Imipenem Renders Serum resistant Enterobacter aerogenes and Escherichia coli to Serum sensitive Bacteria

Abstract

A main virulence factor of gram-negative bacteria is the resistance to the bactericidal activity of serum. The ineffectiveness of this host defense mechanism is due to a resistance to the attack of complement. According to the literature, certain β-lactam antibiotics influence the resistance of bacteria against the attack of complement. Several reports are listed in Table 1. Since the method of determination and the definition of serum-resistance differ from one report to another, the results of these experiments are very controversial and the findings are difficult to compare. The aim of this investigation was to study the influence of imipenem and other new β-lactam antibiotics on the serum resistance of enterobacteriaceae. In this study, serum resistance was defined merely on the basis of growth curves. A strain is determined as “serum-resistant” if there is growth or no decrease of viable counts in 20% NHS, and as “serum-sensitive” when no further growth takes place after incubation in 5% NHS.