Antimicrobial drugs: General consideration, Classifications of Antibiotics, MCQs for GPAT, NIPER, Drug inspector and pharmacist exam

Antimicrobial drugs: General consideration, Classifications of Antibiotics, MCQs for GPAT, NIPER, Drug inspector and pharmacist exam


Antimicrobial drugs: Antimicrobial drugs are chemical substances of natural or synthetic origin that suppress the growth of, or destroy, micro-organisms including bacteria, fungi, helminths, protozoa and viruses. Antimicrobial drugs include: antibiotics, chemotherapeutic agents.


These drugs can be classified on the basis of many characteristics:

A. Chemical structures: 

  1. Sulfonamides and related drugs:

a. Sulfadiazine and others

b. Sulfones- Dapsone(DDS), paraminosalicylic acid (PAS)

2. Diaminopyrimidines:

a. Trimethoprim

b. Pyrimethamine

3. Quinolones:

a. Nalidixic acid

b. Norfloxacin

c. Ciprofloxacin

d. Prulifloxacin

  4. Beta- lactam  antibiotics:

a. Penicillins

b. Cephalosporins

c. Monobactams

d. Carbapenems

5. Tetracyclines:

a. Oxytetracyclines

b. Doxycycline

6. Nitrobenzene derivative:

a. Chloramphenicol

    7. Aminoglycosides:

a. Streptomycin

b. Gentamycin

c. Amikacin

d. Neomycin

8. Macrolide antibiotics:

a. Erythromycin

b. Clarithromycin

c. Azithromycin

   9. Lincosamide antibiotics:

a. Lincomycin

b. Clindamycin

10. Glycopeptide antibiotics:

a. Vancomycin

b. Teicoplanin

 11. Oxazolidinone:

a. Linezolid

     12. Polypeptide antibiotics:

a. Polymyxin-B

b. Colistin

c. Bacitracin

d. Tyrothricin

     13. Nitrofuran derivative:

a. Nitrofurantoin

b. Furazolidone

14. Nitroimidazoles:

a. Metronidazole

b. Tinidazole

 15. Nicotinic acid derivative:

a. Isoniazid

b. Pyrazinamide

c. Ethionamide

16. Polyene antibiotics:

a. Nystatin

b. Amphotericin-B

c. Hamycin

 17. Azole derivatives:

a. Miconazole

b. Ketoconazole

c. Fluconazole

d. Clotrimazole

18. Others:

a. Rifampin

b. Spectinomycin

c. Cycloserine

d. Viomycin

e. Griesofulvin

B. Type of organisms against which primarily active:

1. Antibacterial:

a. Pencillins

b. Aminoglycosides

c. Erythromycin

d. Fluoroquinolones

    2. Antifungal:

a. Griseofulvin

b. Amphotericin-B

c. Ketoconazole

    3. Antiviral:

a. Acyclovir

b. Amantadine

c. Zidovudine

    4. Antiprotozoal:

a. Chloroquine

b. Pyrimethamine

c. Metronidazole

d. Diloxanide

5. Anthelmintic:

a. Mebendazole

b. Pyrantel

c. Niclosamide

d. Diethyl carbamazine

 C. Spectrum of activity:

 1. Narrow-spectrum:

a. Pencillin-G

b. Streptomycin

c. Erythromycin

2. Broad-spectrum:

a. Tetracycline

b. Chloramphenicol

  D. Types of action:

  1. Primarily bacteriostatic:

a. Sulfonamides

b. Erythromycin

c. Tetracyclines

d. Chloramphenicol

e. Clindamycin

f. Linezolid

g. Ethambutol

   2. Primarily bactericidal:

a. Penicillin

b. Aminoglycosides

c. Polypeptides

d. Rifampin

e. Isoniazid

f. Pyrazinamide

g. Cephalosporins

h. Vancomycin

i. Fluoroquinolones

j. Metronidazole

k. Cotrimoxazole

E. Natural sources of antibiotics:

  1. Fungi:

a. Penicillin

b. Cephalosporin

c. Griseofulvin

 2. Bacteria:

a. Polymyxin

b. Tyrothricin

c. Colistin

d. Bacitracin

e. Aztreonam

3. Actinomycetes:

a. Aminoglycosides

b. Macrolides

c. Tetracyclines

d. Polyenes

e. Chloramphenicol

Mechanism of action of antibacterial drugs:

