• Polymorphonuclear leukocytes;
  • activation;
  • phagocytosis;
  • salmonella

The interaction of polymorphonuclear leukocytes (PMN) with salmonella, as studied by chemiluminescence and phagocytosis, was very different for a number of clinical isolates. Particularly bacteria in the serogroups C1 and E4 deviated from other Salmonella. The differences were observed in the rate of activation, peak value, duration of the chemiluminescence, and in the extent of association and ingestion as studied microscopically. Old laboratory S-strains such as Salmonella typhimurium 395 MS and S. minnesota S99, which did not associate with the PMN, showed little activation of the PMN, whereas their phagocytosis-sensitive R-mutants induced rapid activation, high peak values, and short duration of the chemiluminescence. Certain isolates belonging to the C1/E4 group induced intermediate types of reactions. The kinetics of the activation was related to the physicochemical surface properties of the bacteria. Heating the bacteria at 70 °C for 45 min enhanced the activation of PMN by the S-type strains conspicuously but in different ways, whereas that of R-mutants was delayed. Different clinical isolates of salmonella have shown different physico-chemical surfaces, liability to phagocytosis by PMNs and different degrees of eliciting inflammatory mediators from PMNs in vitro. The results indicate that the C1/E4 group of Salmonella has pathogenicity mechanisms different from most salmonellae.