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Penicillins

Penicillins

Definition

Penicillins are a group of closely related antibiotics that kill bacteria.

Description

There are several types of penicillins, each used to treat different kinds of infections, such as skin infections, dental infections, ear infections, respiratory tract infections, urinary tract infections, gonorrhea, and other infections caused by bacteria. These drugs will not work for olds, flu, and other infections caused by viruses.

Examples of penicillins are penicillin V (Beepen-VK, Pen-Vee K, V-cillin K, Veetids) and amoxicillin (Amoxil, Polymox, Trimox, Wymox). Penicillins are sometimes combined with other ingredients called beta-lactamase inhibitors, which protect the penicillin from bacterial enzymes that may destroy it before it can do its work. The drug Augmentin, for example, contains a combination of amoxicillin and a beta-lactamase inhibitor, clavulanic acid. Penicillins are available only with a prescription.

The original form of penicillin is called penicillin G. It is a narrow-spectrum antibiotic, which can be destroyed by stomach acid, but it is still useful against anaerobic bacteria (bacteria that can live in the absence of air). Newer penicillins are resistant to stomach acid, such as penicillin V, or have a broader spectrum, such as ampicillin and amoxicillin.

General use

Penicillins are useful against infections in many parts of the body, including the mouth and throat, skin and soft tissue, tonsils, heart, lungs, and ears. However, since many bacteria are resistant to penicillin, it is often wise to do a culture and sensitivity test before using penicillins. In some cases, there are only a few types of bacteria that are likely to be a problem, and so it is appropriate to use a penicillin without testing. For example, dentists often prescribe penicillin to prevent infections after dental surgery.

Precautions

Penicillins are usually very safe. The greatest risk is an allergic reaction, which can be severe. People who have been allergic to cephalosporins are likely to be allergic to penicillins. Moreover, people with certain medical conditions or who are taking certain other medicines can have problems if they take penicillins. Before taking these drugs, patients should be sure to let the physician know about any of the following conditions.

Low-sodium diet

Some penicillin medicines contain large enough amounts of sodium to cause problems for people on low-sodium diets. Parents of children on on such a diet should make sure that the physician treating the infection knows about the special diet.

Diabetes

Penicillins may cause false positive results on urine sugar tests for diabetes. People with diabetes should check with their physicians to see if they need to change their diet or the doses of their diabetes medicine.

Phenylketonuria

Some formulations of Augmentin contain phenylalanine. People with phenylketonuria (PKU) should consult a physician before taking this medicine.

Side effects

The most common side effect of penicillin is diarrhea . Nausea , vomiting , and upset stomach are also common. With some penicillins, particularly the broad spectrum products, there is a risk of increased growth of organisms that are not affected by penicillin. This situation can lead to candidal infections of the mouth and vagina.

Most side effects of penicillin cannot be prevented. Amoxicillin has a lower incidence of diarrhea than ampicillin and is the preferred drug in most cases.

Interactions

Birth control pills may not work properly when taken at the same time as penicillin. Penicillins may also interact with many other medicines. When this happens, the effects of one or both of the drugs may change or the risk of side effects may be greater. People who take penicillin should let their physician know all other medicines they are taking. Among the drugs that may interact with penicillins are the following:

  • acetaminophen (Tylenol) and other medicines that relieve pain and inflammation
  • medicine for overactive thyroid
  • other antibiotics
  • blood thinners
  • antiseizure medicines such as Depakote and Depakene
  • blood pressure drugs such as Capoten, Monopril, and Lotensin

The list above does not include every drug that may interact with penicillins. A physician or pharmacist should be consulted before a patient combines penicillins with any other prescription or nonprescription (over-the-counter) medicine.

Parental concerns

Parents should verify that their children have an infection requiring antibiotic therapy. Unnecessary use of antibiotics leads to development of bacterial resistance, while it subjects the child to some needless risk of adverse effects and wastes money.

Liquid forms of penicillin should be refrigerated after reconstitution. These preparations must be shaken well before use and measured with a medicinal teaspoon, not a household teaspoon.

Any adverse effects should be discussed with the prescriber. Penicillin should not be used in patients allergic to the drug; however, an incorrect report of an allergy to penicillin may cause prescribers to select a different drug which may cause even more severe side effects.

