RT Journal Article
SR Electronic
T1 Detection and prevalence of pneumococci with increased resistance to penicillin
JF Canadian Medical Association Journal
JO CMAJ
FD Canadian Medical Association
SP 1159
OP 1161
VO 117
IS 10
A1 Dixon, J. M.
A1 Lipinski, A. E.
A1 Graham, M. E.
YR 1977
UL http://www.cmaj.ca/content/117/10/1159.abstract
AB Susceptibility to penicillin was determined for 6000 strains of pneumococci isolated during 1974--76 from patients in Alberta and the adjacent region of the Northwest Territories. Strains were considered to be relatively resistant if the minimum inhibitory concentration (MIC) of penicillin was 0.16 microgram (0.26 U)/mL or more, which is eight or more times greater than the MIC for fully susceptible strains. Resistance was detected in 143 strains (2.4%) isolated from 122 patients and belonging to four capsular types. The MIC of the most resistant strains was 0.32 microgram (0.53 U/mL. Penicillin-resistant strains were highly resistant to oxacillin, the MIC being at least 30 times greater than that for penicillin-susceptible strains. Pneumococci resistant to penicillin may readily be detected by the narrowness or absence of a zone of inhibition around a 1-microgram oxacillin disc in susceptibility tests on blood agar. The degree of resistance reported here is relative and does not necessarily preclude successful treatment with full therapeutic doses of penicillin G, but penicillin preparations that give low blood concentrations may not be suitable for treating infections caused by these strains.