Health Information and Tips

molecular mechanism of drug resistance drug resistance is to reduce the effectiveness of a drug in the treatment of a disease or improve patient symptoms. If the drug is not intended to inhibit or kill a pathogen, the term is synonymous with failure or tolerated dose of drugs. Most often, the term is due in part by disease pathogens. Pathogens are said to be drug resistant when the drugs mean less to neutralize its effect. If an organism is resistant to several drugs, it is its multi-resistant. Drug resistance is an example of the evolution of micro-organisms. People who are not vulnerable to the effects of drugs capable of surviving drug treatment, and therefore have a greater ability than susceptible individuals. Through the process of natural selection, more resistant traits in the offspring later, which is selected in a resistant population. The multidrug resistance or multidrug resistance is a condition for a pathogen resistant to various drugs or chemicals from a variety of structure and function to the elimination of the target organism. organizations of resistance that can display multiple pathological cells, including bacteria and neoplastic (tumor) cells. Cross-resistance is tolerance to a toxic substance usually as a result of exposure to a similar active substance. Is a phenomenon that pesticides and antibiotics. For example, rifabutin and rifapin crossreactivity in the treatment of tuberculosis. Several micro-organisms to survive for thousands of years by their being able to adapt to antimicrobial agents. They do it by spontaneous mutation or by DNA transfer. This very process that some bacteria are able to resist the attack of certain antibiotics, making antibiotics ineffective. These micro-organisms use several mechanisms to achieve multidrug resistance: remove more than one cell wall glycoprotein enzymatic inactivation of antibiotics increasingly permeability of cell wall antibiotics destinations Altered mechanisms of antibiotic efflux antibiotics mutation rate increased in response to stress, many different bacteria, now show multidrug resistance, including staphylococci, enterococci, gonococci, streptococci, salmonella, Mycobacterium tuberculosis and others. In addition, some resistant bacteria are able to make copies of the DNA codes of a mechanism of resistance to other bacteria, which creates resistance against their neighbors, who were then transferred to the situation on the passport resistance genes. To ensure the development of resistance to antibiotics, you must: Use antibiotics only for bacterial infections caused by the pathogen, if possible, use the right antibiotic, and not on a wide range of antibiotics depending on when antibiotics do not stop the decision to relieve the symptoms, which of course not all antibiotics for most colds, coughs, bronchitis, sinusitis and eye infections caused by viruses. He argues that the legislation is fit to raise awareness of the increasing importance of the restrictive use of antibiotics, not only for clinical use rights, but also for the treatment of animals to aid human consumption. Causes and risk factors, such as the chart available to the antibiotic produced by natural selection. The upper part represents a population of bacteria from exposure to an antibiotic. The middle section shows the population directly after exposure, the phase that took place in the selection. The final section presents the distribution of resistance to a new generation of bacteria. The legend indicates the resistance levels of the individual. Resistance to antibiotics by horizontal gene transfer can, and the link between mutations in the genome of the pathogen and a rate of about 1108 for chromosomal replication. The antibiotic activity against the pathogen can be considered as pollution of the environment, bacteria that survive a change so they can live to reproduce. They were then sent to the property to their descendants, resulting in a fully resistant colony. Several studies have shown that patterns of antibiotic use influence on the number of resistant organisms to develop some. Overuse of broad spectrum antibiotics such as cephalosporins of second and third, have greatly accelerated the development of resistance to methicillin. Other factors contributing to resistance include incorrect diagnosis, unnecessary prescriptions, improper use of antibiotics in patients, the infiltration of household items and toys with low levels of antibiotics and administration of antibiotics Animal Farm by mouth to sustain growth. So unhealthy practices in the pharmaceutical industry can contribute to the likelihood of creating antibiotic resistant strains. Researchers have recently demonstrated the bacterial protein LexA may play a key role in the acquisition of bacterial mutations. Drug resistance occurs in many classes of pathogens: bacteria, viruses, parasites are resistant to antibiotics antiviral mechanisms mushrooms cancer, four main mechanisms by which microorganisms exhibit resistance to antimicrobial agents: drug inactivation or modified E. g. enzymatic inactivation of penicillin G in bacteria resistant to penicillin by the production of?