This set of Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Normal Flora and the Human Host”.
1. Who among the following was successful in raising 17 germ-free chickens for 40 days?
a) Pasteur
b) Schottelius
c) Cohendy
d) Reyniers
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Explanation: In 1912, Cohendy at the Pasteur Institute raised 17 germ-free chickens for 40 days and concluded that vertebrate life is possible in the absence of microorganisms.
2. Within how many days after birth a stable flora develops?
a) 1 day
b) 7 days
c) 30 days
d) 7-14 days
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Explanation: The initial flora may change considerably in composition during the first few days or weeks after birth until a stable flora becomes established and forms the normal flora.
3. Animals that are contaminated with germs are said to be gnotobiotic.
a) True
b) False
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Explanation: Animals that are either germ-free or that live in association with one or more known organisms are said to be gnotobiotic.
4. How many day-old embryonated eggs were used by Reyniers to rear first germ-free animals?
a) 20
b) 50
c) 2
d) 7
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Explanation: The first germ-free animals reared by Reyniers were chickens obtained by sterilizing the shells of 20-day-old embryonated eggs.
5. Which among the following was the first germ-free animal to be reared?
a) guinea pigs
b) rats
c) chickens
d) monkey
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Explanation: The first germ-free animals reared by Reyniers were chickens obtained by sterilizing the shells of 20-day-old embryonated eggs with an effective germicide and placing them in sterile containers.
6. Which of the following vitamins are not required by normal animals?
a) Vit K
b) Vit B
c) Vit C
d) Vit A
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Explanation: The germ-free animals require higher levels of Vitamin K, which normal animal do not require.
7. Germ-free animals require lower levels of B vitamins.
a) True
b) False
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Explanation: Germ-free animals require higher levels of B vitamins than do normal animals, and they require vitamin K, which normal animals do not require.
8. Pseudomembranous colitis is caused by the strains of which of the following microorganism?
a) Streptococcus mutans
b) Clostridium difficile
c) Streptococcus salivarius
d) Clostridium botulinum
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Explanation: Pseudomembranous colitis is a severe disease caused by excessive growth of toxin-producing strains of Clostridium difficile.
9. Where does the Streptococcus mutans adhere to the body site?
a) intestinal tract
b) tongue
c) teeth
d) hairs
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Explanation: Microorganisms may often adhere specifically to one body site. Streptococcus mutans selectively binds to the smooth surface of the teeth.
10. Which of the following microorganism produces colicins in the intestine?
a) E.coli
b) B.subtilis
c) Clostridium botulinum
d) Streptococcus salivarius
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Explanation: Many strains of E.coli in the intestines produce colicins which may help to protect the intestinal tract from closely related pathogenic bacteria.
Sanfoundry Global Education & Learning Series – Microbiology.
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