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Dr Rahul Kunkulol's Power point Presentations
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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
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• 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
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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.
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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
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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
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• 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
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Type of bacteria
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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
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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
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Protein synthesis inhibitors
• Macrolides
• Aminoglycosides
• Tetracyclines
• Chloramphenicol
• Oxazolidinones
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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
04/11/2023DR RAHUL KUNKULOL 17
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
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• β-lactams• Penicillins
• Cephalosporins
• Carbapenems
• Monobactams
• β-lactamase inhibitors• Clavulanic acid
• Sulbactam
• Tazobactam
5. Cell wall synthesis inhibitors
Vancomycin & Bacitracin
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Modes of action
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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…
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