This presentation provides a comprehensive introduction to antibiotics, exploring their historical significance, classifications, and essential role in modern medicine. Attendees will gain a profound understanding of the diverse mechanisms through which antibiotics act to combat bacterial infections. Outline: Introduction to Antibiotics Definition and historical context Significance in treating bacterial infections Classification of Antibiotics Broad-spectrum vs. narrow-spectrum antibiotics Classes: penicillins, cephalosporins, tetracyclines, etc. Mechanisms of Antibiotic Action Inhibition of cell wall synthesis (e.g., penicillins) Disruption of protein synthesis (e.g., macrolides) Inhibition of nucleic acid synthesis (e.g., quinolones) Interference with metabolic pathways (e.g., sulfonamides) Selective Toxicity Understanding the concept and importance How antibiotics target bacterial structures without harming human cells Resistance to Antibiotics Factors contributing to antibiotic resistance Consequences and global impact Case Studies Examples of well-known antibiotics and their mode of action Real-world applications and success stories Future Trends and Challenges Emerging technologies in antibiotic development Strategies to address antibiotic resistance Conclusion Recap of key points Emphasis on the critical role antibiotics play in public health This presentation aims to provide a solid foundation for understanding antibiotics and their mode of action, catering to both beginners and those looking to deepen their knowledge in the field. Through engaging visuals and clear explanations, you will have a heightened awareness of the vital role antibiotics play in preserving human health while being mindful of the challenges posed by antibiotic resistance.

1. ANTIBIOTICS
AND THEIR MODE OF
ACTION
1
By
Akhtar Ali
Staff Nurse EICU
2020

2. Objectives
2
 After the completion of the session the learner
will be able to
 Define antibiotics.
 Understand the structure and function of bacterial
cell.
 Recall some common terminologies.
 Discuss the criteria for selecting an antimicrobial
agent.

3. continue…
3
 Know the antibiotic spectra.
 Classify antibiotics according to there mode of
actions.
 Define the term pharmacokinetics and
Pharmacodynamics.

4. Structure of Bacteria
4

5. Some common terminologies
5
 Antibiotics.
Agent that kill or static the growth of microorganism
without harming the host cell.
 DNA (Deoxyribo Nucleic Acid).
Material which helps in cell division and
transmit the genetical characteristics in the
offspring.
 Cell wall
The outer protective covering of the cell.

6. Continue….
6
 Bactericidal.
Agents that kill the bacteria.
 Bacteriostatic.
Agents that inhibit the growth or multiplication
of bacteria.
(Mycek JM. Et al.2004)

7. Continue…………..
7
 Beta lactam Ring
 Beta-lactamase or penicillinase
An enzyme produce by the bacteria which
destroy the beta lactam ring in the chemical
structure of the beta lactam antibiotics.
(Mycek JM. Et al.2004)

8. Selection of antimicrobial Agent
8
 Empirical therapy prior to organism
identification.
 Identification and sensitivity of the organism.
 The effect on the site of infection.
 Status of the patient.(immune system, Renal and hepatic
dysfunction, poor perfusion, pregnancy, Lactation, Age)
 Safety of the agent.
 Cost of therapy.
(Katzung .GB 2007)

9. Antibiotic spectra
9
 Narrow spectrum
Agent acting only on a single or limited group of
microorganism
e.g. Isoniazid is active only against
mycobacterium
 Extended spectrum
Antibiotics that are effective against gram positive
organism and also against significant number of
gram negative bacteria
e.g.ampiciilin act against gram positive and some
gram negative bacteria.

10. Broad spectrum
10
 Drugs such as tetracycline and
chloramphenicol affect a wide variety
of microbial species are referred to as
broad spectrum antibiotics.
(Danish.IM 2000)

11. Classification of Antimicrobials
11
 Antibacterial
 Antiviral
 Antifungal
 Antiamoebic
 Antimalarial
 Antiprotozoal
(Mycek JM. Et al.2004)

12. Antibacterial classification
12
Antibacterial classification is based on the mode of
action there are four major classification
A. Cell wall synthesis inhibitor.
B. Metabolism inhibitor.
C. DNA synthesis inhibitor.
D. Protein synthesis
inhibitor.
(Mycek JM. Et al.2004)

