This set of Microbiology online quiz focuses on “Distribution and Occurrence of the Normal Flora”.
1. Which of the following viruses are termed as ‘orphan’ viruses?
Explanation: Certain human intestinal viruses were discovered only by noting their cytopathogenic effects in tissue cultures; thus they were termed as ‘orphan’ viruses or echoviruses.
2. Bacteria can be grown on the dry surface of skin.
Explanation: The relatively dry surface of the skin is inhibitory to microbial growth. Moist regions of the skin have higher numbers of normal flora.
3. Which of the following causes the disease acne vulgaris?
a) Staphylococcus epidermis
Explanation: In the deep sebaceous glands are found lipophilic anaerobic bacteria such as Propionibacterium acnes which is associated with the skin disease known as acne vulgaris.
4. Which of the following bacteria are found in the nose?
a) Haemophilus sp.
b) S. pneumoniae
c) Corynebacterium sp.
d) S. epidermidis
Explanation: The bacteria most frequently and most consistently found in the nose are S. epidermidis and S. aureus.
5. The microorganisms stick to which of the following regions of the respiratory tract?
a) nasal baffle
Explanation: Microorganisms will impinge on and stick to the thin moist layer of highly viscous mucus that overlies the surface of the respiratory tract.
6. Alveolar macrophages are phagocytic in nature.
Explanation: Bacteria that manage to travel the air passages all the way to the alveoli of the lungs are usually engulfed and destroyed by phagocytic body cells known as alveolar macrophages.
7. Saliva generally has a microbial population of _______ bacteria per milliliter.
Explanation: Saliva itself generally contains transient microbes from other sites of the oral cavity, particularly from the upper surface of the tongue, and generally has a microbial population of about 108 bacteria per milliliter.
8. Fusobacterium belongs to which type of bacterial group?
b) facultative anaerobes
c) obligate anaerobes
Explanation: As the first teeth appear, obligate anaerobes, such as species of the genera Bacteroides and Fusobacterium, become more evident because the tissue surrounding the teeth provides an anaerobic environment.
9. Which enzyme is required for the production of glucan?
a) glycosyl transferase
Explanation: Glucan is formed only in the presence of the disaccharide sucrose by means of an enzyme called glycosyl transferase located on the surface of the cocci.
10. Which of the following microorganism is found in the gingival crevices at puberty?
b) Treponema sp.
Explanation: Probably as a result of hormonal changes, anaerobic bacteria, especially oral spirochetes like Treponema sp. and Bacteroides melaninogenicus, colonize the oxygen-deficient gingival crevices at puberty.
11. Enterococci is found in which part of the intestine?
d) large intestine
Explanation: In the jejunum there are occasionally found species of enterococci,lactobacilli, and diphtheroids.
12. Which body part contains the largest microbial population?
b) small intestine
c) large intestine
Explanation: In the human body the colon, or large intestine has the largest microbial population. It has been estimated that the number of microorganisms in stool specimens is about 1011 organisms per gram wet weight.
13. Which of the following is not a Gram-positive bacilli?
Explanation: The Gram-positive bacilli are represented mainly by species of Bifidobacterium, Eubacterium, and Lactobacillus. But Bacteroides are anaerobic Gram-negative bacilli.
14. Which microorganism among the following can live as a commensal but can also be pathogenic?
a) Trichomonas hominis
b) Entamoeba histolytica
Explanation: Entamoeba histolytica can live as a commensal but can also be pathogenic, causing amoebic dysentery; it is capable of penetrating the intestinal mucosa and invading various organs of the body.
Sanfoundry Global Education & Learning Series – Microbiology.
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