-lactamases. modified antibiotic is the best known: the resistant bacteria will retain the same target sensitive antibiotic sensitive strains, but the antibiotic can not reach. This occurs for example with the lactamase enzyme lactamase cleaves four-membered ring lactam, which inactivates antibiotics. describes over 200 species of lactamase was (Table). Most lactamases act to some extent against penicillins and cephalosporins, while others are more specific, namely AmpC (found, for example, an AmpC enzyme in Enterobacter spp) or penicillinase (such as Staphylococcus aureus penicillinase). Lactamases are many types of bacteria (both Gram positive and Gram-negative) and have different degrees of inhibition by lactamase inhibitors clavulanic as widespread. Change the target site: the change g. E. the site of a binding target PBP penicillins MRSA and other bacteria resistant to penicillin. Changes in the primary site of action may mean that the antibiotic enters the cell and reaches the target site is unable to inhibit the activity of the target because of structural changes in the molecule. Enterococci also naturally resistant to cephalosporins because the enzymes responsible for synthesis of cell wall (peptidoglycan polymer production are taken into account), known as penicillin binding proteins have low affinity for them and therefore are not inhibited. Most strains of Streptococcus pneumoniae are highly susceptible to penicillins and cephalosporins, but the DNA from other bacteria, the enzyme is altered so that they develop a low affinity for penicillins and hence resistant to inhibition by purchase to penicillin. The enzyme synthesis of peptidoglycan changed yet, but he now has a different structure. Mutants of Streptococcus pyogenes that are resistant to penicillin and penicillin-modified proteins Express selected in the laboratory but they were not observed in patients, probably because of binding cell wall protein is more anti- phagocytic M. Alteration of metabolic pathway: E. g. some bacteria resistant to sulfonamides does not require para-amino benzoic acid, (PABA), an important precursor for the synthesis of folic acid and nucleic acids in bacteria inhibited by sulfonamides. Instead, like mammalian cells, they turn to using preformed folic acid. efflux rapid efflux pump is a mechanism for the extrusion of toxic substances and antibiotics outside the cell, it must be regarded as an essential component of xenobiotics. This mechanism is important in medicine, how it can contribute to bacterial resistance to antibiotics. efflux systems function on an energy-dependent mechanism (active transport of the pump), toxic reactions in specific efflux pumps. Some systems are efflux of specific drugs, while others may take several drugs, thus contributing to bacterial multidrug resistance (MDR). There are three known mechanisms of resistance to fluoroquinolones. Some types of efflux pumps can act to reduce the intracellular concentration of quinolones. In Gram-negative bacteria producing plasmid resistance genes, proteins can bind to DNA gyrase, protecting them against the effects of quinolones. Finally, mutations in the most important sites of DNA gyrase and topoisomerase IV quinolone-binding affinity lower, reducing the effectiveness of the drug.

Bacterial efflux pumps are transport protein in the cytoplasmic membrane of all cell types located. They are active transporter means they need a source of chemical energy to perform its function. Some carriers are active mainly use adenosine triphosphate hydrolysis as an energy source, while other secondary active transporter (uniporter, symporter or antiporters) in which the transport of an electrochemical potential difference by pumping the hydrogen or sodium ions is produced outside the cell are coupled. Bacterial efflux carriers are used in five major superfamilies, the amino acid sequence and source of energy from their substrates export: The major facilitator superfamily (MFS) superfamily of ATP-binding cassette (ABC) small multidrug resistance family ordered (SMR) superfamily division resistance nodule cells (RND) and the Multi family proteins antimicrobial extrusion (MATE). Of these, only the superfamily of ABC transporters are primary, the rest is secondary to proton or sodium gradient as carriers of energy. Although MFS is dominant in Gram-positive, the RND family is unique to Gram-negative. In case of Pseudomonas aeruginosa resistant to imipenem, the absence of specific D2 porin confers resistance, as imipenem could not enter the cell. This mechanism is also observed with a low resistance to fluoroquinolones and aminoglycosides. Increase efflux pump requiring transport of energy is an established practice of resistance to tetracyclines and is encoded by a wide range of genes that tet (A) which is distributed in Enterobacteriaceae. Although antibiotics are clinically important feature of substrates of efflux systems, it is likely that most efflux pumps have