13. Monobactum
Beta lactam
antibiotics
Cephalosporins
Other antibiotics
Penicillins
2nd
generation
Beta lactamase
antibiotics
Inhibitors of cell
wall synthesis
Carbapenums
3rd
generation
1st
generation
4th
generation
Vancomycin
Bacitracin
Imipenum
Meropenum
Aztreonem
Ampicillin
Amoxicilli
n
Piperacilli
n
Methicillin
Oxacillin
Cloxacillin
Cephradine
Cephalexin
Cefadroxil
Cefaclor
Cefuraxime
Cefamandole
Cefoxitin
Cefotaxime
Ceftrixone
Cefoperezone
Ceftazidme
Cefixime
Cefipime
Clavulanic acid
Sulbactum
Tazobactum
13
(Mycek JM. Et al.2004)

14. A. Cell wall synthesis inhibitor.
14
 Antibiotics that inhibit the formation of cell wall
of bacteria no cell wall no bacteria. They are
further divided in to six groups
1) Penicillin group.
2) Cephalosporin.
3) Carbapenum group. (Beta-lactam
antibiotics)
4) Monobactum.
5) Combination.
6) Others.

15. 1.Penicillin group
15
 Most widely effective antibiotics and are
among the least toxic drugs the major adverse
reaction is hypersensitivity.

16. Some common penicillin
16
 Ampicillin
 Amoxicillin
 Piperacillin
 Methiciilin
 Oxacillin
 Cloxaciilin

17. Cephalosporins
17
 Cephalosporins are beta lactam antibiotic that
are closely related both structurally and
functionally to the penicillin.
 Mode of action of Cephalosporins is same as
that of penicillin but they are more resistant to
beta lactamase than penicillins.
(Mycek JM. Et al.2004)

18. Classification of cephalosporin
18
First generation cephalosporins:
 Display good activity against gram positive organism but
have some activity against gram negative e.g. proteus E
.Coli and klebsilla.
 No effect on pseudomonas.
 Resistant to beta lactamase of staphylococci.
 Indication
 Gram positive infection and UTI.
 Some common first generation cephalosporin.
 Cephradine(velosef) oral,inj
 Cephalexin(Ceporex ,keflex) oral , inj
 Cefadroxil monohydrate(oral).

19. Second generation
cephalosporins
19
 More effective against gram negative less effective
against gram positive as compare to first
generation.e.gE.Coli,klebsella enterobactur, proteus,
 Indication
 skin or soft tissue infections ,urinary tract infections (UTIs) ,strep throat ,ear infections
,pneumonia
 sinus infections ,meningitis, gonorrhea
 Examples
• Cefaclor
• Cefuraxime
• Cefamandole

20. Third generation
cephalosporins
20
 Mainly effective against gram negative organisms there
activity against gram positive is very less as compared to first
and second generations.
 Indication
 Serious infections caused by gram negative infection
 Meningitis
 Gonorrhea
 As an empirical therapy of sepsis of unknown origin.
Examples
 Cefotaxime
 Ceftrixone
 Cefoperezon
 Ceftazidme
 Cefixime

21. Fourth generation
Cephalosporin
21
 It is similar to third generation but is more
resistant to beta lactamase.
 Indication
 Good activity against pseudomonas, S.aureus, S.
pnumoniae and H.influinza.
 Cefipime (Cefstar) Inj.
 Only one antibiotic in fourth generation

22. 3.Carbapenum group
22
 Are synthetic beta lactam antibiotics
 Imipenum and Meropenum are currently
available antibiotics.
 These drugs play a role in empiric therapy
since it is active against pencilliniase
producing gram positive and gram negative
organism, anaerobes and pseudomonas
aerogenosia

23. 4.Monobactum
23
 Cell wall synthesis inhibitor
 Aztreonam is the only available
antibiotic
 Less commonly use

24. 5.Combination
24
 These are the combinations of beta-lactam
and Beta-lactamase inhibitor.
 Beta lactam inhibits the cell wall while the beta
lactamase inhibitor inhibits the enzyme beta
lactamase which destroy the beta lactam ring
thus inhibit the function of beta-lactam.
 Some Common Combinations
 Amoxicillin+Clavulanic acid= Co-Amoxiclav
 Piperacillin+Tazobactum=Tazocin
 Cefoperezone+salbactam=Sulzon
(Mycek JM. Et al.2004)

25. 6.Others
25
 A . Vancomycin
Become increasingly important due to
its effectiveness against multiple drug
resistant organism such as MRSA .
 B . Bacitracin
Active against wide variety of gram
positive organism.
(Mycek JM. Et al.2004)

