Learning Catalytics Exam 3

Identify the growth phase in which cephalosporin would be most effective.

Cephalosporin targets the "building" of peptidoglycan, which is what the cell wall is composed of. Cell walls are "built" when the cell is undergoing binary fission, which is at its peak during the log phase. Thus, cephalosporin would be most effective in preventing the "building" of the cell wall when the bacteria are most actively producing it, which is the log phase.

What type of antibiotic is this?

Cephalosporins

The highest levels of antibiotic in the blood would result from which type of administration ?

Continuous Intravenous

The Kirby-Bauer disk diffusion test is used to determine whether a microorganism is sensitive, intermediate, or resistant to an antibiotic. From the antibiotic sensitivity table and data table, determine which antibiotic all three microorganisms are resistant to.

Erythromycin

After staining the background, many strains of B. pertussis resemble the staining pattern shown in the figure below. What structure do they possess that contributes to their virulence?

capsule

In conjugation, F+ cells.....

contain an F plasmid.

Which of the following infectious agents is least resistant to methods of microbial control?

enveloped viruses

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

higher temperature and increased time

Normal flora ________ colonization of pathogenic organisms.

prevent

Which of the following causes mutations by creating thymine dimers?

ultraviolet light

If you were preparing a medium for microbial culture at home but did not have an autoclave, what would be the most effective way to sterilize the medium?

using a pressure cooker at 121 C for 15 minutes

Most drug resistance genes are located on the ____________.

R plasmid

What is one disadvantage associated with the use of broad-spectrum antibiotics?

They kill normal microbiota.

Most antibiotics come from what source?

bacteria

Which of the following disease cannot be treated with antibiotics?

-Influenza -A Cold -smallpox

Which of the following is correct pertaining to endotoxins?

-Made up of the lipid A portion of the LPS complex. -Considered moderately toxic and requires a large amount to be fatal. -Can lead to fever, diarrhea, and vomiting.

Identify all of the mechanisms that contribute to the huge diversity of microorganisms.

-Mutation -Transposition -Recombination -Transduction -Transformation -Conjugation -Natural selection

Which of the following would be correct about our microbiota?

-The lower respiratory tract typically lacks microflora in healthy individuals. -Women are more prone to urinary tract infections.

Which of the following are true about exotoxins?

-They can be categorized as superantigens, AB toxins, or cytolytic toxins. -A small amount can be lethal. -They can be destroyed by heat.

Which of the following are ways that humans acquire normal microbiota?

-during first meals. -during first breaths. -during birth.

A population of bacteria may evolve resistance to a drug over time. Draw the rest of the curve on this graph to show how the population size would change after the introduction of a new antibiotic. Assume that there are some drug-resistant bacteria in the population.

After the addition of a new antibiotic, the bacterial population size would decrease almost to zero, except for a few drug-resistant bacteria. Those drug-resistant bacteria would then multiply and the overall population size would increase again (this time composed of all drug-resistant bacteria).

Which of the following methods of DNA repair involves enzymes that recognize and correct nucleotide errors in unmethylated strands of DNA?

Mismatch repair

A population of bacteria may evolve resistance to a drug over time. This graph shows the growth of a bacterial population before and after the introduction of an antibiotic, with some bacteria becoming resistant to the antibiotic. Mark the point on the graph's curve to indicate when the antibiotic was first added.

The addition of an antibiotic would kill most of the bacteria in a population, causing the population size to decline rapidly. This time point is seen on the graph where the population is the highest, just before the bacterial population size begins to rapidly decline.

The therapeutic index is a useful measure of an antibiotic when is comes to choosing which antibiotic to use. It assesses the antibiotic based on the criteria that_________________.

The best drug to use is that for which the organism is most sensitive and which is the least toxic to the host

Identify a target for an antimicrobial drug that could only affect bacteria.

The cell wall. Only bacteria have peptidoglycan. Targeting protein synthesis, DNA replication, and the plasma membrane could affect mitochondria and/or chloroplasts. Targeting inhibition of essential metabolite synthesis could affect archaea and/or the host organism.

Antibiotic resistance is a growing problem in healthcare. Imagine you are working for a drug company looking for new antibiotics that can be used to more effectively treat bacterial infections. Your ideal drug will not only kill pathogens, but it will not harm eukaryotic cells. Keeping these goals in mind, which three prokaryotic structures/features would you choose to target?

There are several viable options to target. Some would include: peptidoglycan, ribosome, porins, LPS, teichoic acid.

Microbial biofilms form on virtually every surface in environments exposed to microbes. In fact, the biofilm may indeed be the "default" mode of growth for most microbes. Below are confocal microscopic images of a biofilm forming on a surface at various time intervals (bacterial cells are green in these images). See if you can match the confocal images with the model diagrams illustrating the stages of typical biofilm formation on a surface.

a. - 2. colonization b. - 3. maturation c. - 1. attachment Biofilm formation typically progresses through stages in which a few cells attach to a surface, the cells then grow and form colonies on the surface, changing their mode of growth from planktonic to biofilm-producing in the process, and eventually the biofilm develops into a spatially-complex, diverse three-dimensional community.

Clostridium difficile (C. diff) can proliferate after antibiotic therapy because

antibiotics reduce microbial antagonism by normal microbiota

Which of the following is not considered a virulence factor for attaching bacteria to host tissue surfaces?

streptolysin

The most frequent portal of entry for pathogens is...

the respiratory tract.