Antibiotic susceptibility of streptococci isolated from blood from neutropenic patients

MICs were performed on 62 streptococci isolated from the blood of neutropenic patients from 1986 to 1992 using the NCCLS broth microdilution procedure. Species isolated were 43 S. mitis, 6 S.pneumoniae, 5 S.sanguis, 1 S.pyogenes, 1 beta-hemolytic streptococcus of the group G, 1 S.adjacens, 1 S.intermedius, 4 not identified isolates (2 alpha-hemolytic, 1 non-hemolytic and 1 nutritionally variant strains). 26% of all strains were resistant or intermediate to penicillin (MIC 90: 2 mg/l) and 89% to norfloxacine (MIC 90: 32 mg/l). All were susceptible to vancomycin. Among cephalosporins, all strains were susceptible to cefotaxime (MIC 90: 1 mg/l), ceftriaxone (MIC 90: 1 mg/l) and cefepime (MIC 90: 2 mg/l) while 19% were R or I to ceftazidime (MIC 90: 16 mg/l). All were susceptible to imipenem (MIC 90: 0.5 mg/l) and meropenem (MIC 90: 1 mg/l). Among the third generation cephalosporins, ceftazidime--the agent of this class of antibiotics that is most often used for the empirical therapy of febrile episodes in neutropenic patients (in combination but also in monotherapy)--has a high resistance rate as compared to the other compounds.