This is very important to study about microbes and their control

1. Antimicrobial Agents
(General Considerations)

2. Objectives
–Terminologies used in antimicrobial treatment
example: antimicrobials, antibiotics
–Classification of antimicrobials
• Based on mechanism of action
• Based on organisms affected
• Based on spectrum of activity
• Based on type of action
• Based on source
• Based on Chemical structure
–Mechanisms of action of antimicrobials
–Resistance development in antimicrobials
–Multidrug resistant microorganisms

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

4. 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.

5. Terminology
5
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

7. Gram positive & Gram Negative
• Gram positive bacteria have
– thick cell wall
• Gram negative bacteria have
– Thin cell wall
– Surrounded by inner and outer membrane
lipopolysaccharide, phospholipids, and proteins
– Outer membrane is a barrier to diffusion of antibiotics
• Limited antibiotics may diffuse through porins

8. 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

9. Antimicrobial Classification
Based on
• Chemical structure
• Mechanism of Action
• Type of Organism affected
• Spectrum of activity
• Type of action (Static or Cidal)
• Origin of antimicrobials (source)

10. 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

11. 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

12. Synthetic
a.Sulfonamide
b.Trimethoprim
c.Quinolones
d.Nitrofurans
e.Nitroimidazole
Based on Origin of antimicrobials (source)
• Fungi-
– Penicillin
– Cephalosporins
– Griseofulvin
• Bacteria-
– Polymyxin B
– Colistin
– Bacitracin
Actinomycetes- Most common
– Aminoglycosides, Tetracyclines,
Chloramphenicol
– Macrolides
Synthetic
– a.Sulfonamide
– b.Trimethoprim
– c.Quinolones
– d.Nitrofurans
– e.Nitroimidazole

13. Spectrum
• Narrow
– Penicillin G
– Streptomycin
– Erythromycin
• Broad
– Tetracycline
– Chloramphenicol
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

14. Spectrum
(Narrow, Broad)

15. 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-
Aminoglycosides, tetracyclines, Chloramphenicol, Macrolides, Clindamycin,
Linezolid

16. Cell Wall
Beta Lactams

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

18. PABA
Dihydrofolic acid
Tetrahydrofolic acid
Purines and Pyrimidines
DNA 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)

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

20. Cell Wall synthesis inhibition-
Beta-lactams, Vancomycin, Cycloserines
Cell membrane Leakage-
Polypeptides, Polyenes
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)
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5
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7
8

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22. • 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-trimoxazole
Antimalarial- Co-trimazine
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23. THE MECHANISMS OF RESISTANCE TO ANTIBIOTICS
• “Microorganisms can develop resistance to
antibiotics used in the treatment with a variety
of mechanisms.”
• In this presentation, the general mechanisms of
resistance to antibiotics and resistance
mechanisms that are frequently encountered in
antibiotic groups were summarized.
• Key words: Antibiotics, antibiotic resistance,
mechanisms.

24. Resistance Concept
• Resistance is the ability of a bacteria against
the antogonizing effect of an antibacterial
agent upon reproduction prevention or
bactericidal
• The development of resistance to antibiotics
in bacteria often develop as a result of
unnecessary and inappropriate use of
antibiotics

25. • Through the intense use of antibiotics, resistant
microorganisms have emerged over the years,
and problems were started to be experienced
for the treatment of these infections emerged
with these resistantmicroorganisms.
Today, on the one hand trying to develop new
drugs, on the other hand, there are difficulties in
treatment as a result of development of
resistance
The development of resistance to antibiotics is a
major public health problem in all over the world

26. • The main four types of resistance to
antibiotics develops;
1. Natural (Intrensic) resistance
2. Acquired resistance
3. Cross-resistance
4. Multi-drug resistance and pan-resistance

27. 1. Natural (Intrensic, Structural)
resistance
• This kind of resistance is caused by the
structural characteristics of bacteria and it is
not associated with the use of antibiotics.
• It has no hereditary property.
• It develops as result of the natural resistance
of the microorganisms not including the
structure of the target antibiotic.

28. For example
Gram negative bacteria
• Vancomycin does not pass in the outer
membrane so Gram-negative bacteria is
naturally resistant to vancomycin.

29. 2. Acquired resistance
• As result of the changes in the genetic
characteristics of bacteria.
• An acquired resistance occurs due to its not
being affected from the antibiotics it has been
responsive before.
• This kind of resistance occurs due to mainly
a) structures of chromosome
b) extrachromosomal (plasmid, transposon,
etc.)

