Chapter 7: The Control of Microbial Growth

Hydroxyl radicals

most reactive of the toxic forms of oxygen cause DNA damage

Iodine

stains, irritating,

Answer: E Iodophors

7) Iodophors differ from iodine (I2) in that iodophors A) Don't stain. B) Are less irritating. C) Are longer lasting. D) Are combined with a nonionic detergent. E) All of the above.

Answer: C) c

Assume that one culture is a freshly opened package of dried yeast with 0.1% moisture, another culture is the same yeast with 7.5% moisture, and the third culture is a package of yeast mixed with water. Each culture was exposed to 130°C in a hot-air oven. Which graph in Figure 7.1 most likely shows the yeast with 0.1% moisture? A) a B) b C) c D) a and b E) b and c

surfactants

A contraction of surface active agents; substances that allow oil and water to mix, or emulsify.

Answer: E

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. 23) In Figure 7.2, the thermal death point for this culture is A) 15 min. B) 50°C. C) 30 min. D) 170°C. E) Can't tell from the data provided.

Iodophors

Complex of iodine and alcohol Have replaced free iodine solutions in medical antisepsis

Ethanol

Bactericide. Alcohol made by converting starches and sugars from plant material into alcohol and CO2.

Answer: E) Pressure cooker at 121°C for 15 minutes

If you were preparing nutrient agar at home and didn't have an autoclave, what could you use to sterilize the nutrient agar? A) Bleach B) Boiling for 1 hour C) Hydrogen peroxide D) Oven at 121°C for 1 hour E) Pressure cooker at 121°C for 15 minutes

Answer: B 60 min

In Figure 7.1, what is the thermal death time for culture (a)? A) 150°C B) 60 min. C) 120 min. D) 100°C E) Can't tell

Answer: B 15 min.

In Figure 7.2, the decimal reduction time (D value) for the culture is approximately A) 0 min. B) 15 min. C) 30 min. D) 45 min. E) 60 min.

Answer: E

In Figure 7.2, the thermal death time for this culture is A) 0 min. B) 10 min. C) 20 min. D) 40 min. E) 60 min.

Ag

Silver helps with burns

Answer: E

Table 7.1 A disk-diffusion test using Staphylococcus gave the following results: Disinfectant Zone of inhibition (mm) A 0 B 2.5 C 10 D 5 In Table 7.1, which compound was the most effective against E. coli? A) A B) B C) C D) D E) Can't tell

Answer: B Sodium Benzoate

Table 7.2 The fate of E. coli O157:H7 in apple cider held at 8°C for 2 weeks, with and without preservatives, is shown below: Bacteria/ml Cider only 2.2 Cider with potassium sorbate 2.0 Sodium benzoate 0 Sorbate + benzoate 0 32) In Table 7.2, which preservative is most effective? A) Sorbate B) Sodium Benzoate C) Sorbate + benzoate D) No preservative

Answer: A. Doom

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) Doom K.O. Dilution Initial Subculture Initial Subculture 1:16 - + + + 1:32 - + + + 1:64 - + + + 1:128 + + + + Mortum Sterl Dilution Initial Subculture Initial Subculture 1:16 - - - + 1:32 - + + + 1:64 + + + + 1:128 + + + + 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) Can't tell

Answer: C

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) Doom K.O. Dilution Initial Subculture Initial Subculture 1:16 - + + + 1:32 - + + + 1:64 - + + + 1:128 + + + + Mortum Sterl Dilution Initial Subculture Initial Subculture 1:16 - - - + 1:32 - + + + 1:64 + + + + 1:128 + + + + In Table 7.3, which disinfectant was bactericidal? A) Doom B) K.O. C) Mortum D) Sterl E) Can't tell

Answer: B Glutaraldehyde

Which of the following substances is NOT an oxidizing agent? A) Chlorine B) Glutaraldehyde C) Hydrogen peroxide D) Iodine E) Ozone

Answer: A Alcohol

Which of the following substances is NOT effective against nonenveloped viruses? A) Alcohol B) Chlorine C) Ethylene oxide D) Ozone E) All are equally effective.