Penicillins should be administered exactly as directed. Users should never give larger, smaller, more frequent, or less frequent doses. To make sure the infection clears up completely, patients should take the medicine for as long as it has been prescribed. They should not stop taking the drug just because symptoms begin to improve. This point is important with all types of infections, but it is especially important with strep infections, which can lead to serious heart problems if they are not cleared up completely.

This medicine should be used only for the infection for which it was prescribed. Different kinds of penicillins cannot be substituted for one another. Do not save some of the medicine to use on future infections. It may not be the right treatment for other kinds of infections, even if the symptoms are the same.

KEY TERMS

Anaerobic An organism that grows and thrives in an oxygen-free environment.

Beta-lactamase An enzyme produced by some bacteria that destroys penicillins.

Broad spectrum A term applied to antibiotics to indicate that they are effective against many different types of bacteria.

Enzyme A protein that catalyzes a biochemical reaction without changing its own structure or function.

Microorganism An organism that is too small to be seen with the naked eye, such as a bacterium, virus, or fungus.

Mononucleosis An infection, caused by the Epstein-Barr virus, that causes swelling of lymph nodes, spleen, and liver, usually accompanied by extremely sore throat, fever, headache, and intense long-lasting fatigue. Also called infectious mononucleosis.

Resources

BOOKS

Beers, Mark. H., and Robert Berkow, eds. The Merck Manual, 2nd home ed. West Point, PA: Merck & Co., 2004.

Mcevoy, Gerald K., et al. AHFS Drug Information 2004. Bethesda, MD: American Society of Healthsystems Pharmacists, 2004.

Siberry, George K., and Robert Iannone, eds. The Harriet Lane Handbook, 15th ed. Philadelphia, PA: Mosby Publishing, 2000.

PERIODICALS

Apter Andrea J., et al. "Represcription of penicillin after allergic-like events." Journal of Allergy and Clinical Immunology 113, no. 4 (April 2004): 764770.

ORGANIZATIONS

American Academy of Pediatrics. 141 Northwest Point Boulevard, Elk Grove Village, IL 600071098. Web site: <www.aap.org>.

Centers for Disease Control. 200 Independence Avenue, SW, Washington, DC, 20201. Web site: <www.cdc.gov>.

WEB SITES

"Penicillins (Systemic)." Available online at <www.nlm.nih.gov/medlineplus/druginfo/uspdi/202446.html> (accessed September 29, 2004).

"Treat Sore Throat without Penicillin." Available online at <www.medicinenet.com/script/main/art.asp?articlekey=25627> (accessed September 29, 2004).

Nancy Ross-Flanigan Samuel Uretsky, PharmD

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Ross-Flanigan, Nancy; Uretsky, Samuel. "Penicillins." Gale Encyclopedia of Children's Health: Infancy through Adolescence. 2006. Encyclopedia.com. 28 Jun. 2016 <http://www.encyclopedia.com>.

Ross-Flanigan, Nancy; Uretsky, Samuel. "Penicillins." Gale Encyclopedia of Children's Health: Infancy through Adolescence. 2006. Encyclopedia.com. (June 28, 2016). http://www.encyclopedia.com/doc/1G2-3447200431.html

Ross-Flanigan, Nancy; Uretsky, Samuel. "Penicillins." Gale Encyclopedia of Children's Health: Infancy through Adolescence. 2006. Retrieved June 28, 2016 from Encyclopedia.com: http://www.encyclopedia.com/doc/1G2-3447200431.html

Penicillins

Penicillins

Definition

Penicillins are medicines that kill bacteria or prevent their growth.

Purpose

Penicillins are antibiotics (medicines used to treat infections caused by microorganisms). There are several types of penicillins, each used to treat different kinds of infections, such as skin infections, dental infections, ear infections, respiratory tract infections, urinary tract infections, gonorrhea, and other infections caused by bacteria. These drugs will not work for colds, flu, and other infections caused by viruses.

Description

Examples of penicillins are penicillin V (Beepen-VK, Pen-Vee K, V-cillin K, Veetids) and amoxicillin (Amoxil, Polymox, Trimox, Wymox). Penicillins are sometimes combined with other ingredients called beta-lactamase inhibitors, which protect the penicillin from bacterial enzymes that may destroy it before it can do its work. The drug Augmentin, for example, contains a combination of amoxicillin and a betalactamase inhibitor, clavulanic acid.

