It is widely accepted among clinicians, medical researchers, microbiologists and pharmacologists, that antibiotic resistance will, in the very near future,leave healthcare professionals without effective therapies for bacterial infections. As an example, it is now estimated that about  half of all Staphylococcus aureus strains found in many medical institutions are resistant to antibiotics such as methicillin (Roder et al. 1999). The emergence among enterococci of resistance to another useful and widely effective antibiotic, vancomycin , might accelerate the spread of vancomycin-resistant genes, via plasmids, throughout other species, eventually limiting the efficacy of this drug. Consequently, the priority for the next decades should be focused in the development of alternative drugs and/or the recovery of natural molecules that would allow the consistent and proper control of pathogen-caused diseases. Ideally, these molecules should be as natural as possible, with a wide range of action over several pathogens, easy to produce, and not prone to induce resistance.

The new generation of native peptide molecules, also known as Anti Microbial Peptides (AMPs), isolated from  a full range of organisms and species from bacteria to man, seem to fit this description. As a consequence, they have been termed “natural antibiotics”, because they are active against a large spectrum of microorganisms, including bacteria and filamentous fungi - in addition to protozoan and metazoan parasites(Liu et al. 2000; Vizioli and Salzet, 2003) . All of these molecules are key elements directly implicated in the innate immune response of their hosts, which includesthe expression of fluid phase proteins that recognize pathogen-associated molecular patterns, instead of specific features of a given agent to promote their destruction. As a result, the response is very fast, highly efficient and applicable to a wide range of infective organisms .  Additionally, the effect of AMPs can go beyondisolated bacterial cells, as shown by the inhibition they can exert over clusters of pathogenic bacteria, such in biofilm development (Singh et al. 2002).

References

RODER, B.L.; WANDALL, D.A.; FRIMODT-MOLLER, N.; ESPERSEN, F.; SKINHOJ, P. and ROSDAHL, V.T. Clinical features of Staphylococcus aureus endocarditis: a 10-year experience in Denmark. Archives Internal Medicine, 1999, vol. 159, no. 5, p. 462-469.

LIU, Y.; LUO, J.; XU, C.; REN, F.; PENG, C.; WU, G. and ZHAO, J. Purification, characterization, and molecular cloning of the gene of a seed-specific antimicrobial protein from pokeweed. Plant Physiology, 2000, vol. 122, no. 4, p. 1015-1024.

VIZIOLI, J. and SALZET, M. Antimicrobial peptides: new weapons to control parasitic infections? Trends in Parasitology, 2003, vol. 19, In press.

SINGH, P.K.; PARSEK, M.R.; GREENBERG, E.P. and WELSH, M.J. A component of innate immunity prevents bacterial biofilm development. Nature, 2002, vol. 417, no. 6888, p. 552-555.

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