Classification of antibiotics, Antibiotics Sources, Drug Resistance, Reproduction in Bacteria, Transformation, Transduction, Conjugation

1. Bacteriology
Presented by
D. Mona Othman Albureikan
Lectures (13,14)

2. Antibiotics
• It is chemical substance that destroys or inhibits
the growth of other pathogenic microorganisms
and is used in the treatment of external or
internal infections.
• While some antibiotics are produced by
microorganisms, most are now manufactured
synthetically.

3. Classification of antibiotics
• Antibiotics are classified several ways. 1- On the basis of mechanism of action

5. Classification of antibiotics
• Antibiotics are classified several ways. 2- On the basis of spectrum of activity

6. Classification of antibiotics
• Antibiotics are classified several ways. 3- On the basis of mode of action
- Bacteriostatic effect: To
inhibit multiplication
- MIC minimal inhibitory
concentration.
- Bactericidal effect: To kill
(destroy) the bacteria
population
- MBC minimal bactericidal
concentration.

7. Antibiotics Sources
- 1. Natural
a.Fungi – penicillin, griseofulvin
b.Bacteria – Bacillus sp. (polymixin,
bacitracin) ; Actinomycetes
(tetracycline, chloramphenicol,
streptomycin)
- 2. Synthetic

8. Complications of Antibiotic Therapy
- Resistance – inappropriate use of
antibiotics
- Hypersensitivity – penicillin
- Direct toxicity – aminoglycosides =
ototoxicity
- Super infections – broad spectrum
antimicrobials cause alteration of the
normal flora; often difficult to treat.

9. Drug Resistance
1. Alteration of the target
site of the antibiotic
One of the most problematic
antibiotic resistances
worldwide, methicillin
resistance among Staphylococcus
aureus.

10. Drug Resistance
2. Enzyme inactivation of the
antibiotic
β-lactam antibiotics (penicillins &
cephalosporins) can be
inactivated by β-lactamases.

11. Drug Resistance
3. Active transport of the
antibiotic out of the bacterial
cell (efflux pumps)
Removal of some antibiotics (i.e.
tetracyclines, macrolides, &
quinolones)

12. Drug Resistance
4. Decreased permeability of the
bacterial cell wall to the
antibiotic
Alteration in the porin proteins
that form channels in the cell
membrane – Resistance of
Pseudomonas aeruginosa to a variety
of penicillins and cephalosporins.

13. 1- Alexander Fleming observed that the Penicillium fungus inhibited
the growth of a bacterial culture. He named the active ingredient
penicillin (1928) .
2- Penicillin has been used clinically as an antibiotic;; since the
1940s.
3- Researchers arc facing the problem of drug-resistant microbes.
4- Drug resistance results from genetic changes in microbes that
enables them to tolerate a certain amount of an antibiotic that
would normally inhibit them , VRE- MRSA.
The Birth of Modern Chemotherapy: Dreams of a "Magic Bullet

14. Reproduction in Bacteria
Binary Fission
It is the most common mode of asexual
reproduction.
The cytoplasm and nucleoid of a bacterial cell
divide equally into two, following replication
of DNA.
The cell wall and cytoplasm also split resulting
in the formation of two daughter cells.

15. Reproduction in Bacteria
Asexual reproduction.
- Budding in bacteria
- Fragmentation in bacteria
- All called Vegetative reproduction.

16. Reproduction in Bacteria
Sexual Reproduction
- In bacterial sexual reproduction there is no
meiosis, formation of gametes and zygote.
- Instead, it involves transfer of a portion
of genetic material (DNA) from a donor
cell to a recipient cell.
- This process is called as genetic
recombination.
Sexual Reproduction
It is known to occur in the
following three ways.
- Transformation
- Transduction
- Conjugation.

17. Transformation
Many bacteria can acquire new
genes by taking up DNA molecules
from their surroundings.

18. Transduction
Transduction is the process by
which bacterial DNA is moved
from one bacterium to another by
a virus.

19. Conjugation
- Some bacteria can transfer a portion
of their chromosome to a recipient
with which they are in direct contact.
- As the donor replicates its
chromosome, the copy is injected
into the recipient.
- At any time that the donor and
recipient become separated, the
transfer of genes stops.