Microbiology exam 3 Flashcards

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Filtration is a(n) ________ method of achieving sterilization.



Which of the following is most susceptible to antimicrobial agents?

vegetative bacteria


Compared to moist heat methods, dry heat needs which of the following in order to sterilize effectively?

higher temperature and increased time


Hydrogen peroxide is an example of __________ and can serve as an effective disinfectant, though it does NOT work well as an antiseptic.

an oxidizing agent


Elements such as iodine, chlorine, and bromine are examples of (oxidizers/halogens/metals), which are the basis for many effective antimicrobial agents.



Why are endospores used to measure the effectiveness of autoclave sterilization?

Endospores are very hard to kill.


An antimicrobial chemical used on the skin is usually called __________.

an antiseptic


Milk that can be stored for months at room temperature has been treated by which of the following methods?

ultrahigh-temperature sterilization


Which of the following could be used to sterilize a heat-sensitive liquid such as urea broth?



A piece of medical equipment is heat-sensitive and water-sensitive. The best method of sterilization for this equipment would be

treatment with a gaseous agent like ethylene oxide


An antimicrobial drug that blocks the transport of NAG and NAM from the cytoplasm is targeting which of the following cellular processes?

cell wall synthesis


An antimicrobial disk on a Kirby-Bauer plate that shows no zone of inhibition indicates that the microbe being tested is __________ to the drug.



Inhibiters of DNA synthesis specifically effective on prokaryotes are



The majority of broad spectrum antibacterial medications inhibit (DNA/protein/RNA) synthesis.



Second-generation drugs are semisynthetic drugs developed to combat (immunity/resistance) against an existing drug.



Some bacterial cells are resistant to a variety of antimicrobials because they actively pump the drugs out of the cell.

true * Efflux pumps


Alterations in the structure of which of the following are an important aspect of Gram-negative bacterial resistance to antimicrobial drugs?



Which of the following can result when antibiotic therapy disrupts the normal microbiota?

both pseudomembranous colitis and thrush


Recent years have seen a significant increase in antibiotic-resistant bacteria. Perhaps the best known is methicillin-resistant Staphylococcus aureus (MRSA), which is resistant to beta-lactam antibiotics (e.g., penicillin, oxacillin). The emergence of more and more resistant organisms underscores not only the need for responsible use of antimicrobials, but also the importance of discovering new antibiotics that can treat infections in new ways. You are a microbiologist working in the drug discovery and development (D&D) group at a pharmaceutical company. Drug discovery refers to the actual process of identifying compounds with pharmaceutical potential. While this represents a significant task, it is only the first step in many on the way to generating a new antibiotic. When promising antimicrobial compounds are discovered, development of the antibiotic for commercial use begins. Drug development refers to all of the events that must occur following discovery to move ahead with the drug as a potential therapeutic. This includes everything from the extraction and large-scale production of the drug to designing effective methods of delivery. As you answer the following questions, imagine yourself working as part of the D&D team to identify and validate potential new antibiotics.



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?

The exposure of bacteria to an antibiotic causes the 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.


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?

chemotherapeutic agent



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.


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?

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.


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 __________.

8 μg/mlμg/ml; 16 μg/mlμg/ml

You have completed some of the important initial steps necessary in the development of a new antibiotic. From here, more extensive testing will be required to determine the effectiveness in a eukaryotic host. Experiments will also need to be conducted in order to determine safe and effective dosage and delivery. While this activity has highlighted some of the important steps taken during the discovery and development of a new antibiotic, it is important to realize that this is a time- and funding-intensive process. In reality, new antibiotic discovery and development can take decades and cost millions of dollars.


A new drug blocks the adhesins on the surface of a bacterial pathogen. What would likely be the major effect of this drug?

It will prevent infection by this pathogen.


Infection and disease are NOT the same thing because __________.

one can be infected without showing any signs or symptoms of disease


A patient's immune system is typically fully responsive during which of the following stages of disease?



An epidemiologist collects drinking glasses, tissues, and bed sheets from the apartment of an individual infected with a particular disease. Which of the following modes of transmission is being investigated for this disease?

indirect contact transmission


Fecal-oral infections are usually a result of __________.

waterborne infection


Which of the following might result in a nosocomial infection (HAI)?

a hospital aide forgetting to wash his or her hands before tending a patient


The bacterium that causes tuberculosis can be expelled from the lungs by a cough and remain viable in the air for an hour or more. If a person inhales the bacteria from the air, what type of transmission has occurred?



