Antibiotic Totally Explained

Everything about Antibiotic totally explained

An antibiotic (from Greek αντί - anti, "against" + βιοτικός - biotikos, "fit for life") is a chemotherapeutic agent that inhibits or abolishes the growth of micro-organisms, such as bacteria, fungi, or protozoa. The term originally referred to any agent with biological activity against living organisms; however, "antibiotic" now refers to substances with anti-bacterial, anti-fungal, or anti-parasitical activity. The first widely used antibiotic compounds used in modern medicine were produced and isolated from living organisms, such as the penicillin class produced by fungi in the genus Penicillium, or streptomycin from bacteria of the genus Streptomyces. With advances in organic chemistry many antibiotics are now also obtained by chemical synthesis, such as the sulfa drugs. Many antibiotics are relatively small molecules with a molecular weight less than 2000 Da.

Overview

Unlike previous treatments for infections, which often consisted of administering chemical compounds such as strychnine and arsenic, with high toxicity also against mammals, antibiotics from microbes had no or few side effects and high effective target activity. Most anti-bacterial antibiotics don't have activity against viruses, fungi, or other microbes. Anti-bacterial 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 wide range of bacteria.
   The environment of individual antibiotics varies with the location of the infection, the ability of the antibiotic to reach the site of infection, and the ability of the microbe to inactivate or excrete the antibiotic. Some anti-bacterial antibiotics destroy bacteria (bactericidal), whereas others prevent bacteria from multiplying (bacteriostatic).
   Oral antibiotics are simply ingested, while intravenous antibiotics are used in more serious cases, such as deep-seated systemic infections. Antibiotics may also sometimes be administered topically, as with eye drops or ointments.
   In the last few years three new classes of antibiotics have been brought into clinical use. This follows a 40-year hiatus in discovering new classes of antibiotic compounds. These new antibiotics are of the following three classes: cyclic lipopeptides (daptomycin), glycylcyclines (tigecycline), and oxazolidinones (linezolid). Tigecycline is a broad-spectrum antibiotic, while the two others are used for gram-positive infections. These developments show promise as a means to counteract the growing bacterial resistance to existing antibiotics.

History

Although potent antibiotic compounds for treatment of human diseases caused by bacteria (such as tuberculosis, bubonic plague, or leprosy) were not isolated and identified until the twentieth century, the first known use of antibiotics was by the ancient Chinese over 2,500 years ago. Many other ancient cultures, including the ancient Egyptians and ancient Greeks already used molds and plants to treat infections, owing to the production of antibiotic substances by these organisms, a phenomenon known as antibiosis Antibiosis was first described in 1877 in bacteria when Louis Pasteur and Robert Koch observed that an airborne bacillus could inhibit the growth of Bacillus anthracis. The antibiotic properties of Penicillium sp. were first described in France by Ernest Duchesne in 1897. However, his work went by without much notice from the scientific community until Alexander Fleming's discovery of Penicillin (see below).
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. In 1939, Rene Dubos isolated gramicidin, one of first antibiotics to be manufactured commercially used during World War II proving highly effective in the treatment of wounds and ulcers.. Florey credited Dubos for reviving his research on penicillin Antibiotics>

Gastrointestinal upset and diarrhea

Nausea (if alcohol taken concurrently)

