In vitro Susceptibility of Pseudomonas aeruginosa Isolated from a Burn Center to Silver Sulfadiazine and Silver Nitrate in Shiraz, South of Iran

Pseudomonas aeruginosa, as an etiological agent, has a prominent infection role in serious burned patients. Burned patients usually treated with antiseptic ointments such as silver sulfadiazine (SSD). This study evaluated the effectiveness of 1% SSD and different concentrations of silver nitrate solution (SNS) on resistant isolates of P. aeruginosa. Three groups of P. aeruginosa isolates were collected consisting of 63 strains from burned patients (group I), 15 strains from burn-hospital environment (group II) and 70 strains from non-burn patients as control group. The Minimum Inhibitory Concentrations (MICs) of SSD and SNS were determined by agar dilution method and their susceptibility to SSD was evaluated by agar well diffusion method. In group I, 60 (95%) strains were resistant to SSD, whereas only 5 of them were resistant to SNS. In group II, eight out of 15 strains were resistant to SSD with MICs similar to group I while they did not show any resistance to SNS (P<0.001). In control group, all strains were sensitive to SSD and SNS (P<0.001 Most of burned patient isolates were resistant to SSD while most of them were sensitive to SNS. In contrast, all the control isolates were sensitive to SSD and SNS. Frequent administrations of SSD ointment in burned patients surely have caused resistant strains to emerge. Cessation of SNS application in clinic or less administration of SSD in non-burn patients did not induce resistance strains.