ANTIMICROBIALS

AmbashRiazAdeelaHussainSohailSamual

Overview

What are Antimicrobials? Classification of Antimicrobials What are Antibiotics? Classification of Antibiotics Example of Penicillin What are Antivirals? What are Antifungals? What are Ant parasites? Antimicrobial Therapy Antimicrobial Resistance Side Effects of Antimicrobials Modern research about Antimicrobials Case Study

Anti-microbial

An anti-microbial is a substance that kills or inhibits the growth of microorganisms. 

Bacteria  Fungi Protozoans

Anti-microbial

Natural Fungi- Penicillin, Griseofulvin Bacteria- Polymixin, Bacitracin (Bacillus) - Tetracycline, Chloramphenicol streptomycin (Actinomycetes) Synthetic

Mode of Action

Inhibit the cell wall synthesis Cause leakage from cell membrane Inhibit protein synthesis Cause misreading of mRNA code and

affect permeability Interfere with DNA Interfere with metabolism

Classification

Antibiotics Antifungals Antiviruls Antiprasitics

ANTIBIOTICS

Antibiotics

Antibiotics are also known as antibacterials Antibiotics are medicinal products that have

an anti-bacterial effect. Antibiotics are widely used in the prevention

and treatment of infectious diseases. The most widely known antibiotic is perhaps

penicillin

What are antibiotics for?

An antibiotic is given for the treatment of an infection caused by bacteria.

They are not effective against viruses. Important to know whether it is caused by

bacteria or a virus

Classification of antibiotics

The antibiotics are classified according to three criteria

According to spectrum According to mode of action

According to spectrum

The spectrum means the number of the organisms affected by the same drug

There are two type of spectrum Narrow spectrum antibiotics Wide spectrum antibiotics

According to mode of action

Bactericidal Bacteriostatic

PENICILLIN

History

1896- Ernest Duchesne- first discover penicillin

1928- Alexander Fleming- rediscover it accidentally

 Howard Florey and Ernst Chain- isolated the bacteria-killing substance 

1941- Charles Fletcher- first applied on a patient

Mechanism

Structurally, penicillins are β-lactam antibiotics

Which directly hit cell wall of bacteria

Mechanism

Bacterial cell wall Bacterial cell walls are consisting of a

protective peptidoglycan layer. peptidoglycan layer: N-acetylmuramic acid (NAM) N-acetylglucosamine (NAG)Two enzymes are involved: autolycinetranspeptidase

Mechanism

Autolysine: break the cross link of peptides Transpeptidase: cross link the peptidase Remodeling of cell wall maintain the rigidity

of cell wall

Mechanism

The penicillins act by inhibiting transpeptidase enzyme.

This enzyme has a site to bind with penicillin – penicilline binding protein.

Unable it to do its function Loss of integrity of bacterial cell wall Leak its celluler component Bacterial cell perish

 Beta-lactam ring

very unstable and therefore it participates  Transpeptidase attacks the beta-lactam ring

which opens up to give a more stable compound

This compund remains bound to the transpeptidase via covalent linkage and thereby inhibits the enzyme by acylation of the active site.

Resistance to penicillin

Mutations in the active site of the transpeptidase enzyme.

use of newer penicillin antibiotics Many bacteriassysthesise an enzyme named

Beta- Lactamase

Video ……………….

ANTIVIRALS

Antivirals

Antivirals are drugs that kill or prevent the growth of viruses

 Viral infections are much harder to treat than bacterial infections

Acyclovir is an antiviral drug that targets the herpes virus

Viral life cycle

Attachment to a host cell. Release of viral genes and possibly enzymes

into the host cell. Replication of viral components using host-

cell machinery. Assembly of viral components into complete

viral particles. Release of viral particles to infect new host

cells.

Anti-viral targeting

antiviral drug design is to identify viral proteins, or parts of proteins, that can be disabled

targets should be unlike any proteins or parts of proteins in humans

The targets should also be common across many strains of a virus, or even among different species of virus in the same family, so a single drug will have broad effectiveness

Key characteristics of Antivirals

Able to enter the cell infected with virus Interfere with viral nucleic acid synthesis or

regulation Some agents interfere with ability of virus to

bind to cells Some agents stimulates the body’s immune

system

Interferons

Protein- made and released by host cells belong to the large class

of glycoproteins known as cytokines

Functions

activate immune cells natural killer cells macrophages increase recognition of infection or tumor cells increase the ability of uninfected host cells to

resist new infection by virus

Mode of action

An infected cell releases interferons the infected cell can warn neighboring cells of

a viral presence by releasing interferon The neighboring cells, in response to

interferon, produce large amounts of an enzymes

Several different types of interferon are now approved for use in humans.

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