DIFFERENTIAL UPTAKE AND KILLING POTENTIAL OF CAMPYLOBACTER-JEJUNI BY HUMAN PERIPHERAL MONOCYTES MACROPHAGES/

The ability of Campylobacter jejuni to survive in monocytes after phag ocytic uptake was tested in a new in vitro model using adherent macrop hages derived from human peripheral monocytes. The cells were stimulat ed with cytokines before use to ensure full phagocytic and killing act ivity. The kinetics of uptake and killing of bacteria was followed for 72 h with 16 strains, including stool and blood isolates and laborato ry adapted strains. Significant bacterial strain differences were not observed, but the viability of phagocytosed bacteria was dependent on the individual donating the macrophages. The majority of blood donors carried macrophages that killed phagocytosed Campylobacter within 24 o r 48 h. There was no correlation between the source of isolation of th e strains and relative intracellular survival. Bacterial mutants of su peroxide dismutase, catalase or polyphosphate kinase were all as sensi tive to macrophage killing as their isogenic wildtype strain. In contr ast, about 10% of the voluntary blood donors carried monocytes which w ere incapable of killing phagocytosed bacteria. Such macrophages displ ayed normal uptake, but killing was insufficient and bacterial growth was observed with all strains and mutants tested. We conclude that (1) since in most cases activated human macrophages kill C. jejuni effici ently after phagocytosis, intra-phagocytic survival is not a common ph enomenon during Campylobacter infection; and (2) those individuals car rying macrophages that are unable to destroy phagocytosed bacteria are at risk to develop a bacteremia during Campylobacter infection.