Efficacy and acceptability of rectal and perineal sampling for identifying gastrointestinal colonisation with ESBL-Enterobacteriaceae

Objectives We evaluated ‘pre-laboratory’ factors associated with the detection of ESBL-producing Enterobacteriaceae (ESBL-E) colonisation including anatomical site, and staff and patient factors. Methods All admissions to a large London hospital over three months were approached to provide rectal and perineal swabs, which were cultured for ESBL-E using chromogenic media. ESBL-E detection rates for patient or staff-collected rectal or perineal swabs were compared using McNemar Tests. Binary logistic regression was used to explore factors associated with patients declining to provide a rectal swab. The impact of simplifying the verbal study description to patients to improve the participation rate was evaluated. Results ESBL-E carriage was significantly higher in rectal vs. perineal swabs (7.8% of 4006 vs. 3.8% of 4006, p<0.001), whether collected by staff or patients. 31.9% of 869 patients did not provide a rectal swab before the change in study description compared with 7.6% of 3690 patients afterwards (p<0.001). In multivariable analysis, factors associated with patients declining to provide a rectal swab were younger age (odds ratio (OR) 0.99, 95% confidence interval (CI) 0.99-1.00), female gender (OR 1.26, CI 1.04-1.52), transfers from other hospitals (OR 1.77, CI 1.07-2.93) or an unknown admission route (OR 1.61, CI 1.09-2.37), being admitted before the change in study description (OR 0.39, CI 0.31-0.48), and the staff member who consented the patient (p<0.001); ethnicity was not a significant factor.. Conclusions Rectal swabs are recommended for the detection of ESBL-E colonisation. Staff and patient factors influence whether patients participate in prevalence studies, which may skew their findings.