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Comparison of the in-vitro activities
of the topical antimicrobials azelaic acid, nitrofurazone, silver
sulphadiazine and mupirocin against methicillin-resistant
Staphylococcus aureus.
J Antimicrob Chemother 29: 661-8
(1992)[92372539]
Department of Medical Microbiology, Royal Free Hospital School
of Medicine, Hampstead, London, UK.
Abstract
The in-vitro activities of the topical agents azelaic
acid, nitrofurazone, silver sulphadiazine and mupirocin have
been determined against 80 strains of MRSA collected from
worldwide sources. MICs were determined by agar dilution
(with an inoculum of approximately 5.0 x 10(5) cfu) in
Iso-Sensitest agar, and MBCs were measured by replica-plating
from MIC plates using velvet pads. The agents tested were
uniformly active against MRSA, mupirocin being the most
active (MIC50 0.15 mg/L) followed by nitrofurazone (MIC50 19
mg/L), silver sulphadiazine (MIC50 85 mg/L) and azelaic acid
(MIC50 850 mg/L). Concentrations of azelaic acid,
nitrofurazone and silver sulphadiazine close to the MIC were
bactericidal, but mupirocin was only bactericidal at
concentrations substantially greater than the MIC. In time-kill experiments,
azelaic acid and nitrofurazone were gradually bactericidal, silver sulphadiazine was rapidly
bactericidal and mupirocin was not
bactericidal. Silver sulphadiazine killed
sulphonamide-sensitive and sulphonamide-resistant strains
equally rapidly. No resistant mutants were found to azelaic
acid, nitrofurazone or silver sulphadiazine in an inoculum of
10(9) cfu, but two strains yielded (frequency: 1.0 x 10(-9))
mutants resistant to mupirocin. Our
in-vitro results suggest azelaic acid, nitrofurazone and
silver sulphadiazine could be of use for clearing
staphylococcal carriage.
P. A. Maple, J. M. Hamilton-Miller & W.
Brumfitt