El Helalyaالمؤسسة
تاريخ التسجيل : 08/08/2008
 |  موضوع: Antibiotic drugs السبت 5 يونيو 2010 - 18:38 | |
| yents
the growth of bacteria.
They have no effect against viruses
or fungal infections.
Antibiotics are one class of antimicrobials, a
larger group which also
includes anti-viral, anti-fungal, and
anti-parasitic drugs. They are
relatively harmless to the host, and
therefore can be used to treat infections. The term,
coined by Selman Waksman,
originally described only
those formulations derived from living
organisms, in contrast to
"chemotherapeutic agents", which are
purely synthetic. Nowadays the term
"antibiotic" is also applied to synthetic
antimicrobials, such as the sulfa drugs.
Antibiotics are generally small molecules with a molecular weight less
than 2000 Da.
They are not enzymes.
Some antibiotics have been derived
from mold, for example the penicillin class.
 
Points of attack on bacteria by antibiotics
Unlike previous treatments for infections, which included
poisons such
as strychnine
and arsenic, antibiotics
were labeled "magic
bullets": drugs which targeted
disease
without harming the host. Conventional antibiotics are not
effective
in viral, fungal and other
nonbacterial infections, and
individual antibiotics vary widely in
their effectiveness on various
types of bacteria. Antibiotics can be
categorized based on their target
specificity: "narrow-spectrum"
antibiotics target particular types of
bacteria, such as Gram-negative or Gram-positive bacteria,
while broad-spectrum
antibiotics
affect a larger range of bacteria.
The
effectiveness of individual antibiotics varies with the ******** of
the
infection, the ability of the antibiotic to reach the site of
infection,
and the ability of the bacteria to resist or inactivate the
antibiotic.
Some antibiotics actually kill the bacteria (bactericidal),
whereas
others merely prevent the bacteria from multiplying
(bacteriostatic)
so that the host's immune system can overcome them.
Oral antibiotics
are the simplest approach when effective, with intravenous antibiotics
reserved for more
serious cases. Antibiotics may sometimes be
administered topically,
as with eye drops
or ointments.
Antibiotics
can also be classified by the organisms against which they
are
effective, and by the type of infection in which they are useful,
which
depends on the sensitivities of the organisms that most commonly
cause
the infection and the concentration of antibiotic obtainable in
the
affected tissue.
*******s
[hide]
class=toclevel-1>1 History
- 2 Classes of
antibiotics
- 3 Production
class=toclevel-1>4 Side effects
class=toclevel-1>5 Antibiotic
misuse
- 6 Antibiotic
resistance
- 7 Beyond
antibiotics
- 8 References
class=toclevel-1>9 See also
- 10 External links
- 10.1 Resources
//
[edit]
History
See also: Timeline of
antibiotics
Penicillin
Although the
principles of antibiotic action were not discovered until
the
twentieth century, the first known use of antibiotics was by the ancient Chinese over
2,500 years ago.[1] Many other ancient
cultures, including
the ancient Egyptians and ancient Greeks already
used moulds and plants to
treat infections. This worked
because some moulds
produce antibiotic substances. However, they
couldn't distinguish or
distill the active component in the moulds.
Modern
research on antibiotic therapy began in Germany with the
development of the
narrow-spectrum antibiotic Salvarsan by Paul Ehrlich in 1909, for the first
time allowing an
efficient treatment of the then-widespread problem
of Syphilis. The drug,
which was also effective
against other spirochaetal
infections,
is no longer in use in modern medicine.
Antibiotics were further
developed in Britain following the discovery of
Penicillin in 1928 by Alexander Fleming. More
than ten years
later, Ernst Chain and Howard Florey became
interested in his work, and
came up with the purified form of
penicillin. The three shared the 1945
Nobel Prize in Medicine.
"Antibiotic" was originally used to refer only
to substances
extracted from a fungus
or other microorganism,
but has come to include also
the many synthetic and semi-synthetic
drugs that have antibacterial
effects.
