antibiotic resistance & classification

1. Antibiotic
Asifur Rahman
Contact: 01747137920

2. Definitions
Antibiotics are the Substance (such as
penicillin) that destroys or inhibits the growth
of other pathogenic microorganisms and is
used in the treatment of external or internal
infections.
Originally the term antibiotic referred only to
organic compounds, produced by bacteria or
molds, that are toxic to other microorganisms
but most are now manufactured synthetically.

3. Classification of Antibiotic
• Mode of action
• BACTERICIDAL (kills the bug)
• BACTERIOSTATIC (stops the bug multiplying)
• Spectrum of activity
• BROAD (e.g. effective a variety of gram –ve & gram +ve bacteria)
• NARROW (e.g. effective only against gram –ve or gram +ve bacteria
• Mechanism of action / site of action;
• Inhibitors of cell wall synthesis; (β-Lactam, Vancomycin)
• Inhibitors of cell metabolism; (Sulfonamides, Trimethoprim)
• Inhibitors of protein synthesis; (Tetracyclines, Aminoglycosides, Macrolides, Clindamycin, Chloramphenicol)
• Inhibitors of nucleic acid function or synthesis; (Floroquinolones, Rifampin)
• Inhibitors of cell membrane function; (Isoniazid, Amphotericin B)

5. Site of action of Antibiotics

6. Inhibitors of cell wall synthesis
• Interfere with the synthesis of the bacterial cell wall
• Little or NO effect on bacteria that are NOT growing and dividing
Non β-lactamβ-lactam group
VancomycinPenicillins
BacitracinCephalosporins
Polymixin BCarbapenems
TelavancinMonobactams
Daptomycinβ-lactam inhibitors +
antibiotic combinations

7. Penicillin
• Most widely effective and least
toxic
• Produced from fungi
• Contain β lactam ring
• Mechanism of action: Inhibit
transpeptidase so cross linking
between peptides not occur →
Peptidoglycan of cell wall will NOT
be formed.

8. Protein Synthesis Inhibitors
• 50S ribosome inhibitors
-Macrolides e.g. Erythromycin
-Lincosamides e.g. clindamycin, lincomyin
• 30S ribosome inhibitors
-Aminoglycosides
-Tetracyclines

9. Tetracycline
• Most common protein sythesis inhibitor
• Having a nucleus of four cyclic rings
• Mechanism of action :
Inhibit protein synthesis: by binding to 30s ribosomes
Prevent attachment of aminoacyl-t-RNA to the mRNA ribosome complex.

10. Inhibitors of nucleic acid function or
synthesis
• Which interefere with the
metabolism of bacteria.
• Floroquinolone
• Rifampin
• Metronidazole

11. Quinolones
Mechanism of action:
Inhibitors of DNA Gyrase (= Topoisomerase II) [a bacterial enzyme that winds and unwinds DNA (required for
supercoiling the bacterial genome)]  inhibition of DNA synthesis and transcription

12. Folic acid synthesis inhibitor
Sulfonamides
Mechanism of action:
Inhibition of folic acid
synthesis
Example:
Sulfacetamide
Trimethoprim
• Has similar activity to
sulphonamides
• Give synergistic effect in
combination with
sulphonamides
(= Cotrimoxazole)

13. Antibiotics side effects:
The most common side effects of antibiotics :
Diarrhoea
Bloating and indigestion
Abdominal pain
Loss of appetite
Being sick
Feeling sick
Itchy skin rash
Coughing
life-threatening allergic reaction

14. What Is The Rules Of Pharmacist
• The pharmacist should review the
previous diseases history of the patient
• Hypersensitivity reaction of Drug
• Drug-drug interaction
• Exact dose and frequency of the drug
• When the drug should be taken before
or after meal
• Suggest not to stop the antibiotics
without complete the course even feel
better

15. Antibiotics resistance
• If the concentration of drug requires
to inhibit or kill the microorganism is
greater than normal use then the
microorganism is considered to be
resistant to the drug.
OR
• The ability of a microorganism to
produce a protein that disables an
antibiotic or prevents transport of the
antibiotic into the cell.

17. Misuse of antibiotics :
• Antibiotic misuse, sometimes called
antibiotic abuse or antibiotic overuse.
• The misuse or overuse of antibiotics,
may produce serious effects on health.
• It is a contributing factor to the
creation of multidrug-resistant
bacteria, informally called "super
bugs" relatively harmless bacteria can
develop resistance to multiple
antibiotics and cause life-threatening
infections.

18. Inappropriate prescription
• In an analysis of prescribing practices in
teaching hospitals worldwide, more than
40 % of all antimicrobials prescribed
were considered inappropriate
Antibiotic resistance comes mainly because of
inappropriate or improper use of antibiotics by
physicians. Some 150 million
prescriptions are written annually in
the USA And Of those, 50 million are
absolutely unnecessary or
inappropriate”.

19. Mr: Don’t forget to take one of our
antibiotics free sample before you
leave the hospital