30. a. Chromosomal resistance
• Arise from mutations in developing in spontaneous
bacterial chromosome (spontaneous).
• Such mutations may occur according to some physical
(ultraviolet, etc.) and chemical factors.
• This can be a result of structural changes in bacterial cells.
• The result may be reduced permeability of bacterial drug
or changes of the target of the drug may be in the cell.
Streptomycin, aminoglycosides, erythromycin,lincomycin
can develop resistance against these types.
• Therefore such resistance in the clinic are less and often
does not cause a problem

31. b. Extrachromosomal resistance
• Depends extrachromosomal genetic elements that can
be transferred in various ways like plasmids,
transposons and integro.
• Plasmids are extrachromosomal DNA fragments that
can replicate independently from chromosome.
• Plasmid genes are usually responsible for the
generation of enzymes which inactive antibiotics.
• Resistance genes and plasmids carrying the genetic
material from a bacterium in three ways those are
transduction, transformation, conjugation, and
transposition mechanism.

32. 3. Cross resistance
• Some microorganisms which are resistant to a certain
drug, that acts with the same or similar mechanism
and also resistant to other drugs.
• This condition is usually observed in antibiotics whose
structures are similar such as resistance between
erythromycin, neomycin-kanamycin or resistance
between cephalosporins and penicillins.
• However, sometimes it can also be seen in a
completely unrelated drug groups.
• There is an example of cross-resistance between
erythromycin-lincomycin. This may be chromosomal or
extrachromosomal origin

33. 4. Multi-drug resistance and pan-
resistance:
• Multidrug-resistant organisms are usually
bacteria that have become resistant to the
antibiotics used to treat them
• This means that a particular drug is no longer
able to kill or control the bacteria.
• Inapropriate use of antibiotics for therapy
resulted in the selection of pathogenic
bacteria resistant to multiple drugs.

34. MECHANISMS OF RESISTANCE TO
ANTIBIOTICS
a. The changes that occur in the receptor
that connected to the drug and the region of
the connection ‘Connection of the antibiotics’
target areas are different.
Resistance associated with alterations in the
ribosomal target are the most frequently
observed in macrolide antibiotics.

35. b. Enzymatic inactivation of
antibiotics
• Most of Gram-positive and Gram-negative bacterias
synthesize enzymes that degrade antibiotics.
• This enzymatic inactivation mechanism is one of the
most important mechanisms of resistance.
• In this group, beta-lactamases,aminoglycosides,
modifying enzymes (acetylase, fosforiaz adenilaz and
enzymes) degrade beta-lactam antibiotics and
continually increasing their number of which
inactivates enzymes include chloramphenicol and
erythromycin

36. c. Reduction of the inner and outer
membrane permeability
• This resistance due to changes in the internal
and external membrane permeability,
decrease in drug uptake into the cell or quickly
ejected from the active resistance of the
pump systems
• As a result of a change in membrane
permeability decreased porin mutations in
resistant strains can occur in proteins.

37. Susceptibility testing techniques
Laboratory antimicrobial susceptibility testing can be performed
using:
– A dilution technique
– A disc diffusion technique.
Disc diffusion susceptibility tests: Disc diffusion techniques are used
by most laboratories to test routinely for antimicrobial susceptibility.
A disc of blotting paper is impregnated with a known volume and
appropriate concentration of an antimicrobial, and this is placed on
a plate of susceptibility testing agar uniformly inoculated with the
test organism. The antimicrobial diffuses from the disc into the
medium and the growth of the test organism is inhibited at a
distance from the disc that is related to the susceptibility of the
organism

38. A disc diffusion technique.
i. Kirby-Bauer technique
ii. Stokes disc diffusion technique
Stokes disc diffusion technique: In this disc technique both the
test and control organisms are inoculated on the same plate.
The zone sizes of the test organism are compared directly with
that of the control.

40. A dilution technique
 Dilution susceptibility tests: Manual or semi-automated dilution
susceptibility tests are performed in Microbiology Reference Laboratories
for epidemiological purposes or when a patient does not respond to
treatment thought to be adequate, relapses while being treated, or when
there is immunosuppression.
 Dilution techniques measure the minimum inhibitory concentration (MIC).
They can also be used to measure the minimum bactericidal concentration
(MBC) which is the lowest concentration of antimicrobial required to kill
bacteria.
 A dilution test is carried out by adding dilutions of an antimicrobial to a
broth or agar medium. A standardized inoculum of the test organism is then
added. After overnight incubation, the MIC is reported as the lowest
concentration of antimicrobial required to prevent visible growth. By
comparing the MIC value with known concentrations of the drug obtainable
in serum or other body fluids, the likely clinical response can be assesse

41. Refer Monica Cheesbrough Part 2
Second Edition from pge 132 to 143