Clearance of Serratia marcescens from blood in mice: Role of hydrophobic versus mannose-sensitive interactions

In the present study, we examined the potential roles of cell surface hydrophobicity and mannose-sensitive (MS) interactions in blood clearance of Serratia marcescens in mice. Hydrophobic strain RZ, partially hydrophobic mutant 3162, and nonhydrophobic mutant 3164 were coinoculated into BALB/c male mice, and blood samples were plated out at different time intervals; colonies of the three strains were distinguished by their different morphologies. All three strains were cleared from the blood stream at similar rates, despite their large relative differences in cell surface hydrophobicity. Clearance from blood was subsequently studied by coinoculating two clinical isolates which differ in their abilities to adhere via MS interactions. MS⁺ strain 1785 was cleared much more rapidly than MS^- strain 3255; moreover, in the presence of D-mannose, clearance of strain 1785 was inhibited to a rate similar to that of MS^- strain 3255. When D-glucose was substituted for D-mannose, inhibition was not observed. The results suggest that MS, rather than hydrophobic, interactions are primarily responsible for the rapid clearance of S. marcescens from blood observed.