Objective:To investigate the relationship of pks gene islands with virulence genes, capsular serotypes and biofilm formation in Klebsiella pneumoniae ( Kp). Methods:A total of 113 Kp clinical isolates were collected in the First Affiliated Hospital of Fujian Medical University and divided into two groups based on the presence of pks gene islands: pks+ and pks- groups. The hypermucoviscous (HM) phenotype was detected by string test. Five virulence genes ( peg-344, rmpA, rmpA2, iucA, iroB) and six common capsular serotypes (K1, K2, K5, K20, K54, K57) were detected by polymerase chain reaction (PCR). The biofilm formation ability was measured by crystal violet staining. Results:Among the 113 Kp isolates, 46 were pks+ strains and 67 were pks- strains. The detection rate of HM phenotype was higher in the pks+ group than in the pks- group [87.0% (40/46) vs 43.3% (29/67)]. The detection rates of virulence genes ( peg-344, rmpA, rmpA2, iucA, iroB) and K1 serotype in the pks+ group were also higher than those in the pks- group ( P<0.05). The biofilm formation ability of the pks+ strains was higher than the pks- strains ( P<0.05). Conclusions:Kp strains carrying pks gene islands were likely to display a HM phenotype and mainly belonged to the K1 serotype. Most of the pks+Kp strains carried the virulence genes of peg-344, rmpA, rmpA2, iucA and iroB, and had a greater ability to form biofilms.