A person is exposed to desert air containing fungus spores and develops valley fever as a result. Valley fever is an example of a ________ disease.



Several days after a walk in the woods, Cheryl develops a localized rash. It is not painful and soon fades so she thinks nothing of it. Several months later she experiences increasing fatigue, low-grade fever, and pain in the joints. These symptoms persist for months before she seeks medical attention. This description is most consistent with a(n) ________ infection.



Toxins that affect the lining of the gastrointestinal tract are (endotoxins/enterotoxins/exotoxins).



Rubella, or three-day measles, passes through the (parenteral/placenta/mucous/skin) route to establish congenital infection of a fetus.



Nervous system function may be impaired by the action of (endotoxins/neurotoxins/cytotoxins)



Lipid A is a(n) (cytotoxin/endotoxin/exotoxin) that stimulates the body to release chemicals that cause fever, inflammation, diarrhea, hemorrhaging, shock, and blood coagulation.



Normal microbiota may cause disease if they are introduced into an unusual site in the body.



There were 100 new cases of syphilis last year in a given population of 100,000 people. At that time, 500 people in this population already had syphilis. The incidence of syphilis in this population is __________.

100 per 100,000


The pattern of new cases reported in North America represented in this graph is consistent with ________ transmission.

mosquito vector


Which of the following is NOT a reason that bacterial capsules are effective in the inhibition of phagocytosis?

They contain chemicals that are lethal to phagocytes.


A young woman was taking antibiotic pills for a urinary infection. Several days into her course of medication, she began to experience peculiar symptoms. At first they were hardly noticeable. Very quickly, however, they worsened and became embarrassing and unbearable.

She noticed a white coating on her tongue, bad breath, and an awful taste in her mouth. Despite persistent brushing and mouthwash applications, she was unable to completely remove the film. Furthermore, she had excessive vaginal discharges consisting of a cheeselike white substance. When she began to have vaginal itching, she finally decided it was time to seek help.

Reluctantly she revisited her personal physician and described the symptoms. Her doctor explained the symptoms and provided additional prescriptions to alleviate her distress.

What is microbial antagonism?

the ability of the normal flora to outcompete and outgrow pathogens

Normal flora is well adapted to its niche. These bacteria may utilize nutrients more quickly or produce bacteriocins that inhibit growth of other microbes.


What is a superinfection?

Superinfection is a disease caused by an organism that is often an opportunist or one that was present in low numbers. Superinfection is a sequel to removal of the normal flora by antibiotic treatment.

Removal of the normal flora allows opportunists that are normally present in low numbers to proliferate and produce disease.


What causes thrush?

Candida albicans causes thrush, especially in patients taking antibiotics. Antibiotics kill off the normal bacterial flora, and then the yeast can proliferate.


Which of the following classifications would best describe Candida albicans?


Candida albicans is a unicellular chemoheterotroph that has a nucleus.


If the patient were to get a subsequent urinary tract infection, what should the doctor prescribe knowing that she is susceptible to thrush?

The doctor should prescribe an antibiotic specific for the bacterial species causing the urinary infection.

By using an antibiotic specific for the bacterial species causing the infection it will increase the chances of the remaining normal flora still being present to counter any secondary infections.


A strain of Neisseria gonorrhea has a mutation which has caused it to lose the ability to produce fimbriae and become less virulent as a consequence. What function has this pathogen lost?

the ability to adhere to cells of the body


Rabies is an example of a zoonosis that is hard to control because __________.

its reservoir contains both domestic and wild animals


All of the following might lead to a disease caused by an opportunistic pathogen EXCEPT __________.

an encounter with an infected animal

Immune suppression, changes in one's diet, and hormonal changes can all lead to an opportunistic infection resulting in disease.


Microbes known as transient microbiota are

organisms that remain in the body for a short time.


A patient contracted a disease just by being in the same room with an infected individual for an extended period of time. Which of the following modes of disease transmission is most applicable in this situation?

vehicle transmission

Any of these modes of transmission are theoretically possible. However, evidence suggests that the infectious agent was probably spread through the air, a type of vehicle transmission.


The degree to which a microbe is able to cause disease is known as its (morbidity/virulence/toxicity).