Lesson 7 Homework and Quiz

Immunopathogenesis

- Damage to host tissues caused by the immune system's response to an infection - The damage done by "friendly fire," or that done by the host's own immune system during an immune response to a pathogen

Reservoir

- Harbors infectious microbes

Primary Pathogen

- Have mechanisms that help the organism overcome host defenses in a healthy host - Can breach healthy host defenses

The cholera toxin, an AB exotoxin, creates a(an) ___________ environment in the intestinal lumen when compared to the cytoplasm of the intestinal cells.

- Hypertonic

Virulence is measured by __________, or the dose needed to __________ of hosts.

- ID50, cause symptoms in 50%

Best treatment for MRSA

- If this organism was the cause of an infection, the patient would benefit most by taking rifampin. This is because there is a large zone of inhibition, and the organism is clearly susceptible to this drug. From the Kirby-Bauer test results, there is no zone of inhibition around the penicillin, erythromycin, or tetracycline disks. Therefore, this organism is resistant to those drugs. Penicillin, erythromycin, and tetracycline are not ideal choices to treat an infection caused by this bacterial species.

What is evidence that a pathogenicity island was initially acquired by horizontal transfer?

- It contains higher GC content that the rest of the genome

Who discovered the epidemiology for cholera in the mid-nineteenth century?

- John Snow ** He used a geographic approach to an outbreak to identify the source of infection.

The term used to designate how many bacteria or viruses are required to kill 50% of an experimental group of hosts is

- LD50

A pathogenic bacterium has a low lethal dose 50% (LD50). What does this mean?

- Only a few of the bacteria are required to kill 50% of infected hosts Explanation: The LD50 is the number of bacteria, or virions, required to kill 50% of an experimental group of animals. Determining the LD50 of a pathogen is a way of measuring its virulence, which is a measure of the severity of a disease. The lower a pathogen's LD50, the more virulent the pathogen.

A bacterial strain exhibiting a DNA gyrase mutation would most likely inhibit the activity of this

- Quinolones

Endotoxins

- Released by dead cells - Harm the host by overstimulating the host's immune system - Component of lipopolysaccharide - Produced by Gram-Negative bacteria - Virulence factor

Opportunistic Pathogen

- Requires a compromised host - Ex. staph infection in wounds

Exotoxins

- Secreted by living cells - Composed of protein - Include hemolysins - Produced by Gram-Positive and Negative bacteria - Virulence factor

A chef cut her finger accidentally. The next morning, she felt pain and warmth and had a little swelling and redness on that finger (which are signs of inflammation). By that night, she was just fine. Which of the following pertains to the chef?

- She had an infection

The cholera toxin, an AB exotoxin, attaches an ADP-ribose group to the host's stimulatory G factor (Gs). The normal function of Gs is to stimulate the host's adenylate cyclase, which produces the second messenger molecule cAMP. This toxin-mediated ADP-ribosylation of Gs has what effects?

- The constant activation of Gs, causing an increase in cAMP levels resulting in increased ion transport from the infected cell

What best defines the desirable selective toxicity of an antibacterial drug?

- The drug negatively impacts prokaryotic cell biology but does not alter eukaryotic cell biology.

Minimum Inhibitory Concentration

- The in vitro effectiveness of an antimicrobial agent is determined by measuring how little of it is needed to stop growth. This amount is classically measured in terms of an antibiotic's minimal inhibitory concentration (MIC), defined as the lowest concentration of the drug that will prevent the growth of an organism. The tube you selected demonstrates the lowest concentration of tetracycline that prevents turbidity of the medium. Recall that turbidity is cloudiness of the medium that develops as bacterial growth happens.

Epidemiology

- The study of diseases in populations

What do the following infections have in common: periodontitis, recurrent tonsillitis, chronic otitis media, and osteomyelitis?

- They are all found in bacterial biofilms

What makes multidrug efflux pumps such a dangerous resistance mechanism?

- They can export a wide range of antibiotics almost regardless of structure.

Pandemic

- a disease outbreak that occurs over a wide geographic area, usually the world. These may be long-lived, such as the bubonic plague in the fourteenth century and the AIDS in the late twentieth and early twenty-first centuries, or they may be short-lived, as with the 1918 flu.

The identification of a microbe using an algorithm means that

- a series of yes/no answers leads to the next test

A bacterial diagnosis of Mycobacterium avium in a sputum sample from an AIDS patient would be best determined by which method?

- acid-fast (Ziehl Neeson) staining

An example of an antibiotic that binds to the 30S ribosomal subunit would be

- aminoglycosides

An antibiotic is ________ if it kills the target microbe, whereas it is ________ if it merely prevents bacterial growth.

- bactericidal - bacteriostatic

Differential media help discriminate among organisms based on their

- biochemistry

What is nonproteinaceous, yet toxic, compound found in all Gram-negative bacteria?

- endotoxin

A disease is an _________ when larger-than-normal numbers of individuals in a population become infected over a short time.

- epidemic

Collaborators necessary to solve and control a human epidemic include

- epidemiologists, ecologists, veterinarians, and scientists

If a drug were designed that only seemed to affect the growth of Burkholderia pseudomallei, this drug would be considered ________ range.

