Impact of Penicillin Nonsusceptibility on Clinical Outcomes of Patients with Nonmeningeal Streptococcus pneumoniae Bacteremia in the Era of the 2008 Clinical and Laboratory Standards Institute Penicillin Breakpoints

To investigate the impact of penicillin nonsusceptibility on clinical outcomes of patients with nonmeningealStreptococcus pneumoniae bacteremia (SPB), a retrospective cohort study was performed. The characteristics of 39 patients with penicillin-nonsusceptible SPB (PNSPB) were compared to those of a group of age- and sex-matched patients (n = 78) with penicillin-susceptible SPB (PSSPB). Susceptibility to penicillin was redetermined by using the revised Clinical and Laboratory Standards Institute (CLSI) penicillin breakpoints in CLSI document M100-S18. Although the PNSPB group tended to have more serious initial manifestations than the PSSPB group, the two groups did not differ significantly in terms of their 30-day mortality rates (30.8% versus 23.1%;P = 0.37) or the duration of hospital stay (median number of days, 14 versus 12;P = 0.89). Broad-spectrum antimicrobial agents, such as extended-spectrum cephalosporins, vancomycin, and carbapenem, were frequently used in both the PNSPB and PSSPB groups. Multivariate analysis revealed that ceftriaxone nonsusceptibility (adjusted odds ratio [aOR] = 4.88; 95% confidence interval [CI] = 1.07 to 22.27;P = 0.041) was one of the independent risk factors for 30-day mortality. Thus, when the 2008 CLSI penicillin breakpoints are applied and the current clinical practice of using wide-spectrum empirical antimicrobial agents is pursued, fatal outcomes in patients with nonmeningeal SPB that can be attributed to penicillin nonsusceptibility are likely to be rare. Further studies that examine the clinical impact of ceftriaxone nonsusceptibility in nonmningeal SPB may be warranted.