Allergic reactions

Generic Name	Brand Names	Common Uses	Possible Side Effects	Mechanism of action
Aminoglycosides
Amikacin	Amikin	Infections caused by Gram-negative bacteria, such as Escherichia coli and Klebsiella particularly Pseudomonas aeruginosa. Effective against Aerobic bacteria (not obligate/facultative anaerobes).	Hearing loss Vertigo Kidney damage	Binding to the bacterial 30S ribosomal subunit (some work by binding to the 50S subunit), inhibiting the translocation of the peptidyl-tRNA from the A-site to the P-site and also causing misreading of mRNA, leaving the bacterium unable to synthesize proteins vital to its growth.
Gentamicin	Garamycin
Kanamycin	Kantrex
Neomycin
Netilmicin	Netromycin
Streptomycin
Tobramycin	Nebcin
Paromomycin	Humatin
Ansamycins
Geldanamycin		Experimental, as antitumor antibiotics
Herbimycin		Experimental, as antitumor antibiotics
Carbacephem
Loracarbef	Lorabid			prevents bacterial cell division by inhibiting cell wall synthesis.
Carbapenems
Ertapenem	Invanz	Bactericidal for both Gram-positive and Gram-negative organisms and therefore useful for empiric broad-spectrum antibacterial coverage. (Note MRSA resistance to this class.)	Gastrointestinal upset and diarrhea Nausea Seizures Headache Rash and Allergic reactions	Inhibition of cell wall synthesis
Doripenem	Finibax
Imipenem/Cilastatin	Primaxin
Meropenem	Merrem
Cephalosporins (First generation)
Cefadroxil	Duricef		Gastrointestinal upset and diarrhea Nausea (if alcohol taken concurrently) Allergic reactions	Same mode of action as other beta-lactam antibiotics: disrupt the synthesis of the peptidoglycan layer of bacterial cell walls.
Cefazolin	Ancef
Cefalotin or Cefalothin	Keflin
Cefalexin	Keflex
Cephalosporins (Second generation)
Cefaclor	Ceclor		Gastrointestinal upset and diarrhea Nausea (if alcohol taken concurrently) Allergic reactions	Same mode of action as other beta-lactam antibiotics: disrupt the synthesis of the peptidoglycan layer of bacterial cell walls.
Cefamandole	Mandole
Cefoxitin	Mefoxin
Cefprozil	Cefzil
Cefuroxime	Ceftin, Zinnat
Cephalosporins (Third generation)
Cefixime	Suprax		Gastrointestinal upset and diarrhea Nausea (if alcohol taken concurrently) Allergic reactions	Same mode of action as other beta-lactam antibiotics: disrupt the synthesis of the peptidoglycan layer of bacterial cell walls.
Cefdinir	Omnicef
Cefditoren	Spectracef
Cefoperazone	Cefobid
Cefotaxime	Claforan
Cefpodoxime
Ceftazidime	Fortaz
Ceftibuten	Cedax
Ceftizoxime
Ceftriaxone	Rocephin
Cephalosporins (Fourth generation)
Cefepime	Maxipime		Gastrointestinal upset and diarrhea Nausea (if alcohol taken concurrently) Allergic reactions	Same mode of action as other beta-lactam antibiotics: disrupt the synthesis of the peptidoglycan layer of bacterial cell walls.
Cephalosporins (Fifth generation)
Ceftobiprole
Glycopeptides
Teicoplanin				inhibiting peptidoglycan synthesis
Vancomycin	Vancocin			inhibiting peptidoglycan synthesis
Macrolides
Azithromycin	Zithromax, Sumamed, Zitrocin	Streptococcal infections, syphilis, respiratory infections, mycoplasmal infections, Lyme disease	Nausea, vomiting, and diarrhea (especially at higher doses) Jaundice	inhibition of bacterial protein biosynthesis by binding irreversibly to the subunit 50S of the bacterial ribosome, thereby inhibiting translocation of peptidyl tRNA.
Clarithromycin	Biaxin
Dirithromycin
Erythromycin	Erythocin, Erythroped
Roxithromycin
Troleandomycin
Telithromycin	Ketek	Pneumonia	Visual Disturbance, LIVER TOXICITY.
Spectinomycin		Antimetabolite, Anticancer
Monobactams
Aztreonam				Same mode of action as other beta-lactam antibiotics: disrupt the synthesis of the peptidoglycan layer of bacterial cell walls.
Penicillins
Amoxicillin	Novamox, Amoxil	Wide 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)	Same mode of action as other beta-lactam antibiotics: disrupt the synthesis of the peptidoglycan layer of bacterial cell walls.
Ampicillin
Azlocillin
Carbenicillin
Cloxacillin
Dicloxacillin
Flucloxacillin	Floxapen
Mezlocillin
Meticillin
Nafcillin
Oxacillin
Penicillin
Piperacillin
Ticarcillin
Polypeptides
Bacitracin		Eye, ear or bladder infections; usually applied directly to the eye or inhaled into the lungs; rarely given by injection	Kidney and nerve damage (when given by injection)	Inhibits isoprenyl pyrophosphate, a molecule which carries the building blocks of the peptidoglycan bacterial cell wall outside of the inner membrane
Colistin				Interact with the bacterial cytoplasmic membrane, changing its permeability.
Polymyxin B
Quinolones
Ciprofloxacin	Ciproxin, CiploxESTECINA	Urinary tract infections, bacterial prostatitis, community-acquired pneumonia, bacterial diarrhea, mycoplasmal infections, gonorrhea	Nausea (rare), tendinosis (rare)	inhibit the bacterial DNA gyrase or the topoisomerase IV enzyme, thereby inhibiting DNA replication and transcription.
Enoxacin
Gatifloxacin	Tequin
Levofloxacin	Levaquin
Lomefloxacin
Moxifloxacin	Avelox
Norfloxacin	NOROXIN
Ofloxacin	Ocuflox
Trovafloxacin	Trovan
Sulfonamides
Mafenide		Urinary 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	Folate synthesis inhibition. They are competitive inhibitors of the enzyme dihydropteroate synthetase, DHPS. DHPS catalyses the conversion of PABA (para-aminobenzoate) to dihydropteroate, a key step in folate synthesis. Folate is necessary for the cell to synthesize nucleic acids (nucleic acids are essential building blocks of DNA and RNA), and in its absence cells will be unable to divide.
Prontosil (archaic)
Sulfacetamide
Sulfamethizole
Sulfanilimide (archaic)
Sulfasalazine
Sulfisoxazole
Trimethoprim
Trimethoprim-Sulfamethoxazole (Co-trimoxazole) (TMP-SMX)	Bactrim
Tetracyclines
Demeclocycline		Syphilis, chlamydial infections, Lyme disease, mycoplasmal infections, acne rickettsial infections	Gastrointestinal upset Sensitivity to sunlight Staining of teeth (especially in children) Potential toxicity to mother and fetus during pregnancy	inhibiting the binding of aminoacyl-tRNA to the mRNA-ribosome complex. They do so mainly by binding to the 30S ribosomal subunit in the mRNA translation complex.
Doxycycline	Vibramycin
Minocycline	Minocin
Oxytetracycline	Terracin
Tetracycline	Sumycin
Others
Arsphenamine	Salvarsan	Spirochaetal infections (obsolete)
Chloramphenicol	Chloromycetin
Clindamycin	Cleocin	acne infections, prophylaxis before surgery
Lincomycin		acne infections, prophylaxis before surgery
Ethambutol		Antituberculosis
Fosfomycin
Fusidic acid	Fucidin
Furazolidone
Isoniazid		Antituberculosis
Linezolid	Zyvox
Metronidazole	Flagyl	Giardia
Mupirocin	Bactroban
Nitrofurantoin	Macrodantin, Macrobid
Platensimycin
Pyrazinamide		Antituberculosis
Quinupristin/Dalfopristin	Syncercid
Rifampin or Rifampicin		mostly Gram-positive and mycobacteria	Reddish-orange sweat, tears, and urine	Binds to the β subunit of RNA polymerase to inhibit transcription
Tinidazole
Generic Name	Brand Names	Common Uses	Possible Side Effects	Mechanism of action

