E. Coli: Prior Colonization Adds to Risk

Prior colonization is one of the leading risk factors for Extended-Spectrum Beta-Lactamase (ESBL) -producing Escherichia coli (ESBL-EC) bacteremia a French study suggests. It is published in the October 2015 volume of International Journal of Infectious Diseases.

Denis Blandine, MD, of the Department of Infectious Diseases at Hôpital Saint-Louis, Paris, France, and colleagues investigated ESBL-EC bacteremia in patients with hematological diseases over a period of five years. Data was sourced from the hospital's microbiology lab using cases in adults from January 2005 to December 2009. Controls were established using additional cases during correlating times at the facility.

Debate exists on the impact on mortality of ESBL-EC bacteremia. Due to the limited treatment options and dramatic increase of ESBL-EC infections worldwide, the team analyzed the impact of these infections on length of hospital stay and 30-day mortality rates. They also isolated risk factors for hospitalization.

Data confirmed the rising trend in ESBL-EC bacteremia with an 8.3% increase (p = 0.003) throughout the study. Analysis of the 31 isolates found showed increased antibiotic resistance, ranging from 5% to 67%, within confirmed infections.

Of the studied cases, 13 were positive for previous colonization. The authors note, “DiversiLab patterns showed >92% similarity, with no band differences between the ESBL-EC bacteremia strain and the colonization strain in eight out of 10 patients. For the two remaining patients, DiversiLab patterns between ESBL-EC bacteremia strains and E. coli colonization strains (5/5c and 25/25c) showed 91% similarity (two different bands) and 59% similarity (six different bands), respectively.”

The most common portal of entry for the control group was urinary while a majority of the ESBL-EC group showed hematological malignancies. After univariate analysis, the researchers determined, “the only independent risk factor for ESBL-EC bacteremia was a known ESBL-EC colonization in the last 6 months (OR 11.3, 95% CI 1.2—107; p = 0.035).”

Research also focused on the impact of initial adequate treatment and its relation to length of stay and mortality. Overall, mortality was high with 30% for ESBL-EC cases and 27% for control cases (p = 0.82). Length of stay was noticeably similar with 15 days (Interquartile range IQR 10 — 21 days) for ESBL-EC cases and 11 days (IQR 7 – 17 days) for control cases (p = 0.88).

The researchers added that high Acute Physiology and Chronic Health Evaluation (APACHE) scores might influence both length of stay and mortality results. They also acknowledge limitations of the retroactive nature of the study, small sample size and the impact of a single institution on overall scope.