Antimicrobials overview

1. ANTIMICROBIALS
MECHANISM OF ACTION
Dr.Elza Joy Munjely
JR-I
Depmt. Of Pharmacology
Govt. Medical College,Kottayam.

2.  CHEMOTHERAPY – treatment of
systemic or topical infection with
drugs that have selective toxicity
for an invading pathogen without
harming the host cells.
 Takes advantage of the
biochemical & physiological
differences that exist between
microorganism & human beings.

3. Antimicrobials
 Drugs that inhibit microbial growth &
multiplication
 Antibacterial
 Antiviral
 Antifungal
 Antiprotozoal
 Antihelminthics
 Cidal/static
 Narrow/Extended/Broad spectrum

4.  BACTERIOSTATICArrest the growth &
replication & limit the spread of infection.
 Macrolides -Oxazolidones
 Chloramphinicol -Tetracyclines
 Sulphonamides -Trimethoprim
 Clindamycin -Nitrofurantoin
 Ethambutol -Linezolid
 Erythromycin


5.  BACTERICIDALKill or irreversibly damage the multiplying
bacteria.
 Betalactam -Vancomycin
 Polymixin -Bacitracin
 Isoniazid -Pyrazinamide
 Rifampicin -Aminoglycosides
 Nalidixic acid -Ciprofloxacin
 Metronidazole -Cotrimoxazole
 Chloramphenicol - static against gram –ve rods & cidal
against pneumococci
 Sulphonamides/trimethoprim-static when used alone ,cidal
when used in combination.
 Cidal is preferred when host defences are impaired & for
complicated infections.

6.  BROAD SPECTRUM
 effective against a wide range of infectious
microorganisms which includes gram positive,
gram negative & atypical bacteria
 Can be used emperically in case of serious
infections
 may give rise to drug resistance.
 Example
 Tetracycline
 Chloramphenicol

7.  NARROW SPECTRUM
 active against a selected group of bacterial
types.Either gram negative or gram positive.
 used for the specific infection when the causative
organism is known.
 cause less resistance of the bacteria as it will deal
with only specific bacteria.
 Examples:
 Azithromycin
 Clarithromycin
 Clindamycin
 Erythromycin
 Vancomycin
 Streptomycin

8. EXTENDED-SPECTRUM ANTIBIOTIC 
 As a result of chemical modification, affects
additional types of bacteria ie, gram-negative
+ one or two gram positive & vice versa.
 Examples- carboxypenicillins &
urideopenicillins.

9. Targets of antimicrobials
 Cell wall
 Cell membrane
 Protein synthesis
 Intermediary metabolism
 Intracellular organelles
 Nucleic acid metabolism
 Muscle fibres

10. Cell wall synthesis inhibitors
 Bacteria – peptidoglycan
 Inhibitors of peptidoglycan
synthesisBetalactam,Vancomycin,Bacitracin,Cy
closerin & Phosphomycin.
 Mycobacteria – mycolic acid &
arabinoglycans
 INH, Ethambutol, Pyrazinamide
 Fungi – chitin
 Echinocandins

11. Cell membrane
 Cell membrane disrupting drugs
 Anti-bacterial - polymixins
 Antifungal – polyene antibiotics
 Inhibitors of cell membrane synthesis
 Azoles
 Terbinafine

12. Protein Synthesis
rRNA
•30s
•Aminoglycosides, Tetracyclines ,Spectinomycin
•50s
•Macrolides, Choramphenicol, Lincosamides,
• Streptogramins, linezolid
tRNA
•Mupirocin

13. Intermediary metabolism
DHF
THF
Nucleic acid
synthesis
PABA
DHS
DHR
Sulfonamides
Dapsone
PAS
Trimethoprim
Pyrimethamine
Proguanil
Trimetrexate

14. Intracellular organelles
 Mitotic spindle
 Griseofulvin
 Benzimidazoles
 Food vacuole
 Chloroquine, Quinine, Halofantrine, Mefloquine
 Mitochondrial electron transport chain
 Atovoquone

15. Muscle fibre
 Ivermectin,
 Pyrantel pamoate,
 Piperazine

16. Nucleic acid
 RNA synthesis
 RNA polymerase
 Rifampicin
 DNA synthesis
 DNA gyrase
 Quinolones
 DNA polymerase inhibitors
 Acyclovir, Ganciclovir
 Reverse transcriptase
 Anti HIV RT inhibitors
 DNA damage - metronidazole

17. PP
DHFA
PABA
THFA
DNA
m-RNA
INHIBITION OF DNA
SYNTHESIS
Inhibits DNA gyrase
Fluroquinolones
DNA-directed RNA
polymerase. Inhibits
RNA synthesis
Rifampicin
INHIBITION OF
FOLIC ACID
SYTHESIS
Trimethoprim
Pyrimethamine
Proguanil
Trimetrexate
Sulphonamides
Dapsone
PAS
,
Inhibition of 50
S
Chloramphenic
ol
Macrolides
Clindamycin
Telithromycin
Linezolid
StreptograminsInhibition of 30
S
Aminoglycosid
es
Tetracyclines
Spectinomycin
INHIBITION OF CELL WALL
SYNTHESIS
Betalactams,Bacitracin,cycloserin
e
Vancomycin,Teicoplanin
Monobactams,Carbopenems,
INH,Ethanbutol,Pyrazinamide
Alteration of cell
membrane integrity
Polymixins
Amphotericin B
Azoles

18. THANK YOU