exam lesson name: the human body
exam number: 700946rr
exam guidelines
exam instructions

question 18 of 20 :
select the best answer for the question.
18. which of the following is not a postulate of the germ theory of disease?
a. the pathogen must be isolated from the organism and grown in the lab.
b. the pathogen must be reisolated from lab organisms.
c. the pathogen must be absent from any organisms that arent infected.
d. the pathogen must reinfect lab organisms.

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Question

exam lesson name: the human body
exam number: 700946rr
exam guidelines
exam instructions

question 18 of 20 :
select the best answer for the question.
18. which of the following is not a postulate of the germ theory of disease?
a. the pathogen must be isolated from the organism and grown in the lab.
b. the pathogen must be reisolated from lab organisms.
c. the pathogen must be absent from any organisms that arent infected.
d. the pathogen must reinfect lab organisms.

mark for review (will be highlighted on the review page)

Accepted Answer

# Brief Explanations:
The germ theory of disease (Koch's postulates) includes: 1. The pathogen is found in all diseased organisms, absent in healthy (so C is a postulate). 2. Pathogen is isolated and grown in lab (A is a postulate). 3. Lab - grown pathogen causes disease in healthy organism (re - infects, D is a postulate). 4. Pathogen is reisolated from the newly infected (diseased) lab organism (B is a postulate? Wait, no—wait, the postulates: Let's recall Koch's postulates properly. The four postulates (simplified): 1. The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms (C is part of this). 2. The microorganism must be isolated from a diseased organism and grown in pure culture (A). 3. The cultured microorganism should cause disease when introduced into a healthy organism (D - reinfect lab organisms, which are healthy in this context). 4. The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent (B is about reisolating from lab organisms, which is part of postulate 4). Wait, but the question is which is NOT a postulate. Wait, maybe I misremembered. Wait, the options: Let's check each.

Option C: "The pathogen must be absent from any organisms that aren't infected." — This is part of Koch's postulate (pathogen present in diseased, absent in healthy).

Option A: Isolate from organism and grow in lab (postulate 2).

Option B: Reisolate from lab organisms (postulate 4: reisolated from the inoculated (lab) organism).

Option D: "The pathogen must reinfect lab organisms." — Wait, the postulate is that the cultured pathogen should cause disease in a healthy organism (so reinfecting a healthy lab organism to cause disease). But the wording of D: "reinfect lab organisms" — maybe the confusion is: the postulate is about causing disease in a healthy organism (so infecting a healthy one, not reinfecting, but maybe terminology). Wait, no—let's re - evaluate. Wait, the correct non - postulate: Wait, maybe the error is in option D? No, wait, let's check the postulates again. Koch's postulates:

1. The microorganism must be present in every case of the disease but absent from healthy individuals. (So C is a postulate.)

2. The microorganism must be isolated from the diseased host and grown in pure culture. (A is a postulate.)

3. The pure culture of the microorganism must cause the disease when inoculated into a healthy, susceptible host. (This is about infecting a healthy host, not reinfecting. So D's "reinfect" is incorrect? Wait, no—"reinfect" might be a misnomer. Wait, maybe the answer is D? Wait, no, let's check the options again. Wait, maybe I made a mistake. Wait, the postulates: after inoculating the healthy host (lab organism) with the cultured pathogen, the host should get the disease, and then we re - isolate the pathogen from that now - diseased host (postulate 4: reisolated from the inoculated host). So:

- A: isolate from diseased (organism) and grow in lab (postulate 2)

- B: reisolated from lab organisms (postulate 4: the lab organisms are the inoculated ones, now diseased, so reisolating from them)

- C: pathogen absent from non - infected (postulate 1)

- D: "The pathogen must reinfect lab organisms." — The postulate is that the cultured pathogen should infect (not reinfect) a healthy lab organism to cause disease. So "reinfect" is incorrect. Wait, but maybe the options are using "reinfect" to mean infect a new (healthy) lab organism. But maybe the correct answer is D? Wait, no, let's check standard Koch's postulates. The third postulate is that the cultured microbe causes disease in a healthy host. So the action is infecting a healthy host, not reinfecting (which implies the host was already infected). So D is not a postulate. Wait, but let's check the options again. Wait, maybe I got it wrong. Wait, the question is which is NOT a postulate. Let's re - examine each option:

A: Isolate from organism (diseased) and grow in lab — postulate 2: correct.

B: Reisolate from lab organisms (the ones we inoculated, now diseased) — postulate 4: correct.

C: Pathogen absent from non - infected — postulate 1: correct.

D: Pathogen must reinfect lab organisms — the postulate is that the cultured pathogen should infect a healthy lab organism (not reinfect, as reinfect implies the lab organism was already infected). So D is not a postulate. Wait, but maybe the answer is D? Wait, no, maybe I made a mistake. Wait, let's check a reference. Koch's postulates:

1. The microorganism must be found in all organisms suffering from the disease, but not in healthy organisms.

2. The microorganism must be isolated from a diseased organism and grown in pure culture.

3. The cultured microorganism should cause disease when introduced into a healthy organism.

4. The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.

So:

- A: matches postulate 2.

- B: matches postulate 4 (reisolated from lab organisms, which are the inoculated ones).

- C: matches postulate 1.

- D: "reinfect lab organisms" — the postulate is about infecting a healthy lab organism (not reinfecting). So D is not a postulate. Therefore, the answer is D.
# Answer:
D. The pathogen must reinfect lab organisms.

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