Penicillins are available only with a physician's prescription. They are sold in capsule, tablet (regular and chewable), liquid, and injectable forms.

Recommended dosage

The recommended dosage depends on the type of penicillin, the strength of the medicine, and the medical problem for which it is being taken. Check with the physician who prescribed the drug or the pharmacist who filled the prescription for the correct dosage.

Always take penicillins exactly as directed. Never take larger, smaller, more frequent, or less frequent doses. To make sure the infection clears up completely, take the medicine for as long as it has been prescribed. Do not stop taking the drug just because symptoms begin to improve. This is important with all types of infections, but it is especially important with "strep" infections, which can lead to serious heart problems if they are not cleared up completely.

Take this medicine only for the infection for which it was prescribed. Different kinds of penicillins cannot be substituted for one another. Do not save some of the medicine to use on future infections. It may not be the right treatment for other kinds of infections, even if the symptoms are the same.

Penicillins work best when they are at constant levels in the blood. To help keep levels constant, take the medicine in doses spaced evenly through the day and night. Do not miss any doses.

Some penicillins, notably penicillin V, should be taken on an empty stomach, but others may be taken with food. Check package directions or ask the physician or pharmacist for instructions on how to take the medicine.

Precautions

Symptoms should begin to improve within a few days of beginning to take this medicine. If they do not, or if they get worse, check with the physician who prescribed the medicine.

Penicillins may cause diarrhea. Certain diarrhea medicines may make the problem worse. Check with a physician before using any diarrhea medicine to treat diarrhea caused by taking penicillin. If diarrhea is severe, check with a physician as soon as possible. This could be a sign of a serious side effect.

Penicillins may change the results of some medical tests. Before having medical tests, patients who are taking penicillin should be sure to let the physician in charge know that they are taking this medicine.

Special conditions

People with certain medical conditions or who are taking certain other medicines can have problems if they take penicillins. Before taking these drugs, be sure to let the physician know about any of these conditions:

ALLERGIES. People who have hay fever, asthma, eczema, or other general allergies (or who have had such allergies in the past) may be more likely to have severe reactions to penicillins. They should be sure their health care provider knows about their allergies.

Anyone who has had unusual reactions to penicillins or cephalosporins in the past should let his or her physician know before taking the drugs again. The physician should also be told about any allergies to foods, dyes, preservatives, or other substances.

LOW-SODIUM DIET. Some penicillin medicines contain large enough amounts of sodium to cause problems for people on low-sodium diets. Anyone on such a diet should make sure that the physician treating the infection knows about the special diet.

DIABETES. Penicillins may cause false positive results on urine sugar tests for diabetes. People with diabetes should check with their physicians to see if they need to change their diet or the doses of their diabetes medicine.

PHENYLKETONURIA. Some formulations of Augmentin contain phenylalanine. People with phenylketonuria (PKU) should consult a physician before taking this medicine.

OTHER MEDICAL CONDITIONS. Before using penicillins, people with any of these medical problems should make sure their physicians are aware of their conditions:

  • bleeding problems
  • congestive heart failure
  • cystic fibrosis
  • kidney disease
  • mononucleosis ("mono")
  • stomach or intestinal problems, especially ulcerative colitis

USE OF CERTAIN MEDICINES. Taking penicillins with certain other drugs may affect the way the drugs work or may increase the chance of side effects.

Side effects

The most common side effects are mild diarrhea, headache, vaginal itching and discharge, sore mouth or tongue, or white patches in the mouth or on the tongue. These problems usually go away as the body adjusts to the drug and do not require medical treatment unless they continue or they are bothersome.

More serious side effects are not common, but may occur. If any of the following side effects occur, get emergency medical help immediately:

  • breathing problems, such as shortness of breath or fast or irregular breathing
  • fever
  • sudden lightheadedness or faintness
  • joint pain
  • skin rash, hives, itching, or red, scaly skin
  • swelling or puffiness in the face

Other rare side effects may occur. Anyone who has unusual symptoms after taking penicillin should get in touch with his or her physician.

Interactions

Birth control pills may not work properly when taken at the same time as penicillin. To prevent pregnancy, use additional methods of birth control while taking penicillin, such as latex condoms or spermicide.

