Article Subject: Medical Bacteriology 10.30699/ijmm.13.3.164 Background and Aims: The type IV Pilin is an important colonization factor for opportunistic pathogens of Pseudomonas aeruginosa, which plays a role in the formation of biofilms and binding to the host cells. Each type of Pilin is coded with a particular auxiliary gene. This specific relationship can be used as a therapeutic target for detecting P. aeruginosa strains as well as its molecular classification. The purpose of this study was to evaluate the frequency of different types of auxiliary genes in cystic fibrosis, burns, and environmental samples. Materials and Methods: Pseudomonas aeruginosa samples were collected from patients with cystic fibrosis, burns as well as environmental wastewaters during 2016-2017. Samples were cultured and identified using standard microbial and biochemical methods. DNA extraction was performed by boiling and PCR was performed through specific primers. Results: Totally, 90 isolates of P. aeruginosa samples (35 environmental, 30 burns, and 25 cystic fibrosis) were examined. tfpO and tfpZ were positive in 71 and 2 isolates, respectively. Conclusion: The results indicated that Pseudomonas aeruginosa Pilin types are very diverse. Regardless of the source of the samples, the most common tfp was tfpO. Taking into account the fact that tfpZ was found only in burns, it can be assumed that this particular type may appear in severe clinical conditions. Ultimately, larger statistical population and use of more comprehensive typing methods is suggested for better results.