224. Risk Factors for Extended-Spectrum Beta-Lactamase Producing Organisms: A Case-Case-Control Study
Session: Poster Abstract Session: Antimicrobial Resistance: Clinical Studies
Friday, October 21, 2011
Room: Poster Hall B1
Background: Multiple studies have observed an increase in the frequency of ESBL-producing organisms. At our medical center, the incidence of ESBL-producing E. coli and Klebsiella sp rose from 2.5 and 9.8% in 1999 to 25 and 28% in 2010, respectively. This prospective case-case-control study examines the risk factors for acquiring infections with ESBL-producing E. coli and Klebsiella sp, with special emphasis on prior antibiotic intake.

Methods: The first group of cases included patients with infections due to ESBL-producing E. coli and Klebsiella sp, and the second group were patients with infections due to sensistive strains matched by site of infection. Controls were patients hospitalized during the same period as the cases but who did not develop infections during their hospital stay. Two multivariable models were constructed, one including predictors of infection with ESBL-producing organisms, and the other including predictors of infection with susceptible strains.

Results: 453 patients were included in the study (152 resistant cases, 124 susceptible cases, and 177 uninfected controls). Bivariable analysis showed that both groups of cases were older and had higher Charlson scores. Cases (resistant and sensitive) were also more likely than controls to have the following risk factors within 30 days of admission: prior hospitalization, ICU stay, urinary catheter, central catheter, mechanical ventilation, surgery, and antibiotic use. 

The result of multivariable analysis is shown below:

 

Variable

Odds ratio

Resistant cases vs. controls

Susceptible cases vs. controls

Age

14.6

20.4

Surgery*

NS

4.5

Urinary catheter*

8.4

NS

Antibiotics*

25.7

5.5

*Within 30 days of admission

NS = not significant

Conclusion: Urinary catheter placement within 30 days seems to be a unique risk factor towards developing a resistant infection. Although antibiotic use within 30 days was a risk factor for both resistant and susceptible infections, it was a much stronger predictor of resistant infections, as evidenced by the considerable difference in odds ratios in the two models. The design of this study allows for a more reliable assessment of the risk factors for acquiring resistant infections compared to a traditional case-control design.


Subject Category: C. Clinical studies of bacterial infections and antibacterials including sexually transmitted diseases and mycobacterial infections (surveys, epidemiology, and clinical trials)

Mohamad Yasmin, Tania Baban, Souha Kanj, Rima Hanna Wakim, George Araj, Ghassan Matar, Ghassan Dbaibo and Zeina Kanafani, American University of Beirut Medical Center, Beirut, Lebanon

Disclosures:

M. Yasmin, US Department of Defense: Study Coordinator, Research grant

T. Baban, US Department of Defense: Study Coordinator, Research grant

S. Kanj, US Department of Defense: Investigator, Research grant

R. Hanna Wakim, US Department of Defense: Investigator, Research grant

G. Araj, US Department of Defense: Investigator, Research grant

G. Matar, US Department of Defense: Investigator, Research grant

G. Dbaibo, US Department of Defense: Grant Investigator, Research grant

Z. Kanafani, US Department of Defense: Investigator, Research grant

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