Production

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, usually in strongly aerobic fermentation.

Usage

Antibiotics are only intended to be used by a doctor's prescription. Doctors always specify dosage and duration of antibiotic treatment. It is very important to follow the prescription and complete the entire course (see Antibiotic misuse).
In general, alcohol should be avoided when taking antibiotics as it causes a variety of things to happen in the body, and some of them can impair the effectiveness of antibiotics; It also competes with liver enzymes, which break down the antibiotics. Additionally, certain antibiotics chemically react with alcohol, leading to serious body reactions (severe vomiting, nausea, etc.). These include (but not limited to): Metronidazole, Tinidazole, co-trimoxazole, cephamandole, ketoconazole. Such antibiotics are explicitly prohibited to be used with alcohol.

Side effects

Possible side effects are varied, depending on the antibiotics used and the microbial organisms targeted. Adverse effects can range from fever and nausea to major allergic reactions including photodermatitis. 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 the intestinal flora, Such overgrowth of pathogenic bacteria may be alleviated by ingesting probiotics during a course of antibiotics. . An antibiotic-induced disruption of the population of the bacteria normally present as constituents of the normal vaginal flora may also occur, and may lead to overgrowth of yeast species of the genus Candida in the vulvo-vaginal area. 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.
Hypothetically, some antibiotics might interfere with the efficiency of birth control pills. However there have been no conclusive studies that proved that; on the contrary, the majority of the studies indicate that antibiotics don't interfere with contraception, even though there's a possibility that a small percentage of women may experience decreased effectiveness of birth control pills while taking an antibiotic.

Antibiotic misuse

Common forms of antibiotic misuse include failure to take the entire prescribed course of the antibiotic, or failure to rest for sufficient recovery to allow clearance of the infecting organism. These practices may facilitate the development of bacterial populations with antibiotic resistance. Inappropriate antibiotic treatment is another common form of antibiotic misuse. A common example is the prescription and use of antibiotics to treat viral infections such as the common cold that have no effect.

Animals

It is estimated that greater than 70% of the antibiotics used in U.S. are given to feed animals (for example chickens, pigs and cattle) in the absence of disease. Antibiotic use in food animal production has been associated with the emergence of antibiotic-resistant strains of bacteria including Salmonella spp., Campylobacter spp., Escherichia coli, and Enterococcus spp. Evidence from some US and European studies suggest that these resistant bacteria cause infections in humans that don't respond to commonly prescribed antibiotics. In response to these practices and attendant problems, several organizations (for example The American Society for Microbiology (ASM), American Public Health Association (APHA) and the American Medical Association (AMA)) have called for restrictions on antibiotic use in food animal production and an end to all non-therapeutic uses. However, delays in regulatory and legislative actions to limit the use of antibiotics are common, and may include resistance to these changes by industries using or selling antibiotics, as well as time spent on research to establish causal links between antibiotic use and emergence of untreatable bacterial diseases. 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 public health and medical organizations including the American Nurses Association (ANA), the American Academy of Pediatrics (AAP), and the American Public Health Association (APHA).

