In cystic fibrosis individuals, chronic lung infections and hospital-acquired pneumonia are caused by Pseudomonas aeruginosa. P. aeruginosa generates siderophores such as pyoverdine (PVD) as iron uptake systems to cover its needs of iron ions for growth and infection. lasR quorum sensing (QS) gene has a crucial function in PVD production and biofilm generation in P. aeruginosa. Fifty isolates of P. aeruginosa were obtained from clinical specimens of sputum (collected from individuals suffering from pulmonary infections). Antibiotic sensitivity test was performed for 50P. aeruginosa isolates by using 10 different types of antibiotics. All isolates of P. aeruginosa showed resistance for all 10 using antibiotics in this study. Ten multidrug resistant isoloates of P. aeruginosa were selected for next tests. Virulence factors of ten multidrug resistant isolates of P. aeruginosa, such as biofilm generation, PVD production, and lasR gene were detected. From results, all 10P. aeruginosa isolates can produce biofilm, PVD, and contain lasR gene. The produced amplicon for the lasR gene was 725 bp. After mice injection by fresh and heated PVD produced by P. aeruginosa PS10 LC619328.2, the fresh PVD caused 100 % mortality within five days using 0.3 ml of its concentration (37.4 lM), while (15.3 lM) of heated PVD (toxoid) caused 50 % mortality