History And Working Of Antibiotics Biology Essay


The word "antibiotics" comes from the Greek anti ("against") and bios ("life"). An antibiotic is defined as a substance produced by microorganism or a similar substance produced wholly or partially by chemical synthesis that is capable of inhibiting the growth or causing death of other microorganism in low concentration.

For example, chloramphenicol was originally obtained from streptomyces Venezuela but now it is produced completely by a synthesis process.

Antibiotics are used to treat many different bacterial infections. Antibiotics cure disease by killing or injuring bacteria. Bacteria are simple one-celled organisms that can be found, by the billions, all around us: on furniture and counter-tops, in the soil, and on plants and animals. They are a natural and needed part of life. Bacteria cause disease and infection when they are able to gain access to more vulnerable parts of our bodies and multiply rapidly. Bacteria can infect many parts of the body: eyes, ears, throat, sinuses, lungs, airways, skin, stomach, colon, bones, and genitals.

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Some antibiotics are 'bactericidal', meaning that they work by killing bacteria. Other antibiotics are 'bacteriostatic', meaning that they work by stopping bacteria multiplying.

Some antibiotics are 'bactericidal', meaning that they work by killing bacteria. Other antibiotics are 'bacteriostatic', meaning that they work by stopping bacteria multiplying.

Each different type of antibiotic affects different bacteria in different ways. For example, an antibiotic might inhibit a bacterium's ability to turn glucose into energy, or its ability to construct its cell wall. When this happens, the bacterium dies instead of reproducing.

Some antibiotics can be used to treat a wide range of infections and are known as 'broad-spectrum' antibiotics. Others are only effective against a few types of bacteria and are called 'narrow-spectrum' antibiotics.


The ancient Egyptians, the Chinese, and Indians of Central America all used molds to treat infected wounds. However, they did not understand the connection of the antibacterial properties of mold and the treatment of diseases.

Late 1800s

The search for antibiotics began in the late 1800s, with the growing acceptance of the germ theory of disease, a theory which linked bacteria and other microbes to the causation of a variety of ailments. As a result, scientists began to devote time to searching for drugs that would kill these disease-causing bacteria.


The surgeon Joseph Lister, began researching the phenomenon that urine contaminated with mold would not allow the successful growth of bacteria.


German doctors, Rudolf Emmerich and Oscar Low were the first to make an effective medication that they called pyocyanase from microbes. It was the first antibiotic to be used in hospitals. However, the drug often did not work.


Sir Alexander Fleming observed that colonies of the bacterium Staphylococcus aureus could be destroyed by the mold Penicillium notatum, demonstrating antibacterial properties.


Prontosil, the first sulfa drug, was discovered in 1935 by German chemist Gerhard Domagk (1895-1964).


The manufacturing process for Penicillin G Procaine was invented by Howard Florey (1898-1968) and Ernst Chain (1906-1979). Penicillin could now be sold as a drug. Fleming, Florey, and Chain shared the 1945 Nobel Prize for medicine for their work on penicillin.


In 1943, American microbiologist Selman Waksman (1888-1973) made the drug streptomycin from soil bacteria, the first of a new class of drugs called amino glycosides. Streptomycin could treat diseases like tuberculosis; however, the side effects were often too severe.


Tetracycline was patented by Lloyd Conover, which became the most prescribed broad spectrum antibiotic in the United States.


Nystatin was patented and used to cure many disfiguring and disabling fungal infections.


SmithKline Beecham patented Amoxicillin or amoxicillin/clavulanate potassium tablets, and first sold the antibiotic in 1998 under the trade names of Amoxicillin, Amoxil, and Trimox. Amoxicillin is a semisynthetic antibiotic.


3 .Classification of antibiotics and their side effects :-

Although there are several classification schemes for antibiotics, based on bacterial spectrum (broad versus narrow) or route of administration (inject able versus oral versus topical), or type of activity (bactericidal vs. bacteriostatic), the most useful is based on chemical structure. Antibiotics within a structural class will generally have similar patterns of effectiveness, toxicity, and allergic potential.

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Most commonly used types of antibiotics are: Amino glycosides, Penicillin, Fluoroquinolones, Cephalosporins, Macrolides, and Tetracycline. While each class is composed of multiple drugs, each drug is unique in some way.


The penicillin are the oldest class of antibiotics. Penicillin have a common chemical structure which they share with the Cephalosporins. Penicillin are generally bactericidal, inhibiting formation of the cell wall. Penicillin are used to treat skin infections, dental infections, ear infections, respiratory tract infections, urinary tract infections, gonorrhea.

