ScienceBiologyChapter 7 example #1719
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Chapter 7

Yaqub Clark avatar Yaqub Clark
25 July 2022
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disinfectant
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An agent used to reduce the number of bacteria on a toilet would most accurately be called a(n)
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the cells in a population die at a constant rate
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which of the following best describes the pattern of microbial death? not all the cell in a culture are killed all the cells in a culture die at once the cells in a population die at a constant rate the pattern varies depending on the species the pattern varies depending on the antimicrobial agent
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toxins produced by the microbe
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When microbial control methods are used, microbes are destroyed at a constant rate; there is no instantaneous death of all the microbes present. That microbial death rate is influenced by all the following factors except the time of exposure the number of microbes toxins produced by the microbe the microbial characteristics
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a true antimicrobial control agent is equally effective against both bacteria and viruses
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Which of the following regarding antimicrobial control agents is FALSE? a true antimicrobial control agent is equally effective against both bacteria and viruses contaminating organic debris such as blood or sputum will decrease effectiveness some agents affect microbial membranes by dissolving lipids some agents are utilized as both antiseptic and a disinfectant some agents kill by denaturing microbial cell proteins
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mitochondria
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Microbial control methods usually target any of the following microbial structures EXCEPT which one? plasma membrane permeability microbial proteins mitochondria nuclei acids
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freezing
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which of the following methods is used to preserve food by slowing the metabolic processes of food borne microbes? lyophilization freezing non ionizing radiation ionizing radiation pasteurization
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gamma radiation
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Which of the following could be used to sterilize plastic Petri plates is a plastic wrapper microwaves autoclave sunlight gamma radiation ultraviolet radiation
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false
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Microorganisms placed in high concentrations of slats and sugars undergo lysis
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true
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Moist heat destroys organisms by denaturing proteins
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non of the answers are correct; all of these factors may contribute to hospital-acquired infection
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All of the following factors contribute to hospital-acquired infections EXCEPT invasive procedures can provide a portal entry for bacteria some bacteria metabolize disinfectant bacteria may be present in commercial products such as mouthwash gram-negative bacteria are often resistant to disinfectant non of the answers are correct; all these factors may contribute to hospital-acquired infection
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gram-positive bacteria, fungi, endospores, prions
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Which of the following correctly lists, in increasing order, the resistance of microorganisms to chemical biocides? protozoan cysts, fungi, gram-negative bacteria, prions gram-negative bacteria, fungi, protozoan cysts, mycobacteria prions, gram-negative bacteria, vegetative protozoa, gram-positive bacteria gram-positive bacteria, fungi, endospores, prions
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the exposure of bacteria to an antibiotic causes bacteria to produce resistance genes In the absence of a selective pressure, such as a certain drug, bacteria that possess genes that confer antibiotic resistance will reproduce more slowly due to the energy expense of maintaining resistance genes. In the presence of a selective pressure, however, the sensitive bacteria will be killed and the bacteria that possess genes that confer antibiotic resistance will have a reproductive advantage. Therefore, over time the genes for resistance will increase in frequency within the population.
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The project that you are working on was initiated in response to the growing threat of antibiotic resistance in both hospital and community settings. Even in the early discovery and development phase, it is important to think ahead to try to minimize the likelihood that bacteria will be able to evolve resistance to your new drug. Understanding how resistance emerges is an essential part of this process. Which of the following statements is NOT true regarding the evolution of antibiotic resistance in bacteria?
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antibiotic chemotherapeutic agent natural You have found bacteria that demonstrate antimicrobial activity in early testing. D&D chemists on your team have successfully extracted and purified the natural antibiotic from the bacteria. Your focus now turns to microbiological evaluation of the compound.
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Part complete One approach that is becoming more common in drug D&D is to search for antimicrobial-producing organisms in relatively pristine environments. A pristine environment is one that has been relatively unperturbed by humans and/or domestic animals. Your D&D team is searching for novel antimicrobials produced by bacteria in a remote area of a temperate rainforest in the Pacific Northwest. Which of the following terms would accurately describe your drug? antibiotic synthetic semisynthetic chemotherapeutic agent natural
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selective toxicity refers to the ability of an antimicrobial to kill microbes with minimal damage to the host Your studies using both in vitro and in vivo models indicate that your drug has a high selective toxicity. This means that it is effectively toxic against bacterial pathogens while having minimal toxic effects on the host (eukaryotic) cells.
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One aspect that must be evaluated during the development phase is the interaction of your drug with the host (i.e., what effect will the drug have on human cells?). There are several important factors to consider in this interaction, including the selective toxicity of your potential drug. Which of the following statements most accurately describes the principle of selective toxicity?
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inhibition of cell wall synthesis- penicillin inhibition of protein synthesis-streptomycin disruption of cytoplasmic membrane- gramicidin inhibition of general metabolic pathway- sulfanilamide inhibition of DNA or RNA synthesis- trifluoride
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Match each antibiotic with the appropriate mechanism of action inhibition of cell wall synthesis Inhibition of protein synthesis Disruption of cytoplasmic membrane Inhibition of general metabolic pathway Inhibition of DNA or RNA synthesis gramicidin penicillin sulfonamide trifluoride streptomycin
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8 ug/ml; 16ug/ml
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While in the development phase, you are also required to determine both the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for your drug. While these values directly relate to the efficacy of the drug against bacteria, they will also be informative for the next stages of development, which include studies to determine effective dosages within a host. The picture depicts the results of an MBC test. Based on these data, the MIC for your drug would be __________ and the MBC would be __________.
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1,000 cells
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This graph shows a microbial death curve for a bacterial population subjected to a heat treatment. Treatment began at time zero. About how many cells were still living after 4 minutes of treatment? 0 min= 5.0 log of # surviving cells 2 min= 4.0 log of # surviving cells 4 min= 3.0 log of # surviving cells
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10^5
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Part complete An antimicrobial chemical was added to a population of bacteria. The initial population was 107 living cells (10,000,000). After 2 minutes, only 106 cells still remained alive. After another 2 minutes (4 minutes of total treatment), about how many cells would still be alive?
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most of the cell death occurs early in the treatment
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Which of the following best describes why microbial death curves are typically plotted logarithmically?