Penicillins may interact with many other medicines. When this happens, the effects of one or both of the drugs may change or the risk of side effects may be greater. Anyone who takes penicillin should let the physician know all other medicines he or she is taking. Among the drugs that may interact with penicillins are:

  • Acetaminophen (Tylenol) and other medicines that relieve pain and inflammation
  • medicine for overactive thyroid
  • male hormones (androgens)
  • female hormones (estrogens)
  • other antibiotics
  • blood thinners
  • Disulfiram (Antabuse), used to treat alcohol abuse
  • antiseizure medicines such as Depakote and Depakene
  • blood pressure drugs such as Capoten, Monopril, and Lotensin

KEY TERMS

Enzyme A type of protein that brings about or speeds up chemical reactions.

Microorganism An organism that is too small to be seen with the naked eye.

Mononucleosis An infectious disease with symptoms that include severe fatigue, fever, sore throat, and swollen lymph nodes in the neck and armpits. Also called "mono."

The list above does not include every drug that may interact with penicillins. Be sure to check with a physician or pharmacist before combining penicillins with any other prescription or nonprescription (over-the-counter) medicine.

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Ross-Flanigan, Nancy. "Penicillins." Gale Encyclopedia of Medicine, 3rd ed.. 2006. Encyclopedia.com. 28 Jun. 2016 <http://www.encyclopedia.com>.

Ross-Flanigan, Nancy. "Penicillins." Gale Encyclopedia of Medicine, 3rd ed.. 2006. Encyclopedia.com. (June 28, 2016). http://www.encyclopedia.com/doc/1G2-3451601223.html

Ross-Flanigan, Nancy. "Penicillins." Gale Encyclopedia of Medicine, 3rd ed.. 2006. Retrieved June 28, 2016 from Encyclopedia.com: http://www.encyclopedia.com/doc/1G2-3451601223.html

Penicillin

Penicillin

One of the major advances of twentieth-century medicine was the discovery of penicillin. Penicillin is a member of the class of drugs known as antibiotics . These drugs either kill (bacteriocidal) or arrest the growth of (bacteriostatic) bacteria and fungi (yeast ), as well as several other classes of infectious organisms. Antibiotics are ineffective against viruses . Prior to the advent of penicillin, bacterial infections such as pneumonia and sepsis (overwhelming infection of the blood) were usually fatal. Once the use of penicillin became widespread, fatality rates from pneumonia dropped precipitously.

The discovery of penicillin marked the beginning of a new era in the fight against disease. Scientists had known since the mid-nineteenth century that bacteria were responsible for some infectious diseases, but were virtually helpless to stop them. Then, in 1928, Alexander Fleming (18811955), a Scottish bacteriologist working at St. Mary's Hospital in London, stumbled onto a powerful new weapon.

Fleming's research centered on the bacteria Staphylococcus, a class of bacteria that caused infections such as pneumonia, abscesses, post-operative wound infections, and sepsis. In order to study these bacteria, Fleming grew them in his laboratory in glass Petri dishes on a substance called agar . In August, 1928 he noticed that some of the Petri dishes in which the bacteria were growing had become contaminated with mold , which he later identified as belonging to the Penicillum family.

Fleming noted that bacteria in the vicinity of the mold had died. Exploring further, Fleming found that the mold killed several, but not all, types of bacteria. He also found that an extract from the mold did not damage healthy tissue in animals. However, growing the mold and collecting even tiny amounts of the active ingredientpenicillinwas extremely difficult. Fleming did, however, publish his results in the medical literature in 1928.

Ten years later, other researchers picked up where Fleming had left off. Working in Oxford, England, a team led by Howard Florey (18981968), an Australian, and Ernst Chain, a refugee from Nazi Germany, came across Fleming's study and confirmed his findings in their laboratory. They also had problems growing the mold and found it very difficult to isolate the active ingredient

Another researcher on their team, Norman Heatley, developed better production techniques, and the team was able to produce enough penicillin to conduct tests in humans. In 1941, the team announced that penicillin could combat disease in humans. Unfortunately, producing penicillin was still a cumbersome process and supplies of the new drug were extremely limited. Working in the United States, Heatley and other scientists improved production and began making large quantities of the drug. Owing to this success, penicillin was available to treat wounded soldiers by the latter part of World War II. Fleming, Florey, and Chain were awarded the Noble Prize in medicine. Heatley received an honorary M.D. from Oxford University in 1990.