Humans

One study on respiratory tract infections found "physicians were more likely to prescribe antibiotics to patients who they believed expected them, although they correctly identified only about 1 in 4 of those patients". Multifactorial interventions aimed at both physicians and patients can reduce inappropriate prescribing of antibiotics. Delaying antibiotics for 48 hours while observing for spontaneous resolution of respiratory tract infections may reduce antibiotic usage; however, this strategy may reduce patient satisfaction.
Excessive use of prophylactic antibiotics in travelers may also be classified as misuse.

Antibiotic resistance

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've descended from those few organisms that survived the original treatment. This survival often results from an inheritable resistance to the compound that was infrequent in the original population, but became more frequent in the descendants.
Antibiotic resistance has become a serious problem in both developed and underdeveloped nations. By 1984 half of those with active tuberculosis in the United States had a strain that resisted at least one antibiotic. In certain settings, such as hospitals and some childcare locations, the rate of antibiotic resistance is so high that the usual, 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 to the rise of resistance to those drugs. A struggle to develop new antibiotics ensues to prevent losing future battles against infection. To date, tuberculosis and pneumococcus are prominent examples of once easily treated infections where drug-resistance has become a problem. Another example of selection is Staphylococcus aureus ('golden staph'), 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 complicated 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 made more widespread when antibiotics are used to treat disorders in which they've no efficacy, such as the common cold or other viral complaints, and when they're used broadly as prophylaxis rather than treatment (as in, for example, animal feeds), because this exposes more bacteria to selection for resistance.

Resistance modifying agents

One solution to combat resistance currently being researched is the development of pharmaceutical compounds that would revert multiple antibiotic resistance. These so called resistance modifying agents may target and inhibit MDR mechanisms, rendering the bacteria susceptible to antibiotics to which they were previously resistant. These compounds targets include among others

Efflux inhibition(Phe-Arg-β-naphthylamide)

Beta Lactamase inhibitors - Including Clavulanic acid and Sulbactam

Beyond antibiotics

The comparative ease of identifying compounds which safely cured bacterial infections was more difficult to duplicate in treatments of fungal and viral infections. Antibiotic research led to great strides in the knowledge of biochemistry, establishing large differences between the cellular and molecular physiology of the bacterial cell and that of the mammalian cell. This explained the observation that many compounds that are toxic to bacteria are non-toxic to human cells. In contrast, the basic biochemistries of the fungal cell and the mammalian cell are much more similar. This restricts the development and use of therapeutic compounds that attack a fungal cell, while not harming mammalian cells. Similar problems exist in antibiotic treatments of viral diseases. Human viral metabolic biochemistry is very closely similar to human biochemistry, and the possible targets of antiviral compounds are restricted to very few components unique to a mammalian virus.
Research into bacteriophages for use as antibiotics is presently ongoing. Several types of bacteriophage appear to exist that are specific for each bacterial taxonomic group or species. Research into bacteriophages for medicinal use is just beginning, but has led to advances in microscopic imaging. While bacteriophages provide a possible solution to the problem of antibiotic resistance, there's no clinical evidence yet that they can be deployed as therapeutic agents to cure disease.
Phage therapy has been used in the past on humans in the US and Europe during the 1920s and 1930s, but these treatments had mixed results. With the discovery of penicillin in the 1940s, Europe and the US changed therapeutic strategies 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. However, phage are living and reproducing; concerns about genetic engineering in freely released viruses currently limit certain aspects of phage therapy. Bacteriocins are also a growing alternative to the classic small-molecule antibiotics . Different classes of bacteriocins have different potential as therapeutic agents. Small molecule bacteriocins (microcins, for example, and lantibiotics) may be similar to the classic antibiotics; colicin-like bacteriocins are more likely to be narrow-spectrum, demanding new molecular diagnostics prior to therapy but also not raising the spectre of resistance to the same degree. One drawback to the large molecule antibiotics is that that'll have relative difficulty crossing membranes and travelling systemically throughout the body. For this reason, they're most often proposed for application topically or gastrointestinally. Because bacteriocins are peptides, they're more readily engineered than small molecules. This may permit the generation of cocktails and dynamically improved antibiotics that are modified to overcome resistance. Probiotics are another alternative that goes beyond traditional antibiotics by employing a live culture which may establish itself as a symbiont, competing, inhibiting, or simply interfering with colonization by pathogens. It may produce antibiotics or bacteriocins, essentially providing the drug in vivo and in situ, potentially avoiding the side effects of systemic administration.

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