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Interview MCQ Set 1

1. Which of the following is the most accurate method for microbial assay of antibiotics?
a) Physical assay
b) Chemical assay
c) Biological assay
d) Chemical and biological assay

View Answer

Answer: b [Reason:] Chemical-assay methods are generally more accurate and require less time than biological methods, but they are less sensitive, and caution must be used lest biologically inactive degradation products give misleading results.

2. The international unit of penicillin is defined by how much amount of International Standard?
a) 1 mg
b) 0.262 µg
c) 0.5988 µg
d) 0.5 mg

View Answer

Answer: c [Reason:] The international unit of penicillin is the amount of activity produced under defined conditions by 0.5988 µg of the International Standard, which is a sample of pure benzyl-penicillin.

3. Zone of inhibition is observed in tube-dilution method.
a) True
b) False

View Answer

Answer: b [Reason:] Small paper disks impregnated with known amounts of chemotherapeutic agents are placed upon the surface of an inoculated plate.So after incubation in disk-plate methods, a zone of inhibition around the disk indicates that the organism was inhibited by the drug.

4. Pigs respond dramatically to the addition of which of the following antibiotics to their diet?
a) aureomycin
b) terramycin
c) penicillin
d) oxytetracycline

View Answer

Answer: d [Reason:] It has been suggested that pigs respond dramatically to the addition of oxytetracycline to their diet because the antibiotic inhibits the growth of Clostridium perfringens in their intestines and prevents a chronic but subclinical toxemia.

5. Which of the following antibiotic have a sparing effect on the B12 in the diet?
a) Streptomycin
b) Tetracycline
c) Anthramycin
d) Chloramphenicol

View Answer

Answer: a [Reason:] Streptomycin may have a “sparing effect” on the B12 in the diet, making it available in greater quantities for utilization by the animals.

6. Antibiotics are not effective against plant pathogens.
a) True
b) False

View Answer

Answer: b [Reason:] Some antibiotics are effective against plant pathogens and are attractive for treatment of plant diseases. The extent of this practice is limited mainly by economic factors, i.e, the cost of the antibiotic.

7. Nystatin is produced from the strain _____________________
a) Streptomyces noursei
b) Streptomyces aureofaciens
c) Streptomyces kanamyceticus
d) Streptomyces fradiae

View Answer

Answer: a [Reason:] Nystatin is an antifungal agent produced during fermentation by a strain of Streptomyces noursei.

8. Griseofulvin is useful in the therapy of nonsystemic fungal infections.
a) True
b) False

View Answer

Answer: b [Reason:] Griseofluvin is used in the treatment of many superficial fungal infections of the skin and body surfaces ans is also effective in the treatment of systemic mycoses.

9. Acycloguanosine is a nucleoside analog which is active against ___________________
a) Influenza A virus
b) HIV virus
c) Herpes virus
d) Influenza B virus

View Answer

Answer: c [Reason:] Acycloguanosine is a nucleoside analog which is active against the herpes virus in animals. Its mode of action appears to be that of inhibition of nucleotide utilization.

10. Which of the following has its antiviral action attributed to interference of protein synthesis?
a) Amantadine
b) Interferons
c) Acycloguanosine
d) 5’-iododeoxyuridine

View Answer

Answer: b [Reason:] The antiviral action of interferons is attributed to interference of protein synthesis. Interferons is among the most promising chemotherapeutic agents for treating viral diseases.

11. Amantadine is very effective against influenza A virus.
a) True
b) False

View Answer

Answer: a [Reason:] Amantadine is a low-molecular weight compound which is very effective against influenza A virus; it is not effective against influenza B.The incidence of influenza A infections is greatly reduced by use of this drug.

12. Which of the following is effective in the control of tuberculosis in humans?
a) Nitrofurans
b) Nalidixic Acid
c) Sibromycin
d) Isoniazid

View Answer

Answer: d [Reason:] Isonicotinic acid Hydrazide or Isoniazid has proved to be very useful in the control of tuberculosis in humans and is more effective when given alternately with streptomycin.

13. Anthramycin is which of the following type of antibiotic?
a) Antiviral
b) Antitumor
c) Antifungal
d) Antibacterial

View Answer

Answer: b [Reason:] The anthramycin group (anthramycin, sibromycin, tomaymycin and neothramycin) is an example of potent antitumor agents. Their antitumor activity is directed towards DNA structure and function.

Interview MCQ Set 2

1. Pseudomonas bacteria uses which of the following as an electron acceptor for anaerobic respiration?
a) Oxygen
b) Nitrate
c) Phosphate
d) Sulphate

View Answer

Answer: b [Reason:] All pseudomonads can grow aerobically, but some can also grow anaerobically by using nitrate as an electron acceptor.