Penicillin's mode of action is to block the construction of cell walls in certain bacteria. The bacteria must be reproducing for penicillin to work, thus there is always some lag time between dosage and response.

The mechanism of action of penicillin at the molecular level is still not completely understood. It is known that the initial step is the binding of penicillin to penicillin-binding proteins (PBPs), which are located in the cell wall. Some PBPs are inhibitors of cell autolytic enzymes that literally eat the cell wall and are most likely necessary during cell division. Other PBPs are enzymes that are involved in the final step of cell wall synthesis called transpeptidation. These latter enzymes are outside the cell membrane and link cell wall components together by joining glycopeptide polymers together to form peptidoglycan . The bacterial cell wall owes its strength to layers composed of peptidoglycan (also known as murein or mucopeptide). Peptidoglycan is a complex polymer composed of alternating N-acetylglucosamine and N-acetylmuramic acid as a backbone off of which a set of identical tetrapeptide side chains branch from the N-acetylmuramic acids, and a set of identical peptide cross-bridges also branch. The tetrapeptide side chains and the cross-bridges vary from species to species, but the backbone is the same in all bacterial species.

Each peptidoglycan layer of the cell wall is actually a giant polymer molecule because all peptidoglycan chains are cross-linked. In gram-positive bacteria there may be as many as 40 sheets of peptidoglycan, making up to 50% of the cell wall material. In Gram-negative bacteria, there are only one or two sheets (about 510% of the cell wall material). In general, penicillin G, or the penicillin that Fleming discovered, has high activity against Gram-positive bacteria and low activity against Gram-negative bacteria (with some exceptions).

Penicillin acts by inhibiting peptidoglycan synthesis by blocking the final transpeptidation step in the synthesis of peptidoglycan. It also removes the inactivator of the inhibitor of autolytic enzymes, and the autolytic enzymes then lyses the cell wall, and the bacterium ruptures. This latter is the final bacteriocidal event.

Since the 1940s, many other antibiotics have been developed. Some of these are based on the molecular structure of penicillin; others are completely unrelated. At one time, scientists assumed that bacterial infections were conquered by the development of antibiotics. However, in the late twentieth century, bacterial resistance to antibioticsincluding penicillinwas recognized as a potential threat to this success. A classic example is the Staphylococcus bacteria, the very species Fleming had found killed by penicillin on his Petri dishes. By 1999, a large percentage of Staphylococcus bacteria were resistant to penicillin G. Continuing research so far has been able to keep pace with emerging resistant strains of bacteria. Scientists and physicians must be judicious about the use of antibiotics, however, in order to minimize bacterial resistance and ensure that antibiotics such as penicillin remain effective agents for treatment of bacterial infections.

See also Antibiotic resistance, tests for; Bacteria and bacterial infection; Bacterial adaptation; Bacterial growth and division; Bacterial membranes and cell wall; History of the development of antibiotics

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Penicillin

Penicillin

Penicillin is a chemical produced in common molds which has potent antibacterial properties. Bacteria are tiny organisms that have the potential to cause a huge variety of infections in every organ system of the human body. The accidental discovery of penicillin in the twentieth century may be one of the greatest milestones in medical history. Penicillin opened the door to a variety of new "miracle drugs" that have saved the lives of millions. Until the discovery of penicillin, the only treatments available for bacterial infections were quinine, arsenic and sulfa drugs. All of these were highly toxic (poisonous).

Fleming's Mold

Scottish bacteriologist Alexander Fleming (1881-1955) discovered penicillin by accident in 1928. While conducting research using several petri dishes of bacteria cultures, he accidentally left one of the cultures uncovered for several days. Fleming found the dish contaminated with a mold. He was about to discard the culture when he noticed that the mold was dissolving all the bacteria near it.

Fleming recognized the importance of what was happening. He put a sample of the mold under his microscope and tested it against several types of bacteria. Fleming found that something in the mold stopped or slowed the growth of the bacteria. Because the mold was from the genus Penicillium, Fleming named the part of the mold that attacked bacteria "penicillin." He was unable to separate the penicillin from the mold, however.

