Resistance to antimicrobials

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). 

Although not reviewed in detail here, C. jejuni and C. coli are another major cause of inflammatory colitis that may be complicated by Guillain-Barre syndrome or reactive arthritis. In addition, their resistance to antimicrobials (particularly to quinolones) is increasing. In the United States, fluoroquinolone resistance of C. jejuni rose from 13% in 1997 to 18% in 1999 [112],... 

They examined the proposal that bacterial resistance to antimicrobials is Increasing worldwide at an alarming pace. They obtained data that included over 43 million individual tests. The study (19), showed that the resistance of most bacteria to most antibiotics had not changed during the past 12 years. Lorian... 

Global Strategy of the WHO on Suppression of Resistance to Antimicrobial Preparations (2001) World Health Organization. Geneva, Switzerland, 20 pp... 

Foster, T.J. (1983). Plasmid-determined resistance to antimicrobial drugs and toxic metal ions in bacteria. Microbiological Reviews, 47, 361-409-... 

Braoudaki, M. and Hilton, A.C., Adaptive resistance to biocides in Salmonella enterica and Escherichia coli 0157 and cross resistance to antimicrobial agents. J. Clin. Microbiol. 42, 73-78, 2004. 

Lipopolysaccharides are heat-stable complex amphiphilic macromolecules indispensable for the bacterial growth, viability and for the correct assembly of the external membrane they represent a defensive barrier which helps bacteria to resist to antimicrobial compounds and environmental stresses and are involved in many aspects of host-bacterium interactions as recognition, adhesion, colonization, and, in the case of extremophile bacteria, in the survival under harsh conditions (Alexander and Rietschel, 2001 Raetz and Whitfield, 2002 Raetz et al 2007). LPS are also called endotoxins because they are cell-bound and, once released, play a key role in the pathogenesis of Gram-negative infections, in mechanisms as... 

Gunn, J. Bacterial modification of LPS and resistance to antimicrobial peptides. J Endotoxin Res... 

Macfarlane, E.L., Kwasnicka, A., Hancock, R.E. Role of Pseudomonas aeruginosa PhoP-phoQ in resistance to antimicrobial cationic peptides and aminoglycosides. Microbiology 146(Pt 10) (2000) 2543-2554. 

Davies, J., and Smith, D. I. (1978). Plasmid Determined Resistance to Antimicrobial Agents. Annu Rev Microbiol 32 469. 

The main methods by which microorganisms exhibit resistance to antimicrobials are ... 

Ellermeier, C.D., andLosick, R. (2006). Evidence for a novel protease governing regulated intramembrane proteolysis and resistance to antimicrobial peptides in Bacillus subtUis. Genes Dev 20 1911-1922. 

The organism is sensitive to physical agents such as heat sterilisation, radiation and cold shock [6,7], and it is therefore its resistance to antimicrobial agents which poses the major problem. The continued use of antibacterial agents will no doubt exacerbate the situation unless more effective agents are discovered. 

Microbial resistance to antimicrobials is a matter of great importance if sensitive strains are supplanted by resistant ones, then a valuable drug may become useless. Just as ... 

Compared with suspended (planktonic) cells, bacteria on surfaces as biofilms are invariably phe-notypically more resistant to antimicrobial agents. With biofilms, suspension tests can be modified to involve biofilms produced on small pieces of an appropriate glass or metal substrate, or on the bottom of microtitre tray wells. After being immersed in, or exposed to the disinfectant solution for the appropriate time interval, the cells from the biofilm are removed, e.g. by sonication, and resuspended in a suitable neutralizing medium. Viable counts are then performed on the resulting planktonic cells. 

Resistance to antimicrobial agents typically occurs by one or more of the following mechanisms ... 

There are many different mechanisms by which micro-organisms might exhibit resistance to antimicrobial drugs. Inherent and acquired resistance to an... 

Jacoby, G.A. Archer, G.L. (1991) New mechanisms of bacterial resistance to antimicrobial agents. New England Journal of Medicine, 324, 601-612. 

Biofilm bacteria are also notorious for being highly resistant to antimicrobial agents. Some possible explanations are listed as follows (Cloete, 2003) ... 

M. C. McManus Mechanisms of bacterial resistance to antimicrobial agents [see comments]. American Journal of Health System Pharmacy 54 1420 quiz 1444(1997). 

Kaye KS, Fraimiw HS, Abrutyn E. Pathogens resistant to antimicrobial agents Epidemiology, molecular mechanisms, and clinical management. Infect Dis Clin North Am 2000 14 293-319. 

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