OBJECTIVETo explore the risk factors for nosocomial infection caused by extended-spectrum beta-lactamases (ESBLs)-producing bacteria in hospitals of Zhejiang province.

METHODSOne hundred and eighty-five cases with nosocomial infection (108 men and 77 women, with an average age of 55 +/- 17 years) caused by positive-ESBLs bacteria, including 59 cases of respiratory infection, 71 with urinary infection, ten with blood infection, 30 with wound infection and 59 with other infection, and 77 controls with nosocomial infection (54 men and 23 women, with an average age of 54 +/- 20 years) caused by negative-ESBLs bacteria, including 38 cases of respiratory infection, 20 with urinary infection, six with blood infection, eight with wound infection and five with other infection, from six hospitals in Zhejiang Province were studied during May 1999 to May 2000. Data were analyzed with unconditional logistic regression and principal component analysis (PCA).

RESULTSMultivariate unconditional logistic regression analysis showed that the independent risk factors for nosocomial infection were use of the third generation cephalosporins for more than three days (odds ratio, OR 4.52, 95% confidence interval of OR 2.30 - 8.89), combined use of antibiotics (OR 2.86, 95% CI 1.51 - 5.43), use of quinolones for more than three days (OR 2.44, 95% CI 1.18 - 5.04), use of adrenal cortical hormone (OR 2.16, 95% CI 1.08 - 4.31) and oxygen inhalation (OR 2.56, 95% CI 1.14 - 5.72). Five principal components were extracted from the 14 risk factors for nosocomial infection with ESBLs-producing bacteria by principal component analysis, with a contribution of cumulative variance of 60.2%, and arranged in an order as follows, use of ventilator, tracheal intubation or tracheotomy, oxygen inhalation, retaining needle in vein, indwelling urethral catheter, use of the third generation cephalosporins over three days, hospitalization over ten days, use of quinolones over three days, combined use of antibiotics, use of aminoglycosides antibiotic over a week, use of adrenal cortical hormone, catheterized examination and prophylactic use of antibiotics.

CONCLUSIONSNosocomial infection with ESBLs-producing bacteria could attribute to multiple factors, mainly to invasive manipulation and use of antibiotics.