Silver resistance in Pseudomonas aeruginosa and Acinetobacter baumannii isolated from burn patients

Introduction: Burn infections are a serious obstacle to the patient’s recovery. Infection is estimated to account for 75% of burn patient mortality. Widespread and often indiscriminate administration of antibiotics and lack of basic infection control methods are major factors in the emergence of drug-resistant bacteria. Due to the growing and serious threat of antibiotic resistance, interest in silver compounds has grown in modern medicine. Objectives: The aim of this descriptive study was to evaluate the frequency of sil genes and its phenotypic expression in Pseudomonas aeruginosa and Acinetobacter baumannii isolates isolated from the burn ward of Imam Khomeini hospital in Urmia. Patients and Methods: P. aeruginosa (n=16) and A. baumannii (n=32) isolates were collected from burn wound samples in an 8-month period from August to March 2017 from the burn ward of the hospital. The minimum inhibitory concentration of silver nitrate on the clinical isolates was determined using microdilution method. The presence of silP, silE and silS silver resistance genes was investigated by polymerase chain reaction (PCR). Results: The results of minimum inhibitory concentration (MIC) test showed that 62.5% (n = 10) of P. aeruginosa isolates and 56.25% (n = 18) of A. baumannii isolates showed MIC above 512 mg/ml. Polymerase chain reaction results revealed that only one P. aeruginosa isolate had silE gene and among A. baumannii isolates, 20 isolates had silE gene and six isolates had silS gene. None of the isolates showed positive results for the silP gene. Conclusion: Based on the results, A. baumannii was the most common microorganism of burn wounds in the burn ward of our hospital in Urmia. This study showed a high degree of phenotypic resistance to silver in A. baumannii and P. aeruginosa isolates which silE and silS genes were also observed in some isolates.