[edit]
Classes of
antibiotics
At the highest level, antibiotics
can be classified as either bactericidal or bacteriostatic.
Bactericidals kill bacteria
directly where bacteriostatics prevent
them from dividing. However,
these classifications are based on
laboratory behaviour; in practice,
both of these will end a
bacterial infection.
Antibiotics[2]Generic
NameBrand
NamesCommon UsesSide EffectsAminoglycosidesAmikacinAmikinInfections caused
by Gram-negative
bacteria,
such as Escherichia coli
and
Klebsiella
- Hearing loss
- Vertigo
- Kidney damage
GentamicinGaramycinKanamycinNeomycinNetilmicinStreptomycinTobramycinNebcinCarbacephemLoracarbefLorabidCarbapenemsErtapenemImipenem/CilastatinPrimaxinMeropenemCephalosporins (First generation)CefadroxilDuricef
- Gastrointestinal
upset and diarrhea
- Nausea (if alcohol taken concurrently)
- Allergic
reactions
CefazolinAncefCephalexinKeflexCephalosporins (Second
generation)CefaclorCeclor
- Gastrointestinal
upset and
diarrhea
- Nausea (if alcohol taken
concurrently)
- Allergic reactions
CefamandoleMandoleCefoxitinCefprozilCefzilCefuroximeCeftinCephalosporins (Third generation)Cefixime
- Gastrointestinal
upset and
diarrhea
- Nausea (if alcohol taken
concurrently)
- Allergic reactions
CefdinirOmnicefCefditorenCefoperazoneCefobidCefotaximeClaforanCefpodoximeCeftazidimeFortumCeftibutenCeftizoximeCeftriaxoneRocephinCephalosporins (Fourth
generation)CefepimeMaxipime
- Gastrointestinal
upset and diarrhea
- Nausea (if alcohol taken concurrently)
- Allergic
reactions
GlycopeptidesTeicoplaninVancomycinVancocinMacrolidesAzithromycinZithromax, Sumamed, ZitrocinStreptococcal
infections,
syphilis, respiratory
infections,
mycoplasmal
infections,
Lyme disease
- Nausea,
vomiting, and
diarrhea (especially at higher doses)
- Jaundice
ClarithromycinBiaxinDirithromycinErythromycinRoxithromycinTroleandomycinMonobactamAztreonamPenicillinsAmoxicillinNovamoxWide
range of
infections; penicillin used for streptococcal
infections,
syphilis, and Lyme disease
- Gastrointestinal
upset
and diarrhea
- Allergy with serious anaphylactic
reactions
- Brain and kidney damage (rare)
AmpicillinAzlocillinCarbenicillinCloxacillinDicloxacillinFlucloxacillinMezlocillinNafcillinPenicillinPiperacillinTicarcillinPolypeptidesBacitracinEye, ear or
bladder infections;
usually applied directly to the eye or inhaled
into the lungs; rarely
given by injectionKidney and nerve damage
(when given by injection)ColistinPolymyxin BQuinolonesCiprofloxacinCiproxin, CiploxUrinary tract
infections, bacterial
prostatitis,
bacterial
diarrhea, gonorrheaNausea
(rare), tendinosis (rare)EnoxacinGatifloxacinTequinLevofloxacinLevaquinLomefloxacinMoxifloxacinAveloxNorfloxacinOfloxacinOcufloxTrovafloxacinTrovanSulfonamidesMafenideUrinary tract
infections
(except sulfacetamide and mafenide); mafenide
is used topically for
burns
- Nausea, vomiting, and
diarrhea
- Allergy
(including skin rashes)
- Crystals in urine
- Kidney failure
- Decrease
in white blood cell
count
- Sensitivity to sunlight
Prontosil (archaic)SulfacetamideSulfamethizoleSulfanilimide (archaic)SulfasalazineSulfisoxazoleTrimethoprimTrimethoprim-Sulfamethoxazole (Co-trimoxazole) (TMP-SMX)BactrimTetracyclinesDemeclocyclineSyphilis, chlamydial infections, Lyme disease, mycoplasmal
infections,
acne rickettsial infections
- Gastrointestinal
upset
- Sensitivity to sunlight
- Staining of teeth
- Potential
toxicity to mother and fetus during pregnancy
DoxycyclineVibramycinMinocyclineMinocinOxytetracyclineTetracyclineSumycinOthersArsphenamineSalvarsanSpirochaetal infections
(obsolete)ChloramphenicolChloromycetinClindamycinCleocinEthambutolFosfomycinFurazolidoneIsoniazidLinezolidZyvoxMetronidazoleFlagylMupirocinNitrofurantoinMacrodantin, MacrobidPlatensimycinPyrazinamideQuinupristin/DalfopristinSyncercidRifampinSpectinomycinTelithromycinKetekPneumoniaVisual
