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INTRODUCTION OF CHEMOTHERAPHY
BY
K.SAMINATHAN. M.PHARM.(PhD), M.B.A .(PhD)

1
LEARNING OBJECTIVES
I.

DEFINITIONS

II. HISTORY
III. MECHANISMS OF ANTIMICROBIAL AGENTS
IV. MECHANISMS OF ANTIBACTERIAL R...
I.DEFINITIONS
Chemotherapy is the drug treatment for the
diseases caused by pathologic microorganisms,
parasites, and tum...
WHAT IS AN ANTIBIOTIC?
“Antibiotic” is from antibiosis, meaning
against life.
Substances produced by various species
of ...
Antimicrobial spectrum : the scope that
a drug kills or suppresses the growth of
microorganisms.
Narrow-spectrum: The drug...
The minimal inhibitory concentration (MIC)
the minimum amount of a drug required to inhibit the
growth of bacteria in vitr...
II.HISTORY
1929 Penicillin discovered by Alexander
Fleming
Messy lab, cool damp weather, luck

1940 Florey and Chain ma...
8
III. MECHANISMS OF ANTIMICROBIAL AGENTS
1.INHIBITION OF CELL WALL SYNTHESIS
2.INHIBITION OF FUNCTIONS OF CELLULAR MEMBRANE...
CON ...
10
1. Inhibition of cell wall synthesis
– Penicillins and cephalosporins stop synthesis
of wall by preventing cross linking o...
2. Inhibition of functions of cellular
membrane:
– The bacterial cell membrane is also called
cytoplasmic membrane. Its ma...
3. Inhibition of protein synthesis
– Due to differences in ribosomes
– Eucaryotic cells have 80S (60S + 40S subunits)
ribo...
4. Inhibition of nucleic acid synthesis
– Stop DNA replication
• Example: Quinolones-inhibiting DNA
gyrase; Metronidazole?...
5. Inhibition of folic acid synthesis
A drug mimics a normal metabolite and
acts as a competitive inhibitor.
– Enzyme of c...
IV.RESISTANCE TO ANTIBACTERIAL AGENTS
• Drug resistance is the phenomenon that
susceptibility of pathogenic microorganisms...
TYPES OF RESISTANCE
• Intrinsic or natural resistance
• e.g., no target site in the bacteria
• Acquired resistance
–Resist...
MECHANISMS OF ANTIBACTERIAL RESISTANCE
① Produce enzymes that destroy the
chemical structures of drugs
② Change their cell...
1. Mechanisms of antibacterial resistance
• Antibiotic inactivation
– bacteria acquire genes encoding
enzymes that inactiv...
2. Mechanisms of antibacterial resistance
Altered uptake of antibiotics, resulting in:
– decreased permeability
– increase...
3. Mechanisms of antibacterial resistance
Structurally modified antibiotic target site,
resulting in:
– For example, as th...
4.Mechanisms of antibacterial resistance
Develop an altered metabolic pathway
– Bacteria can develop an altered metabolic
...
V. GENERAL PRINCIPLES OF ANTI-INFECTIVE
THERAPY
Selection of an appropriate anti-infective agent
① Identification of the i...
VI. IDEAL ANTIMICROBIAL DRUG
Have highly selective toxicity to the
pathogenic
microorganisms in host body
Have no or le...
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Introduction of chemotheraphy

