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The US Environmental Protection Agency (USEPA) is currently using several approaches to ascertain the long-term and short-termutility of the Virulence Factor Associated Relationships (VFARs) concept for evaluating CCL organisms and for identifying currentlyunknown pathogens from the environment. A datamining effort has been funded to find common DNA sequences among diverse species of pathogenicbacteria. One research approach uses proteomics to examine andcompare gene products from virulent and avirulent isolates of Aeromonas that aregrowing in cell culture. Another approach, which will be accomplished through anInteragency Agreement, will compare gene products and genes in Cryptosporidiumstrains that cause illness in humans with those from Cryptosporidium isolates that areavirulent in humans. Other protozoan species that infect humans will then be examinedfor genes that are analogous to those associated with those Cryptosporidium strains thatare virulent to humans.The most creative approach that the USEPA is currently using compares the responses ofmammalian cells to pathogenic strains of Aeromonas to the responses observed withavirulent strains from the same genus. If the responses are significantly different, thisapproach should eliminate the need to identify the entire array of genes necessary forvirulence in order to distinguish between virulent and avirulent isolates. This approachwill accurately characterize as avirulent those strains that carry one ormore virulence genes but do not express them. In addition, this approach will screen newly discovered microorganisms for virulence potential. The preliminaryresults obtained from these in-house studies are promising. Neonatal mice werechallenged with a virulent isolate of A. hydrophila and an avirulent isolate of A. caviae.Five hours later microarrays were used to measure host mRNA responses. Thedifferences were dramatic; over 400 genes were up-regulated after exposure of the host tothe virulent strain, whereas only 28 host genes were up-regulated after exposure to theavirulent strain. Furthermore, many of the genes that were induced by the virulent isolatewere genes that are associated with immune responses. These experiments will berepeated using tissue culture and eventually using other genera of pathogens.

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Edition: Vol. - No. Published: 11/15/2004 Number of Pages: 2File Size: 1 file , 170 KB