answer

watching

views

redrabbit274Lv1

28 Sep 2019

*QUESTION: Provide examples of one major flaw for each of Koch'sfour postulates.

Koch's four postulates:
1.) The microorganism must be present in all instances ofsickness
2.) The pathogen can be isolated from the diseased host and grownin pure culture
3.) The culture must duplicate the ailment in another host
4.) The microorganism should thusly be discovered and refined fromthis new host

answer

watching

views

For unlimited access to Homework Help, a Homework+ subscription is required.

You have 0 free answers left.
Get unlimited access to 3.8 million step-by-step answers.

Get unlimited access

Already have an account? Log in

Elin HesselLv2

28 Sep 2019

Unlock all answers

Get 1 free homework help answer.

Already have an account? Log in

Related questions

QUESTION 7

Which statement most accurately describes the evolutionaryrelationships among the three domains?

		Bacteria and Archaea diverged from a common ancestor morerecently than they diverged from their common ancestor withEukarya
		Bacteria and Eukarya diverged from a common ancestor morerecently than they diverged from their common ancestor withArchaea
		Eukarya and Archaea diverged from a common ancestor morerecently than they diverged from their common ancestor withBacteria
		All three domains diverged from a common ancestor at the sametime.

10 points

QUESTION 8

Bird influenza is an emerging disease. If you were given thetask of using Koch's postulates of finding the pathogen causingbird flu, what sequence of procedures should you use?

		(1) Inoculate a healthy bird with the suspected pathogen to seewhether it becomes sick, (2) compare symptoms of that bird withthose of a bird known to have the disease, (3) isolate the pathogenfrom both birds in pure culture and stain them to see whether theyare both Gram-positive, and (4) make a vaccine from the pureculture of one bird and inject it into another to see if itrecovers.
		1) Take blood samples from a sick bird, (2) isolate the pathogenin pure culture, (3) treat the bird for the disease and when itrecovers take a second blood sample, and (4) test the blood tocheck whether it no longer contains the pathogen.
		1) Inject a bird with the suspected pathogen, (2) inject anotherbird with a control that doesn't contain the suspected pathogen,(3) repeat with more birds, and (4) plate out samples of blood fromboth kinds of birds to see if you can isolate the pathogen in pureculture.
		(1) Check whether the suspected pathogen is present in sickbirds, then (2) isolate the pathogen from an infected bird and growit in pure culture, (3) inoculate cells from pure culture into ahealthy bird to see whether it causes the disease, and (4) attemptto isolate the suspected pathogen from the inoculated bird.

10 points

QUESTION 9

The evolution of organisms that use oxygen in their respirationwas possible only because of the action of a group of bacteria thatproduced oxygen and changed the Earth's atmosphere from an anoxicone to one rich in oxygen. That group of bacteria was:

		cyanobacteria
		spirochaetes
		proteobacteria
		Staphylococcus

10 points

QUESTION 10

Microcystis aeruginosa is a species of cyanobacteria.What CANNOT be true of this species?

		It synthesizes organic molecules.
		It is an obligate anaerobe
		Its cells contain an extensive thylakoid
		It uses ammonia to produce proteins.

1. Select which of the following are mechanisms used by pathogens to avoid host defenses and to successfully colonize the host.

A. Producing siderphores to obtain iron from the host for growth

B. producing adhesins for damaging host cells

C. Avoiding IgA proteases for avoiding secretory IgA

D. Avoiding secretory IgA by rapid turnover of pili

E. Producing toxic substances to suppress host responses

2. People considered obese have a different normal flora in the gastrointestinal tract compared to people who are considered lean.

A. true

B. false

3. Which of the following is NOT a mechanism used by pathogens for avoiding or surviving phagocytosis?

A. Killing macrophages and neutrophils

B. Colonizing the phagocyte

C. inhibiting opsonization

D. Inhibiting phagocte chemotaxis

E. these are all methods of avoiding or surviving phagocytosis

4.Which of the following immune responses is best suited to prevent a virus from infecting a cell?

A. complement cascade

B. inflammation

C. Virus-specific antibodies

D. Fever

E. phagocytic cells

5. Which of the following is NOT a method used by pathogens for penetrating skin or mucous membranes?

A. Injection of effector proteins that induce endocytosis

B. Exploiting antigen-sampling processes

C. these are all mechanisms for penetrating skin or mucous membranes

D. Exploiting an injury

E. Production of endotoxin

6. Antibodies, which are produced as part of the adaptive immune response, can sometimes be damaging rather than beneficial. People suffering from an autoimmune disease called antiphospholipid antibody syndrome (APS) make antibodies that bind to phospholipids. Some of the signs and symptoms affected individuals experience are blood clots, stroke, heart attack, and kidney damage. What is the likely cause of these symptoms?