DisturbanceGeneric NameBrand
NamesCommon UsesSide Effects
[edit]
Production
Main article: Production of
antibiotics
Since the first pioneering efforts of Florey
and Chain
in 1939, the importance of antibiotics
to medicine has led to
much research into
discovering and producing them. The process of
production usually
involves screening of wide ranges of
microorganisms, testing and
modification. Production is carried out
using fermentation;
a process
that is important in anaerobic conditions when there is
no oxidative
phosphorylation to maintain the production of adenosine
triphosphate
(ATP) by glycolysis.
[edit]
Side effects
Possible side effects are varied, and range from
fever and nausea to
major allergic reactions. One of the more common
side effects is diarrhea,
sometimes caused by the anaerobic
bacterium Clostridium
difficile,
which results from the antibiotic disrupting
the normal balance of intestinal flora[3], (which some people
believe may be
re-balanced by taking probiotics). Other side
effects can result from interaction with other drugs, such as elevated
risk
of tendon damage from
administration of a quinolone
antibiotic with a systemic corticosteroid.
It
is a common assertion that some antibiotics can interfere with the
efficiency
of birth control pills. Although there remain few known cases
of
complication, the majority of antibiotics do not interfere with
contraception,
despite widespread misinformation to the contrary.[4]
[edit]
Antibiotic
misuse
Common forms of antibiotic misuse include
failure to take the entire
prescribed course of the antibiotic,
usually because the patient feels
better, but before the infecting
organism is completely eradicated. In
addition to treatment failure,
these practices can result in antibiotic
resistance
in which the bacteria survive the abbreviated
treatment. Taking
antibiotics in inappropriate situations is another
common form of
antibiotic misuse. Common examples of this would be
the use of
antibacterials for viral infections such as the common cold.
Currently,
it is estimated that greater than 50% of the antibiotics used
in
the U.S. are given to food animals (e.g. chickens, pigs and cattle)
in
the absence of disease.[5] Antibiotic use in
food animal production
has been associated with the emergence of
antibiotic resistant strains
of bacteria including Salmonella,
Campylobacter, Escherichia coli and
Enterococcus among others. There
is substantial evidence from the US and
the EU that these resistant
bacteria cause antibiotic resistant
infections in humans. The
American Society for Microbiology (ASM), the
American Public Health
Association (APHA) and the American Medical
Association (AMA) have
called for substantial restrictions on antibiotic
use in food animal
production including an end to all non-therapeutic
uses. The food
animal and pharmaceutical industries have fought hard to
prevent new
regulations that would limit the use of antibiotics in food
animal
production. For example, in 2000 the US Food and Drug
Administration
(FDA) announced their intention to rescind approval for
fluoroquinolone
use in poultry production because of substantial
evidence linking
it to the emergence of fluoroquinolone resistant
Campylobacter
infections in humans. The final decision to ban
fluoroquinolones
from use in poultry production was not made until 5
years later
because of challenges from the food animal and
pharmaceutical
industries. Today, there are two federal bills (S.742 and
H.R. 2562)
aimed at phasing out non-therapeutic antibiotics in US food
animal
production. These bills are endorsed by many public health and
medical
organizations including the American Nurses Association (ANA),
the
American Academy of Pediatrics (AAP), and the American Public Health
Association (APHA).
