Microbiology Procedure

Index >> Bacterial Cheomotherapy >>Inactivation Of Antibiotics OR Enzymatic Detoxification

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Bacterial Chemotherapy Part 1 Blocking of Antibiotic Transport Inactivation of Antibiotics OR Enzymatic Detoxification Bypass Mechanisms Inhibition of Protein Synthesis Stages of Translation in Protein Synthesis Initiation Process in Translation in Protein Synthesis Elongation Process in Translation in Protein Synthesis Termination Process in Translation in Protein Synthesis

Inactivation Of Antibiotics OR Enzymatic Detoxification

	Inactivation Of Antibiotics OR Enzymatic Detoxification - Resistance mechanisms involving resistance to penicillin and cephalosporins (β-lactams) are concerned with enzymatic detoxification or inactivation of antibiotic. The β- lactam antibiotics are among the most used antibiotics. The range of these antibiotics is matched by corresponding β-lactamases. These enzymes catalyze the hydrolysis of the β-lactam ring and detoxify the drug β-lactamases are determined both chromosomally and by plasmids.Plasmid determined β-lactamases are fewer in number than the chromosomally determined enzymes.
The β-lactamases are the primary cause of bacterial resistance to penicillin and cephalosporin. In gram negative bacteria about four fifths of plasmid-determined resistance to β-lactam antibiotics is due to either TEM-1 or TEM-2 lactamase. The genes for these, enzymes are usually found on transposable elements (TnA).N. gonorrhoea has become resistant as a result of transfer of (β-lactam resistance. It is a matter of concern that this resistance may be transferred to other organisms for which β-lactams are used as antibiotics. There are some types of β-lactam resistance which do not involve detoxyfying enzymes.
Chloramphenicol is one of the most effective antibiotics for treating anaerobic infections(e.g. bacteroides and clostridia)The predominant method of chloramphenicol resistance in gram positive and gram negative bacteria is by acetylation of chloramphenicol by acetyl transferases. These enzymes (monomeric MW22.500-24,500) are believed to be chromosomally coded, with possible hyperproduction by plasmids or by mutation. The chloramphenicol transposon is Tn9. Specialized transduction of chloramphenicol resistance by bacteriophages PI and lambda has been reported. There is structural homology between gram positive and gram negative chloramphenicol acetyl transferases. However, the enzymes from gram positive and gram negative organism show a large degree of sequence difference. Streptomyces venezuelae, which is used for the industrial production of chloramphenicol, does not contain any chloramphenicol modifying activity.
Heavy metals are sometimes used as antimicrobial agents, although their use is not as extensive as in the past. Plasmid-determined resistance to heavy metals is commonly found in bacteria. Resistance to a number of cations such as arsenate, arsenite, lead, cadmium, bismuth, antimony, silver, zinc, nickle and cobalt bas been described. In plasmid-bearing E .coli, Pseudomonas aeruginosa and S aureus strains, R plasmid coded reducing systems convert mercury salts to metallic mercury.
	The later evaporates from the culture due to its high vapour presure. Two phenotypes of mercury resistance have been recognized in clinical isolates, resistance to Hg (II) salts and resistance to Hg (II) salts plus organomercurials.In both case, the end product is the volatile Hg (0). It is believed that the reduction process takes place by the joint action of host enzymes and plasmid coded enzymes. The plasmids provide the specific mercury salt reductases that act in conjunction with bacterial NADPH oxidation.

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Bacterial Chemotherapy Part 1 Supernatant Folic Acid Antagonists Aminoalkyl Adenylates Diptheria Toxin 30S/40S Ribosomal Subunits Aminoglycosides Streptomycin Neomycin, Kanamycin and Gentamycin Tetracycines Edeine 50S/60S Ribosomal Subunit Chloramphenicol Macrolides Lincosamides Puromycin Sparsomycin Glutarimides Cycloheximide Ipeal Alkaloids Emetine

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