The cantaloupe melon has been associated with outbreaks of Salmonella infections. It is suspected that bacterial surface charge and hydrophobicity may affect bacterial attachment and complicate bacterial
detachment from cantaloupe surfaces. The surface charge and hydrophobicity of strains of Salmonella, Escherichia coli (O157:H7 and non-O157:H7), and Listeria monocytogenes were determined
by electrostatic and hydrophobic interaction chromatography, respectively. Initial bacterial attachment to cantaloupe surfaces and the ability of bacteria to resist removal by washing with water were compared
with surface charge and hydrophobicity. Whole cantaloupes were submerged in inocula containing individual strains or in cocktails containing Salmonella, E. coli, and L. monocytogenes,
either as a mixture of strains containing all three genera or as a mixture of strains belonging to a single genus, for 10 min. Inoculated cantaloupes were dried for 1 h in a biosafety cabinet and then stored
for up to 7 days at 4°C. Inoculated melons were washed with water, and bacteria still attached to the melon surface, as well as those in the wash water, were enumerated. Initial bacterial attachment
was highest for individual strains of E. coli and lowest for L. monocytogenes, but Salmonella exhibited the strongest attachment on days 0, 3, and 7. When mixed-genus cocktails were
used, the relative degrees of attachment of the three genera ware altered. The attachment of Salmonella strains was the strongest, but the attachment of E. coli was more extensive than that
of L. monocytogenes on days 0, 3, and 7. There was a linear correlation between bacterial cell surface hydrophobicity (r2 = 0.767), negative charge (r2 = 0.738),
and positive charge (r2 = 0.724) and the strength of bacterial attachment to cantaloupe surfaces.
Document Type: Research Article
U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, Pennsylvania 19038,
Publication date: July 1, 2002
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