Types of Antibiotics

The great number of diverse antibiotics currently available can be classified in different ways, e.g., by their chemical structure, their microbial origin, or their mode of action. They are also frequently designated by their effective range. Tetracyclines, the most widely used broad-spectrum antibiotics, are effective against both Gram-positive and Gram-negative bacteria, as well as against rickettsias and psittacosis-causing organisms (see Gram's stain). Ciprofloxacin (Cipro) is another broad-spectrum antibiotic, effective in the treatment of mild infections of the urinary tract and sinuses. The medium-spectrum antibiotics bacitracin, the erythromycins, penicillin, and the cephalosporins are effective primarily against Gram-positive bacteria, although the streptomycin group is effective against some Gram-negative and Gram-positive bacteria. Polymixins are narrow-spectrum antibiotics effective against only a few species of bacteria.

Administration and Side Effects

Antibiotics are either injected, given orally, or applied to the skin in ointment form. Many, while potent anti-infective agents, also cause toxic side effects. Some, like penicillin, are highly allergenic and can cause skin rashes, shock, and other manifestations of allergic sensitivity. Others, such as the tetracyclines, cause major changes in the intestinal bacterial population and can result in superinfection by fungi and other microorganisms. Chloramphenicol, which is now restricted in use, produces severe blood diseases, and use of streptomycin can result in ear and kidney damage. Many antibiotics are less effective than formerly because antibiotic-resistant strains of microorganisms have emerged (see drug resistance).

Nonmedical Use

Antibiotics have found wide nonmedical use. Some are used in animal husbandry, along with vitamin B12, to enhance the weight gain of livestock. However, some authorities believe the addition of antibiotics to animal feeds is dangerous because continuous low exposure to the antibiotic can sensitize humans to the drug and make them unable to take the substance later for the treatment of infection. In addition low levels of antibiotics in animal feed encourage the emergence of antibiotic-resistant strains of microorganisms. Drug resistance has been shown to be carried by a genetic particle transmissible from one strain of microorganism to another, and the presence of low levels of antibiotics can actually cause an increase in the number of such particles in the bacterial population and increase the probability that such particles will be transferred to pathogenic, or disease-causing, strains. Antibiotics have also been used to treat plant diseases such as bacteria-caused infections in tomatoes, potatoes, and fruit trees. The substances are also used in experimental research.

Production of Antibiotics

The mass production of antibiotics began during World War II with streptomycin and penicillin. Now most antibiotics are produced by staged fermentations in which strains of microorganisms producing high yields are grown under optimum conditions in nutrient media in fermentation tanks holding several thousand gallons. The mold is strained out of the fermentation broth, and then the antibiotic is removed from the broth by filtration, precipitation, and other separation methods. In some cases new antibiotics are laboratory synthesized, while many antibiotics are produced by chemically modifying natural substances; many such derivatives are more effective than the natural substances against infecting organisms or are better absorbed by the body, e.g., some semisynthetic penicillins are effective against bacteria resistant to the parent substance.

History

Although for centuries preparations derived from living matter were applied to wounds to destroy infection, the fact that a microorganism is capable of destroying one of another species was not established until the latter half of the 19th cent. when Pasteur noted the antagonistic effect of other bacteria on the anthrax organism and pointed out that this action might be put to therapeutic use. Meanwhile the German chemist Paul Ehrlich developed the idea of selective toxicity: that certain chemicals that would be toxic to some organisms, e.g., infectious bacteria, would be harmless to other organisms, e.g., humans.

In 1928, Sir Alexander Fleming, a Scottish biologist, observed that Penicillium notatum, a common mold, had destroyed staphylococcus bacteria in culture, and in 1939 the American microbiologist René Dubos demonstrated that a soil bacterium was capable of decomposing the starchlike capsule of the pneumococcus bacterium, without which the pneumococcus is harmless and does not cause pneumonia. Dubos then found in the soil a microbe, Bacillus brevis, from which he obtained a product, tyrothricin, that was highly toxic to a wide range of bacteria. Tyrothricin, a mixture of the two peptides gramicidin and tyrocidine, was also found to be toxic to red blood and reproductive cells in humans but could be used to good effect when applied as an ointment on body surfaces. Penicillin was finally isolated in 1939, and in 1944 Selman Waksman and Albert Schatz, American microbiologists, isolated streptomycin and a number of other antibiotics from Streptomyces griseus.

Generations of Cephalosporin Antibiotic Medications

Cephalosporins are one of the classes of antibiotic medications which are the most often prescribed. By their structure these medications related to the penicillin antibiotics. These drugs work by interfering the synthesis of the cell walls of bacteria which results in killing the bacteria.

The first Cephalosporin drug was manufactured by a pharmaceutical company Eli Lilly in 1964.

