Antimicrobial Agents(General Considerations)
Prof. R. K. DixitPharmacology and Therapeutics
K.G.M.U. [email protected]
Objectives• After this lecture you will be able to answer
– What are antimicrobials, antibiotics, chemotherapeutic agents (Terminologies used in antimicrobial treatment)
– Classification of antimicrobials • Chemicals• Mechanism• Spectrum
– Mechanisms of action of antimicrobials– Resistance development in antimicrobials– Multidrug resistant microorganisms
A naturopath tells “One should never take antibiotics
Except in Pneumonia, a kidney infection, boils, meningitis, encephalitis, osteomyelitis, occular infections, or other serious illness………………………………………………….”
Allopath is Lucky to have the help of Antimicrobials
But This Luck may not last long due to reasons……– Inappropriate use,… Overuse…..– Antimicrobial resistance– Reduced immunity and worsening of environment – patients having co morbid illnesses like diabetes,
malnutrition………………..– Less interest of pharmaceuticals in this field– Costly new antimicrobials
Antimicrobials , Antimicrobials , Antimicrobials , Antimicrobials, Antimicrobials , Antimicrobials
Antimicrobials!!!
Penicillin, ampicillin, amoxycillin, ticarcillin, piperacillin, flucloxacillin, dicloxacillin, oxacillin, methicillin, nafcillin, carbenicillin, eryhtromycin, clindamycin, roxythromycin clarithromycin, tetracycline, doxycycline, minocycline, vancomycin, teicoplanin, augmentin, gentamicin, tobramycin, amikacin, streptomycin, azithromycin, aztreonam, cephalexin, cefotaxime, cephamandole, cefepime, ceftriaxone, ceftazidime, cefpirome, imipenem, chloramphenicol, cotrimoxazole, ciprofloxacin, norfloxacin, trimethoprim,……. ………………………………………………………………………………………………………………………………………………….. hundreds of different antimicrobial agents on the market.
TerminologyTerminology
6
Chemotherapy –
Use of drugs to treat infections and malignancy. (Antimicrobials and Antineoplastic agents)
Pharmacodynamic agents-
Drugs regulating physiological process of body and act on the body cells.
Chemotherapeutic agents-
Selectively acting against microbes or malignant cells. (Don’t touch body cells)
Antimicrobials –
Used in treating infectious diseases.
Antibiotics –
Produced from microbes to inhibit or kill other microbes. (Antimicrobials from microbes)
All antibiotics are antimicrobials but all antimicrobials are not antibiotics
Bacteriostatic- Stop the growth of bacteria
Bactericidal- Kill the bacteria
PAE- Post antibiotic effect
Minimum Inhibitory Concentration (MIC)- Which stops the growth
Minimum Bactericidal Concentration (MBC)- Which kills by 99.99%
(Bactericidal -less value of MBC-MIC, Bacteriostatic - more value of MBC-MIC)
• Prebiotics- – Stimulate the growth of intestinal commensals and
prevent multiplication and establishment of pathogenic bacteria.
– Lactulose, Lactitol, Inulin• Probiotics-
– Live microbial substances used as supplements to maintain or improve the intestinal bacterial flora.
