1. Antimicrobial Agents (General Considerations)
Prof. R. K. Dixit
Pharmacology and Therapeutics
K.G.M.U. Lucknow

2. 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

3. A naturopath tells “One should never take antibiotics Except in
Pneumonia, a kidney infection, boils, meningitis, encephalitis, osteomyelitis, occular infections, or other serious illness………………………………………………….”

4. 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

5. 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.

6. Terminology
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

7. Minimum Inhibitory Concentration (MIC)-
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)

8. Prebiotics- Probiotics- Lactulose, Lactitol, Inulin
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

10. 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

11. Historical Perspectives
Chenopodium-
for intestinal worms
Mouldy curd –
for boils
Chaulmoogra oil-
for Leprosy
Mercury –
for Syphilis
Cinchona Bark-
for Malaria

12. 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

13. Introduction of Class of antimicrobial agents (SPECTM)
Sulphonamides
Penicillins
Aminoglycosides
Cephalosporins
Chloramphenicol
Tetracyclines
Macrolides
Glycopeptides
Rifamycins
Nitroimidazoles
Quinolones
Trimethoprim
Oxazolidinones
Lipopeptides

14. Antimicrobial Classification
Chemical structure
Mechanism of Action
Organism type
Spectrum of activity
Static or Cidal
Origin of antimicrobials

15. 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

16. Organism affected Sources Anti-viral Fungi- Anti-bacterial Anti-fungal
Anti-protozoal
Anthelmintic
Sources
Fungi-
Penicillin
Cephalosporins
Griseofulvin
Bacteria-
Polymyxin B
Colistin
Bacitracin
Actinomycetes-
Most common
Aminoglycosides, Tetracyclines, Chloramphenicol
Macrolides

17. Spectrum Bacteristatic Bactericidal Narrow Broad Extended
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

18. Spectrum (Narrow, Broad, Extended)

19. 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

20. 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 6 7 8

21. Cell Wall
Beta Lactams

22. Protein Synthesis Chloramphenicol- Macrolides-
Erythromycin, Azithromycin etc.
Aminoglycosides. Gentamicin, Amikacin, etc.

23. 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

24. Enzyme that relieves strain while double-strand DNA is being unwound by helicase. Causing negative super coiling of the DNA.
DNA gyrase is particularly unique because it is the only Topoiosmerase that can both relax positively super coiled DNA and introduce negative supercoils into the DNA (most Topoiosmerase only relieve the positively super coiled DNA)
This process occurs in prokaryotes (in particular, in bacteria), whose single circular DNA is cut by DNA gyrase and the two ends are then twisted around each other to form super coils

25. There are three main types of topology:
supercoiling,
knotting, and 
catenation.
(Outside of the essential processes of replication or transcription, DNA must be kept as compact as possible, and these three states help this cause. However, when transcription or replication occurs, DNA must be free, and these states seriously hinder the processes. In addition, during replication, the newly replicated duplex of DNA and the original duplex of DNA become intertwined and must be completely separated in order to ensure genomic integrity as a cell divides.)

26. As a transcription bubble proceeds, DNA ahead of the transcription fork becomes over wound, or positively super coiled, while DNA behind the transcription bubble becomes under wound, or negatively super coiled.
As replication occurs, DNA ahead of the replication bubble becomes positively super coiled, while DNA behind the replication fork becomes entangled forming pre-catenanes.
One of the most essential topological problems occurs at the very end of replication, when daughter chromosomes must be fully disentangled before mitosis occurs. Topoiosmerase IIA plays an essential role in resolving these topological problems

27. Quinolones

28. Purines and Pyrimidines
PABA
Sulphonamides (PABA analogue and inhibitor of DHFAS)
Dihydro-folic acid Synthetase
Dihydrofolic acid
Dihydro-folic acid reductase
Trimethoprim and Pyrimethamine (inhibitor of DHFAR)
Tetrahydrofolic acid
Purines and Pyrimidines
DNA
And RNA
Quinolones
(Inhibitor of DNA gyrase and Topoisomerase IV)
DNA unwinding (DNA gyrase)
DNA multiplication
Threads sepeartion (Topoisomerase IV)
DNA dependent RNA Polymerase
Rifampicin
(inhibitor of DNA dependant RNA Polymerase)
Chloramphenicol, Macrolides (50S)
Ribosome unit (50S)
Protein Synthesis
mRNA
Ribosome unit (30S)
tRNA +
Amino Acids
Aminoglycosides, Tetracyclines (30S)

29. 3 4 5 6 7 8 PABA Dihydrofolic acid Tetrahydrofolic acid
Purines and Pyrimidines
DNA
And RNA
Dihydro-folic acid Synthetase
Dihydro-folic acid reductase
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
DNA unwinding (DNA gyrase)
Threads sepeartion (Topoisomerase IV) 5
RNA Polymerase 6 7
tRNA +
Amino Acids
Ribosome unit (50S)
Ribosome unit (30S)
Protein Synthesis
mRNA 8

30. Beta-lactams, Vancomycin, Cycloserines 1
Cell Wall synthesis inhibition-
Beta-lactams, Vancomycin, Cycloserines
Cell membrane Leakage-
Polypeptides, Polyenes 1 2
PABA
Dihydrofolic acid
Tetrahydrofolic acid
Purines and Pyrimidines
DNA
And RNA
DNA unwinding (DNA gyrase)
Threads sepeartion (Topoisomerase IV)
RNA Polymerase
mRNA
tRNA +
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) 3 4 5 6 7 8

31. 3 2 4 5 6 7 1 8

32. Dose-dependent (With PAE)
ANTIBIOTICS
Dose-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

33. Post-Antibiotic Effect
4/22/2017
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.

35. 1 2 2 3 4 5 6 7 8 Antibacterial - Co-trimoxazole
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 1 2 2 3
Antibacterial - Co-trimoxazole
Antimalarial- Co-trimazine 4 5 6 7 8

36. Mechanisms Of Resistance
4/22/2017
Mechanisms Of Resistance
Resistance
Intrinsic Acquired
Mutation Transferred
Conjugation
Transformation
Transduction
Not Dangerous/
less clinical importance
Dangerous/
clinical importance

37. 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.

38. 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.

39. Cellular Resistance
4/22/2017
ATTACK OF THE SUPERBUGS: ANTIBIOTIC RESISTANCE By Grace Yim, Science Creative Quarterly. Jan 07

40. 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.

41. Resistance to Antibiotics

42. Resistance in some antibiotics
4/22/2017
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

43. Factors favoring Resistance
Prescription related factors:
Overuse
Early discontinuation
Over continuation
Less dose, duration
Livestock doping:
Animals exposure

46. 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

47. Why worry? MDRO are dangerous Resource-intensive Difficult to treat
More virulent
Increase mortality and morbidity
Resource-intensive
More expensive and toxic antibiotics
Increase length of hospitalization
Increase demand for isolation-facilities

48. The number of new antibiotics is falling

49. Thanks