Today, around 5,000 bacteria have been classified by microbiologists. Unfortunately, this number barely accounts for the millions of bacteria that supposedly exist. Bacteria are known to interact with other organisms. These symbiotic interactions include commensalism, mutualism and parasitism. Of the three, parasitic interactions cause bacterial infections. Bacterial infections, if untreated, can cause serious health complications such as chronic wounds, gangrene, amputation of infected limb and worse, even death. General symptoms of infection may include high fever, pains, swelling, chills, tiredness and sometimes, discharge of white or yellowish substance. Diagnosis of bacterial infection can be done by taking a sample of the person’s blood and checking for changes in the white blood cell (WBC) count. An increase in WBC usually indicates a bacterial infection. Medical practitioners then prescribe antibiotics to treat the bacterial infection. Belonging to the group of antimicrobials, drugs specifically intended for killing bacteria that cause infection in any living thing are commonly known as antibiotics. Most antibiotics have been derived from microorganisms as products of secondary metabolism. But certain antibiotics are purely synthetic; particularly those used as chemotherapeutic agents. Although many antibiotics are used to kill a large range of bacteria, certain antibiotics are categorized based on the type of bacteria they kill: Gram-negative or Gram-positive. Their effects on bacteria are also classified into two: bactericidal or bacteriostatic. Bactericidal effects involve killing the target bacteria, while bacteriostatic merely prevents the target bacteria from multiplying, leaving the killing to the person’s immune system. Producing antibiotics has become challenging for pharmaceutical companies. Bacteria are screened, cultured and tested to see if they produce any anti-microbial products. They must be tested for possible toxicities and mode of therapeutic actions. A rational design program is being used today to make this approach simpler. This program involves screening of natural products that inhibit specific, rather than general targets. Industrial production of antibiotics involves fermentation of bacteria in a growth medium. The bacteria are also supplied with the right amount of oxygen, temperature, nutrients and pH levels, to enhance growth. The antibiotics produced are extracted and then purified, converting them to crystalline substances. The wild type of bacteria is seldom used in fermentation. Microbiologists resort to genetic modification of these bacteria to produce large amounts of antibiotics. Such genetic modification involves the introduction of mutagen or mutation-causing substances like chemicals and x-rays. Recently, gene amplification has become useful in antibiotic production. Copies of the gene that codes for the specific proteins responsible for antibiotic production are produced and put back into the bacterial cell. For your guidance, antibiotics are classified into: § Aminoglycosides: used primarily on infections caused by Gram-negative bacteria such as Pseudomonas, Acinetobacter and Enterobacter. These include intraabdominal infections, urinary tract infections, septicemia and nosocomial or secondary infections. Antibiotics belonging under this class are Amikacin, Gentamycin, Neomycin and Streptomycin. § Cephalosporins: derived from Cephalosporium acremonium, these antibiotics have bactericidal effects on both Gram-positive and Gram-negative bacteria. They disrupt the peptidoglycan synthesis in bacterial cell walls, thus rendering the bacteria defenseless against attacks from the body’s immune system. These antibiotics are grouped into generations based on their antibacterial properties. Examples of antibiotics under this class are Cephalexin, Cefaclor, Cefdinir, and Cefepime. § Macrolides: antibiotics under this classification are generally used for streptococcal infections, respiratory infections, syphilis, mycoplasmal infections and for Lyme disease. These antibiotics include Clarithromycin, Erythromycin and Azithromycin. § Penicillins: discovered by Alexander Fleming in 1928, penicillin is derived from the mold Penicillium chrysogenum. These antibiotics treat a wide range of infection including syphilis, streptococcal infections and Lyme disease. § Quinolones: prescribed to treat urinary tract infections, bacterial diarrhea, gonorrhea and urinary tract infections, these antibiotics include Ciprofloxacin, Levofloxacin and Ofloxacin. § Sulfonamides: commonly used to treat urinary tract infections. Bactrim, Sulfasalazine and Trimethoprim are some example of antibiotics under this classification. § Tetracyclines: generally treats chlamydial infections, syphilis, Lyme disease, mycoplasmal infections, acne and rickettsial infections. These include Clindamycin, Chloramphenicol and Isoniazid. Like any other drugs, antibiotics have possible side effects like fever, nausea and the most common, allergic reactions. Broad spectrum antibiotics also kill non-target bacteria or those bacteria referred to as probiotics. In the intestines, probiotic bacteria aid in the digestion by secreting enzymes. On the other hand, bacteria found in the vaginal area regulate pH balance and growth of harmful organisms like yeast. You should only take antibiotics prescribed by licensed doctors and only after undergoing diagnostic tests. Taking the wrong antibiotics causes bacteria to develop resistance to the drug. In the United States, the use of drugs on animals such as chicken, pigs and cattle has created antibiotic-resistant bacteria. The discovery of fluroquinolone-resistant Campylobacter infections in humans has ended the debate between the Food and Drug Administration and pharmaceutical companies that supplies non-therapeutic antibiotics. 

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