Excessive use of prophylactic
antibiotics
in travelers may also be classified as misuse.
[edit]
Antibiotic
resistance
Main article: Antibiotic
resistance
SEM
depicting methicillin-resistant
Staphylococcus
aureus bacteria.
Use
or misuse of antibiotics may result in the development of antibiotic
resistance by the infecting organisms, similar to the development
of
pesticide
resistance in
insects. Evolutionary theory of
genetic selection
requires that as close as
possible to 100% of the infecting
organisms be killed off to avoid
selection of resistance; if a small
subset of the population survives
the treatment and is allowed to
multiply, the average susceptibility of
this new population to the
compound will be much less than that of the
original population,
since they have descended from those few organisms
which survived
the original treatment. This survival often results from
an
inheritable resistance to the compound which was infrequent in the
original
population but is now much more frequent in the descendants
thus
selected entirely from those originally infrequent resistant
organisms.
An abscess caused by
methicillin-resistant Staphylococcus
aureus bacteria (MRSA).
Antibiotic resistance has become a serious problem in both the
developed
and underdeveloped nations. By 1984 half of the people
with active tuberculosis
in the United States
had a strain that resisted at
least one antibiotic. In certain
settings, such as hospitals and some
child-care ********s, the rate
of antibiotic
resistance
is so high that the normal, low cost
antibiotics are virtually useless
for treatment of frequently seen
infections. This leads to more frequent
use of newer and more
expensive compounds, which in turn leads
inexorably to the rise of
resistance to those drugs, and a race to
discover new and different
antibiotics ensues, just to keep us from
losing ground in the battle
against infection. The fear is that we will
eventually fail to keep
up in this race, and the time when people did
not fear
life-threatening bacterial infections will be just a memory of a
golden era.
Another example of selection is Staphylococcus
aureus,
which could be treated successfully with penicillin in the 1940s
and 1950s. At
present, nearly all strains are resistant to
penicillin, and many are
resistant to nafcillin, leaving only
a narrow selection of drugs such as vancomycin useful for
treatment. The
situation is worsened by the fact that genes coding
for antibiotic
resistance can be transferred between bacteria via plasmids, making it
possible for bacteria
never exposed to an antibiotic to acquire
resistance from those which
have. The problem of antibiotic
resistance is worsened when antibiotics
are used to treat disorders
in which they have no efficacy, such as the
common cold or other
viral complaints, and when they are used widely as
prophylaxis
rather than treatment (as in, for example, animal feeds),
because
this exposes more bacteria to selection for resistance.
[edit]
Beyond
antibiotics
Unfortunately, the comparative ease of
finding compounds which safely
cured bacterial infections proved
much harder to duplicate with respect
to fungal and viral
infections. Antibiotic research led to great strides
in our
knowledge of basic biochemistry and to the current biological
revolution;
but in the process it was discovered that the susceptibility
of
bacteria to many compounds which are safe to humans is based upon
significant
differences between the cellular and molecular physiology of
the
bacterial cell and that of the mammalian cell. In contrast, despite
the seemingly huge differences between fungi and humans, the basic
biochemistries
of the fungal cell and the mammalian cell are much
more similar; so much
so that there are few therapeutic
opportunities for compounds to attack
a fungal cell which will not
harm a human cell. Similarly, we know now
that viruses represent an
incredibly minimal intracellular parasite,
being stripped down to a
few genes' worth of DNA or
RNA and the minimal
molecular equipment
needed to enter a cell and actually take over
the machinery of the cell
to produce new viruses. Thus, the great
bulk of viral ----bolic
biochemistry is not merely similar to human
biochemistry, it actually is
human biochemistry, and the possible
targets of antiviral compounds are
restricted to the relatively very
few components of the actual virus
itself.
