Susceptibility of bacteria to serum lysis or phagocytosis following growth in subinhibitory levels of lincosaminide or spectinomycin related antibiotics.

Abstract

The effects of subinhibitory concentrations of antibiotics on polymorphonuclear leukocyte (PML) and serum killing of Staphylococcus aureus 502A (UC 9116) and Escherichia coli UC 9451 were studied. Exposure of these bacteria to subinhibitory levels of certain lincosaminides, spectinomycin, or 6'-n-propylspectinomycin altered their susceptibility to these host defense mechanisms, while exposure to gentamicin had no effect. However, each organism responded differently to treatment with the antibiotics. S. aureus pretreated during log phase growth with subinhibitory concentrations of clindamycin, lincomycin, or pirlimycin was more susceptible to killing by PMLs than untreated bacteria. No effect on phagocytic killing was found when S. aureus was pretreated with spectinomycin, 6'-n-propylspectinomycin, or gentamicin. The S. aureus remained resistant to serum lysis despite antibiotic treatment. In contrast, spectinomycin and 6'-n-propylspectinomycin as well as clindamycin dramatically increased the susceptibility of E. coli to serum lysis (greater than 99% destroyed). Moderate killing of E. coli by PMLs was also found.