In 1935, at Oxford University in England, researchers Howard Walter Florey (1898-1968) and Ernst Boris Chain (1906-1979) stumbled across an article by Fleming about his work with penicillin. They obtained a culture (sample) of Fleming's original mold and were able to separate and purify the penicillin. Florey began testing the penicillin on animals and found that it was nontoxic (did not harm living cells) as well as an effective antibiotic. Furthermore, it did not interfere with the activity of white blood cells (the body's natural defenders against infection).

Penicillin in World War II

Trials of the drug on humans were so successful that great quantities of penicillin were used to treat infections suffered by wounded and ill soldiers during World War II (1939-1945). England was not able to manufacture penicillin in quantity because of its involvement in the war. Florey traveled to the United States and convinced the government to sponsor research on the mass production of penicillin. An efficient method of mass-producing penicillin was developed using fermentation and a cornstarch medium. This basic technique is still used to produce many antibiotics.

Penicillin prevented thousands of wartime deaths from gas gangrene and other infections. Now the race began to discover its molecular structure so that it could be produced synthetically (in a laboratory from its chemical compounds).

In the mid-1940s English researcher Dorothy Crowfoot Hodgkin (1910-) used X-ray crystallography and an early IBM card-punch computer to determine the chemical structure of penicillin. The door was now open to other scientists to develop methods to synthesize it. Robert Burns Woodward (1917-1979), an organic chemist at Harvard University, completed the first penicillin synthesis in the 1950s.

Penicillin is used to treat any number of infections, including syphilis, meningitis, and pneumonia. Penicillin has reduced the threat of bacterial infections. The capability to treat potentially life-threatening infections has permitted the development of surgical operations, organ transplants, and open heart surgery. It has also vastly improved the treatment of burns.

Because the discovery and uevelopment of penicillin is rightly regarded as one of the greatest achievements in medical history, many of the scientists who worked on it have been highly honored. Fleming, Florey, and Chain shared the 1945 Nobel Prize in medicine for the development of penicillin. For their work with penicillin as well as other research, Hodgkin and Woodward also received the Nobel Prize, in 1964 and 1965, respectively.

[See also Antibiotic ; Open-heart surgery ; Quinine

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Penicillin

Penicillin


Penicillin was discovered accidentally in 1929 when Sir Alexander Fleming observed bacterial cultures contaminated with a mold that inhibited bacterial growth. The antibiotic penicillin was subsequently isolated from cultures of the Penicillium mold. In 1938 two other British scientists, Howard

Florey and Ernst Chain, first used purified preparations of penicillin to treat bacterial infections. Penicillin may have been present in folk remedies used as early as 600 b.c.e., at around which time molded soybean curd was used by the Chinese to treat boils and carbuncles, and moldy cheese was used by Chinese and Ukrainian peasants to treat infected wounds.

Initially it was thought that penicillin was a pure substance, but further studies revealed that a number of closely related compounds were present in Penicillium cultures. Naturally occurring penicillins, such as penicillin G, are most effective against gram-positive bacteria, but much less effective against gram-negative bacteria. A further limitation to the use of Penicillin G is that it is not well absorbed when administered orally. Research programs to produce chemically modified penicillins with improved properties have resulted in a large number of clinically useful penicillin derivatives. Examples of such penicillin derivatives include ampicillin and amoxicillin, which have much greater efficacy against gram-negative bacteria than penicillin, retain good activity against gram-positive bacteria, and are well absorbed when administered orally. The principal adverse reaction associated with the penicillins is the occurrence of allergic response.

The molecular targets for the antibacterial activity of the penicillin and related β -lactam antibiotics such as the cephalosporins are a group of bacterial enzymes known as penicillin-binding proteins (PBPs). The PBPs are essential to the final stages of bacterial cell wall biosynthesis . Penicillin and other β -lactam antibiotics inhibit PBPs, thereby inhibiting bacterial cell wall biosynthesis, which eventually results in bacterial cell lysis . (Vancomycin and cycloserine are nonpenicillin antibiotics that also inhibit bacterial cell wall biosynthesis through other mechanisms.)