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  1. 1. INTRODUCTION OF CHEMOTHERAPHY BY K.SAMINATHAN. M.PHARM.(PhD), M.B.A .(PhD) 1
  2. 2. LEARNING OBJECTIVES I. DEFINITIONS II. HISTORY III. MECHANISMS OF ANTIMICROBIAL AGENTS IV. MECHANISMS OF ANTIBACTERIAL RESISTANCE V. GENERAL PRINCIPLES OF ANTI-INFECTIVE THERAPY VI. IDEAL ANTIMICROBIAL DRUG 2
  3. 3. I.DEFINITIONS Chemotherapy is the drug treatment for the diseases caused by pathologic microorganisms, parasites, and tumour cells. The objective of chemotherapy is to study and to apply the drugs that have highly selective toxicity to the pathogenic microorganisms and have no or less toxicity to the host. CON ... 3
  4. 4. WHAT IS AN ANTIBIOTIC? “Antibiotic” is from antibiosis, meaning against life. Substances produced by various species of microorganisms: bacteria, fungi, actinomycetes— to kill or suppress the growth of other microorganisms. Today the term antibiotic extends to include synthetic antibacterial agents: sulfonamides and quinolones. CON ... 4
  5. 5. Antimicrobial spectrum : the scope that a drug kills or suppresses the growth of microorganisms. Narrow-spectrum: The drugs that only act on one kind or one strain of bacteria. (isoniazid ) Broad-spectrum: The drugs that have a wide antimicrobial scope. (tetracycline, chloramphenicol ) CON ... 5
  6. 6. The minimal inhibitory concentration (MIC) the minimum amount of a drug required to inhibit the growth of bacteria in vitro. • The minimal bactericidal concentration (MBC) the minimum amount of a drug required to kill bacteria in vitro. TYPE Natural Antibiotics Antimicrobial drugs produced by microorganisms. Synthetic Antibiotics Antimicrobial drugs synthesized in the lab. CON ... 6
  7. 7. II.HISTORY 1929 Penicillin discovered by Alexander Fleming Messy lab, cool damp weather, luck 1940 Florey and Chain mass produce penicillin for war time use, becomes available to the public. 1935 Sulfa drugs discovered 1943 Streptomycin discovered Western civilization fundamentally changed 7
  8. 8. 8
  9. 9. III. MECHANISMS OF ANTIMICROBIAL AGENTS 1.INHIBITION OF CELL WALL SYNTHESIS 2.INHIBITION OF FUNCTIONS OF CELLULAR MEMBRANE 3. INHIBITION OF PROTEIN SYNTHESIS 4.INHIBITION OF NUCLEIC ACID SYNTHESIS 5.INHIBITION OF FOLIC ACID SYNTHESIS CON ... 9
  10. 10. CON ... 10
  11. 11. 1. Inhibition of cell wall synthesis – Penicillins and cephalosporins stop synthesis of wall by preventing cross linking of peptidoglycan units. – Bacitracin and vancomycin also interfere here. – Excellent selective toxicity CON ... 11
  12. 12. 2. Inhibition of functions of cellular membrane: – The bacterial cell membrane is also called cytoplasmic membrane. Its main compounds are proteins and lipids. – Polymyxins can selectively combine with phosphatide in the cell membrane and cause the increase of membranous permeability. As the result, some important materials will outflow from bacterial cells and result in death of bacteria. CON ... 12
  13. 13. 3. Inhibition of protein synthesis – Due to differences in ribosomes – Eucaryotic cells have 80S (60S + 40S subunits) ribosomes. – Procaryotic cells have 70S (50S + 30S subunits) ribosomes. – Examples: • Chloramphenicol,Macrolides and Clindamycin bind to the 50S subunit. • Tetracyclines and Aminoglycosides bind to the 30S subunit. CON ... 13
  14. 14. 4. Inhibition of nucleic acid synthesis – Stop DNA replication • Example: Quinolones-inhibiting DNA gyrase; Metronidazole???-DNA Polymerase – Or stop RNA synthesis • Example: Rifampin -binds to the bacterial DNA-dependent RNA polymerase. CON ... 14
  15. 15. 5. Inhibition of folic acid synthesis A drug mimics a normal metabolite and acts as a competitive inhibitor. – Enzyme of cell recognizes the drug instead of the normal metabolite-Pathway stops. – Example: Sulfonamides and trimethoprim are similar to PABA (para aminobenzoic acid). inhibit folic acid synthesis by blocking dihydrofolic acid synthase and reductase respectively. CON ... 15
  16. 16. IV.RESISTANCE TO ANTIBACTERIAL AGENTS • Drug resistance is the phenomenon that susceptibility of pathogenic microorganisms to drugs becomes lower or even loses after the microorganisms contact with drugs many times. • When the bacteria show resistance to one drug, they are also resistant to some other drugs. This phenomenon is called cross drug resistance. CON ... 16
  17. 17. TYPES OF RESISTANCE • Intrinsic or natural resistance • e.g., no target site in the bacteria • Acquired resistance –Resistance acquired by mutation is unusual, –Resistance acquired by R-factors on plasmids is common, very rapid method of acquiring resistance that often involves resistance to many antibiotics. (R factor contains genes coding for enzymes that make the cell resistant to antibiotics) CON ... 17
  18. 18. MECHANISMS OF ANTIBACTERIAL RESISTANCE ① Produce enzymes that destroy the chemical structures of drugs ② Change their cell membrane and cell wall permeability to the drug ③ Develop an altered structural target for the drug ④ Develop an altered metabolic pathway CON ... 18
  19. 19. 1. Mechanisms of antibacterial resistance • Antibiotic inactivation – bacteria acquire genes encoding enzymes that inactivate antibiotics • Examples include: – b-lactamases – aminoglycoside-modifying enzymes – chloramphenicol acetyl transferase CON ... 19
  20. 20. 2. Mechanisms of antibacterial resistance Altered uptake of antibiotics, resulting in: – decreased permeability – increased efflux – For example, gram-negative bacillus can induce some special proteins to block porin channels in cell wall and prevent tetracyclines into the bacillus. CON ... 20
  21. 21. 3. Mechanisms of antibacterial resistance Structurally modified antibiotic target site, resulting in: – For example, as the receptor protein on the 30s ribosomal subunit may be deleted or altered as a result of mutation, some aminoglycosides cannot combine with the bacteria. CON ... 21
  22. 22. 4.Mechanisms of antibacterial resistance Develop an altered metabolic pathway – Bacteria can develop an altered metabolic pathway that bypasses the reaction inhibited by drugs. – For example, sulfonamide resistance my occur as a result of mutations that cause over-production of PABA or cause production of a folic acid-synthesizing enzyme that has low affinity for sulfonamides. Mechanisms of antibacterial resistance PABA, p-aminobenzoic acid 22
  23. 23. V. GENERAL PRINCIPLES OF ANTI-INFECTIVE THERAPY Selection of an appropriate anti-infective agent ① Identification of the infecting organism should precede antimicrobial therapy when possible. ② The pathogenic microorganism susceptibility to antimicrobial agents should be determined, if a suitable test exists. ③ Factors that influence the choice of an antiinfective agent or its dosage for a patient include the age, renal and hepatic function, pregnancy status, and the site of infection, etc. 23
  24. 24. VI. IDEAL ANTIMICROBIAL DRUG Have highly selective toxicity to the pathogenic microorganisms in host body Have no or less toxicity to the host. Low propensity for development of resistance. Not induce hypersensitive in the host. Have rapid and extensive tissue distribution Be free of interactions with other drugs. Be relatively inexpensive 24
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