Comparative in vitro activity of silver sulfadiazine, alone and in combination with cerium nitrate, against Staphylococci and gram-negative bacteria

Silver sulfadiazine (SSD), a topical antimicrobial agent, has been widely used for the prophylaxis and treatment of burn infections during the past 30 years. We determined the antimicrobial activity of SSD, alone and in combination with cerium nitrate (CN), gentamicin and amikacin against 130 recent clinical isolates, including multiresistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) or Pseudomonas aeruginosa. The overall activity of SSD was good against all the tested strains and it was particularly high against MRSA (MIC₉₀ 100 μg/ml). CN showed no inhibitory effect, even up to 800 μg/ml, on bacterial strains tested. The combination of SSD and CN was as active as SSD alone. In conclusion, SSD has a broad spectrum of activity at concentrations lower than those commonly used in clinical preparations. All strains were inhibited by less then one-fiftieth of the SSD 'in use' concentration (10 mg/ml). Our data confirm the efficacy of this topical agent in the prevention and treatment of infections in bums or other surgical wounds and suggest its possible use in clearing staphylococcal carriage as an alternative to mupirocin.