- extremely narrow

Which of the following does NOT result from the release of endotoxin from Gram-negative bacteria? a. activation of the alternate complement pathway b. vasodilation c. hypertension d. shock e. fever

c. hypertension

Sulfonamides are antibiotics that target

- intermediary metabolism explanation: Sulfonamides are antibiotics that target intermediary metabolism. The sulfa drugs, originally discovered by Gerhard Domagk, belong to a group of drugs known as antimetabolites because they interfere with the synthesis of metabolic intermediates. Drugs such as sulfamethoxazole or sulfanilamide work at the metabolic level to prevent the synthesis of tetrahydrofolic acid (THF). The drugs inhibit a biochemical pathway. All organisms use THF to synthesize nucleotides, so why are the sulfa drugs selectively toxic to bacteria? The selectivity occurs because mammals do not synthesize folic acid, a precursor of THF. Higher mammals generally rely on bacteria and green leafy vegetables as sources of folic acid.

If a disease is endemic, it is always present in the population at a (low, high) frequency.

- low

The (lower, higher) the LD50, the more virulent the microbe is.

- lower

Chocolate agar is considered ________ in comparison to blood agar.

- more nutrient rich; can grow a larger variety of bacteria

The acid-fast stain is used to identify

- mycobacteria

Penicillin has a relatively (narrow, broader) spectrum of activity. This is because the drug primarily targets Gram-positive bacteria. However, ampicillin is penicillin with an added amino group that allows the drug to more easily penetrate the Gram-negative outer membrane. As a result of this chemically engineered modification, ampicillin kills Gram-positive and Gram-negative organisms, giving it a more (narrow, broad) spectrum of activity than penicillin has.

- narrow - broad

A persister cell is an unsolved mystery of microbiology because these cells

- neither grow or die in the presence of antibiotics

Quinolones are antibiotics that target

- nucleic acid function

Beta-lactamase can provide resistance to

- penicillin

The modern antibiotic revolution began with the discovery of ________ in 1928 by Sir Alexander Fleming.

- penicillin

Chloramphenicol and tetracyclines are antibiotics that target

- protein biosynthesis

Bactrim, a sulfa drug used to treat urinary tract infections, does NOT harm host cells because eukaryotic cells

- take in folic acid in the diet

Which of the following represents part of the mechanism of penicillin resistance? A. Beta-lactamase is activated within the cytoplasm of the bacterial cell. B. Beta-lactamase is transported out of the cell and into the surrounding medium. C. Penicillin is endocytosed by the cell and degraded within a lysosome. D. Penicillin is converted into tetracycline which has a shorter half-life.

B. Beta-lactamase is transported out of the cell and into the surrounding medium. explanation: Resistance to penicillin is achieved when a cell produces beta-lactamase and transports it out of the cell and into the surrounding medium. This allows the drug to become deactivated at its site of activity—the bacterial cell wall. Beta-lactamase is not active within the cytoplasm of the bacterial cell. The target of penicillin is the cell wall, and cytoplasmic activity would not achieve resistance to the drug. Penicillin is not endocytosed by a bacterial cell, bacterial cells do not contain lysosomes, and penicillin is never converted into tetracycline.

Which of the following statements about virulence factors is true? A. They are defined as being any genes that are required for microbial survival. B. They increase the ability of a pathogen to cause disease. C. They are found in nonpathogenic strains of a microbe as well as pathogenic strains. D. They always activate host defenses.

B. They increase the ability of a pathogen to cause disease.

A gene coding for __________ proteins is likely to be found in a genomic island of a pathogenic bacterial strain and NOT found in a nonpathogenic strain. A. tRNA amino acyl synthase B. host cell attachment C. RNA polymerase D. glucose transporter

B. host cell attachment Explanation: A host cell attachment protein is an example of a protein that can contribute to pathogenicity. It is not part of the needed bacterial core machinery like the other choices listed. The tRNA amino acyl synthase is part of the core translational machinery, RNA polymerase is part of the core transcriptional machinery, and glucose transporters are part of the core transport machinery.

A bacterium may be penicillin resistant due to all of the following EXCEPT a. a Gram-positive cell wall. b. beta-lactase production. c. a Gram-negative cell wall. d. modified transpeptidases. e. modified transglycosylases.

a. a Gram-positive cell wall.

Which of the following would NOT be a task for an epidemiologist? a. helping to assess the effectiveness of treatments of preventions b. performing basic research to understand how the etiological agents causes symptoms c. finding patient zero d. coordinating global measures to minimize an outbreak or epidemic e. keeping track of the incidence and prevalence of disease and reportable diseases

b. performing basic research to understand how the etiological agents causes symptoms

Bacteria that exhibit antigenic shifts and phase variations will most likely cause a. host immunity b. recurrent infections in the exposed host c. death each time a host is infected d. mild, acute infections e. subclinical infections

b. recurrent infections in the exposed host

Which of the following is considered a virulence factor? a. RNA b. TNF-Alpha c. capsules d. IFN-gamma e. Strep. pyogenes

c. capsules explanation: Virulence factors are encoded by virulence genes, include toxins, attachment proteins, capsules, and other devices used to avoid host innate adaptive immune systems.