different natural physiological functions. Examples: the bacterium E. coli AcrAB efflux system, a physiological role of pumping bile acids and fatty acids for their toxicity is lower. The MFS family Ptr pump in Streptomyces pristinaespiralis autoimmunity seems to be a pump for this organization when it turns on production of pristinamycin I and II AcrAB TolC system in E. coli is suspected of having a role in the transport of calcium channel components of the bacterium E. coli cone. MtrCDE system plays a protective role in the resistance in fecal lipids gonorrhoeae rectal isolates of Neisseria. The AcrAB efflux system of Erwinia amylovora is important for the virulence of this organism, plant (host), colonization and resistance against toxins in plants. The efflux system capacity, a large number of compounds that can be seen other than their natural substrates, probably because the recognition of substrate on physicochemical properties such as hydrophobicity, aromaticity and ionizable nature based only defined chemical properties, as in music recognition enzyme-substrate or ligand-receptor. Because most antibiotics are amphiphilic molecules recognized – both hydrophilic and hydrophobic character, they are easily accessible from many efflux pumps. Impact on antimicrobial resistance, the effects of efflux mechanisms of resistance to antimicrobials is high, this is usually the result: the genetic elements coding for efflux pumps are on the chromosomes and / or plasmids, thus contributing to both intrinsic (naturally coded) and acquired resistance, or as an important mechanism of resistance genes of efflux pump can survive a hostile environment (for example, in the presence of antibiotics), for selection of mutants , which allows over-express these genes. Its genetic elements such as transposons or plasmids transpoable is also advantageous for micro-organisms, because it facilitates the sharing of genes between distant species efflux. Antibiotics may act as inducers and regulators of the expression of some efflux pumps. Expression of efflux pumps in several specific bacteria can cause a wide spectrum of resistance when the common substrates of several efflux pumps, which can efflux pump resistance against a broad spectrum of antibiotics lead to action. Molecular epidemiology of resistance genes for resistance in bacteria can be intrinsic or acquired. Intrinsic resistance is a natural feature of the biology of the organism, eg resistance to vancomycin, in Escherichia coli. Acquired resistance occurs when the bacterium is sensitive to antibiotic resistance by mutation of what can be done or created by the acquisition of new DNA. The mutation is a spontaneous event, regardless of whether antibiotics are produced there. A bacterium carries such a mutation is a big advantage that the sensitive cells are quickly destroyed by the antibiotic, so that a resistant subpopulation. Transferable resistance was recognized in 1959 when resistance genes in Shigella plasmid-borne E. coli. Plasmids are circular pieces of self-reproducing DNA, smaller than the bacterial genome encoding the replication through their transfer to another bacterial strain or species. can transport and transfer of multiple resistance genes that can on a section of DNA that can transfer from one plasmid to another or into the genome of a transposon (or “jumping genes”). Since the spectrum of bacteria, plasmids can spread is often limited transposons are important in the dissemination of resistance genes across borders. mecA gene in MRSA may have been acquired by transposition. plasmid evolution can be complex, but modern molecular techniques can provide a understanding (as is the case with plasmids containing FiltreteTM gonorrhoeae gene and are all over the world Neisseria) found. bacteriophages (viruses that infect bacteria) can also transfer resistance, which is often seen in staphylococci. When the bacteria die, they release DNA, which can be taken by competent bacteria, a process known as transformation. This process is more important than detected for the environment and is probably pneumoniae is the most important pathway for the spread of penicillin resistance in Streptococcus, through the creation of mosaic penicillin binding protein gene. origins of resistance genes, origins of antibiotic resistance genes are not known, because at the time that antibiotics were the biochemical and molecular basis of resistance has been established, not yet discovered. bacteria collected 1914-1950 (Murray collection) have later been found fully sensitive to antibiotics. They have, however, contain A number of plasmids No conjugation was able to strains resistant to sulfonamides, Murray reported, although in the mid-1930s had been imported, resistance was in the early 1940s streptococci and gonococci. The introduction of streptomycin in the treatment of tuberculosis thwarted by the rapid development of resistance by mutation of target genes. mutation is now recognized as the most common mechanism of resistance of Mycobacterium tuberculosis and the molecular nature of