Answer: A) Biguanides

Which of the following substances is NOT used to preserve foods? A) Biguanides B) Nisin C) Potassium sorbate D) Sodium nitrite E) Sodium propionate

Answer: C Chlorhexidine

Which of the following substances is used for surgical hand scrubs? A) Phenol B) Chlorine bleach C) Chlorhexidine D) Soap E) Glutaraldehyde

Answer: D They are equivalent treatments.

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

Answer: A) Boiling

Which of the following will NOT destroy prions? A) Boiling B) Incineration C) NaOH + autoclaving at 134°C D) Proteases E) All of the above destroy prions.

Answer: C) High pressure

Which of the following will NOT inactivate endospores? A) Autoclave B) Chlorine dioxide C) High pressure D) Plasma E) Supercritical CO2

Answer: D

Which of the following will NOT preserve foods? A) Desiccation B) High pressure C) Ionizing radiation D) Microwaves E) Osmotic pressure

Answer: C Bisphenols

Which of these disinfectants acts by denaturing proteins? A) Alcohols B) Aldehydes C) Bisphenols D) Halogens E) Phenolics

Answer: A -Acid-anionic detergents

Which one of the following does NOT belong with the others? A) Acid-anionic detergents B) Benzoic acid C) Supercritical CO2 D) Pasteurization E) Peracetic acid

Answer: D Hydrogen peroxide

Which one of the following does NOT belong with the others? A) Beta-propiolactone B) Glutaraldehyde C) Ethylene oxide D) Hydrogen peroxide E) Propylene oxide

Answer: C) Mycobacteria

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

Answer: E) Ultraviolet radiation - desiccation

Which one 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

Heat-labile solutions

are typically sterilized by filtration.

Prions

infectious protein particles that do not have a genome

ionizing radiation

radiation with enough energy to knock electrons off some atoms of a bombarded substance to produce ions

Thermal death time (TDT)

shortest length of time required to kill all test microbes at a specified temperature

Mycobacterium tuberculosis

tuberculosis

hypochlorous acid (HOCl)

bleach The antimicrobial activity of chlorine is due to

desiccation

dehydration; the process of being rendered free from moisture

gamma radiation

High-energy radiation emitted by the nuclei of radioactive atoms.

Answer: C Ethylene oxide

Which of the following substances can sterilize? A) Alcohol B) Phenolics C) Ethylene oxide D) Chlorine E) Soap

organic acids/carboxylic acids

- food preservation R--COOH (carboxyl group), prepared by mild oxidation of aldehydes, simpliest is methanoic acid (in ants, bees, etc), add -oic to alkane stem

Mycobacteria

Acid Fast; fever, night sweats, wt loss, hemoptysis M. tuberculosis: TB, M. kansasii: TB-like sx M. avium-intracellulare: AIDS prophyl: Azithromycin

Glutaraldehyde (Cidex)

Antiseptic and Germicidal and disinfectant for hospitals. Its safe, acts quickly, attacks all mirobes, not hampered by organic materials

Answer: E) Supercritical fluids.

Bone and tendons for transplant are decontaminated by A) Ethylene oxide. B) Glutaraldehyde. C) Peroxygens. D) Plasma sterilization. E) Supercritical fluids.

Bisphenols

Denaturate protiens, disrupt plasma membranes, Hexacholorphene, triclosan

Ultraviolet Radiation (UV)

Electromagnetic waves between visible light and X-rays in the electromagnetic spectrum.

