30 minutes B) 72°C for 15 seconds C) 140°C for 4 seconds D) They are equivalent treatments. E) None of the answers is correct. Answer: D 20 20) 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 Answer: B 21 21) 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. Answer: E 22

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. 22) In Figure 7.1, what is the thermal death time? A) 150°C B) 60 minutes C) 120 minutes

D) 100°C E) The answer cannot be determined based on the information provided. Answer: B 23

23) In Figure 7.1, the thermal death point for this culture is 1. A) 15 minutes. 2. B) 50°C. 3. C) 30 minutes. 4. D) 170°C. 5. E) The answer cannot be determined based on the information provided Answer: E 24

24) 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. Answer: B 25 25) 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 Answer: E 26 26) 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 Answer: B 27

27) 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 Answer: B 28

28) Which graph in Figure 7.2 best depicts the effect of placing the culture at 7°C at time x? A) a B) b

C) c D) d E) e Answer: D 29

29) 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 determined based on the information provided. Answer: C 30

30) 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. Answer: E 31

31) 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. Answer: E 32

32) In Table 7.2, which preservative is most effective? A) potassium sorbate B) sodium benzoate C) potassium sorbate + sodium benzoate D) no preservative Answer: B 33 33) 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. Answer: E 34 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. Answer: D 35 35) All of the following substances are used to preserve foods EXCEPT A) biguanides. B) nisin. C) potassium sorbate. D) sodium nitrite. E) calcium propionate. Answer: A 36

36) 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. Answer: A 37

37) In Table 7.3, which disinfectant was bactericidal? 1. A) Doom 2. B) K.O. 3. C) Mortum 4. D) Sterl 5. E) The answer cannot be determined based on the information provided. Answer: C 38 38) 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. Answer: E 39 39) All of the following are effective for destroying prions EXCEPT A) boiling.

B) incineration. C) NaOH + autoclaving at 134°C. D) proteases. E) None of the answers are correct; each of these will destroy prions. Answer: A 40 40) 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 Answer: E 41 41) All of the following are methods of food preservation EXCEPT A) desiccation. B) high pressure. C) ionizing radiation. D) microwaves. E) osmotic pressure. Answer: D 42 42) 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 Answer: C 43 43) 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 121°C for one hour E) pressure cooker at 121°C for 15 minutes Answer: E 44 44) Bone and tendons for transplant are decontaminated by A) ethylene oxide. B) glutaraldehyde. C) peroxygens. D) plasma sterilization. E) supercritical fluids. Answer: E 45 45) Which one of the following is most resistant to chemical biocides? 1. A) gram-negative bacteria 2. B) gram-positive bacteria 3. C) mycobacteria 4. D) protozoan cysts 5. E) viruses with lipid envelopes Answer: A 46 46) 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. Answer: C

1 THE TERMINOLOGY OF MICROBIAL CONTROL Aseptic Surgery

Techniques used in surgery to prevent microbial contamination from the instruments, operating personnel, and the patient. 2 THE TERMINOLOGY OF MICROBIAL CONTROL Sterilization The destruction or removal of all microbial life, including endospores. 3 THE TERMINOLOGY OF MICROBIAL CONTROL How do you sterilize liquids or gases? By using filtration. 4 THE TERMINOLOGY OF MICROBIAL CONTROL Sterilant Is a sterilizing agent. 5 THE TERMINOLOGY OF MICROBIAL CONTROL Commercial Sterilization The process of treating canned goods aimed at destroying the endospores of Clostridium botulinum (a kind of food poisoning). 6 THE TERMINOLOGY OF MICROBIAL CONTROL Why is commercial sterilization important? Clostridium botulinum produces a deadly toxin. More-resistant endospores of thermophilic (heat-loving) bacteria are capable of causing food spoilage but not human disease, and they will not germinate and grow at normal food storage temperatures. 7 THE TERMINOLOGY OF MICROBIAL CONTROL Disinfection Any treatment used on inanimate objects to kill or inhibit the growth of microorganisms; removing pathogens. 8 THE TERMINOLOGY OF MICROBIAL CONTROL Antisepsis A chemical method for disinfection of the skin and mucous membranes; removing pathogens from living tissues. 9

