antibiotics seminar2

8/3/2019 Antibiotics Seminar2

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Presented by:

Sheetal Singh

M.sc(Bio-Chem) III Sem

Suresh Gyan Vihar University, Jaipur


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INTRODUCTION

CHARACTERISTICS

ANTIBIOTICS RESISTANCE

CLASSIFICATION

ANTIFUNGAL DRUGS

ANTI VIRAL DRUGS


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A substance of low molecular

weight produced by micro-

organism as secondary metabolites

that inhibit or stop the growth ofother micro-organism in vitro and

in vivo selectively, when it is used

in low concentration.


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It must be able to

reach the part of the

human body where the

infection is occurring. It should not cause the

development of

resistant forms of

parasites


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It should not produce

undesirable side effects

in the host such as

allergic reaction, nerve

damage or irritation of

the kidneys and

gastrointestinal tract.


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It should be given

orally without

inactivation by

stomach acid, or byinjection (parenterally)

without binding to the

blood proteins.


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Finally, it should have ahigh level of solubility inthe body fluids and be

possible to achieveconcentrations in thetissue or blood, which aresufficiently high to inhibitor kill the infectious

agent.


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Bacteria either have pre- existing resistance to drugs or developresistance. The internal or acquired resistant are identical andcan be explained by following reasons

1) Inactivation or modification of drug by bacterial enzyme.

2) Formation of impermeable barrier so that drug can not reach thedesired region of action.

3) Changing the target itself so drug cant bind or have an effect onit.

4) DNA transfer of drug resistance from one organism to other by

transformation ,transduction or bacterial conjugation.5) Development of altered metabolic pathway which commit the

effect of the drug to be bypassed.


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Antimicrobials are classified in several ways.

1. On basis of spectrum of study.

2. On basis of effect on bacteria.3. On basis of mode of action

a) Cell wall synthesis inhibitor

b)

Protein synthesis inhibitorc) Nucleic acid inhibitor

d) Other metabolic functions inhibitor


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Depending on the range ofbacterial species susceptibleto these agents,

antibacterials are classifiedas :

1. Broad-spectrum

2. Narrow- Spectrum

3. Extended -spectrum


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Because of differences in themechanisms by whichantibiotics affect bacteria, the

clinical use of antibacterialsmay have very differenteffects on bacterial agents,leading to an endpoint ofeither inactivation or actualdeath of the bacteria.

Bactericidal drugs

Bacteriostatic drugs


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Differentantibiotics havedifferent modes ofaction, owing to

the nature of theirstructure anddegree of affinityto certain target

sites within

bacterial cells.


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-lactam inhibitors other antibiotics

penicillin cephalosporins

carbapenem monobactams

Bacitracin Vancomycin

Penicillin G

Penicillin V

Oxacillin

Cloxacillin

Dicloxacillin

PARENETRAL

Imipenem

Meropenem

Aztreonam

Cefazolin

Cefmetazole

Ceftizoxime

Cefepime

ORAL

CefadroxilCefaclor


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Antimicrobial drug selectively interfere withsynthesis of the bacterial cell wall.

The cell wall is made by polymer calledpeptidoglycan that consist of a glycan unit joined toeach other by peptide cross links.

Synthesis occurs in three steps:

1) Occurs in cytoplasm.

2)

Inner surface of cytoplasmic membrane.3) Occurs in peri-plasmic space(in gram negative

bacteria).


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Protein synthesis is an essential process necessary formultiplication and survival of all bacterial cells.

Several types of antibacterial agent s target bacterialprotein synthesis by binding either to 30S or 50S

subunits of intracellular ribosomes.

The result is disruption of normal cellularmetabolism of bacteria and leads to death orinhibition of its growth .EXAMPLES-

Aminoglycosides, chloramphenicol, tetracyclines,macrolides, etc.


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Some chemotherapeutic agents affect the synthesis

of DNA or RNA or can bind to them so that

message can not be read and they can block the

growth of cell.

FLUOROQUINOLONES INHIBITORS OF FOLATE

SYNTHESIS

1stgeneration

2nd

generation

3rd

generation

4th

generation

Mefinide

Nalidixicacid

Ciprofloxacin

Gatifloxacin

trovafloxacin

Sulfadiazine, Silver Sulfadiazine,Sulfamethoxazolenorfloxac

inlavofloxacin


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Quinolones inhibit DNA gyrase

(also called as topoisomerase)

This enzyme introduces

negative superhelical turns into

duplex DNA using the energy of

ATP.

Fluoroquinolones enters the

bacterium and inhibiyt

replication of bacterial DNA by

interfering with action of DNA

gyrase .


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Some antibiotics act on

selected cellular processes

that are essential for

survival of bacterial

pathogen. SULFONAMIDES and

TIRIMETHOPRIM

disrupts folic acid

pathway , which isessential step for bacteria

to produce precusors

important for DNA

synthesis.


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An antifungal agent is a drug that selectively eliminates

fungal pathogens from a host with minimal toxicity to the

host.

Infectious disease caused by fungi is called MYCOSIS.

CLASSIFICATION

Drugs for systemicmycosis

Drugs for sub-cutaneousmycosis

Amphotericin B Econazol

Flucytosine Griseofluvin

Fluconazole Nystatin


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Different classes of drugtarget plasma membrane,sterol biosynthesis , DNAbiosynthesis and -glucanbiosynthesis.

Fungal membranes andsterol biosyntheticenzymes are differentenough from ours that

these agents kill fungi andnot us.


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Virus are intracellular parasites that lack independentmetabolism and can replicate only within living hostcell.

Amantadine and - globulininhibit penetration of cell

by virus. Acycloviris very selective as it remain inactive until

phosphorylated by enzymes that are synthesized byvirus.

Antiretroviral drugs suppress the replication of HIV . Protease inhibitors ,in HIV m-RNA are translated into

inert proteins.


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Dixon B .2006 . Sullfas true

significance. Microle 1(11):500-501

Pharmacological module

Microbiology Michael J Pelczar


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antibiotics seminar2

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