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Antibiotic resistance develops through mutation or plasmid exchange between bacteria of the same species. If a bacterium carries several resistance genes, it is called multiresistant or, informally, a superbug.
Antibiotic resistance is a consequence of evolution via natural selection. The antibiotic action is an environmental pressure; those bacteria which have a mutation allowing them to survive will live on to reproduce. They will then pass this trait to their offspring, which will be a fully resistant generation.
Several studies have demonstrated that patterns of antibiotic usage greatly affect the number of resistant organisms which develop. Overuse of broad-spectrum antibiotics, such as second and third generation cephalosporins, greatly hastens the development of methicillin resistance, even in organisms that have never been exposed to the selective pressure of methicillin per se. Other factors contributing towards resistance include incorrect diagnosis, unnecessary prescriptions, improper use of antibiotics by patients, and the use of antibiotics as livestock food additives for growth promotion.
Staphylococcus aureus (colloquially known as "Staph aureus") is one of the major resistant pathogens. Found on the mucous membranes and the skin of around a third of the population, it is extremely adaptable to antibiotic pressure. It was the first bacterium in which penicillin resistance was found -- in 1947, just four years after the drug started being mass-produced. Methicillin was then the antibiotic of choice. MRSA ( methicillin-resistant Staphylococcus aureus) was first detected in Britain in 1961 and is now "quite common" in hospitals. MRSA was responsible for 37% of fatal cases of blood poisoning in the UK in 1999, up from 4% in 1991. Half of all S. aureus infections in the US are resistant to penicillin, methicillin, tetracyclineThis article deals with the specific Tetracycline antibiotic. For the group of antibiotics know as the Tetracyclines, see Tetracycline_antibiotics. Tetracycline is an antibiotic produced by the streptomyces bacterium, indicated for use against many bacter and erythromycinErythromycin is a macrolide antibiotic which has an antimicrobial spectrum similar or slightly wider to that of penicillin, and is often used for people who have an allergy to penicillins. For respiratory tract infections, it has better coverage of atypic.
This left vancomycinVancomycin is an antibiotic used in the prophylaxis and treament of infections caused by Gram-positive bacteria. It is a branched tricyclic glycosylated nonribosomal peptide produced by the fermentation of the actinomycete bacteria Amycolatopsis orientali as the only effective agent available at the time. A new class of antibiotics, oxazolidinone s, became available in the 1990s, and the first commercially available oxazolidinone, linezolidLinezolid is a synthetic systemic antibiotic drug. It was the first commercially available oxazolidinone antibiotic and is usually reserved for the treatment of serious bacterial infections where older antibiotics have failed due to antibiotic resistance., is comparable to vancomycin in effectiveness against MRSA. However, VRSA ( Vancomycin-resistant Staphylococcus aureusVancomycin-resistant Staphylococcus aureus (VRSA) is a strain of Staphylococcus aureus that has become resistant to the glycopeptide antibiotic vancomycin. With the increase of staphylococcal resistance to methicillin, vancomycin (or teicoplanin) is often) was first identified in Japan in 1997 and has since been found in hospitals in England, France and the US.
VRSA is also termed GISA (glycopeptide intermediate Staphylococcus aureus) or VISA (vancomycin intermediate Staphylococcus aureus), indicating resistance to all glycopeptide antibiotics.
Enterococcus faeciumEnterococcus is a bacterium, of the phylum Firmicutes. They are round gram-positive cells which occur in pairs and are difficult to distinguish from Streptococcus''. Two species are common commensal organisms in the intestines of humans: E. faecalis and E is another superbug found in hospitals: penicillin resistance was seen in 1983, vancomycin resistance (VRE) in 1987 and linezolidLinezolid is a synthetic systemic antibiotic drug. It was the first commercially available oxazolidinone antibiotic and is usually reserved for the treatment of serious bacterial infections where older antibiotics have failed due to antibiotic resistance. resistance (LRE) in the late 1990s.
Penicillin-resistant pneumoniaPneumonia is defined as an infection involving the alveoli of the lungs. It occurs in patients of all age groups, but young children and the elderly, as well as immunocompromised and immune deficient patients, are especially at risk. Causal therapy is wit (or pneumococcus, caused by Streptococcus pneumoniae) was first detected in 1967, as was penicillin-resistant gonorrhea. Resistance to penicillin substitutes is also known beyond S. aureus. By 1993 Escherichia coli was resistant to five fluoroquinolone variants. Mycobacterium tuberculosis is commonly resistant to isoniazid and rifampin and sometimes universally resistant to the common treatments. Other pathogens showing some resistance include Salmonella, Campylobacter, and Streptococci.
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