introduction to chemotheraphy : dr rahul kunkulol's power point presentations

DR.RAHUL

Introduction to

Chemotherapy

Chemotherapy

04/11/2023DR RAHUL KUNKULOL 2

“Treatment of systemic infections with specific drugs that selectively suppress the infecting microorganism without

affecting the host”.

Chemotherapy


• Treatment of neoplastic diseases with drugs is also called as Chemotherapy

• This is due to analogy between the pathogenic organism and malignant cells

Definitions• Antibiotics :

Naturally occurring substance produced by the microorganism, that inhibits or kills other microorganism at very low concentration


Definitions• Antibacterial :

Natural, semi-synthetic or synthetic substance that inhibits the growth or kills bacteria• Antimicrobial agent :

Natural, semi-synthetic or synthetic substance that inhibits the growth or kills microorganisms.


Antibiotics• Medications used to treat

bacterial infections

• Ideally, before beginning antibiotic therapy, the suspected areas of infection should be cultured to identify the causative organism and potential antibiotic susceptibilities. 04/11/2023DR RAHUL KUNKULOL 6

Antibiotics• Empiric therapy: Treatment of

an infection before specific culture information has been reported or obtained

• Prophylactic therapy: Treatment with antibiotics to prevent an infection, as in intra-abdominal surgery


ANTIMICROBIAL CLASSIFICATION

• Chemical structure

• Type of action

• Spectrum of activity

• Type of organism against which primarily active

• Source of antibiotics

• Mechanism of action04/11/2023DR RAHUL KUNKULOL 8

Chemical structure

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9

• Sulfonamides

• Tetracycline

• Macrolides

• Aminoglycosides

Type of action•Bactericidal: Kill bacteria

•Bacteriostatic: Inhibit growth of susceptible bacteria, rather than killing them immediately; will eventually lead to bacterial death


• Antibiotics inhibit a narrow range of bacteria

• Preferable when organism has been identified

• Antibiotics inhibit a wide range of bacteria

• Indicated if infecting organism not yet identified

Antibiotic Spectrum of Activity

Broad spectrum Narrow spectrum


Type of bacteria


Microbial Sources of Antibiotics

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Modes of actionAntimicrobial agents inhibit 5

essential bacterial processes1. Protein synthesis2. Folic acid synthesis3. DNA synthesis4. RNA synthesis5. Cell wall synthesis


1. Protein synthesis inhibitors

DNA mRNA Protein transcription translation

• Ribosome is a protein factory in bacteria takes mRNA in and produces proteins from them.

• Bacterial ribosome has 2 parts: • 30S binds to mRNA to translate mRNA into amino

acids, which form proteins• 50S required for peptide elongation

• 3 phases from mRNA to protein• Initiation• Elongation• Termination


Protein synthesis inhibitors

• Macrolides

• Aminoglycosides

• Tetracyclines

• Chloramphenicol

• Oxazolidinones


2. Folic acid synthesis inhibitors

Trimethoprim

(Diaminopyrimidines)

Sulphamethoxazole

(Sulphonamides)

Structural analogues of PABA

Dihydropteroate synthetase

Dihydrofolate reductase

Pterdine + Para-amino Benzoic acid

Dihydropterate

Dihydrofolate

TetrahydrofolateDNA/RNA


3. DNA synthesis inhibitors

• Enzymes required for DNA replication• Topoisomerase II (DNA gyrase): GyrA

and GyrB

• Topoisomerase IV: ParC and ParE

• Quinolones interact/bind to the topoisomerases, which stops DNA replication e.g. Nalidixic Acid, Ciprofloxacin 04/11/2023DR RAHUL KUNKULOL 18

4. RNA synthesis inhibitors

• RIFAMPICIN• Forms a stable complex with

bacterial DNA-dependent RNA polymerase

• Prevents chain initiation process of DNA transcription

• Mammalian RNA synthesis not affected as RNA polymerase is much less sensitive to Rifampicin


• β-lactams• Penicillins

• Cephalosporins

• Carbapenems

• Monobactams

• β-lactamase inhibitors• Clavulanic acid

• Sulbactam

• Tazobactam

5. Cell wall synthesis inhibitors

Vancomycin & Bacitracin


Modes of action


What Factors Promote Antimicrobial Resistance?

• Exposure to sub-optimal levels of antimicrobial

• Exposure to microbes carrying resistance genes

Inappropriate Antimicrobial Use

• Prescription not taken correctly• Antibiotics for viral infections• Antibiotics sold without medical

supervision• Spread of resistant microbes in

hospitals due to lack of hygiene

Inappropriate Antimicrobial Use

• Lack of quality control in manufacture or outdated antimicrobial

• Poverty or war• Use of antibiotics in foods

Antibiotics in Foods

• Antibiotics are used in animal feeds and sprayed on plants to prevent infection and promote growth

• Multi drug-resistant Salmonella typhi has been found in 4 states in 18 people who ate beef fed antibiotics

Consequences of Antimicrobial Resistance

• Infections resistant to available antibiotics

• Increased cost of treatment

04/11/2023 28DR RAHUL KUNKULOL

THANK YOU…THANK YOU…

04/11/2023 29DR RAHUL KUNKULOL

introduction to chemotheraphy : dr rahul kunkulol's power point presentations

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