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Detection of penicillin resistance in Streptococcus pneumoniae by diffusion tests
Author(s) -
Poulsen Rikke Lykke,
Knudsen Jenny Dahl,
Petersen Mette Barendorff,
Fuursted Kurt,
Espersen Frank,
FrimodtMØLler Niels
Publication year - 1996
Publication title -
apmis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.909
H-Index - 88
eISSN - 1600-0463
pISSN - 0903-4641
DOI - 10.1111/j.1699-0463.1996.tb04910.x
Subject(s) - penicillin , microbiology and biotechnology , agar dilution , streptococcus pneumoniae , antibiotics , agar diffusion test , agar dilution method , minimum inhibitory concentration , biology , bacteria , antibacterial activity , genetics
Four different diffusion tests used to detect penicillin resistance in Streptococcus pneumoniae were evaluated for 34 penicillin‐susceptible pneumococci (MIC <0.1 μg/ml), 35 intermediate penicillin‐resistant (MIC 0.1–1.0 μg/ml) and 23 penicillin‐resistant strains (MIC >2 μg/ml). The 1 μg oxacillin disk from AB Biodisk, the 1 μg oxacillin Neo‐Sensitabs from Rosco, the 5 μg penicillin Low Neo‐Sensitabs and the penicillin E test were tested on Mueller‐Hinton blood agar, PDM Antibiotic Sensitivity Medium II supplemented with blood, and Danish Blood Agar. MICs obtained by the agar dilution method were used as reference. The 1 μg oxacillin AB Biodisk was able to separate all the penicillin‐susceptible pneumococci correctly from those with reduced penicillin susceptibility (MIC 0.1 μg/ml), whereas use of the 1 μg oxacillin Neo‐Sensitabs resulted in high frequencies (14–29%) of intermediate penicillin‐resistant strains interpreted as penicillin susceptible. The 5 μg penicillin Low Neo‐Sensitabs proved completely useless for detecting penicillin resistance in pneumococci. High rates of agreement (82–93%) were found between the penicillin E test and the reference MIC determination method on all the tested media.