There are four types of penicillin:

The natural penicillin:-These are based on the original penicillin-G structure. Penicillin-G types are effective against gram-positive strains of streptococci, staphylococci, and some gram-negative bacteria such as meningococcal.

Penicillinase-resistant penicillins:-, notably methicillin and oxacillin, are active even in the presence of the bacterial enzyme that inactivates most natural penicillins.

Aminopenicillins:- such as ampicillin and amoxicillin have an extended spectrum of action compared with the natural penicillins. Extended spectrum penicillins are effective against a wider range of bacteria.

Penicillins side effects:-

Penicillins are among the least toxic drugs known. The most common side effect of penicillin is diarrhea. Nausea, vomiting, and upset stomach are also common. In rare cases penicillin can cause immediate and delayed allergic reactions - specifically, skin rashes, fever, and anaphylactic shock. Penicillin are classed as category B during pregnancy.


Cephalosporins have a mechanism of action identical to that of the penicillins. However, the basic chemical structure of the penicillins and Cephalosporins differs in other respects, resulting in some difference in the spectrum of antibacterial activity. Like the penicillins, Cephalosporins have a beta-lactam ring structure that interferes with synthesis of the bacterial cell wall and so are bactericidal. Cephalosporins are derived from cephalosporin C which is produced from Cephalosporium acrimonies.

Cephalosporins are used to treat pneumonia, strep throat, staph infections, tonsillitis, bronchitis, otitis media, various types of skin infections, gonorrhea, urinary tract infections Cephalosporin antibiotics are also commonly used for surgical prophylaxis. Cephalexin can also be used to treat bone infections.

Cephalosporins are among the most diverse classes of antibiotics, they are grouped into "generations" by their antimicrobial properties. Each newer generation has a broader spectrum of activity than the one before.

The first generation cephalosporins include: Their spectrums of activity are quite similar. They possess generally excellent coverage against most gram-positive pathogens and variable to poor coverage against most gram negative pathogens. The first generation cephalosporins include:







The second generation cephalosporins. In addition to the gram positive spectrum of the first generation cephalosporins, these agents have expanded gram negative spectrum. Cefoxitin and cefotetan also have good activity against Bacteroides fragilis. Enough variation exists between the second generation cephalosporins in regard to their spectrums of activity against most species of gram negative bacteria, that susceptibility testing is generally required to determine sensitivity. The second generation cephalosporins include:






The third generation cephalosporins have much expanded gram negative activity. However, some members of this group have decreased activity against gram-positive organisms. They have the advantage of convenient dosing schedules, but they are expensive. The third generation cephalosporins include:














The fourth generation cephalosporins are extended-spectrum agents with similar activity against gram-positive organisms as first-generation cephalosporins. They also have a greater resistance to beta-lactamases than the third generation cephalosporins. Many fourth generation cephalosporins can cross blood brain barrier and are effective in meningitis. The fourth generation cephalosporins include:







Cephalosporins side effects:-

Cephalosporins generally cause few side effects. Common side effects associated these drugs include: diarrhoea, nausea, mild stomach cramps or upset. Approximately 5-10% of patients with allergic hypersensitivity to penicillins will also have cross-reactivity with cephalosporins. Thus, cephalosporin antibiotics are contraindicated in people with a history of allergic reactions

easily spread among people, resistant bacteria can easily occur in places like hospitals and nursing homes, where a lot of people are gathered and antibiotic use is high. The risk of spreading resistant bacteria is even greater if the facilities are overcrowded and hygiene and sanitation is poor.

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Sometimes, doctors feel pressured by their patients' expectations to prescribe an antibiotic. More than 50% of antibiotic prescriptions are given without any evidence that the illness being treated is due to a bacterial infection. Physicians often want to avoid costly and lengthly laboratory tests that would determine the cause of the illness. Antibiotics can not be used to treat illnesses caused by viruses, such as colds, influenza, and viral pneumonia. Of the 235 million doses of antibiotics consumed by humans per year, 20-50% of them are unnecessary.

Another factor that contributes to resistance is that when patients are prescribed antibiotics for a just cause, many do not finish their medication. This allows resistant bacteria to survive more easily. The practice of saving unused medication to treat themselves or others at a later date can also lead to resistant strains.

