Summary Antimicrobial resistance is a well-documented phenomenon. Many microbial agents possess a multi-antimicrobial resistance which can be explained by the presence of a plasmid. Since the presence in Pseudomonas aeruginosa of multiresistant plasmids which demonstrate a resistance to gentamicin has been reported, gentamicin-resistant strains isolated from our burn unit and other areas of the hospital environment were compared with gentamicin-sensitive strains. All resistant and sensitive strains, as determined by the Kirby-Bauer disc diffusion method, were tested using Nathan's agar well diffusion method against the following topical antibacterials: gentamicin sulphate cream, mafenide acetate cream and silver sulphadiazine cream. Zone sizes were calibrated and susceptibility was determined using Nathan's criteria. Twenty-four of 26 strains resistant to gentamicin were concomitantly resistant to silver sulphadiazine. Agar dilution assays confirm the silver sulphadiazine up to 200 μg/ml. The sensitive strains never demonstrated a resistance to silver sulphadiazine. Pyocin typing of all strains revealed that this phenomenon is not pyocin-type specific, but probably plasmid-directed.