Risk factors of extended-spectrum beta-lactamaseproducing Enterobacteriaceae bacteremia in Thai emergency department: a retrospective case-control study

Background: Infections caused by resistant extended-spectrum beta-lactamase (ESBL)-producing enteric bacteria and their risk factors are globally recognized. However, such risk factors have not been explored in emergency department (ED) where the first choice of empirical antimicrobials is crucial.

Objective: Determine risk factors of ESBL bacteremia in ED, especially in our geographic area.

Methods: A retrospective case-double-control study was conducted at King Chulalongkorn Memorial Hospital. All adult ED patients with ESBL-producing E. coli and K. pneumoniae in blood cultures between October 2007 and October 2008 were recruited for this study. The potential risk factors were analyzed and compared with non- ESBL-producing bacteremic patients (control group 1) and matched general ED patients (control group 2). Nonbeta- lactam susceptibility testing among the cohort was also evaluated.

Results: Thirty ESBL (cases), 103 group 1 controls, and 100 group 2 controls were assessed. Based on the univariate analysis, age, chronic kidney diseases, malignancy, poor functional status, previous hospitalization within 90 days, and previous antimicrobial exposure especially to cephalosporins, quinolones, and carbapenems within 30 days were the risk factors for ESBL bacteremia compared with both types of control patients. Age > 60 and previous cephalosporin use were consistently identified as the risk factors by multivariate models using both control groups. The susceptibility to non-beta-lactam agents in the ESBL group was significantly lower than the non-ESBL. No carbapenem resistance was found.

Conclusion: Elderly ED patients, especially those who had previous cephalosporin exposure within 30 days, were at higher risk of ESBL-producing bacteremic infections. ESBLs tended to have less susceptibility to the non-β-lactam agents.