– Lactobacilli and Bifidobacteria
Gram positive & Gram Negative
• Gram positive bacteria have – thick cell wall– Peptidoglycan directly accessible from environment
• Gram negative bacteria have – Thin cell wall– Surrounded by inner and outer membrane– Of lipopolysaccharide, phospholipids, and proteins– Outer membrane is a barrier to diffusion of antibiotics
• Limited antibiotics may diffuse through porins
Historical Perspectives• Chenopodium-
– for intestinal worms• Mouldy curd –
– for boils• Chaulmoogra oil-
– for Leprosy• Mercury –
– for Syphilis• Cinchona Bark-
– for Malaria
Historical perspectives• Pasteur- (1877)
– Phenomenon of antibiosis• Paul Ehrlich- (1906)
– Father of Chemotherapy, Coined term chemotherapy• Domagk- (1935)
– Discovery of sulfonamides (Prontosil to sulphanilamide)• Fleming, Chain, Florey-
– Penicillin (1929, 39, 41) from penicillium• Waksman-
– Streptomycin, from actinomycetes, – Coined term antibiotic
Introduction of Class of antimicrobial agents (SPECTM)• 1935 - Sulphonamides• 1941 - Penicillins• 1944 - Aminoglycosides• 1945 - Cephalosporins• 1949 - Chloramphenicol• 1950 - Tetracyclines• 1952 - Macrolides• 1956 - Glycopeptides• 1957 - Rifamycins• 1959 - Nitroimidazoles• 1962 - Quinolones• 1968 - Trimethoprim• 2000 - Oxazolidinones• 2003 - Lipopeptides
Antimicrobial Classification• Chemical structure• Mechanism of Action• Organism type • Spectrum of activity• Static or Cidal• Origin of antimicrobials
Chemical Classification (Public Loves GOOD Quality BATSMAN)• Polypeptides- Polymyxin, Colistin, Bacitracin• Poyene antibiotics- Nystatin, Amphotericin-B, Hamycin• Lincosamide- Lincomycin, Clindamycin• Glycopeptides- Vancomycin, Teicoplanin• Oxazolidinone- Linezolid• Others-----------------Riampicin, Griseofulvin, etc• Diaminopyrimidines- Trimethoprim, Pyrimethamine• Quinolones- Nalidixic acid, ciprofloxacin• Beta-lactam- Penicillins, Cephalosporins, Monobactams, Carbapenems• Aminoglycosides- Streptomycin, Gentamycin• Tetracyclines- Oxytetracycline, Doxycycline• Sulphonamides- Sulfadiazine, Sulfamethoxazole, • Macrolides- Erythromycin, Clarithromycin• Azoles- Fluconazole, Clotrimazole• Nitroimidazoles- Metronidazole, Tinidazole• Nicotinic acid derivatives- Isoniazide, Pyrizinamide, Ethionamide• Nitrobenzene derivaties- Chloramphenicol• Nitrofuran derivatives- Nitrofurantoin, Furazolidone
Organism affected• Anti-viral• Anti-bacterial• Anti-fungal• Anti-protozoal• Anthelmintic
Sources• Fungi-
– Penicillin– Cephalosporins– Griseofulvin
• Bacteria- – Polymyxin B– Colistin– Bacitracin
• Actinomycetes- – Most common– Aminoglycosides,
Tetracyclines, Chloramphenicol
– Macrolides
Spectrum• Narrow
– Penicillin G– Streptomycin– Erythromycin
• Broad– Tetracycline– Chloramphenicol
• Extended– Ampicillin– Amoxicillin– Most……..
Bacteristatic– Sulfonamides and Trimethoprim– Tetracyclines– Macrolides (Erythromycin)– Chloramphenicol– Ethambutol– Nitrofurantoin
Bactericidal– Cotrimoxazol– Penicillins– Cephalosporins– Aminoglycosides– Vancomycin, Daptomycin – Fluroquinolones (ciprofloxacin)– INH, Rifampicin, Pyrazinamide– Polymixins, Bacitracin– Metronidazole
Mechanism of action• Cell Wall synthesis inhibition-
– Beta-lactams, Vancomycin, Cycloserines
• Cell membrane Leakage-– Polypeptides, Polyenes
• Folate Synthesis inhibition-– Sulfonamides, Pyrimethamine, Cotrimaxazole, PAS, Ethambutol
• DNA gyrase and Topoisomerase inhibition- – Fluroquinolones
• RNA polymerase inhibition- – Rifampicin,,
• Protein Synthesis Inhibition- (ATT)– Aminoglycosides, tetracyclines, Chloramphenicol, Macrolides,
Clindamycin, Linezolid
Differences between human cells Vs Bacterial Cells (Makes the antibacterial selective)
• Human cells don’t posses wall – (Peptidoglycans = peptides + sugar)
• Human cell membrane is different – ( Bacteria Contain Hypanoids in place of Sterol)
• Human cells take preformed dihydrofolic acid – (no need of PABA in human)
• Dihydrofolic acid reducatase enzyme is different – (thousand time affinity)
• Topoisomerase II are different– (in bacteria IV, DNA Gyrase)
• DNA dependent RNA polymerase is different• Ribosome 60S subunit (in bacteria 50S)• Ribosome 40S subunit (in bacteria 30S)
1
2
3
4
5
67
8
Protein SynthesisChloramphenicol-Macrolides- Erythromycin, Azithromycin etc.