Also contributing to antibiotic resistance is the widespread use of antibiotics to promote weight gain and to control disease in cattle, pigs, and chickens. Forty to fifty percent of antibiotics produced are used in livestock feed. This leads to an inc(urticaria, anaphylaxis, interstitial nephritis, etc) to penicillins or cephalosporins. Cephalosporin antibiotics are classed as pregnancy category B.


Fluoroquinolones (fluoridated quinolones) are the newest class of antibiotics. Their generic name often contains the root "floxacin". They are synthetic antibiotics, and not derived from bacteria. Fluoroquinolones belong to the family of antibiotics called quinolones. The older quinolones are not well absorbed and are used to treat mostly urinary tract infections. The newer fluroquinolones are broad-spectrum bacteriocidal drugs that are chemically unrelated to the penicillins or the cephaloprosins. Because of their excellent absorption fluroquinolones can be adm

inistered not only by intravenous but orally as well.

Fluoroquinolones are used to treat most common urinary tract infections, skin infections, and respiratory infections (such as sinusitis, pneumonia, bronchitis).

Fluoroquinolones inhibit bacteria by interfering with their ability to make DNA. This activity makes it difficult for bacteria to multiply. This effect is bacteriocidal.

Commonly used fluoroquinolones include










Fluoroquinolones side effects:-

Fluoroquinolones are well tolerated and relatively safe. The most common side effects include nausea, vomiting, diarrhea, abdominal pain. Other more serious but less common side effects are central nervous system effects (headache, confusion and dizziness), phototoxicity (more common with lomefloxacin and sparfloxacin). All drugs in this class have been associated with convulsions. Fluoroquinolones are classed as pregnancy category C.


Tetracyclines got their name because they share a chemical structure that has four rings. They are derived from a species of Streptomyces bacteria. Tetracycline antibiotics are broad-spectrum bacteriostatic agents, that inhibit bacterial protein synthesis. Tetracyclines may be effective against a wide variety of microorganisms, including rickettsia and amebic parasites.

Tetracyclines are used in the treatment of infections of the respiratory tract, sinuses, middle ear, urinary tract, skin, intestines. Tetracyclines also are used to treat Gonorrhoea, Rocky Mountain spotted fever, Lyme Disease, typhus. Their most common current use is in the treatment of moderately severe acne and rosacea.

The most commonly prescribed tetracycline antibiotics are:





Tetracyclines side effects:-

Drugs in the tetracycline class become toxic over time. Expired drugs can cause a dangerous syndrome resulting in damage to the kidneys.

Common side effects associated with tetracyclines include cramps or burning of the stomach, diarrhea, sore mouth or tongue. Tetracyclines can cause skin photosensitivity, which increases the risk of sunburn under exposure to UV light. This may be of particular importance for those intending to take on holidays long-term doxycyline as a malaria prophylaxis. Rarely, tetracyclines may cause allergic reactions. Very rarely severe headache and vision problems may be signs of dangerous secondary intracranial hypertension.

Tetracycline antibiotics should not be used in children under the age of 8, and specifically during periods of tooth development. Tetracyclines are classed as pregnancy category D. Use during pregnancy may cause alterations in bone development.


The macrolide antibiotics are derived from Streptomyces bacteria, and got their name because they all have a macrocyclic lactone chemical structure. The macrolides are bacteriostatic, binding with bacterial ribosomes to inhibit protein synthesis. Erythromycin, the prototype of this class, has a spectrum and use similar to penicillin. Newer members of the group, azithromycin and clarithyromycin, are particularly

useful for their high level of lung penetration. Macrolide antibiotics are used to treat respiratory tract infections (such as pharyngitis, sinusitis, and bronchitis), genital, gastrointestinal tract, and skin infections.

The most commonly prescribed macrolide antibiotics are:







Macrolides side effects:-

Side effects associated with macrolides include nausea, vomiting, and diarrhea; infrequently, there may be temporary auditory impairment. Azithromycin has been rarely associated with allergic reactions, including angioedema, anaphylaxis, and dermatologic reactions. Oral erythromycin may be highly irritating to the stomach and when given by injection may cause severe phlebitis. Macrolide antibiotics should be used with caution in patients with liver dysfunction. Pregnancy category B: Azithromycin, erythromycin. Pregnancy category C: Clarithromycin, dirithromycin, troleandomycin.


Aminoglycoside antibiotics are used to treat infections caused by gram-negative bacteria. Aminoglycosides may be used along with penicillins or cephalosporins to give a two-pronged attack on the bacteria. Aminoglycosides work quite well, but bacteria can become resistant to them. Since aminoglycosides are broken down easily in the stomach, they can't be given by mouth and must be injected. Generally, aminoglycosides are given for short time periods.