2. Pseudomonas maltophilia is a fluorescent species.
a) True
b) Flase

View Answer

Answer: b [Reason:] Pseudomonas maltophilia is a non-fluorescent species that is also frequently isolated from clinical specimens.

3. Pyocyanin, a blue water-soluble pigment is produced by which of the following pseudomonads?
a) P.mallei
b) P.syringae
c) P.fluorescens
d) P.aeruginosa

View Answer

Answer: d [Reason:] Pseudomonas aeruginosa produces a water-soluble blue pigment, pyocyanin. The organism is mainly a soil and water saprophyte but can also be isolated from wound, burn etc.

4. Which of the following are important plant pathogens?
a) P. aeruginosa
b) P.maltophilia
c) P.syringae
d) P.pseudomallei

View Answer

Answer: c [Reason:] P. syringae are important plant pathogens, causing diseases such as leaf spot, leaf stripe, wilt, and necrosis.

5. What is the color of the pigment xanthomonadin?
a) Blue
b) Yellow
c) Fluorescent
d) Red

View Answer

Answer: b [Reason:] Xanthomonadin is a yellow pigment formed by bacteria of the genus Xanthomonas of the family Pseudomonadaceae.

6. Which of the following is an important characteristic of bacteria belonging to Zoogloea?
a) They are plant pathogens
b) Cells are embedded in a gelatinous matrix
c) Cause diseases in humans
d) Useful for industrial applications

View Answer

Answer: b [Reason:] The outstanding characteristic of the genus Zoogloea is the embedment of cells in a gelatinous matrix to form slimy masses with a fingerlike morphology.They are mainly used in sewage treatment plant.

7. Which of the following family of bacteria fix nitrogen under aerobic conditions?
a) Pseudomonadaceae
b) Azotobacteraceae
c) Rhizobiaceae
d) Methylcoccaceae

View Answer

Answer: b [Reason:] The family Azotobacteraceae have organisms that can fix nitrogen under aerobic conditions.

8. Agrobacterium also fixes atmospheric nitrogen.
a) True
b) False

View Answer

Answer: b [Reason:] Agrobacteria do not fix atmospheric nitrogen. The organisms are plant pathogens that incite tumors when they invade roots,crown and stems.

9. Methylococcus and Methylomonas are all _______________ methane-oxidizers.
a) aerobic
b) facultative
c) obligate
d) anaerobic

View Answer

Answer: c [Reason:] Methylococcus and Methylomonas are all obligate methane-oxidizers i.e., carbon-sources such as glucose cannot be used for growth.

10. Which of the following have peritrichous flagella?
a) Acetobacter
b) Gluconobacter
c) Agrobacteria
d) Rhizobium

View Answer

Answer: a [Reason:] Acetobacter possesses peritrichous flagella. They belong to the family Acetobacteraceae.

11. Bacteria belonging to the genus Legionella contains which of the following amino acid?
a) Lysine
b) Arginine
c) Glycine
d) Cysteine

View Answer

Answer: d [Reason:] Bacteria belonging to genus Legionella are rod-shaped bacteria that require L-cysteine,iron saltsand activated powdered charcoal for growth.

12. Which of the following organism causes whooping cough in humans?
a) E.coli
b) Bordetella pertussis
c) Francisella tularensis
d) F.meningosepticum

View Answer

Answer: b [Reason:] Bordetella pertussis occurs only in humans and causes whooping cough.They are parasitic and pathogenic for various mammalian hosts.

Interview MCQ Set 3

1. Bacterial cells grown in a medium exposed to high osmotic pressure, changes shape from rod-shaped to __________ shaped.
a) spherical
b) rod shaped
c) irregular
d) elongated

View Answer

Answer: a [Reason:] The high osmotic pressure prevents the cells from bursting.Rod-shaped cells become spherical because they lack the cell structure which imparts shape.

2. Cell-wall biosynthesis is inhibited by antibiotics by inhibiting the biosynthesis of which of the following ?
a) lipopolysaccharide
b) cellulose
c) peptidoglycan
d) proteins

View Answer

Answer: c [Reason:] Antibiotics exert their microbial effect by inhibiting biosynthesis of the peptidoglycan polymer, resulting in the inhibition of cell-wall formation.This results in the inability of the bacterium to survive because of the absence of a protective covering.

3. Structurally all penicillins have only beta-lactam present in them.
a) True
b) False

View Answer

Answer: b [Reason:] All penicillins have a common basic nucleus, a fused beta-lactam-thiazolidine ring with different side chains which give each its unique properties.