THE TERMINOLOGY OF MICROBIAL CONTROL Antiseptic Is the chemical used to perform the antisepsis technique. 10 THE TERMINOLOGY OF MICROBIAL CONTROL Sepsis The presence of a toxin or pathogenic organism in blood and tissue; refers to microbial contamination. 11 THE TERMINOLOGY OF MICROBIAL CONTROL Asepsis The absence of contamination by unwanted organisms. 12 THE TERMINOLOGY OF MICROBIAL CONTROL Degerming The mechanical removal of microorganisms in an area or injection site, rather than killing them; also called degermation. 13 THE TERMINOLOGY OF MICROBIAL CONTROL Sanitization The removal of microorganisms from eating utensils and food preparation areas. 14 Biocide, or Germicide A substance capable of killing microorganisms (except endospores). 15 THE TERMINOLOGY OF MICROBIAL CONTROL Suffix -cide Names of treatments that cause the outright death of microbes; meaning kill. 16 Bacteriostasis A treatment capable of inhibiting bacterial growth. 17 EFFECTIVENESS OF TREATMENT Depends on: 1. The number of microbes. 2. Environment (organic matter, temperature, biofilms).

3. The time of exposure. 4. Microbial characteristics. 18 ACTION OF MICROBIAL CONTROL AGENTS 1. Alterations of membrane permeability. 2. Damage to proteins. 3. Damage to nucleic acids. 19 HEAT Thermal death point (TDP) The temperature required to kill all the bacteria in a liquid culture in 10 minutes. 20 HEAT Thermal death time (TDT) The length of time required to kill all bacteria in a liquid culture at a given temperature. 21 HEAT Decimal reduction time (DRT) The time (in minutes) required to kill 90% of a bacterial population at a given temperature; also called D value. 22 MOIST HEAT STERILIZATION Moist heat denatures proteins. 23 MOIST HEAT STERILIZATION Autoclave Equipment for sterilization by steam under pressure; usually operated at 15 psi and 121°C to kill all organisms (except prions)and their endospores in about 15 minutes; guaranteed complete sterilization. 24 Pasteurization The process of mild heating to kill particular spoilage microorganism or pathogens; normal pasteurization is 63°C for 30 minutes; does not achieve complete sterilization only reduces microbes. 25 PASTEURIZATION

1. Reduces spoilage organisms and pathogens. 2. EQUIVALENT TREATMENTS: a) 63°C for 30 min b) High-temperature short-time c) Ultra-high-temperature d) Thermoduric organisms survive 26 PASTEURIZATION High-temperature short-time (HTST) pasteurization Pasteurization at 72°C for 15 seconds. 27 PASTEURIZATION Ultra-high-temperature (UHT)treatments A method of treating food with high temperatures (140-150°C for 4 seconds) for very short times to make food sterile so that it can be stored at room temperature. 28 What are the differences between HTST and UHT? 1. HTST is pasteurization and has to be refrigerated for a certain amount of time (usually 2 weeks) before it spoils. 2. UHT is sterilized and can be stored for several months without refrigeration; an example is the small coffee creamers found in restaurants. 29 Thermoduric bacteria Heat resistant; survive pasteurization; unlikely to cause disease or cause refrigerated milk to spoil. 30 DRY HEAT STERILIZATION Kills by: 1. Dry heat 2. Flaming 3. Incineration 4. Hot-air sterilization 31

DRY HEAT STERILIZATION Dry heat Kills by oxidation effects. 32 DRY HEAT STERILIZATION Flaming The process of sterilizing an inoculating loop by holding it in an open flame. 33 DRY HEAT STERILIZATION Incineration Burning to ashes. 34 DRY HEAT STERILIZATION Hot-air sterilization Sterilization by the use of an oven at 170°C for approximately 2 hours. 35 DRY HEAT STERILIZATION Equivalent treatments Different methods that have the same effect on controlling microbial growth. 36 FILTRATION The passage of a liquid or gas through a screenlike material; a 0.45µm filter removes most bacteria; heat labile (sensitive)substances should be sterilized by filtration and not heat. 37 FILTRATION High-efficiency particulate air (HEPA) filters A screenlike material that removes particles greater than 0.3µm from air. 38 FILTRATION Membrane filters A screen-like material with pores small enough to remove microbes greater than 0.22µm from air; a 0.45µm filter retains most bacteria; used for liquids. 39 FILTRATION Filterable viruses Unseen pathogens that passed through the filters (causing such disease as rabies) made of unglazed porcelain in the early days of microbiology.