mutations of resistance to most drugs against tuberculosis is now known. beneficial mutations occur in bacteria, can be mobilized by insertion sequences and transposons on plasmids and transferred to different bacterial species. Given the growth and spread of resistance genes antibiotic, it is important to the speed of bacterial growth and the continuous exchange of bacteria in animals to estimate human and agricultural hosts throughout the world. It supports the idea that the determinants antibiotic resistance is not observed at the bacterial host, in the opinion of the resistance plasmid. DNA sequencing studies lactamases and aminoglycoside inactivating enzymes derived show that despite the similarities in the protein studies could the two families, there are significant sequence differences. Since the time of evolution must be under 50 years can not possibly be held, one in which evolution by mutation of genes are single common ancestor derived. you have to pull from a large and diverse gene pool probably already present in the environment of bacteria. Many bacteria and fungi that produce antibiotics possess resistance determinants that are similar to those found in clinical bacteria . exchanging genes may occur in the soil or, more likely, in the intestines of humans or animals. It was discovered that commercial antibiotic preparations containing DNA of the organism and the production of gene sequences antimicrobial resistance can help the polymerase chain reaction identified. or genes already exist in nature or may occur rapidly changing. rapid change was found with (a) TEM-lactamase, leading to a longer profile of substrate the third generation cephalosporins (first report to be in Athens in 1963, one year after the introduction of ampicillin) and (b) of IMI-1 lactamase (a California hospital reported approved before imipenem for use in the U.S.). The selection pressure is heavy, and inadequate use of antibiotics, mainly in medical practice probably responsible, although agriculture and veterinary use contributes to the resistance in pathogenic to man. The addition of antibiotics, food or water, whether for growth promotion or, more importantly, for the treatment or prevention of mass (or treatment and prophylaxis) in animals on factory farms is an unquantified effect on the levels of resistance. bacteria clearly a wonderful array of biochemical and genetic systems for the development and spread of antibiotic resistance. resistance mechanism including some antibiotics important first resistance to ß-lactam ß-lactam to a family of antibiotics, beta-lactam ring. penicillins, cephalosporins, clavams is (or oxapenams) are cephamycins and carbapenems members of this family. The integrity of the ß ring -lactam antibiotics is essential for the activity that leads to the inactivation of a number of transpeptidase that catalyze the final reaction of crosslinking of peptidoglycan synthesis events. resistance to beta-lactam antibiotics in clinical isolates is mainly due to hydrolysis the antibiotic with a beta-lactamase. mutational following modification of the PBP (penicillin-binding proteins) or cell permeability may also lead to ß-lactam resistance. ß-lactamases are a heterogeneous group of enzymes. Several classifications have been proposed for their hydrolytic spectrum, susceptibility to inhibitors, genetic localization (plasmid or chromosome), gene or protein sequence of amino acids. The functional classification of ß-lactamases of Bush, Jacoby and Medeiros hit ( 1995) has identified four groups according to their substrate and inhibitor profiles. AmpC is a group that is not inhibited by clavulanic acid, group 2 penicillinase, cephalosporinase and broad-spectrum ß-lactamases, which are generally inhibited by site Active-directed inhibitors of ß-lactamase Group 3 Metallo-beta-lactamase, penicillins, cephalosporins and carbapenem hydrolyzing and are poorly inhibited by almost all molecules containing beta-lactam antibiotics, Group 4 penicillinases not inhibited by acid clavulanic. subgroups have also been price fixed by the hydrolysis of carbenicillin and cloxacillin (oxacillin) in group 2 penicillinase. The first classification by Ambler (1980) and introduced on the basis of the amino acid sequence four molecular classes designated A to D. Classes A, C and D to collect different evolutionary groups of enzymes serine and Class B zinc-dependent (EDTA-inhibited “) enzymes. Fig: beta-lactamase resistance marker common to B-lactams in molecular biology, the gene encoding the bla TEM-1 ß-lactamase is DMPA markers in molecular biology (ACB and plasmids pUC). using TEM-1 beta reaches a wide-lactamase plasmid, narrow-spectrum cephalosporins, cefamandole and cefoperazone, and all anti-Gram-negative penicillin temocillin attacks is the exception. aminothiazole chephalosporins, cephamycins, monobactams and carbapenems are resistant to their action. It is one of the group 2b Bush-Jacoby-Medeiros and Class A. The molecular enzyme TEM-1 was the first time by an E. coli isolate reported in 1965 and today, the beta-lactamase