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In vitro activity of dicloxacillin against methicillin‐susceptible and methicillin‐resistant Staphylococcus‐aureus
Author(s) -
FRIMODTMØLLER NIELS,
ROSDAHL VIBEKE THAMDRUP,
GAHRNHANSEN BENTE
Publication year - 1989
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.1699-0463.1989.tb00779.x
Subject(s) - dicloxacillin , microbiology and biotechnology , medicine , methicillin resistant staphylococcus aureus , penicillin resistance , staphylococcal infections , staphylococcus aureus , antibiotics , penicillin , bacteria , biology , genetics
A total of 54 strains of Staphyloccus aureus , 37 methicillin‐susceptible (MSSA) and 17 methicillin‐resistant (MRSA), were investigated for their susceptibility to dicloxacillin as compared to methicillin and oxacillin by agar plate dilution at two different temperatures of incubation (30 °C and 37 °C). Against MSSA strains we found a slight but significant increase (0–2 dilution steps) in minimal inhibitory concentrations (MICs) for all three antibiotics with decrease in incubation temperature. Against MRSA strains methicillin and oxacillin showed a 3–6 fold increase in median MIC with decrease in incubation temperature. For dicloxacillin, in contrast, there were no significant differences in median MICs (i.e. 0.4 mg/l) against MSSA strains at 30 °C or MRSA strains at either incubation temperature. Population‐analysis of the MRSA strains revealed, however, that a highly dicloxacillin‐resistant subpopulation appeared with a frequency of 10 ‐6 to 10 ‐7 . Such heterogenous resistance of MRSA strains to dicloxacillin probably prohibits the use of dicloxacillin against serious infections caused by these pathogens.