Answer: B

Figure 7.3 Assume 109 E. coli cells/ml are in a flask. Which graph in Figure 7.3 best depicts the effect of placing the culture in an autoclave for 15 min. at time x? A) a B) b C) c D) d E) e

Answer: A Stains and corrodes

Glutaraldehyde is considered one of the most effective disinfectants for hospital use. Which of the following statements about glutaraldehyde is false? A) Stains and corrodes B) Is safe to transport C) Acts rapidly D) Is not hampered by organic material E) Attacks all microorganisms

Membrane filtration

Liquid media containing heat-sensitive components would best be sterilized by

Quats (Quaternary Ammonium Compounds)

Low-Level disinfectant. Cationic, incompatible with soap. denatures essential cell protein, and disrupts cell membranes. Environmental sanitation of non-critical surfaces such as floors, walls, & furniture. Not the disinfectant of choice for use in central service.

H2O2 (hydrogen peroxide)

Organic Peroxides are great for open wounds

Autoclave

Piece of equipment used to sterilize articles by way of steam under pressure and/or dry heat.

Answer: D 3, 2, 1

Place the following surfactants in order from the most effective to the least effective antimicrobial activity: 1-Soap; 2-Acid-anionic detergent; 3-Quats. A) 1, 2, 3 B) 1, 3, 2 C) 2, 1, 3 D) 3, 2, 1 E) 3, 1, 2

Answer: E

Table 7.1 A disk-diffusion test using Staphylococcus gave the following results: Disinfectant Zone of inhibition (mm) A 0 B 2.5 C 10 D 5 29) In Table 7.1, which compound was the most effective against Staphylococcus? A) A B) B C) C D) D E) Can't tell

Answer: E

Table 7.1 A disk-diffusion test using Staphylococcus gave the following results: Disinfectant Zone of inhibition (mm) A 0 B 2.5 C 10 D 5 In Table 7.1, which compound was bactericidal? A) A B) B C) C D) D E) Can't tell

Answer: E. Can't tell

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) Doom K.O. Dilution Initial Subculture Initial Subculture 1:16 - + + + 1:32 - + + + 1:64 - + + + 1:128 + + + + Mortum 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? A) Doom B) K.O. C) Mortum D) Sterl E) Can't tell

Answer: A The formation of hypochlorous acid

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 free O E) Disruption of the plasma membrane

Chlorine dioxide

Used for water treatment Used to disinfect endospores -Congress after the anthrax attacks in 2001

Answer: B 70%

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

Answer: D

Which graph in Figure 7.3 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: E All of the above

Which of the following affects the elimination of bacteria from an object? A) Number of bacteria present B) Temperature C) pH D) Presence of organic matter E) All of the above

Answer: A The cells in a population die at a constant rate.

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: B Gamma radiation

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 Pasteurization

Which of the following does NOT achieve sterilization? A) Dry heat B) Pasteurization C) Autoclave D) Formaldehyde E) Ethylene oxide

Answer: D Cell lysis

Which of the following does NOT directly result from application of heat? A) Breaking of hydrogen bonds B) Breaking of sulfhydryl bonds C) Denaturing of enzymes D) Cell lysis E) Damage to nucleic acids

Answer: E

Which of the following is NOT a factor contributing to hospital-acquired infections? 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) All of the above may contribute to hospital-acquired infection.

Answer: E Heat

Which of the following is NOT used to disinfect water? A) Ozone B) Gamma radiation C) Chlorine D) Copper sulfate E) Heat

Answer: D Cannot be used with heat-labile materials

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

Answer: C Membrane filtration

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: B Alcohols - open wounds

Which of the following pairs is mismatched? A) Ag - burns B) Alcohols - open wounds C) CuSO4 - algicide D) H2O2 - open wounds E) Organic acids - food preservation

nutrient agar

a general "catch-all" agar that will grow anything

nonenveloped viruses

consist only of the nucleic acid and capsid

CuSO4

copper sulfate algicide

Proteases

enzymes that break down proteins but now prions

algicide

killer of algae

Mycobacterium leprae

leprosy (Hansen's disease)

Decimal Reduction Time (DRT)

the time, in minutes, in which 90% of a population of bacteria at a given temperature will be killed

Acid-anionic detergents

used to clean dairy equipment