A. Inhibit cell wall synthesis:

  1. Pencillins
  2.  Cephalosporins
  3. Carbapenems
  4. Monobactams
  5. Vancomycin
  6. Cycloserine
  7. Bacitracin

  B. Cause leakage from cell membranes:

  1. Polymyxin
  2. Colistin
  3. Bacitracin
  4. Amphotericin-B

      C. Inhibit protein synthesis:

  1. Tetracyclines
  2. Chloramphenicol
  3. Erythromycin (other macrolides)
  4. Clindamycin
  5. Linezolid

    D. Cause misreading of m-RNA- affect permeability:

  1. Aminoglycosides

E. Inhibit DNA gyrase:

  1. Ciprofloxacin (other fluoroquinolones)

F. Interfere with DNA function:

1. Rifampin

 G. Interfere with intermediary metabolism:

  1. Sulsonamides
  2. Sulfones
  3. Trimethoprim
  4. Pyrimethamine
  5. Paraaminosalicylic acid
  6. Metronidazole

Side effects of Antimicrobial agents:

  1. Toxicity:

a. Aminoglycosides: 8th cranial nerve and kidney toxicity

b. Tetracyclines: Liver and kidney damage

c. Vancomycin: hearing loss, kidney damage

d. Chloramphenicol: bone marrow depression

e. Polymyxin-B: neurological and renal toxicity

f. Amphotericin-B: kidney, bone marrow and neurological toxicity

      2. Hypersensitivity reactions:

Hypersensitivity reactions cause by penicillins, cephalosporins, sulfonamides and fluoroquinolones.

    3. Drug resistance: 

   a. Natural resistance: Some microbes have always been resistant to certain AMAs. Gram negative bacilli are                  unaffected by penicillin-G. Aerobic organisms are not affected by metronidazole

    b. Acquired resistance: Development of resistance by an organism due to the use of an AMA over a period of time. Gonococci  quickly develop resistance against penicillin.

4. Superinfection: Use of most AMAs causes some alteration in the normal microbial flora of the body.  Sites involved in superinfection are, oropharynx, intestinal, respiratory and genitourinary tracts, occasionally skin.

 5. Nutritional deficiencies: Some b- complex group of vitamins and vit K synthesized by the intestinal flora is utilized by humans. Prolonged use of antimicrobials abnormalities in the intestinal mucosa, which can produce steatorrhoea and malabsorption syndrome.


  1. Which drug belongs to Diaminopyrimidines?

a. Nalidixic acid

b. Norfloxacin

c. Ciprofloxacin

d. Trimethoprim

 2. Which drugs belongs to Quinolone?

a. Norfloxacin

b. Oxytetracyclines

c. Doxycycline

d. None

      3. Which drugs are classified according to chemical structures?

a. Sulfonamides

b. Polyene antibiotics

c. a$b

d. None

4. Select polypeptide antibiotic

a. Nitrofurantoin

b. Polymyxin-B

c. Griseofulvin

d. Amphotericin-B

 5. Which is narrow spectrum antibiotic

a. Penicillin

b. Amphotericin-B

c. Tetracyclines

d. None

6. Select antiviral drug.

a. Nitrofurantoin

b. Polymyxin-B

c. Griseofulvin

d. Zidovudine

  7. Which drug is antifungal?

a. Griseofulvin

b. Macrolides

c. Tetracyclines

d. Polyene

8. Which is broad spectrum antibiotics?

a. Mebendazole

b. Pyrantel

c. Niclosamide

d. Chloramphenicol

9. Which drugs are primarily bacteriostatic?

a. Sulfonamides

b. Erythromycin

c. Tetracyclines

d. All of above

     10. Which drugs are primarily bactericidal?

a. Polypeptides

b. Rifampin

c. Isoniazid

d. All of above

11. What is the natural source of Cephalosporins?

a. Actinomycetes

b. Fungi

c. Bacteria

d. None

    12. which drugs inhibits cell wall synthesis?

a. Cephalosporins

b. Carbapenems

c. Monobactams

d. All of above

    13. Which drug inhibit DNA gyrase?

a. Ciprofloxacin

b. Tetracyclines

c. Chloramphenicol

d. Clindamycin

14. Which drug cause liver and kidney damage?

a. Ciprofloxacin

b. Tetracyclines

c. Amphotericin-B

d. Penicillin

15. Which drug inhibit protein synthesis?

a. Tetracyclines

b. Chloramphenicol

c. Erythromycin

d. All of above


  1. d
  2. a
  3. c
  4. b
  5. a
  6. d
  7. a
  8. d
  9. d
  10. d
  11. b
  12. d
  13. a
  14. b
  15. d


  1. “K.D.Tripathi” Antimicrobials and General considerations, page no-741-745, 8thy edition, june 2018.



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