Aminoglycosides. Gentamicin, Amikacin, etc.
• DNA gyrase (Gyrase) belongs to DNA topo-isomerases
• DNA gyrase, referred to simply as gyrase, • DNA gyrase also known as DNA
topoisomerase IV (In bacteria). • In human Topoisomerase II
PABA
Dihydrofolic acid
Tetrahydrofolic acid
Purines and PyrimidinesDNA And RNA
DNA unwinding (DNA gyrase)
Threads sepeartion (Topoisomerase IV)
DNA dependent RNA Polymerase
tRNA +Amino Acids
Ribosome unit (50S)
Ribosome unit (30S)Protein Synthesis
Dihydro-folic acid Synthetase
Dihydro-folic acid reductase
DNA multiplication
mRNA
Sulphonamides (PABA analogue and inhibitor of DHFAS)
Trimethoprim and Pyrimethamine (inhibitor of DHFAR)
Quinolones (Inhibitor of DNA gyrase and Topoisomerase IV)
Rifampicin (inhibitor of DNA dependant RNA Polymerase)
Chloramphenicol, Macrolides (50S)
Aminoglycosides, Tetracyclines (30S)
DNA unwinding (DNA gyrase)
Threads sepeartion (Topoisomerase IV)
PABA
Dihydrofolic acid
Tetrahydrofolic acid
Purines and PyrimidinesDNA And RNA
Dihydro-folic acid Synthetase
Dihydro-folic acid reductase
RNA Polymerase
tRNA +Amino Acids
Ribosome unit (50S)
Ribosome unit (30S)Protein SynthesismRNA
Sulphonamides (PABA analogue and inhibitor of DHFAS)
Trimethoprim and Pyrimethamine (inhibitor of DHFAR)
Quinolones (Inhibitor of DNA gyrase and Topoisomerase IV)
Rifampicin (inhibitor of DNA dependant RNA Polymerase)
Chloramphenicol, Macrolides (50S)
Aminoglycosides, Tetracyclines (30S)
3
4
5
67
8
Cell Wall synthesis inhibition- Beta-lactams, Vancomycin, Cycloserines
Cell membrane Leakage- Polypeptides, Polyenes
PABA
Dihydrofolic acid
Tetrahydrofolic acid
Purines and PyrimidinesDNA And RNADNA unwinding (DNA gyrase)
Threads sepeartion (Topoisomerase IV)
RNA Polymerase
mRNAtRNA + Amino Acids
Ribosome unit (50S)Ribosome unit (30S)
Protein Synthesis
Dihydro-folic acid Synthetase
Dihydro-folic acid reductase
DNA multiplication
Sulphonamides (PABA analogue and inhibitor of DHFAS)
Trimethoprim and Pyrimethamine (inhibitor of DHFAR)
Quinolones (Inhibitor of DNA gyrase and Topoisomerase IV)
Rifampicin (inhibitor of RNA Polymerase)
Chloramphenicol, Macrolides (50S)
Aminoglycosides, Tetracyclines (30S)
1
2
3
4
5
67
8
ANTIBIOTICSDose-dependent (With PAE) Time-dependent
Antibacterial effect directly depends on their concentrations in the locus of infection (high doses 1-2 times/24h)
•Aminoglycosides •Fluoroqinolones•Metronidazol•Amphotericin B
Effectiveness depends on a period of time, during which concentration in blood overwhelms MIC for a particular causative agent(constant i.v. infusion or 3-6 times/24h)
•Beta-lactames•Glycopeptides•Macrolides•Tetracyclines•Vancomycin
Post-Antibiotic Effect• The capacity to inhibit the growth of bacteria
after removal of the drug from the culture (body)
• Provides additional time for the immune system to remove bacteria that might have survived antibiotic treatment before they can eventually regrow after removal of the drug.
