3. ANTIMICROBIAL THERAPY
Definition:
An ANTIMICROBIAL is any substance of
natural, semisynthetic or synthetic origin
that kills or inhibits the growth of
microorganisms.
A drug used to prevent or treat a
microbial infection.
5. Sir Alexander Fleming
(6 August 1881 – 11 March 1955)
In 1928s, he discovered the
world's first antibiotics
substance benzylpenicillin
(Penicillin G) from the mould
Penicillin notatum, for which
he shared the Nobel Prize in
Physiology or Medicine in
1945.
9. ANTIBIOTICS: Classification
1. According to their effect on bacteria:
a. Bactericidal antibiotics:
Kill microorganisms & eradicate infection.
No need for the body defense mechanisms.
Require actively proliferating microorganisms.
They have no or little effect on non-growing bacteria.
b. Bacteriostatic antibiotics:
Stop growth & division of microorganisms.
Need for the body defense mechanisms to eradicate the
infection.
10. ANTIBIOTICS: Classification
Don’t combine a bactericidal antibiotic with
bacteriostatic one.
Bactericidal
Antibiotic
Bacteriostatic
Antibiotic
No
Effect
12. ANTIBIOTICS: Classification
2. According to their antibacterial spectrum:
a. Narrow-spectrum antibiotics:
Acting only on a single or a limited group of
microorganisms.
b. Extended-spectrum antibiotics:
Acting against gram-positive organisms and
also against a significant number of gram-
negative bacteria.
c. Broad-spectrum antibiotics:
Affecting a wide variety of microbial species.
15. ANTIBIOTICS: Classification
3. According to the mechanism of action:
1) Inhibitors of bacterial cell wall synthesis.
2) Inhibitors of protein synthesis.
3) Inhibitors of nucleic acid synthesis.
4) Inhibitors of metabolic pathways.
5) Drugs affecting cell membrane
permeability.
19. ANTIBIOTIC RESISTANCE
Definition:
Bacteria are said to be resistant to an
antibiotic if the maximal level of that
antibiotic that can be tolerated by the
host does not halt their growth.
Cross-resistance:
Germs that develop resistance to one
antibiotic have the ability to develop
resistance to another antibiotic.
20. Antibiotic Prescription Guidelines
1. Use empirical therapy according to the susceptible
organisms.
2. Start with single narrow spectrum antibiotic which is
specific for the pathogen to avoid resistance with fewer
disturbances of non-pathogenic bacteria.
3. Evaluate the immunity of the patient (e.g., immuno-
compromised bactericidal one).
4. Use the right dose with correct dosing schedule and
duration.
5. Use the alternative &/or two antibiotics if you need it.