The penicillins and related antibiotics have been among the most widely used therapeutic agents since their introduction into clinical practice in the 1940s. However, the widespread use of these antibiotics has resulted in the emergence and spread of bacteria that are resistant to these agents. A major mechanism of resistance to the penicillin and other β -lactam antibiotics is the bacterial production of β -lactamases, enzymes that cleave the β -lactam antibiotics and render them inactive before they can inhibit their PBP targets. Significant efforts have been made to develop β -lactam antibiotics resistant to the β -lactamases, and toward finding inhibitors of the β -lactamases to allow β -lactam antibiotics to be useful antibacterial agents against β -lactamase producing bacteria.

GRAM-POSITIVE AND GRAM-NEGATIVE BACTERIA

Bacteria can be broadly classified into two groups; the gram-positive bacteria, which are stained purple after the gram staining procedure, and the gram-negative bacteria, which are stained red. The difference in staining reflects differences in the structure of the cell walls between gram-positive and gram-negative bacteria. Pathogenic gram-positive bacteria include Staphylococcus aureus and Bacillus anthracis, and pathogenic gram-negative bacteria include Escherichia coli and Neisseria gonorrhoeae.

see also Antibiotics; Enzymes; Fleming, Alexander; Inhibitors.

William G. Gutheil

Bibliography

Mandell, Gerald L., and Petri, William A. (1996). "Antimicrobial Agents: Penicillins, Cephalosporins, and Other β -Lactam Antibiotics." In Goodman & Gilman's Pharmacological Basis of Therapeutics, 9th edition, ed. Joel G. Hardman and Lee E. Limbird. New York: McGraw-Hill.

Nicolaou, K. C., and Boddy, Christopher N. C. (2001). "Behind Enemy Lines." Scientific American 284(5):5461.

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penicillin

penicillin, any of a group of chemically similar substances obtained from molds of the genus Penicillium that were the first antibiotic agents to be used successfully in the treatment of bacterial infections in humans. The antagonistic effect of penicillin on bacteria was first observed by the Scottish biologist Sir Alexander Fleming in 1928. Although he recognized the therapeutic potential of penicillin, it was not until 1941 that a group of biologists working in England, including Oxford's Sir H. W. Florey and E. B. Chain, purified the substance and established its effectiveness against infectious organisms and its lack of toxicity to humans. The first successful treatment of a patient with penicillin occurred in New Haven, Conn., in 1942. Despite the development of hundreds of different antibiotics in recent decades, penicillin remains important in antibiotic therapy.

Small amounts of the antibiotic were first obtained from strains of the mold species P. notatum grown in fermentation bottles. During World War II need for the drug spurred development of better production methods; in the current method highly productive strains of Penicillium are grown in a cornsteep liquor medium in fermentation vats. The main form of penicillin produced by this method is benzylpenicillin, which, like all penicillins, is a derivative of 6-aminopenicillanic acid. Phenoxymethyl penicillin, which can be given orally because it is resistant to degradation by stomach acid, is produced by the species P. chrysogenum.

Effectiveness

Penicillin is effective against many gram-positive bacteria (see Gram's stain), including those that cause syphilis, meningococcal meningitis, gas gangrene, pneumococcal pneumonia, and some staphylococcal and streptococcal infections. Most gram-negative bacteria are resistant to the antibiotic, but some, such as the bacteria that cause gonorrhea, are susceptible, and others are responsive to high penicillin concentrations or to only certain classes of penicillins. Tuberculosis bacteria, protozoans, viruses, and most fungi are not affected by penicillin. The class of penicillins that includes ampicillin and amoxicillin with clavulanate (Augmentin) is active against gram-positive and gram-negative bacteria such as Haemophilus influenzae and Escherichia coli. All penicillins act by interfering with synthesis of the cell wall.

Drug Resistance and Sensitivity

Use of penicillin is limited by the fact that, although it causes fewer side effects than many other antibiotics, it causes allergic sensitivity in many individuals, including skin reactions and allergic shock. In addition, many microorganisms have developed resistance to the penicillins, and serious hospital epidemics involving infants and surgical patients have been caused by penicillin-resistant staphylococci (see drug resistance). Some organisms are resistant because they produce an enzyme, penicillinase, that destroys the antibiotic. Synthetically produced penicillins such as methicillin and oxacillin have been developed that are not degraded by the penicillinase enzyme, but these new penicillins have no effect on bacteria that have developed resistance by other means, e.g., by altered cell wall structure. Other antibiotics, such as erythromycin, have become important in treating infections by microorganisms resistant to penicillin.