Mechanism of action vCephalosporins are antibacterial substances which have the same action as other beta-lactam antibiotic medications including penicillins. Bacterial cells have cell walls which protect them and they are necessary for the bacteria to survive. Cephalosporins inhibit the synthesis of cell walls of bacteria damaging the walls which eventually results in the bacteria to die.

Adverse effects

Typically, Cephalosporin antibiotic medications cause few adverse effects. Among typical adverse effects are those related to the digestive system including mild gastric colic or upset stomach, diarrhea, nausea, and vomiting. Usually, these side reactions are mild and go away soon. In some cases Cephalosporins might provoke increasing amount of fungus which normally present in our body. If it occurs, you might experience such symptoms as a sore tongue and mouth, or vaginal yeast infections.

Cephalosporins might also provoke more complicated but rarely occurred adverse reactions such as black, tarry stools, fever, painful or difficult urination, chest pain, allergy, or serious colitis.

People who are allergic to penicillins can also have an allergy to Cephalosporins as both of the classes of antibiotics have similar structures, and hence effects.

Cephalosporin antibiotic medications are indicated for dealing with bacterial infections. Cephalosporins are divided into several generations.

First generation cephalosporin antibiotics are efficient in killing gram-positive bacteria and following generations of these antibiotics work effectively against gram-negative bacteria.

In comparison with gram-positive bacteria, gram-negative bacteria have a unique external membrane that actually doesn’t allow a number of medications to affect them, making these bacteria more resistant to antibiotic medications. Besides, gram-positive bacteria typically develop a resistance to the antibiotics more slowly.

Cephalosporin antibiotic medications are used for the managing of a wide range of infections provoked by bacteria including respiratory tract infections such as pneumonia, bronchitis, strep throat, tonsillitis, skin as well as urinary tract infections. In some cases these medications are used with other antibiotics. Cephalosporins can be also applied in preventive purposes before, during, and after surgery.

Classification of Cephalosporin antibiotic medications

As it has been mentioned above, Cephalosporin antibiotics are divided into generations according to their range of antimicrobial action. Each newer generation of these antibiotics has considerably greater gram-negative antimicrobial effects than the foregoing generation.

Cephalosporin antibiotics of the first generation

The first generation cephalosporin antibiotics are the agents of a moderate spectrum action. They work effectively against staphylococcal and streptococcal infections, so they can be used in treating skin and soft-tissue infections. The first generation cephalosporin antibiotics include: Cefadroxil, Cephalexin, Cephalothin, Cephaloridine, Cefazolin, Cephapirin, and Cephradine.

Cefazolin is the most widely used cephalosporin antibiotic of the first generation.

Cephalosporin antibiotics of the second generation

Cephalosporins of this generation possess a stronger gram-negative spectrum of action. These medications can be used for managing upper and lower respiratory passages infections. They are also effective against E. coli, Klebsiella and Proteus, so can be effectively used in managing urinary tract infections provoked by these bacterial agents.

This generation of Cephalosporins includes such drugs as: Cefaclor, Cefoxitin, Cefprozil, and Cefuroxime.

Cefoxitin is an antibiotic of the second generation of cephalosporins with anaerobic activity. This drug is not really frequently used as a therapeutic agent, but can be effectively used as a preventive treatment in gastrointestinal surgery.

Cephalosporin antibiotics of the Third generation

Third generation cephalosporin antibiotic medications have a broad spectrum of action and an increased effectiveness against gram-negative bacteria. Some drugs of this group especially those coming in an oral form have decreased effectiveness against gram-positive bacteria. The parenteral Cephalosporin antibiotic medications of the third generation such as ceftriaxone and Cefotaxime have high effectiveness against Streptococcus pneumoniae, including those that have developed the resistance to penicillin. These drugs effectively work against N. gonorrhoeae. Such drug as Ceftazidime has an antipseudomonal activity. Among this group of drugs are the following: Cefdinir, Cefixime, Cefpodoxime, Ceftibuten, Ceftriaxone and Cefotaxime.

Cephalosporin antibiotics of the Fourth generation

These antibiotics have an extended spectrum of action against bacteria. They have a similar effect on gram-positive bacteria as first generation cephalosporin antibiotics. These drugs also possess a greater resistance to beta-lactamases thin comparison with the third generation of these drugs. Many of the drugs of this group are effective in managing meningitis.

Cefepime, an antibiotic of this group, has broad gram-negative action with increased effectiveness against pseudomonas and lesser activity against pneumococci. Cefpirome medication has just the opposite effect to Cefepime drug: it is more effective against pneumococci and has lesser level of effectiveness against pseudomonas. The fourth generation cephalosporin antibiotics includes such drugs as Cefepime, Cefozopran, Cefluprenam, Cefpirome, and Cefquinome.