Antibiotics

Antibiotics
Abstract
Antibiotics are the organic secretion produced by micro –
organisms, which in low concentrations are antagonistic to
the growth of other micro – organisms (mostly pathogens).
Antibiotics have proved very useful in combating several
bacterial diseases in man an animal. Antibiotics are
commonly obtained from actinomycetes and some eubacteria.
Some of the important antibiotics are streptomycin,
Aureomycin, teramycin, Chloromycetin, erythromycin,
neomycin etc.
Soil is a natural medium that harbors several types of micro –
organism .These micro- organisms can be frown on culture
media. The effect of different types of antibiotics can be
studied on the growth of micro - organism growing in culture
medium. This is an important subject, therefore the study of
effect of antibiotics on micro - organism has been taken for
the present project.

Objective of Project
The aim of this project is to study the effect of
antibiotics on micro – organisms.
Experiment
To study the effect of antibiotics on micro-organisms
Requirements
Potato ,agar, dextrose , distilled water , four different types
of antibiotics (such as penicillin, streptomycin , aureomycin,
teramycin ) , syringe , oven sterilized petridish , flasks ,
beakers , pipettes , garden soil , glass marker pen , etc
Procedure
A. Preparation of culture Medium
1. Potato Dextrose Agar (PDA) Medium.
Take 200 g of peeled potato chips. Boil them with 500 ml of
water in a beaker for 15 minutes.
Squeeze the potato pulp thus obtained through a muslin
cloth and keep it in a flask.
Take 20 g of agar in a beaker and warm it with 500 ml of
water .
Mix both the solution of potato and agar and add 20 g
dextrose to it.
Thus one litre of PDA medium is prepared.
Autoclave the medium at 15 pounds pressure for 15
minutes.

B. Effects of antibiotics on soil micro0 organisms
i) Take 2 g of soil and dissolve it in 10 ml of water in a
beaker. Let the soil particle settle down.
ii) Take 5 oven sterilized petridishes and pour 1 ml of soil
suspension in each of the plates. Now pour 1ml of the four
antibiotics separately in four petridishes with the help of
syringe, and mark them with marker pen. Leave the fifth
petridish without antibiotic to serve as control.
iii) Pour PDA in each of the petridishes and mix the
suspension by rotating the petridishes. Leave the petridishes
undisturbed at a warm place
Medical uses
Antibiotics are used to treat or prevent bacterial
infections,[10] and sometimes protozoan infections.
(Metronidazole is effective against a number of parasitic
diseases). When an infection is suspected of being
responsible for an illness but the responsible pathogen has
not been identified, an empiric therapy is adopted.[11] This
involves the administration of a broad-spectrum antibiotic
based on the signs and symptoms presented and is initiated
pending laboratory results that can take several
days.[10][11]
When the responsible pathogenic microorganism is already
known or has been identified, definitive therapy can be
started. This will usually involve the use of a narrow-
spectrum antibiotic. The choice of antibiotic given will also
be based on its cost. Identification is critically important as it
can reduce the cost and toxicity of the antibiotic therapy and

also reduce the possibility of the emergence of antimicrobial
resistance.[11] To avoid surgery, antibiotics may be given
for non-complicated acute appendicitis.[12]
Antibiotics may be given as a preventive measure and this is
usually limited to at-risk populations such as those with a
weakened immune system (particularly in HIV cases to
prevent pneumonia), those taking immunosuppressive
drugs, cancer patients, and those having surgery.[10] Their
use in surgical procedures is to help prevent infection of
incisions. They have an important role in dental antibiotic
prophylaxis where their use may prevent bacteremia and
consequent infective endocarditis. Antibiotics are also used
to prevent infection in cases of neutropenia particularly
cancer-related
Production
With advances in medicinal chemistry, most modern
antibacterials are semisynthetic modifications of various
natural compounds.[55] These include, for example, the
beta-lactam antibiotics, which include the penicillins
(produced by fungi in the genus Penicillium), the
cephalosporins, and the carbapenems. Compounds that are
still isolated from living organisms are the aminoglycosides,
whereas other antibacterials—for example, the
sulfonamides, the quinolones, and the oxazolidinones—are
produced solely by chemical synthesis.[55] Many
antibacterial compounds are relatively small molecules with
a molecular weight of less than 1000 daltons.[56]

Since the first pioneering efforts of Howard Florey and Chain
in 1939, the importance of antibiotics, including
antibacterials, to medicine has led to intense research into
producing antibacterials at large scales. Following screening
of antibacterials against a wide range of bacteria, production
of the active compounds is carried out using fermentation,
usually in strongly aerobic conditions
Uses
A doctor prescribes antibiotics for the treatment of a
bacterial infection. It is not effective against viruses.
Know whether an infection is bacterial or viral helps
to effectively treat it.
Viruses cause most upper respiratory tract infections
(URTIs), such as the common cold and flu. Antibiotics
do not work againstthese viruses.

If people overuseantibiotics or use them incorrectly,
the bacteriamight become resistant. This means that
the antibiotic becomes less effective against that type
of bacterium, as the bacterium has been able to
improve its defenses.
A doctor can prescribea broad-spectrumantibiotic to
treat a wide range of infections. A narrow-spectrum
antibiotic is only effective against a few types of
bacteria.
Some antibiotics attack aerobic bacteria, while others
work against anaerobic bacteria. Aerobic bacteria
need oxygen and anaerobic bacteria do not.
In some cases, a healthcare professionalmay provide
antibiotics to prevent rather than treat an infection, as
might be the case before surgery. This is the
'prophylactic' use of antibiotics. People commonly use
these antibiotics before bowel and orthopedic surgery.
Side effects
Antibiotics commonly causethe following side effects:
 diarrhea
 nausea
 vomiting
 rash

 upset stomach
 with certain antibiotics or prolonged use, fungal
infections of the mouth, digestivetract, and vagina
Observation
The effect of different antibiotics on the micro –
organisms can be assessed by counting the number
and size of the colonies growing in the petridishes.

CONCLUSIONS
Pencillin and Terramycin was most effective antibiotic
against microorganism in soil.

Antibiotics

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Antibiotics