Penicillin-intermediate pneumococci in a children's hospital
L. D. Willett, H. C. Dillon Jr and B. M. Gray
During the three-year period from 1981 to 1984, all clinical isolates of
Streptococcus pneumoniae were screened for resistance to penicillin in the
clinical bacteriology laboratory at The Children's Hospital of Alabama,
Birmingham. Twenty-eight of 828 isolates were presumed resistant by disk
diffusion testing with 1-microgram oxacillin disks (zone diameter, less
than 20 mm). Seventeen of the 28 (61%) were found to be intermediately
sensitive to penicillin by a conventional agar dilution method.
Penicillin-intermediate strains had a minimal inhibitory concentration of
0.125 to 0.5 mg/L; no penicillin-resistant (minimal inhibitory
concentration, greater than 1 mg/L) strains were encountered. The
prevalence of penicillin-intermediate strains was thus 17 of 828 isolates,
or 2.1%. These strains were also examined for susceptibility to ampicillin,
vancomycin, cefotaxime, and chloramphenicol. We present the clinical
features of 17 patients with disease due to penicillin-intermediate
pneumococci.
