Antibiotic Resistance - Essay Example

PAGE INDEX:- Introduction to Antibiotic resistant genes Development of resistance to Antibiotic Mechanism of Antibiotic resistant Where do the antibiotic resistant genes come from? Role of mutations in Antibiotic resistant genes. Role of gene transfer in Antibiotic resistant genes Role of rDNA in Antibiotic resistant genes ANTIBIOTIC RESISTANCE GENES Antibiotics are special kind of chemotherapeutic agent usually obtained from living organisms. the word antibiotics can be referred to a metabolic product of one microorganism that in very a small amount is detrimental or inhibitory to other microorganisms.(Michael J Pelczar,5th edition, page 513) the mode of action of antibiotics on microorganism are:- inhibition of cell wall synthesis, damage to the cytoplasm membrane, inhibition of nucleic acid and protein synthesis, inhibition of specific of enzyme systems. (Michael J Pelczar, 5th edition, page 515) Development of resistance to antibiotics:- Antibiotics resistance is one of the natures never ending process whereby organisms develop a tolerance for new environmental conditions. This resistance may be due to some acquired factors. penicillin resistance, for example, may result from the production of penicillinase acid. on the other hand, some normally susceptible strains of bacteria may acquire resistance to penicillin. Acquired resistance is due to penicillinase production in genetically adapted varieties of microorganisms. in cultures of penicillin-sensitive bacteria, perhaps one organism in a hundred million may be a penicillin resistant mutant .normally the ration to sensitive to resistant organisms are maintained. when penicillin is present the sensitive strains do not produce whereas the resistant mutants do and eventually dominate the population. this is useful in in developing synthetic penicillin’s which are resistant to action of penicillinase..Many organisms which do not produce penicillinase are also resistant to penicillin (Wright G. D., 2007). Other mechanism of antibiotic :-Competitive inhibition between an essential metabolite and a metabolic analog (drug), development of alternative metabolic pathway, which bypasses some reactions that would normally be inhibited by the drug, production of an enzyme altered in such way that it functions behalf of the cell but it is not affected by the drug, synthesis of excess enzyme over the amount that can be inactivated by the antibiotic or drug, inability of the drug to penetrate the cell due to some alteration of the cell membrane, alteration of the ribosomal protein structure. (Michael J Pelczar 5th edition, page 531, chapter 24.) Where do the antibiotic resistance genes come from? Antibiotic resistance genes are produced by mutations, rDNA technology and these resistance genes can be transferred by gene transfer mechanisms such as conjugations, transformation, or transduction. where the antibiotic resistance genes are carried by the carrier molecules, for example:- scientist isolated both antibiotic sensitive and antibiotic resistant organism of the same serotype from patients with enteric infections being treated with sulphonamides, tetracycline’s, streptomycin, or chloramphenicol they went on to demonstrate that this was due to resistant genes in a reservoir of Escherichia coli in the intestinal tract being transferred to Shigella dysenteriae that caused the infection. Since than transfer of antibiotic resistant by bacterial conjugations have developed.(Michael J Pelczar,Transmission of Antibiotic Resistance, page 532) Hence antibiotic resistance takes places when an antibiotic has lost its ability to effectively control or act lethal to bacterial growth. it can be define as “when the bacteria are resistant and continue to multiply in presence of therapeutic levels of an antibiotic”. Antibiotic resistance represents a serious problem for clinical, and great effort is being made to understand the mechanism involved and to prevent its occurrence. The developed can be minimized by 1.) avoiding the indiscriminate use of antibiotics, 2.) refraining from the use of antibiotics commonly employed for generalized infection for topical application, 3.) using correct dosage of proper antibiotic to overcome an infection quickly, 4.) using combinations of antibiotics of proved effectiveness, 5.) using a different antibiotic when an organism gives evidence of becoming resistant to the one used initially.(Michael J Pelczar,5th edition, page 532,last paragraph.) When chemotherapeutic agents such as sulfonamides and antibiotics were used, development of bacterial resistance was rather infrequent. resistance became much more of a problem as the widespread use of antibiotics led to the elimination of sensitive organisms from the population with the accompanying increase in the number of resistant organisms.(Origin of Microbiology,2007) Role of mutations in production of antibiotic resistant genes:- Spontaneous mutations which occur naturally without any known cause or appearance that is they are not induced by any mutagenic agent. these mutations play a major role in production of these genes they are caused by normal cellular events, errors during DNA replication, methylation followed by deamination of cytosine. thus due to these mutation the protein structures and exchange in base pairs take place which eventually leads to change in the reaction of that particular substance and cause mutations. Detection of antibiotic resistant mutants is also employed :-some bacterial strains followed by mutations become resistant to antibiotics, phage attack or metal toxicity etc Often wild type cell are not resistant to phage attack or antibiotics treatment, so it is possible to grow the bacterium in the presence of the agent and look for surviving organisms. consider an example of a phage resistant wild type bacterium. when the organism is cultured in medium lacking the virus and then plated out on selective medium containing phages, any colonies form will be resistant to phage attack and very likely will be mutants in the regard. Antibiotic resistant mutants are isolated by a technique called as Gradient plate technique. in this method , antibiotic is incorporated into the agar medium and poured in the plate in an inclined position so that on one side the medium is thick and contains more of the antibiotic. then the bacterial suspension is spread over the agar. the colonies developing towards the thick agar are taken as antibiotic resistant mutants.( B.D Singh, Fundamental of Genetics,2006) The role of gene transfer in antibiotic resistant genes:-the genes transfer methods involve carrier molecules which play a major role in transfer of resistant genes to antibiotics and converting the antibiotic sensitive gene to antibiotic resistant genes. These carrier molecules are plasmids, vectors and other carrier engines. By conjugation process the genetic material from one cell is transferred to another cell in this process the gene carrying the resistant factor is transferred to female cell from the male cell. besides the main chromosome some of the bacterial cell contains one or more small DNA molecules called as plasmids. this extra chromosomal genetic material can also be transferred from one cell to another cell through conjugation process the transferred genetic material containing the resistant factor undergoes recombination with the genetic material of recipient cell and results in acquisition of new characters by the cell. because of this transfer the new characters attain by the cell include resistant and the cell becomes resistant to antibiotics. (k. Narasimha Murthy, Biotechnology and its Applications, page 104,105) Role of rDNA technology in production of antibiotic resistant genes:- Although natural recombination occurs which makes it possible to produce the resistant genes and transfer from one organism to another .recombinant technology can also be used to make thousands of copies of the same DNA carrying the resistant factors. the steps involved in technology are as follows:-the DNA containing the resistant factor which is the property to be transferred into a bacterium or any other recipient is isolated from the cell and inserted into a vector and then this vector is introduced into a bacterial cell and the transformed bacterial cell is then grown in culture to form a clone of many genetically identical cell. Thus the production of genes resistant to antibiotics can be produced. (Ethical issues in biotechnology Page 236). BIBLIOGRAPHY:- Wright G. D. (2007). The antibiotic resistome: the nexus of chemical and genetic diversity. Nature Reviews Microbiology. Michael J.Pelczar, JR. Tata McGraw-Hill Edition, Fifth edition1993. Origin of Microbiology, Jaya Sai Publications, third Edition 2000. Fundamental of genetics by B. D Singh, India, 2000. Biotechnology and its Applications, k. Narasimha Murthy, Jaya Sai Publications.2006 Ethical issues in biotechnology, Richard Sherlock, John D. Morrey. Figures from E.C.S.Chan, Noel R. Krieg Tata MC Graw-Hill. Fifth Edition 1993. Read More