• Cell mebrane – Polypeptides and Polyenes– Polymyxin, Colistin, Bacitracin, Nystatin, Amphotericin-B, Hamycin
• Cell Wall synthesis by acting on cross linking– Penicillins, Cephalosporins, Monobactams, Carbapenems, Vancomycin, Teicoplanin,
• Cell wall synthesis by acting on inhibition of mycolic acid (Long Fatty acid present in mycobacterial family)
– Isoniazide, Pyrizinamide, Ethambutol• Interfering with folic acid metabolism
– Sulphonamides- Sulfamethoxazole, Sulfadoxine, – Diaminopyrimidines- Trimethoprim, Pyrimethamine
• DNA gyrase and topoisomerase IV inhibitors– Quinolones- Nalidixic acid, ciprofloxacin, Ofloxacin, Pfloxacin, Gatifloxacin, Sparfloxacin
• Inhibition of DNA dependeant RNA Polymerase– Rifampicin,
• Acting on 50S ribosome– Macrolides- Erythromycin, Clarithromycin, Azithromycin, Roxithromycin, – Chloramphenicol, Lincomycin, Clindamycin, Linezolid
• Acting on 30 S ribosome– Aminoglycosides- Streptomycin, Gentamycin, Kanamycin, Amikacin, Tobramycin– Tetracyclines- Oxytetracycline, Doxycycline
Antibacterial - Co-trimoxazoleAntimalarial- Co-trimazine
1
2
34
5
67
8
2
Mechanisms Of Resistance ResistanceIntrinsic Acquired
Mutation Transferred
Conjugation Transformation Transduction
Not Dangerous/less clinical importance
Dangerous/clinical importance
Inherent Resistance(Not Much of clinical importance)
• Bacteria naturally resistant – e.g., Gram-negative bacteria resistant to penicillins– Genes transferred to the bacterial progeny.
• Bacteria may be resistant because – No mechanism to transport the drug into the cell. – Do not contain antibiotic’s target process or protein.
Acquired Resistance• Due to exposure of antimicrobials• Horizontal evolution:
– Resistance genes pass from resistant to nonresistant strain,
– Antibiotics- a selective pressure.– Gene transfer mechanisms:
• Conjugation.• Transduction.• Transformation.
Cellular Resistance
•
• • ATTACK OF THE SUPERBUGS:
ANTIBIOTIC RESISTANCE By Grace Yim, Science Creative Quarterly.
Jan 07
Mechanisms of Resistance• Enzyme-based resistance–
– Break down of antimicrobials.
• Ribosomal modifications–– Methylation of ribosome interferes with antibiotic binding.
• Protein modifications–– Mutations leave target protein unrecognizable to antibiotic
• Metabolic resistance–– Overcome competitive inhibition by alternate pathway.
• Efflux–– Pumps antimicrobials out.
Resistance in some antibiotics• Beta-lactams: - Hydrolysis , mutant PBP• Tetracycline: - Active efflux from the cell• Aminoglycosides- Inactivation by enzymes• Sulfonamides- Alternate pathway, • Fluoroquinolones- Mutant DNA gyrase• Chloramphenicol- Reduced uptake into cell • Macrolides - RNA methylation, drug efflux
Factors favoring Resistance•Prescription related factors:•Overuse•Early discontinuation•Over continuation•Less dose, duration
•Livestock doping:•Animals exposure
Superbugs (Microorganisms with multiple resistance)
• MRSA - Methicillin-resistant Staphylococcus aureus• VISA - Vancomycin intermediate resistant Staphylococcі• VRE - Vancomycin-resistant enterococci• ESBLs - Extended-spectrum beta-lactamases
(microorganisms – resistant to cephalosporins and monobactams)
• PRSP - Penicillin-resistant Streptococcus pneumoniae• MRPA (MDR-PA)- Multidrug resistant Pseudomonas
aeruginosa• MRAB (MDR-AB) - Multidrug resistant Acinetobacter
baumannii
Why worry?n MDRO are dangerous
– Difficult to treat– More virulent– Increase mortality and morbidity
n Resource-intensive – More expensive and toxic antibiotics– Increase length of hospitalization– Increase demand for isolation-facilities