4. The crystalline sodium or potassium salts are slightly soluble in ___________
a) ether
b) dioxane
c) water
d) chloroform

View Answer

Answer: d [Reason:] Natural penicillins can be prepared as salts of sodium, potassium, procaine,and other bases. The crystalline sodium or potassium salts are freely soluble in water, ester, ethers, ethyl alcohol, and dioxane but only slightly soluble in chloroform and benzene.

5. Which of the following does not affect the activity of penicillin?
a) bile
b) hydrochloric acid
c) cysteine
d) sodium hydroxide

View Answer

Answer: a [Reason:]The natural penicillins are inactivated by heat,cysteine,sodium hydroxide, penicillinase,and hydrochloric acid.They are not affected by the action of saliva or bile.

6. Benzylpenicillin is the chemical name for which of the following penicillin?
a) Penicillin G
b) Penicillin V
c) Penicillin F
d) Phenethicilin

View Answer

Answer: a [Reason:] Peniciilin G is also known as Benzylpenicillin which is a natural penicillin and has a basic core of 6-aminopenicillanic acid different side chain.

7. Ampicillin is a bactericidal antibiotic.
a) True
b) False

View Answer

Answer: a [Reason:] Ampicillin is another semisynthetic penicillin which is strongly bactericidal and lacks toxicity, but is not resistant to penicillinases.

8. Streptomyces orientalis produces which of the following antibiotics?
a) Cephalosporins
b) Cycloserine
c) Bacitracin
d) Vancomycin

View Answer

Answer: d [Reason:] Vancomycin is an antibiotic produced by Streptomyces orientalis. It is a complex chemical entity consisting of amino acids and sugars.

9. Which of the following interferes with regeneration of the monophosphate form of bactoprenol from the pyrophosphate form?
a) Vancomycin
b) Ampicillin
c) Bacitracin
d) Cephalosporins

View Answer

Answer: c [Reason:] Bacitracin interferes with regeneration of the monophosphate form of bactoprenol from the pyrophosphate form. It is a polypeptide chemically.

10. Polymyxins inhibits the growth of the microbes by carrying out which of the following actions?
a) inhibition of cell-wall synthesis
b) damage to cytoplasmic membrane
c) inhibition of nucleic acid and protein synthesis
d) inhibition of specific enzyme systems

View Answer

Answer: b [Reason:] Polymyxins,gramicidins,and tyrocidines cause damage to cytoplasmic membrane.They adversely affect the normal permeability characters of the cell membrane.

11. Streptomycin is produced by which of the following organisms?
a) Stretomyces noursei
b) Streptomyces nodosus
c) Streptomyces fradiae
d) Streptomyces griseus

View Answer

Answer: d [Reason:] Streptomycin is produced by Streptomyces griseus, a soil organism isolated by Schatz,Bugie and Waksman, who reported on its antibiotic activities in 1944.

12. Antibiotic produced by Streptomyces rimosus is _______________
a) chlortetracycline
b) oxytetracycline
c) tetracycline
d) doxycycline

View Answer

Answer: b [Reason:] Antibiotic produced by Streptomyces rimosus is oxytetracycline whereas Streptomyces aureofaciens produces chlortetracycline.They are broad spectrum antibiotics with similar antimicrobial spectra, and cross resistance of bacteria to them is common.

13. Which of the following inhibits protein synthesis by combining with the 50S subunit ribosome?
a) Streptomycin
b) Tetracycline
c) Chloramphenicol
d) Penicillin

View Answer

Answer: c [Reason:] Chloramphenicol inhibits protein synthesis by combining with the 50S subunit ribosome. The transpeptidation and translocation functions associated with this site are blocked.

14. Tyrocidines are more effective against ___________________
a) Gram-positive organisms
b) Gram-negative organisms
c) Mycoplasmas
d) Spirochetes

View Answer

Answer: a [Reason:] Tyrocidines and gramicidines are more effective against Gram-positive organisms whereas polymyxins are particularly effective against Gram-negative bacteria.

Interview MCQ Set 4

1. Nystatin is effective in curing ____________
a) Deep mycoses
b) Dermatophyte infections
c) Systemic mycoses
d) Candida infections

View Answer

Answer: d [Reason:] Nystatin is effective in topical Candida infections but not in deep mycoses or even dermatophyte infections.

2. Polyene antibiotics act on the plasma membrane of the fungus.
a) True
b) False

View Answer

Answer: a [Reason:] Polyene antibiotics like the nystatin and amphotericin B act on the plasma membrane of the fungus, combining with membrane sterols, and cause leakage of intracellular potassium and other metabolites.

3. 5-fluorocytosine is which type of antibiotic?
a) polyene
b) pyrimidine antimetabolites
c) imidazole
d) antibacterial

View Answer

Answer: b [Reason:] 5-fluorocytosine is a type of pyrimidine antimetabolite which is especially effective in the treatment of yeast infections.

