Oxacillin-tolerant staphylococcal bacteremia in children

Abstract

S T R A I N s of Staphylococcal aureus that are inhibited, but not killed, by oxacillin in vitro' have been called tolerant because of similarities to the tolerant pneumococci described by Tomasz et al. ~ The cell wall lysis of toler~int strains is impaired as compared to that m nontolerant strains when they are exposed to oxacillin. 1 methicillin. nafcillin, vancomycin, and cephalothin? ' 4 This deficiency of autolytic enzymes diminishes the bactericidal activity of cell wall active antibiotics without affecting in vitro growth inhibition. In most clinical situations, tolerant strains are not readily identified because microbiology laboratories do not routinely test for bactericidal antibiotic activity. Epidemiologic studies o f clinical isolates indicate that 44 to 55% of S. aureus recovered from patients are tolerant? ' Mayhall et al 3 observed three patients with tolerant strains who had a protracted clinical course while receiving oxacillin until an aminoglycoside was added to achieve a bactericidal effect in the patients' serum. The optimal management o f patients with infections from a S. aureus tolerant strain has not been defined. The objectives of our study were to assess the epidemiologlc features of tolerant staphylococcal bacteremic infections of children and to review our experience with the antibiotic therapy of these infections.