40 PHYSICAL METHODS OF MICROBIAL CONTROL Kills by: 1. Low temperature 2. High pressure 3. Desiccation 4. Osmotic pressure 41 PHYSICAL METHODS OF MICROBIAL CONTROL Low temperature 1. Creates a bacteriostatic effect at temperatures of ordinary refrigerators (07°C) because it reduces the metabolic rate of most microbes so that they cannot reproduce or synthesize toxins; rapidly attained subfreezing temperatures tend to render microbes dormant but do not necessarily kill them. 2. INHIBITS MICROBIAL GROWTH: a) Refrigeration b) Deep-freezing c) Lyophilization 42 PHYSICAL METHODS OF MICROBIAL CONTROL Lyophilization In the absence of water (desiccation) microorganisms cannot grow or reproduce but can remain viable for years and then resume their growth and division once water is made available to them; also called freeze-drying, which is a laboratory process for preserving microbes. 43 PHYSICAL METHODS OF MICROBIAL CONTROL High pressure Denatures proteins 44 PHYSICAL METHODS OF MICROBIAL CONTROL Desiccation The removal of water; drying; prevents metabolism. 45

PHYSICAL METHODS OF MICROBIAL CONTROL Osmotic pressure High concentrations of salt and sugars causes PLASMOLYSIS which is the loss of water from a cell in a hypertonic environment; can't metabolize but inhibits their growth 46 RADIATION Types: 1. Ionizing radiation 2. Nonionizing radiation 3. Microwaves 47 RADIATION Ionizing radiation 1.Gamma rays, X rays, or High-energy electron beams, has a wavelength shorter than that of nonionizing radiation less than about 1nm. 2. Ionizes water to release OH. 3. Damages DNA. 48 RADIATION Non-ionizing radiation 1. Short-wavelength radiation that does not cause ionization; radiation is not very penetrating; ultraviolet (UV) radiation (260nm) is an example. 2. Damages DNA. 49 RADIATION Microwaves 1. Electromagnetic radiation. 2. Kill by radiation; not especially antimicrobial. 50 PRINCIPLES OF EFFECTIVE DISINFECTION

1. Concentration 2. Organic matter 3. pH 4. Time 51 USE-DILUTION TEST 1. A method of determining the effectiveness of a disinfectant using serial dilutions. 2. Metal rings dipped in test bacteria are dried. 3. Dried cultures are placed in disinfectant for 10 min at 20°C. 4. Rings are transferred to culture media to determine whether bacteria survived treatment. 52 DISK-DIFFUSION METHOD An agar-diffusion test to determine microbial susceptibility to chemotherapeutic agents; also called Kirby-Bauer test. 53 Phenol Also called carbolic acid; first used by Lister to control surgical infections in the operating room. 54 Phenolics A derivative of phenol used as a disinfectant. 55 PHENOL & PHENOLICS Disrupt plasma membranes 56 Cresol Phenolic derived from coal tar; are very good surface disinfectants. 57 Why are phenolics useful as disinfectants? 1. They remain active in the presence of organic compounds. 2. They are stable. 3. They persist for long periods after application. 58 Bisphenols 1. A derivative of phenol that contains two phenol groups connected by a bridge (bis indicates

two). 2. HEXACHOLORPHENE, TRICLOSAN: disrupt plasma membrane 59 Hexachlorophene A type of bisphenol used to control infections in nurseries; excessive use on infants can lead to nerve damage. 60 Triclosan A bisphenol used in antibacterial soaps, at least one toothpaste, and kitchen cutting boards and plastics; it inhibits an enzyme needed for the biosynthesis of fatty acids (lipids), which mainly affects the plasma membrane; effective againt gram positive bacteria and also works well against gram-negative bacteria. 61 Biguanides CHLORHEXIDINE: disrupt Plasma membrane 62 Chlorhexidine A Biguanide used for microbial control on skin and mucous membranes. 63 Fungicide A substance capable of killing fungi. 64 Virucide A substance capable of inactivating viruses. 65 Suffix -stat or -stasis Names of treatments that inhibit the growth and multiplication of bacteria; meaning to stop or to steady. 66 Several factors influence the effectiveness of antimicrobial treatments: 1. The number of microbes 2. Environmental influences: a. Organic matter b. Microbes in surface biofilms c. Suspended medium 3. Time of exposur...