Abstract: OBJECTIVE To detect the hypermucoviscosity (HM) phenotypes, capsular serotypes and major virulence gene in Klebsiella pneumoniae strains isolated from urine and observe the formation of biofilms. METHODS Totally 89 strains of K.pneumoniae were isolated from patients with urinary tract infection, the HM phenotype was determined by string test and all isolates were assessed for six common types of hypervirulent capsular serotypes (K1, K2, K5, K20, K54, K57) and ten common types of virulence genes (magA,rmpA, rmpA2,aerobactin,wcaG, mrkD,iroN, fimH,uge and ureA) by PCR.The formation of biofilm was determined by using microtiter dish biofilm formation assay. RESULTS Among the 89 strains of K.pneumoniae, all of the common types of high virulence genes were detected except K5.Totally 14 strains showed positive for the string test, accounting for 15.73%.The detection rate of the hypervirulent capsular serotype was 85.71%(12/14) in the HM phenotype strains, 6.67%(5/75) in the non-HM phenotype strains, and there was significant difference (χ²= 42.730, P＜0.001). FimH, uge, urea and mrkD were most prevalent among the virulence genes and distributed consistently in the HM phenotype strains and the non-HM phenotype strains, and there were no significant differences.The detection rates of other 6 types of virulence genes were significantly higher in the HM phenotype strains than in the non-HM phenotype strains (P＜0.05).The drug resistance rates of the HM phenotype strains to the commonly used antibiotics were significantly lower than those of the non-HM phenotype strains(P＜0.05).Totally 2 strains of extended-spectrum -lactamses (ESBLs)-producing HM phenotypes K.pneumoniae were identified, 1 of which was resistant to carbapenems.Totally 55 of 89 strains of K.pneumoniae formed the biofilms, with the positive rate 61.80%; the positive rate of formation of biofilms was 35.71%(5/14) in the HM phenotype strains, 66.67%(50/75) in the non-HM phenotype strains, and there was significant difference between the two groups (χ²=4.790,P=0.029). CONCLUSION It is necessary to attach great importance to the HM phenotype K.pneumoniae strains that result in urinary tract infection and are highly virulent and (or) positive for biofilms so as to prevent the wide spread.