4. Which of the following antibiotics causes inhibition of ergosterol biosynthesis?
a) amphotericin B
b) 5-fluorocytosine
c) ketoconazole
d) miconazole

View Answer

Answer: c [Reason:] The mechanism of action for ketoconazole is inhibition of ergosterol biosynthesis, an important step in synthesis of fungal cell walls and membranes.

5. Miconazole is active against which of the following fungal infections?
a) coccidioidomycosis
b) cryptococcosis
c) moniliasis
d) sporotrichosis

View Answer

Answer: a [Reason:] Miconazole is very active against coccidioidomycosis and paracoccidioidomycosis. It reacts with cytoplasmic membranes and causes them to leak.

6. The antibiotic griseofulvin is active against deep mycoses.
a) True
b) False

View Answer

Answer: b [Reason:] The antibiotic griseofulvin is active against the dermatophyte infections (superficial skin infections) but not against the deep mycoses (systemic diseases caused by fungi).

7. Which drug is used for treatment of leishmaniasis?
a) chloroquine phosphate
b) metronidazole
c) suramin
d) sodium stibogluconate

View Answer

Answer: d [Reason:] Leishmaniasis can be treated with the drug sodium stibogluconate. This drug is used for treatment of protozoan diseases.

8. Which of the following animallike flagellates has a flagellum originating from the midportion of the cell?
a) amastigote
b) promastigote
c) epimastigote
d) trypomastigote

View Answer

Answer: c [Reason:] The epimastigote has a flagellum originating from the midportion of the cell. It is a morphological stage of Leishmania and Trypanosoma.

Interview MCQ Set 5

1. The moisture contained in clouds and precipitated as snow,hail,rain etc constitutes _________________
a) Atmospheric water
b) Surface water
c) Groundwater
d) Subterranean water

View Answer

Answer: a [Reason:] The moisture contained in clouds and precipitated as snow,sleet,hail and rain constitutes atmospheric water. The air is washed by atmospheric water.

2. The surface waters are susceptible to contamination with microorganisms from _______________
a) the air
b) the surface runoff
c) precipitation
d) atmospheric water and the surface runoff

View Answer

Answer: d [Reason:] The surface waters are susceptible to contamination with microorganisms from atmospheric water (precipitation), the surface runoff from soil and any wastes deliberately dumped into them.

3. Which of the following is subterranean water?
a) Atmospheric water
b) Surface water
c) Groundwater
d) Rainwater

View Answer

Answer: c [Reason:] Groundwater is subterranean water that occurs where all pores in the soil or rock-containing materials are saturated.

4. Wells less than ___________ deep are considered to be shallow.
a) 1 ft
b) 100 ft
c) 50 ft
d) 1000 ft

View Answer

Answer: b [Reason:] Wells are made by sinking a shaft into the ground to penetrate the groundwater level. Wells less than 100 ft deep are considered to be shallow.

5. Thermus aquaticus, a common bacterial inhabitant generally prevails in temperatures of ____________
a) 00 C
b) 30-400C
c) 70-720C
d) 80-850C

View Answer

Answer: c [Reason:] Thermus aquaticus, a common bacterial inhabitant of hot springs has an optimum growth temperature of 70 to 720C.

6. Hydrostatic pressure increases the boiling point of water but does not change the solubility of nutrients.
a) True
b) False

View Answer

Answer: b [Reason:] Hydrostatic pressure increases the boiling point of water. It affects chemical equilibrium which in turn results in lowering of pH and a change in the solubility of nutrients such as bicarbonate.

7. Primary producers are found growing in which of the following layers of water?
a) upper layer
b) middle layer
c) intermediate layer
d) bottom layer

View Answer

Answer: a [Reason:] In most aquatic habitats the primary producers i.e. algae have their growth restricted to the upper layers of waters through which light can penetrate.

8. The degree of salinity in freshwater is nearly zero.
a) True
b) False

View Answer

Answer: a [Reason:] The degree of salinity in natural waters ranges from near zero in freshwaters to saturation in salt lakes.

9. The microorganisms from lakes and rivers can grow at a salt concentration of _________
a) 2.5 to 4 percent
b) 5 percent
c) below 1 percent
d) above 1 percent

View Answer

Answer: c [Reason:] Microorganisms from lakes and rivers are salt sensitive and do not grow at a salt concentration of more than 1 percent whereas marine microorganisms are halophilic.

10. Which of the following compounds are required for growth of saprophytic bacteria and fungi?
a) organic compounds
b) nitrates
c) phosphates
d) mercury

View Answer

Answer: a [Reason:] Organic compounds are required for the growth of saprophytic bacteria and fungi whereas nitrates and phosphates are important for the growth of algae.