A. the anti-phospholipid antibodies cuse immune complexes that lodge in the affected organs

B. The person fails to make protective antibodies

C. The anti-phospholipid antibodies weaken certain organs that contain fat

D. the person makes antibodies that bind inappropriately to bacterial capsules, preventing phagocytosis of these cells

E. Cell damage caused by binding of these antibodies initates inappropriate coagulation events which inferfere with blood flow in affected organs.

7. Only Gram-positive bacteria produce exotoxins

A. true

B. False

8. Which of the following members of the normal microbiota inhibit the growth of Candida albicans?

A. Lactobacilus species

B. Staphylococci species

C. E. coli

D. Neisseria species

E. Propionibacterium species

9. Would an antibody response against the B subunit of an A-B toxin protect against the effects of the toxin?

A. yes. if antibodies bind to the B protion, the toxin can no longer bind to target cells and will thus not affect those cells

B. No, even if antibodies bindto the B portion of the toxin, it is the A portion that actually causes damage to the cell

C. This question cannot be answer. The immune system does not mount a strong response against proteins, so this situation is unlikely to occur.

D. Yes, if antibodies bind to the B protein, that portion of the toxin does not become activated, and thus does not damage the host cell

E. No, even if antiibodies bind to the B portion of the toxin, the toxin is still taken into the host cell by phagocytosis, damaging that cell

10. Please select the correct definition of balanced pathogenicity.

A. A host-parasite relationship in which the parasite persists in the host, causing maximal harm. The pathogen becomes more virulent while the host becomes increasingly susceptible.

B. A mechanism that allows bacteria to transfer gene products directly into host cells, inducing changes such as altering the cell's cytoskeleton structure

C. A generated balance in the microbiome that may be caused by taking antimicrobial medication. it generally helps the host maintain optimal health

D. A situation in which an abnormally high number of T-helper cells are stimulated, causing a massive release of cytokines.

E. A host-parasite relationship in which the parasite persists in the host while causing minimal harm. The pathogen becomes less virulent while the host becomes less susceptible

11. Bacteria may survive phagocytosis by

A. preventing encounters with phagocytes AND preventing fusion of two pathogosomes

B. avoiding recognition and attachment of lymphocytes AND lysinf the phagosomes

C. preventing fusion of the lysosome with the phagosome AND mimicking host molecules

D. lysing the phagosome AND mimicking host molecules

E. preventing fusion of the lysosome with the phagosome AND lysing the phagosome

12. In two of Koch's postulates (#2 and #3), a pure culture of the organism is required. Which of the following would NOT be a possible consequence of using a contaminated culture?

A. these would all be consequences of using contaminated cultures

B. Even though there's a contaminating microbe present, as long as the original suspect microbe is also present, the disease should still manifest in test animals and the organism should still be recoverable from test animals. As such, there's really no consequence to using a contaminated culture

C. The problem is that one microbe may be toxic to other. It may have killed all of your suspect microbe in the culture. Therefore, you can't be sure that you're infecting your test animals with the microbe you suspect is causing the illness, or if it's only the sec. microbe.

D. you can't necessarily attribute the illness directly to the microbe in question; it may in fact be caused by the contaminating microbe

E. There's the possibility that the test animal might be acutely susceptible to the contaminating microbe, but completely resistant to the microbe you suspect causes the illness of interest. As such, when you introduce it into the test animal, it could confuse your final results.

Part III â The Physician

June 5th

ree weeks had passed. e swelling was still present and it had become even more di cult for Margo to move

her nger. In addition, the amount of uid oozing from the wound had increased, suggesting that the medication hadnât worked. It was now time to visit a local physician. Following the advice of a neighbor, Margo set up an o ce appointment with Dr. Chan, an internist. After the usual battery of questions, Dr. Chan sent in the nurse to collect a specimen from Margoâs nger. Dr. Chan mentioned to Margo that the specimen would be sent o to the regional hospital laboratory for analysis and that he would provide her with another prescription for Ke ex, which she should continue to take until test results came back.

June 15th

e test results arrived in Dr. Chanâs o ce on June 15th and were as follows: â¢ No yeast or fungal elements were noted

â¢ Gram-stain reaction: no organisms seen

â¢ Culture of anaerobes and aerobes @48 hours yielded no growth

â¢ Enrichment culture results: moderate growth on day 5 of an acid-fast bacterium (AFB). o Growth identi ed as Mycobacterium fortuitum by the Florida State Laboratory.

Armed with a microbial identi cation, Dr. Chan prescribed Doxycycline and Bactrim to be taken for four months. Dr. Chan also mentioned that the isolated organism was known to be found in tap water. Consequently, Margo planned to ask her condo community why an organism that could cause so much pain would be living in the water that was coming out of her faucets. And although she was annoyed to learn of the source of the organism, at least she could take some comfort in the fact that she nally had an accurate diagnosis and that by taking her medicine she could fully recover from her injury and start to enjoy her new home.

Questions

1. Compare and contrast aerobes and anaerobes. Why were no microbes noted upon aerobic and anaerobic culture?