How important is patient-to-patient transmission in extended-spectrum β-lactamase Escherichia coli acquisition

Background Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli is an emerging pathogen. The causal role of antibiotic selective pressure versus patient-to-patient transmission has not been assessed. The objective of this study was to quantify the amount of patient-to-patient transmission among patients who acquire an ESBL-producing E coli infection using perianal surveillance cultures in an intensive care unit (ICU) population. Methods A prospective cohort of patients admitted between September 1, 2001, and September 1, 2004, to the medical and surgical ICUs at a tertiary care hospital was studied. Patients had perianal cultures on admission, weekly, and upon discharge. Strain typing by pulsed-field gel electrophoresis (PFGE) and epidemiologic criteria were used to quantify the amount of patient-to-patient transmission. Results There were 1806 patients admitted to the ICUs. There were 74 patients who had ESBL-producing E coli on admission to the ICU and 23 patients who acquired ESBL-producing E coli. Among these 23 patients, there were 14 PFGE types, and 3 (13%) patient acquisitions were defined as patient-to-patient transmission by similar PFGE type and overlapping time in the hospital. Conclusion Our data suggest that patient-to-patient transmission is not an important cause of the acquisition of ESBL-producing E coli colonization in the ICU setting.