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286 Risk Factors Associated with Extended-Spectrum β-Lactamase (ESBL) Blood Stream Infection (BSI)

Saturday, April 2, 2011
Trinity Ballroom (Hilton Anatole)
Teena Chopra, MD , Detroit Medical Center, Wayne State University, Detroit, MI
Paul C. Johnson, MD , Detroit Medical Center, Wayne State University, Detroit, MI
Indu Chalana, MD , Detroit Medical Center, Wayne State University, Detroit, MI
Sanjeev Patil, MD , Detroit Medical Center, Wayne State University, Detroit, MI
Zeinab Tamam, MD , Detroit Medical Center, Wayne State University, Detroit, MI
Mazin Mohammed, BS , Detroit Medical Center, Wayne State University, Detroit, MI
Shatha Alkatib, MD , Detroit Medical Center, Wayne State University, Detroit, MI
Ryan Tansek, BS , Detroit Medical Center, Wayne State University, Detroit, MI
Khawar Chaudhry, BS , Detroit Medical Center, Wayne State University, Detroit, MI
Dror Marchaim, MD , Detroit Medical Center, Wayne State University, Detroit, MI
Jing J. Zhao, PharmD , Detroit Medical Center, Wayne State University, Detroit, MI
Jason M. Pogue, PharmD , Detroit Medical Center, Wayne State University, Detroit, MI
Sorabh Dhar, MD , Detroit Medical Center, Wayne State University, Detroit, MI
Keith S. Kaye, MD, MPH , Detroit Medical Center, Wayne State University, Detroit, MI

Background: Scant data exist regarding the factors predictive of BSI due to ESBL-producing organisms in hospitalized patients. 

Objective: The objective of this study was to analyze risk factors of BSI due to ESBL organisms. 

Methods: A retrospective matched case-control study including 103 cases of BSI due to ESBLs and 103 matched controls with no positive ESBL infection was conducted at Detroit Medical Center from December 2004 to August 2009.  Patients with positive blood cultures for ESBL organisms were identified from laboratory data.  Controls were matched to case patients in a 1:1 ratio based on admitting hospital, admitting unit, and at risk period (admission to positive culture date).  Patient variables collected included demographics, comorbid conditions, empiric antibiotic use, surgeries, mechanical ventilation, central lines, Foley catheters, and inpatient mortality. Antibiotic exposure in cases was defined as administration of an antibiotic from thirty days prior to culture date up to one day prior to culture date.  In controls, antibiotic exposure was defined as administration of any antibiotic from thirty days prior to discharge. Logistic regression was used to identify risk factors for BSIs due to ESBLs.  

Results: Mean age of cases and controls was similar (67±16 and 59±18 respectively, p=0.001).  51% of cases were male versus 42% of controls (p=0.3). Ethnicity was found to be different with 77% of cases versus 88% of controls being African-American (p=0.04).  Mcabe score was identical between the two cohorts (median score 2, 95% CI 0-6, p-value 0.9). Charlson's comorbidity index was median of 3 (0-6) in cases versus median of 4 (2-7) in controls (p=0.01).  38% of cases were admitted from home versus 82% of controls (p<0.0001).  

On multivariate analysis, the risk factors listed in following table were found to be significant.

Risk Factor

Odds Ratio (95% CI)

p-value

Dementia

3.8 (1.08-13.41)

0.04

Central Line Placed

10.6 (3.23-34.68)

<0.0001

Foley Catheter Placed

4.9 (1.61-14.87)

0.005

When we included prior antibiotics in the model, the following antibiotics were found to be associated with higher ESBL BSI acquisition: cefepime (OR 19.1, 95% CI 1.54-234.87) and β-lactam/β-lactamase-inhibitor combinations (BLABLI) (ampicillin/sulbactam and pipericillin/tazobactam) (OR 25.7, 95% CI 1.01-657.03).  Approaching statistical significance was usage of any carbapenem (OR 80.8, 95% CI 0.51-12859.37).

Conclusions: Central line placement, Foley catheter placement, and history of dementia were associated with higher risk of developing a BSI due to ESBLs. Among antibiotic exposure, use of cefepime, carbapenems, and BLABLI prior to positive culture were strongly associated with development of ESBL BSI.