See E. Lax, The Mold in Dr. Florey's Coat: The Story of the Penicillin Miracle (2004).

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Penicillin

PENICILLIN

The first of the first-generation antibiotics, Penicillium notatum is naturally produced by a mold. It was discovered serendipitously by British bacteriologist Alexander Fleming in 1928, and later developed successfully as a powerful therapeutic weapon by Howard Florey and Ernst Chain. These three men shared the 1945 Nobel Prize in medicine for their work on penicillin. The antibiotic was initially immensely successful in curing previously fatal infections caused by common bacterial pathogens such as streptococcus, staphylococcus and pneumococcus, and in treating common sexually transmitted diseases, notably syphilis and gonorrhea.

Unfortunately, most pathogens became resistant as successive generations of microorganisms included rising proportions that had evolved an enzyme to inactivate penicillin. Also, as penicillin is a complex protein, many who receive it develop allergies that get worse with each subsequent course of treatment. Its efficacy is thereby reduced.

John M. Last

(see also: Antibiotics; Drug Resistance )

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penicillin

penicillin (pen-i-sil-in) n. any one of a number of antibiotics derived from Penicillium moulds and used to treat infections caused by a wide variety of bacteria. Some patients are allergic to penicillin and develop such reactions as skin rashes or potentially fatal anaphylaxis. p. G (benzylpenicillin) a form of penicillin administered by injection. p. V (phenoxymethylpenicillin) an orally administered form of penicillin. semisynthetic p. one of a number of antibiotics derived from the penicillins, such as amoxicillin, ampicillin, and flucloxacillin.

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penicillin

penicillin A type of antibiotic produced, for example, by fungi of the genus Penicillium. Penicillins are active against certain types of bacteria (mainly Gram-positive species; See GRAM-REACTION) and are widely used in the treatment of diseases in animals caused by those bacteria. (Pencillin G was one of the first antibiotics to be used for the treatment of disease.) There is now a wide range of chemically modified penicillins, each with slightly different properties. They function by inhibiting the synthesis of bacterial cell walls.

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MICHAEL ALLABY. "penicillin." A Dictionary of Plant Sciences. 1998. Encyclopedia.com. 28 Jun. 2016 <http://www.encyclopedia.com>.

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penicillin

penicillin A type of antibiotic produced, for example, by fungi of the genus Penicillium. Penicillins are active against certain types of bacteria (mainly Grampositive species) and are widely used in the treatment of diseases in animals caused by those bacteria. (Pencillin G was one of the first antibiotics to be used for the treatment of disease.) There is now a wide range of chemically modified penicillins, each with slightly different properties. They function by inhibiting the synthesis of bacterial cell walls.

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penicillin

penicillin Antibiotic agent derived from moulds of the genus Penicillium. Scottish bacteriologist Sir Alexander Fleming discovered penicillin, the first antibiotic, in 1928. It was synthesised and first became available in 1941. Penicillin was widely used for treating casualties in World War 2. It can produce allergic reactions, and some microorganisms have become resistant.

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penicillin

penicillin An antibiotic derived from the mould Penicillium notatum; specifically it is known as penicillin G and belongs to a class of similar substances called penicillins. They are all active against a wide variety of bacteria, producing their effects by disrupting synthesis of the bacterial cell wall, and are used to treat a variety of infections caused by these bacteria.

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penicillin

pen·i·cil·lin / ˌpenəˈsilən/ • n. 1. an antibiotic or group of antibiotics produced naturally by certain blue molds, now usually prepared synthetically. 2. a blue mold (genus Penicillium, subdivision Deuteromycotina) of a type that produces these antibiotics.

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penicillin

penicillin The first of the antibiotics; found in the culture fluid of the mould Penicillium notatum in 1929. Active against a wide range of bacteria and widely used clinically.

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DAVID A. BENDER. "penicillin." A Dictionary of Food and Nutrition. 2005. Encyclopedia.com. 28 Jun. 2016 <http://www.encyclopedia.com>.

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penicillin

penicillin XX. f. modL. Penicillium generic name of moulds, so named from their brush-like sporangia, f. L. pēnicillum PENCIL; see -IN.

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T. F. HOAD. "penicillin." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. 28 Jun. 2016 <http://www.encyclopedia.com>.

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penicillin

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