Research into bacteriophages is
ongoing
at the moment. Bacteriophages are a specific type of virus that
only
targets bacteria. Research suggests that nature has evolved several
types of bacteriophage for each type of bacteria. While research into
bacteriophages
is only in its infancy the results are promising and have
already
lead to major advances in microscopic imaging.[6] While
bacteriophages provide a possible
solution to the problem of
antibacterial resistance there is as of yet
no proof that we will
actually be able to deploy these microscopic
killers in humans, we
can only continue the research and see where it
leads.
Phage therapy has been
used in the past on
humans in the US and Europe during the 1920s and
1930s, however due to
not fully understanding the mechanism by
which phage therapy worked,
these treatments had mixed results. With
the discovery of penicillin in
the 1940s, Europe and the US changed
to using antibiotics. However, in
the former Soviet Union phage
therapies continued to be studied. In the
Republic of Georgia, the
Eliava Institute of Bacteriophage, Microbiology
& Virology
continues to research the use of phage therapy. Various
companies
and foundations in North America and Europe are currently
researching
phage therapies.
[edit]
References
- ^ How Products Are
Made: Antibiotics
- ^ Robert Berkow (ed.) The Merck Manual of Medical
Information - Home Edition.
Pocket (September 1999), ISBN
0-671-02727-1.
- ^ University of
Michigan Health System: Antibiotic-Associated
Diarrhea,
November 26, 2006
- ^ Planned Parenthood: Does taking
antibiotics make the
pill less effective?, July 15, 2004
- ^
Mellon, M et al. (2001) Hogging
It!: Estimates of
Antimicrobial Abuse in Livestock, 1st ed.
Cambridge, MA: Union of
Concerned Scientists.
- ^ Purdue University
"Biologists build better software, beat path to viral knowledge", see
Imaging
of Epsilon 15, a virus that infects the bacterium Salmonella News report
[edit]
See also
- Antiseptic
- Bacteriocide
- Antibiotic
Resistance in Cancer
Patients
[edit]
External links
Wikimedia Commons has
media related to: Antibiotics
- Antibiotic News
from Genome News
Network (GNN)
- Are Antibiotics
Killing Us?
-Discover Magazine
- JAAPA: New
antibiotics useful in
primary care
- A new method for
controlling
bacterial activity without antibiotics -
Research conducted
at the Hebrew University
[edit]
Resources
- Alliance
for
the Prudent Use of Antibiotics
Major Drug Groups
editBrain
and
Nervous System:Analgesics,
Anesthetics, Anxiolytics, Antidepressants, Antipsychotics, Anticonvulsants, Nervous system stimulants,
Antiemetics, Hallucinogens,
Mood stabilizers
Respiratory
System:Bronchodilators,
Decongestants
Heart
and Circulation:Angiotensin
converting enzyme inhibitors, Antiarrhythmics,
Antianginals, Antihypertensives, Antihyperlipidemics, Anticoagulants, Antiplatelets, Beta blockers, Diuretics, Thrombolytics, Vasodilators,
Gastrointestinal
Tract:Antacids, Antidiarrhoeals, H2-receptor
antagonists,
Proton pump
inhibitors,
Laxatives
Muscles,
Bones, and Joints:Anti-inflammatories, Antirheumatics,
Corticosteroids, Muscle relaxants
Allergy:Antihistamines
Infections
and Infestations:Antibiotics, Antivirals, Vaccines, Antiprotozoals, Antifungals, Anthelmintics
Endocrine
System:Corticosteroids,
Anti-diabetics
Malignant
and Immune Disease:Anticancer agents,
Immunosuppressants
Reproductive
System:Oral
contraceptives, Fertility agents
Skin:Antipruritics
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from "http://en.wikipedia.org/wiki/A
ntibiotic"
Category: Antibiotics  الموضوع : Antibiotic drugs المصدر :منتديات تقى الإسلامية الكاتب: El Helalya |
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