Effect of new susceptibility breakpoints on reporting of resistance in Streptococcus pneumoniae–United States, 2003

In January 2003, the National Committee for Clinical Laboratory Standards (NCCLS) finalized new breakpoints for defining the susceptibility of Streptococcus pneumoniae isolates to cefotaxime and ceftriaxone. The former breakpoints were based on attainable concentrations of these antibiotics in cerebrospinal fluid (CSF) and the level at which it was thought that meningitis treatment failed because of elevated minimum inhibitory concentrations (MICs). The new breakpoints differ for S. pneumoniae isolates causing meningitis and those causing nonmeningeal clinical syndromes. To assess the effect of these new criteria on reporting of nonsusceptible S. pneumoniae isolates, CDC analyzed cefotaxime MIC data from the Active Bacterial Core Surveillance (ABCs) of the Emerging Infections Program (EIP) Network during 1998-2001. This report summarizes the results of that analysis, which indicated that after the new criteria were applied, the number of isolates defined as nonsusceptible to cefotaxime decreased 52.1%-61.2% for each year. Laboratory reports for clinicians should include interpretations using the new breakpoints for meningitis and nonmeningeal syndromes for all non-CSF isolates.