Many antibiotic compounds used in modern medicine are 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 medicinal chemistry many antibiotics are now modified chemically from their original form found in nature. In addition, some modern antibiotics have been created through purely synthetic means. Many antibiotics are relatively small molecules with a molecular weight less than 2000 Da.
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 do not 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.
See also: Timeline of antibiotics
Penicillin
Penicillin
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.[4] Many other ancient cultures, including the ancient Egyptians, ancient Greeks and medieval Arabs already used molds and plants to treat infections, owing to the production of antibiotic substances by these organisms, a phenomenon known as antibiosis[5] 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.[6] 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.[7]. Florey credited Dubos for reviving his research on penicillin[7]
"Antibiotic" was originally used to refer only to substances extracted from a fungus or other microorganism, but has come to also include the many synthetic and semi-synthetic drugs that have antibacterial effects. Antibiotics can help succeed in curing many illnesses.
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 behavior; in practice, both of these are capable of ending a bacterial infection.[8]
* 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). | 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 | ||||
| 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.) |
| Inhibition of cell wall synthesis |
| Doripenem | Finibax | |||
| Imipenem/Cilastatin | Primaxin | |||
| Meropenem | Merrem | |||
| Cephalosporins (First generation) | ||||
| Cefadroxil | Duricef |
| 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 |
| 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 |
| 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 |
| 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 | |||
| Macrolides | ||||
| Azithromycin | Zithromax, Sumamed, Zitrocin | Streptococcal infections, syphilis, respiratory infections, mycoplasmal infections, Lyme disease |
| 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.[10] | |
| 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 |
| 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 [11] | |
| Colistin | Interact with the bacterial cytoplasmic membrane, changing its permeability. | |||
| Polymyxin B | ||||
| Quinolones | ||||
| Ciprofloxacin | Cipro, Ciproxin, Ciprobay | 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 |
| 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 |
| 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.[12] | |
| 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 |
[edit] Production
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, usually in strongly aerobic fermentation.
[edit] 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[13]; It also competes with liver enzymes, which break down the antibiotics.[14] 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.[15]
[edit] 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.[citation needed] 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,[16] Such overgrowth of pathogenic bacteria may be alleviated by ingesting probiotics during a course of antibiotics.[citation needed]. 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. [17] 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 do not interfere with contraception[18], even though there is a possibility that a small percentage of women may experience decreased effectiveness of birth control pills while taking an antibiotic.[19]
[edit] 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.
[edit] Animals
It is estimated that greater than 70% of the antibiotics used in U.S. are given to feed animals (e.g. chickens, pigs and cattle) in the absence of disease.[20] 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 do not respond to commonly prescribed antibiotics. In response to these practices and attendant problems, several organizations (e.g. 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.[citation needed] 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).[citation needed]
[edit] 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".[21] Multifactorial interventions aimed at both physicians and patients can reduce inappropriate prescribing of antibiotics. [22] 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.[23]
Excessive use of prophylactic antibiotics in travelers may also be classified as misuse.
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