Interaction of beta-lactam antibiotics with the bactericidal activity of leukocytes against Escherichia coli.

The effect of beta-lactam antibiotics on phagocytosis and intracellular killing of four isogenic Escherichia coli strains differing in their 0- and K antigens was studied by adopting the rat polyvinyl-sponge model. The penicillins mezlocillin, ticarcillin and piperacillin rendered all four isogenic E. coli strains more susceptible to intraleukocyte killing; the cefalosporins tested exhibited inhomogenous effects; lamoxactam was marginally effective, whereas cefoxitin was completely ineffective; cefotaxime caused an increase in intracellular killing of the capsule-defective mutant only. The beta-lactam promoted increase in intracellular killing could be inhibited by alpha-methylmannoside but not by alpha-methylglucoside. Free-flow electrophoretic separation of mezlocillin-treated bacteria and guinea pig erythrocytes revealed that co-migration of E. coli and erythrocytes respectively could be inhibited by alpha-methylmannoside but not by alpha-methylglucoside. These data indicate that mezlocillin interferes with the mannose sensitive adhesins of E. coli.