Antimicrobial agents resistance

Musser J.M. (1995) Antimicrobial agent resistance in mycobacteria molecular genetic insights. Clin Microbiol Rev, 8, 496-514. 

Ramaswamy, S., Musser, J.M., 1998. Molecular genetic basis of antimicrobial agent resistance in mycobacterium tuberculosis 1998 update. Tuberc. Lung Dis. Off. J. Int. Union Tuberc. Lung Dis. 79 (1), 3—29. Available from http //dx.doi.org/10.1054/ tuld.1998.0002. 

Other Properties. Polyester fibers have good resistance to uv radiation although prolonged exposure weakens the fibers (47,51). PET is not affected by iasects or microorganisms and can be designed to kill bacteria by the iacorporation of antimicrobial agents (19). The oleophilic surface of PET fibers attracts and holds oils. Other PET fiber properties can be found ia the Hterature (47,49). 

Resistance to antimicrobial agents is of concern as it is well known that bacterial resistance to antibiotics can develop. Many bacteria already derive some nonspecific resistance to biocides through morphological features such as thek cell wall. Bacterial populations present as part of a biofilm have achieved additional resistance owkig to the more complex and thicker nature of the biofilm. A system contaminated with a biofilm population can requke several orders of magnitude more chlorine to achieve control than unassociated bacteria of the same species. A second type of resistance is attributed to chemical deactivation of the biocide. This deactivation resistance to the strong oxidising biocides probably will not occur (27). 

Bacteria can develop resistance to antimicrobial agents as a result of mutational changes in the chromosome or via the acquisition of genetic material (resistance genes carried on plasmids or transposons or the recombination of foreign DNA into the chromosome) (Fig. 2). 

Oxazolidinones are a new class of synthetic antimicrobial agents, which have activity against many important pathogens, including methicillin-resistant Staphylococcus aureus and others. Oxazolidinones (e.g. linezolid or eperezolid) inhibit bacterial protein synthesis by inhibiting the formation of the 70S initiation complex by binding to the 50S ribosomal subunit close to the interface with the 3OS subunit. 

Gilbart J., Perry CR. Slocombe B. (1993) High-level mupirocin resistance in Staphylococcus aureus evidence for two distinct isoleucyl-tRNA synthetases. Antimicrob Agents Chemother, 31, 32-38. Godfrey A.J. Bryan L.E. (1984) Intrinsic resistance and whole cell factors contributing to antibiotic resistance, hv. Antimicrobial Drug Resistance (ed. L.E. Bryan), pp. 113-145. New York Academic Press. 

Bacterial spores are the most resistant of all microbial forms to chemical treatment. The majority of antimicrobial agents have no useful sporicidal action, with the exception of the aldehydes, halogens and peroxygen compounds. Such chemicals are sometimes used as an alternative to physical methods for sterilization ofheat sensitive equipment. In these circumstances, correct usage of the agent is of paramount importance since safety margins are lower in comparison with physical methods of sterilization (Chapter 20). 

Susceptibility of viruses to antimicrobial agents can depend on whether the viruses possess a lipid envelope. Non-lipid viruses are frequently more resistant to disinfectants and it is also likely that such viruses cannot be readily categorized with respect to their sensitivities to antimicrobial agents. These viruses are responsible for many nosocomial infections, e.g. rotaviruses, picornaviruses and adenoviruses (see Chapter 3), and it may be necessary to select an antiseptic or disinfectant to suit specific circumstances. Certain viruses, such as Ebola and Marburg which cause haemorrhagic fevers, are highly infectious and their safe destruction by disinfectants is of paramount importance. 

The activity of diamidines is reduced by acid pH and in the presence of blood and serum. Microorganisms may acquire resistance by serial subculture in the presence of increasing doses of the compounds. Propamidine and dibromopropamidine, as the isethionate salts, are the major diamidine derivatives employed as antimicrobial agents propamidine in the form of eye-drops (0.1%) for amoebic infection and dibromopropamidine for topical treatment of minor infections. 

As is apparent from the above information, there is no ideal disinfectant, antiseptic or preservative. All chemical agents have their limitations either in terms of their antimicrobial activity, resistance to organic matter, stability, incompatibility, irritancy, toxicity or corrosivity. To overcome the limitations of an individual agent, formulations consisting of combinations of agents are available. For example, ethanol has been combined with chlorhexidine and iodine to produce more active preparations. The combination of chlorhexidine and cetrimide is also considered to improve activity. QACs and phenols have been combined with glutaraldehyde so that the same effect can be achieved with lower, less irritant concentrations of glutaraldehyde. Some... 

Therefore, despite the 18% and 25% resistance to penicillin and macrolides, the clinical failure rate is less than this. Owing to the empirical treatment of CAP in the outpatient setting, establishing a meaningful clinical failure rate with any therapy is difficult to do. No studies have been performed that established a correlation between clinical failure rates with a particular antimicrobial agent and the percentage of resistant bacterial pathogens. 

Other chemicals evaluated but not yet adopted commercially include organophosphorus compounds, triphenyltin compounds, quaternary ammonium salts, imidazoles, benzimidazoles, carbamates and the precocene anti-juvenile hormones [517]. Although none of the above has found use as an insect-resist agent, several have been used as antimicrobial agents for textiles. 

---