We recently managed an infant with
meningitis caused by Streptococcus pneumoniae in whom
ceftriaxone failed to sterilize the cerebrospinal fluid after 6 days of
therapy. This strain, which had a
penicillin minimal inhibitory concentration (MIC) of 2 micrograms/ml, appeared susceptible to
ceftriaxone (MIC < 0.5 micrograms/ml) when evaluated by a commercial MIC panel (Microtech Medical Systems, Inc., Aurora, CO) but was found to have a
ceftriaxone MIC of 4 micrograms/ml when evaluated by conventional microtiter broth dilution technique. Furthermore
ceftriaxone therapy of
meningitis induced with this strain in a rabbit model was ineffective. Thirteen of 112 pneumococcal strains (11.6%) isolated recently at Children's Medical Center of Dallas were
penicillin-resistant, and 3 of these were highly
penicillin-resistant (MIC > or = 2 micrograms/ml). The incidence of pneumococcal strains with
cefotaxime MICs > or = 1.0 micrograms/ml has increased from 0 of 258 from 1981 to 1983 to 5 of 112 (4.5%) from 1991 to 1992. The definition of cephalosporin resistance for pneumococci requires modification and further studies of the
antibiotic management of
meningitis caused by such strains are needed because resistance to
cephalosporins is increasing and the extended spectrum
cephalosporins may be ineffective as sole
therapy.