MICs of six extended-spectrum cephalosporins (cefotaxime, ceftriaxone, ceftazidime, FK 037, cefpirome, cefepime), three carbapenems (imipenem, meropenem, biapenem), and vancomycin for 49 penicillin-susceptible (S), 77 penicillin intermediate-resistant (I), and 51 penicillin-resistant (R) pneumococci were determined by agar dilution. Compared with ceftazidime (MICs for 90%o of strains tested [MIC90s] of 2.0, 16.0, and 16.0 ,ug/ml for S, I, and R strains, respectively), all other cephalosporins yielded lower MICs (MIC,0s of 0.06 to 0.125, 0.5 to 1.0, and 1.0 to 2.0 ,ug/ml against S, I, and R strains, respectively). All three carbapenems were very active, with MIC%0s, even for R strains, of .1.0 ,ug/ml. All strains were susceptible to vancomycin (MIC90 of 0.5 ,ug/ml).Streptococcus pneumoniae continues to be a significant cause of morbidity and mortality in humans and is the leading cause of bacterial pneumonia, as well as being an important cause of otitis media and meningitis. The past two decades, and in particular the past 5 years, have witnessed a dramatic increase in the incidence of pneumococcal strains which are resistant to penicillin G (R) and other antimicrobial agents (1). In the United States, surveys performed before 1990 showed a prevalence of 4 to 5% (1). One report documented an incidence of 17. 8% between 1990 and 1991 (24). It is not clear whether this increased incidence applies to the whole country or only applies to certain areas. In the absence of recent confirmatory multistate surveys, we do not know precisely the magnitude of this problem in the United States. Although nonmeningitic infections caused by R strain pneumococci may be treated under certain circumstances with high doses of penicillin and other 1-lactams, treatment may not always be successful (17).By contrast, clinical failure of penicillin in treatment of meningitis caused by strains intermediately resistant to penicillin (I) approaches 80%, and no cases of meningitis caused by strains fully resistant to penicillin have responded to penicillin therapy (25).There is an urgent need for antimicrobial agents which can be used for therapy of systemic infections (and especially meningitis) caused by R strain pneumococci. The aim of the current study was to examine the activity of six extendedspectrum cephalosporins (ceftazidime, cefotaxime, ceftriaxone, FK 037, cefpirome [HR 810], cefepime [BMY 28142]) (2, 3, 6, 10, 11, 14-16, 21, 25), three carbapenems (imipenem, meropenem, biapenem [LJC 10,627]) (13,20,25,26), and vancomycin against 49 penicillin-susceptible (S), 77 1, and 51 R strains of S. pneumoniae.A total of 177 isolates of S. pneumoniae isolated from blood, cerebrospinal fluid, ear, nasopharynx, or sputum were examined. S strains (MIC of <0.1 ,ug/ml) were isolated from various The results of susceptibility testing are presented in Table 1 as the cumulative percentage inhibited at a specific MIC. As can be seen, the susceptibility of all cephalosporins and carbapenems increased in line with the MIC of penicillin. Ceftazidime...