26. Monobactum
Beta lactam
antibiotics
Cephalosporins
Other antibiotics
Penicillins
2nd
generation
Beta lactamase
antibiotics
Inhibitors of cell
wall synthesis
Carbapenums
3rd
generation
1st
generation
4th
generation
Vancomycin
Bacitracin
Imipenum
Meropenum
Aztreonam
Ampicillin
Amoxicilli
n
Piperacilli
n
Methiciilin
Oxacillin
Cloxaciilin
Cephradine
Cephalexin
Cefadroxil
Cefaclor
Cefuraxime
Cefamandole
Cefoxitin
Cefotaxime
Ceftrixone
Cefoperezone
Ceftazidme
Cefixime
Cefipime
Clavulanic acid
Sulbactum
Tazobactum
26

27. B.Metabolism Inhibitors
27
 Trimethropin
 Sulfonamides
 Mode of action
 Folic acid is essential for the formation of bacterial DNA .DNA helps
in cell division
 These antibiotics inhibits the formation of folic acid
 In the absence of folic acid cell cannot grow or divide
 Indication
 Sulfonamides alone are less commonly used there
combination with Trimethropin called Cotrimaxole are
more commonly used.
 Silver Sulfa diazineis used to prevent infection in Burn
Wounds.
(Katzung .GB 2007)

28. C.DNA synthesis Inhibitors
28
 Mode of action
 Block bacterial DNA synthesis by inhibiting bacterial
(DNA gyrase),an enzyme involved in DNA
replication. They are rapidly bactericidal.
 All fluroquinolones are DNA synthesis
inhibitors.
 Ciprofloxacin
 Ofloxacin
 Norfloxacin
 Levofloxacin
(Katzung .GB 2007)

29. D. Protein synthesis inhibitors
29
 30 subunits binders
 50 subunits binders
30 sub units of
protein
50 sub units of
protein

30. 30 subunits binders
30
1. Tetracycline.
E.g. Doxycycline
2. Amino glycosides.
 Amikacin sulphate
 Tobramycin sulphate
 Gentamycin
 Streptomycin.
 Neomycin
Inhibit protein synthesis in bacteria exert
inhibitory effects at the ribosome bind specially to
30s ribosomal subunit ,this binding results in the
blocking of the link of transfer RNA to messenger
RNA essential for the transmission of accurate
coding of new protein structure.
50 sub units of
protein
30 sub units of
protein

31. 50 sub units binders
31
1.Chloramphenicol
2.Macrolides
 Erythromycin
 Clarythromycin
 Azithromycin
3. Oxazolidones
Linezolid
 Inhibit protein synthesis in bacteria exert inhibitory
effects at the ribosome bind specially to 50s
ribosomal subunit ,this binding results in the
blocking of the link of transfer RNA to messenger
RNA essential for the transmission of accurate
coding of new protein structure.

32. Mechanism of Action:
1. Inhibition of Cell Wall
Synthesis
2. Disruption of DNA
synthesis.
3. Inhibition of Protein
Synthesis
4. Interference with Metabolic
Processes
32

33. Pharmacokinetics
33
How the Body acts on a drug
 Absorption
 Distribution
 Metabolism
 Elimination
(Mycek JM. Et al.2004)

34. Absorption
34
 The movement of drug From the site
of administration to the systemic
circulation.
 For Oral=First pass effect(liver)
 For I/v = Zero pass effect
 Bioavailability
 Concentration of drug in systemic circulation that
is available for action

35. Distribution
35
 There are many compartments in the body
where drug is distributed.
 Brain
 Lungs
 Liver
 Heart
 kidneys

36. Metabolism
36
Prodrug (inactive) Active Drug
Liver Action
Metabolize Inactive(liver)
Active Water soluble
Elimination

37. Elimination
37
 Kidneys
 Liver
 Lungs
 Skin
 Eyes
 saliva

38. Pharmacodynamics
38
How the drugs act on the body.
 Indication
 Contraindication
 Adverse effect
 Toxic effect
 Drug receptor interaction
 Tolerance
 Potency
(Mycek JM. Et al.2004)

39. References
39
 Mycek JM,Harvey AR,Champe CP(2009) illustrated
pharmacology 6th edition. Lippincott William and Wilkins.
 Katzung GB (2007) Basic and clinical pharmacology 10th
edition. McGraw hill and companies.
 Danish IM (2000) Short text book of clinical pharmacology 3rd
edition. Danish3939 medical publisher.
 Larch AM (2006) Focus on Nursing Pharmacology, 3rd
Edition. Lippincott Williams & Wilkins
 Rang et al (2003) Pharmacology, 5th Edition. Churchill
Livingstone
 Lilley et al (2005) Pharmacology and the Nursing Process, 4th
Edition. Mosby
 Dorland's pocket medical dictionary 27th edition.

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