The aminoglycosides are drugs which stop bacteria from making proteins. This effect is bacteriocidal.

The most commonly-prescribed aminoglycosides:







Aminoglycosides side effects:-

When injected, their side effects include possible damage to the ears and to the kidneys. This can be minimized by checking the amount of the drug in the blood and adjusting the dose so that there is enough drug to kill bacteria but not too much of it.

4. Working of antibiotics:- The work of an antibiotic is to kill the bacteria present in the human body or any other living animal. Bacteria after entering our system, uses the body as a host and starts to multiply, this gives rise to disease and infections. Antibiotics are drugs that can only be prescribed by licensed medical practitioners. So, how long do antibiotics take to work? Depending upon the seriousness of the infection and the potency of the antibiotic taken, the recovery time of an individual may range from a week to a whole month. Antibiotics kill the bacteria present in the body and also eliminate the disease. Antibiotics are supposed to target only the bacteria present in the body, and not the body cells. Hence, they are also referred to as 'selective poison'.

Each antibiotic works in its own special way, like some may suppress the bacteria's ability to convert glucose into energy that is required by them to multiply. Some antibiotics interfere with the formation of the bacterium's cell wall or other cell contents. These effects are typical to one type of antibiotic, called penicillin. Some antibiotics only stop the bacteria from multiplying, and leave it to our immune system to finish the job of killing the now-weakened bacteria. These drugs are referred to as bacteriostatic antibiotics. The function of these antibiotics is to halt the cell division of the bacteria nuclei. Some antibiotics stop the bacteria from generating the chemical required for their survival. However, there are a few that kill the bacteria. This type of antibiotics are referred to as bactericides.

5.Interection with drug:-

Contraceptive pills:-

It has been hypothesized that interference of some antibiotics with the efficiency of birth control pills is thought to occur in two ways. Modification of the intestinal flora may result in reduced absorption of estrogens. Second, induction of hepatic liver enzymes causing them to metabolize the pill's active ingredients faster may affect the pill's usefulness. However, the majority of studies indicate that antibiotics do not interfere with contraception. Even though a small percentage of women may experience decreased effectiveness of birth control pills

while taking an antibiotic, the failure rate is comparable to the failure rate of those taking the pill. Moreover,

there have been no studies that have conclusively demonstrated that disruption of the gut flora affects contraception. Interaction with the combined oral contraceptive pill through induction of hepatic enzymes by the broad-spectrum antibiotic rifampicin has been shown to occur. It is recommended that extra contraceptive measures are applied during antimicrobial therapy using these antimicrobials.


Interactions between alcohol and antibiotics vary depending on the specific antibiotic, and, in some cases, can cause severe side-effects and decreased effectiveness.

"It is sensible to avoid drinking alcohol when taking medication. However, it is unlikely that drinking alcohol in moderation will cause problems if you are taking most "common" antibiotics." However, there are specific types of antibiotics with which alcohol should be avoided completely, because of serious side-effects.

Because of the risks of side-effects and effectiveness, one should check the specific indications on the specific antibiotic, but there is no categorical danger in mixing alcohol and [some] antibiotics. Despite the lack of a categorical counterindication, the belief that alcohol and antibiotics should never be mixed is widespread, as indicated in a survey in one British clinic. One potential source of the myth is from STD

clinics in the 1950s and 1960s. Doctors gave the advice for moral reasons as they were worried that alcohol would reduce the inhibitions of sufferers and lead to further spread of diseases such as gonorrhea. It has been suggested, but not corroborated, that the origin of this myth centers on the fact that, during World War II, penicillin was in short supply and was recycled from urine; convalescing soldiers that drank beer produced a greater volume of urine, and, thus, were banned from drinking beer, leading to the belief that alcohol interacted poorly with antibiotics.

6.Antibiotic Resistance:-Antibiotics are extremely important in medicine, but unfortunately bacteria are capable of developing resistance to them. Antibiotic-resistant bacteria are germs that are not killed by commonly used antibiotics. When bacteria are exposed to the same antibiotics over and over, the bacteria can change and are no longer affected by the drug.

Bacteria have number of ways how they become antibiotic-resistant. For example, they possess an internal mechanism of changing their structure so the antibiotic no longer works, they develop ways to inactivate or neutralize the antibiotic. Also bacteria can transfer the genes coding for antibiotic resistance between them, 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 (e.g. antibiotics are not effective against infections caused by viruses), and when they are used widely as prophylaxis rather than treatment.

