Risk factors and molecular epidemiology of extended-spectrum β-lactamase-producing Klebsiella pneumoniae in Xiamen, China.

Objectives: The aim of this study was to evaluate the risk factors for pneumonia due to extended-spectrum β-lactamase-producing Klebsiella pneumoniae (ESBL-KP) and to analyse the molecular epidemiology of ESBL-KP in Xiamen, China.

Methods: A case-control study was conducted at Zhongshan Hospital from January 2014 to August 2015. Medical records of patients with nosocomial pneumonia caused by K. pneumoniae were collected. A total of 40 cases with ESBL-KP infection and 90 controls with non-ESBL-KP infection were included. The sequence types (STs) of the 40 ESBL-KP strains were determined by multilocus sequence typing (MLST).

Results: Univariate analysis primarily revealed an association between the following seven risk factors and ESBL-KP infection (P<0.10): length of hospitalisation; use of cephalosporins; use of quinolones; presence of a nasogastric tube; presence of an intravenous catheter; mechanical ventilation; and cerebrospinal fluid drainage. Furthermore, multivariate analysis revealed that use of cephalosporins and presence of a nasogastric tube were independent risk factors for ESBL-KP infection (P<0.05), with adjusted odds ratios of 3.473 [95% confidence interval (CI) 1.105-10.911; P=0.033] and 2.488 (95% CI 1.083-5.715; P=0.032), respectively. MLST identified 28 STs. The main STs were ST23 (10.0%) and ST37 (10.0%); three novel STs were identified.

Conclusions: Use of cephalosporins and presence of a nasogastric tube are independent risk factors for ESBL-KP infection. In addition, the discovery of three novel STs serves as a reminder to continuously monitor outbreaks of ESBL-KP infection.