Physicochemical Surface Properties and Phagocytosis by Polymorphonuclear Leucocytes of Different Serogroups of Salmonella

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Abstract
Salmonella isolates belonging to different serogroups were analyzed for physicochemical surface properties and interaction with human polymorphonuclear granulocytes (PMN). Most (22/34) recent isolates showed hydrophilic surface properties and little if any negative charge and were resistant to PMN phagocytosis; these strains were similar to the old laboratory S strains S. typhimurium 395MS and S. minnesota S99 (main group). All isolates belonging to serogroups C1 (5 isolates), E4 (2) and O43 (1) and 1 of 3 E1 isolates (C1/E4 group) differed from the main group. In aqueous biphasic partition in dextran-polyethyleneglycol (PEG) systems, the bacteria in the main group accumulated in the PEG-rich phase to 55-97%, those in the C1/E4 group to < 10% and R mutants only to 1-2%. The bacteria in the C1/E4 group displayed a negative surface charge and a susceptibility to PMN phagocytosis that were greater than those for strains in the main group but much lower than those shown by the R mutants. Bacteria belonging to serogroup C1 also displayed a significant susceptibility to hydrophobic interaction. The results are discussed in relation to the pathogenicity of Salmonella.