Resistance to antibiotics poses a serious and growing problem, because some infectious diseases are becoming more difficult to treat. Resistant bacteria do not respond to the antibiotics and continue to cause infection. Some of these resistant bacteria can be treated with more powerful medicines, but there some infections that are difficult to cure even with new or experimental drugs.

7.Why does antibiotics resistance occur:-

When bacteria are exposed to an antibiotic, they either die or adapt. Those that survive carry genes that protect them against the antibiotic and pass those genes on to other bacteria. The picture below illustrates an antibiotic-resistant bacterial cell. Since bacteria multiply very quickly and can be rease of resistant bacteria in these animals, which is then spread to humans.

8.Ways to prevent antibiotic resistance:-

Wash the right way. There is some concern that the triclosan in antibacterial soaps could lead to resistance, and it's not clear whether they're any more effective than scrubbing for 30 seconds with regular soap and water. Alco­hol and bleach are also effective surface cleaners that don't create resistance.

Buy organic. The antibiotics in the feed of some nonorganic farm animals may contribute to antibiotic resistance. Check your local farmers' markets and food co-ops for the best deals on organic milk and meat.

Don't take an antibiotic unless you absolutely have to. "We could probably cut our antibiotic use by 70% if people only took them when they are absolutely necessary," says Louis Rice, MD, an expert on resistant bugs and chief of medical service at Louis Stokes Cleveland VA Medical Center. With some illnesses that typically go away on their own, like ear infections and sinus infections, you can practice what docs call watchful waiting-get the prescription, but don't fill it unless the condition persists.

Ask for the shortest course of antibiotics. "The optimal length of antibiotic use for most illnesses may be much less than the current recommendations," Dr. Rice says. "There might be a three-day course or a seven-day course that is equally effective as a longer one." For example, when doctors studied treatments for urinary-tract infections, they found that 87% cleared up with a single dose of antibiotics and 94% were cured with a three-day course.

8.Reaction of cats with antibiotics:-

Feline antibiotics are generally lower dosages of human antibiotics, so you probably recognize the name of the medication when your cat's vet hands over the prescribed drugs. The FDA has approved certain human medications for extra-label use in animals because their effectiveness in treating human illnesses extends to cats and other animals as well. Therefore, vets prescribe the same antibiotics we take to felines when they have a bacterial infection that needs healing.


Antibiotics function to effectively destroy the unwanted bacteria causing the infection in the cat's body. They accomplish this one of two ways: they either kill the infective bacteria, or they disable its ability to reproduce, putting a stop to the cyclical spread of bacterium. The cat's body is better able to react to the unwanted infection and fight it offonce the bacteria are destroyed or suppressed.


Antibiotics are prescribed if the cat is suffering from an ear or eye infection, urinary tract or bladder infection, skin infections, respiratory infection or the infectious disease, ehrlichiosis, which is contracted by tick bites, according to VetInfo.com. The cat may need antibiotics from the penicillin class (such as amoxicillin, oxacillin or ticarcillin), aminoglycosides, cephalosporins, tetracyclines or erythromycins depending on the type of infection.


The cat is already sensitive because its body is reacting to the infection itself, but it may react to the antibiotic as well. Side effects of antibiotics include vomiting, diarrhea, weight loss, allergies (including rashes and facial swelling), fever, kidney or liver damage (compromised liver function may be marked with jaundice), light sensitivity, loss of fur and bloody stool. The cat should be taken back to the vet if it has any of these reactions to the prescribed antibiotics.


A pregnant or nursing cat's reaction to an antibiotic extends beyond herself to her kittens. Consequently, should the mother cat become ill with a bacterial infection, she may not be able to take antibiotics as they are dangerous to the offspring. In particular, PetEducation.com calls out erythromycins and tetracyclines as dangerous to the queen and her kittens. These medications may not only cause a bad reaction in the queen, but they may severely harm her unborn fetuses or nursing kittens.


All cats react differently to medication and using antibiotics to fight infection might, ultimately, become an issue of the good outweighing the bad. As VetInfo.com explains, the key is diagnosing the type of bacterial strain causing the infection and prescribing the appropriate antibiotic to combat it. With this ammunition in hand, the vet can prescribe an antibiotic that will not only ease the cat's reaction to the infection, but hopefully not cause any additional negative reactions