ORAL INFECTIVITY AND BACTERIAL INTERACTIONS WITH MONONUCLEAR PHAGOCYTES

The purpose of this study was to clarify the association between the o ral infectivity of a bacterial strain and its susceptibility to ingest ion by mononuclear phagocytes or ability to survive within them. Ten b acterial strains tested-all of known oral infectivity-comprised Salmon ella typhimurium, Listeria monocytogenes (three strains), Escherichia coli (two strains), Proteus mirabilis, Enterococcus faecalis, Bacteroi des fragilis, and a Bacteroides sp. The phagocytic uptake of each stra in was measured as the bacteria to phagocyte ratio after mononuclear p hagocytes in mouse peritoneal exudate were permitted to ingest bacteri a in vivo for 3 min. The three Listeria strains were the most suscepti ble to phagocytic uptake and the Salmonella strain was relatively resi stant. The intracellular survival of each strain was studied during a subsequent 2 h in-vitro incubation of the mononuclear phagocytes that had been permitted to ingest bacteria in vivo. The strains with the be st intracellular survival were Ent. faecalis and two of the three List eria strains. The ability of S. typhimurium to survive intracellularly was intermediate but better than that of the two E. coli strains. Ora l infectivity was not consistently correlated with susceptibility to i ngestion by mononuclear phagocytes or ability to survive within them.