is most commonly found in Enterobacteriaceae. Resistance in more than 50% of clinical isolates of E. DMPA coli TEM initial testing with broad spectrum beta-lactamases (ESBLs) are TEM -1, producing TEM-2 and SHV-1 mutations by 1-4 amino-acid sequence substitutions. aminoglycoside resistance to aminoglycosides second (streptomycin, kanamycin, tobramycin, amikacin ,…) are related compounds by the presence of a ring aminocyclitol characterized for amino sugars in their structure. Their bactericidal activity is the irreversible binding to the ribosomes, was whether their interaction with other cellular structures and metabolic processes assigned study also examined. They had a broad antimicrobial. They are active against aerobic and facultative aerobic Gram-negative and Gram-positive bacteria are staphylococci. aminoglycosides not active against anaerobic bacteria and rikettsia. spectinomycin, which is an amino sugar aminocyclitol the destitute by extension, in the aminoglycoside family. They also differed in their selectivity for its bacteriostatic and his behavior. Spectinomycin acts on protein synthesis in mRNA-ribosome interaction and it is not as aminoglycosides due to a mistranslation. Three mechanisms of resistance have been recognized, namely the modification of the ribosome, reduced permeability and inactivation of drugs by modifying enzyme aminoglycoside. This latter mechanism of most clinical significance, because the genes coding for aminoglycoside-modifying enzymes are spread by plasmids or transposons. ribosome modified high resistance to streptomycin and spectinomycin can only step from chromosomal mutations in genes for ribosomal proteins: RPSL Result (or street), SDB (or Rama or sud2) FSDP (eps or SPC or SPCA ). mutations in STRC (or STRB) to produce resistance to streptomycin low level. Missing or decrease permeability change in transport aminoglycosides, lack of membrane potential changes in the LPS (lipopolysacchaccarides) phenotype in advance of cross-resistance to all aminoglycosides. inactivation of aminoglycosides These enzymes are classified into three broad categories, depending on the type of change: AAC (acetyltransferase), ANT (or Nucleotidyltransferases adenylyltransferase), APH (phosphotransferases). This classification has been widely studied by Shaw et al. (1993). Frequently ant aminoglycoside resistance markers in molecular biology (3”)-Ia (synonyms: aada, AAD (3”) (9)) confers resistance to streptomycin and spectinomycin used. The gene has been associated with several transposon (TN7, Tn21 found …) and is ubiquitous among Gram-negative bacteria. APH (3 ‘)-II (synonyms: APHA -2 nptII) provides resistance to Km (kanamycin), Neo (neomycin), PRM (paromomycin), RSM (ribostamycin), but (Butirosin), GMB (GentamycinB). This gene is rarely found in clinical isolates. APH (3 ‘)-II is associated appears to be light (al Recorbet with transposon Tn5 and observed for Gram-negative and Pseudomonas sp. However, the relative frequency in the kanR environmental isolates., 1992, Leff et al. 1993; Smalla et al., 1993). APH (3 ‘)-III (synonym: NPTII) confers resistance to Km (Kanamycin), Neo (neomycin), PRM (paromomycin), RSM (ribostamycin) Lvdm (lividomycin), but (Butirosin), GMB (GentamycinB). AMK (amikacin) and ISP (isepamicin) are also modified in vitro, but according to NCCLS standards resistance sensitivity is only expressed at low levels by many tribes. APH (3 ‘)-III is widespread among Gram-positive, but also been observed in Campylobacter spp. NPTII is not often used in molecular biology, but may in some Agrobacterium vectors for plant transformation (Bevan, 1984) 3. tetracycline tetracycline resistance (tetracycline, doxycycline, minocycline, oxtetracycline be found), antibiotics are inhibited bacterial growth by stopping protein synthesis. They have often been for the last forty years, used as a therapeutic agent in human and veterinary medicine but also as growth promoters in livestock. The emergence of bacterial resistance to these antibiotics has limited their use today. Three different specific mechanisms of resistance to tetracycline have been identified: tetracycline efflux, ribosome protection and tetracycline modification. Tetracycline efflux is achieved by a protein export from the major facilitator superfamily (MFS). The Export-protein has been found that the operation of an electroneutral antiport that catalyzes exchange of divalent metal cations complex tetracycline for a proton. In Gram negative protein contains 12 TMS Export (transmembrane fragments) whereas in Gram-positive bacteria it displays 14 TMS. Ribosome protection is mediated by a soluble protein whose capital includes homolgy with GTPases involved in protein synthesis, namely EF-Tu and EF-G. The third is a cytoplasmic protein that chemically modified tetracycline. This reaction occurs only in the presence of oxygen and NADPH and not work in the natural host (Bacteroides). The first two mechanisms are the most widespread and most of their genes are normally prepared by transmissible plasmids and / or transposons.