Universal hospital admission screening for carbapenemase-producing organisms in a low-prevalence setting.

Background Carbapenemase-producing Enterobacteriaceae (CPE) are an emerging threat to healthcare providers worldwide. Objectives To determine CPE carriage rates and risk factors in an unselected hospital cohort at the time of admission. Methods We approached 4567 patients within 72 hours of admission to provide a rectal swab and answer a questionnaire on risk-factors for carriage. Rectal swabs were cultured for carbapenem-resistant organisms on chromogenic and non-chromogenic agar, and tested for carbapenemase production by PCR (Check-Direct CPE). The study was approved by the NHS Research Ethics Committee. Results Only 6 CPE were cultured from 5 (0.1%) of 4006 patients who provided a rectal swab; only 1 was cultured using non-chromogenic media. An additional 76 culture-negative rectal swabs were initially PCR positive, but none grew a carbapenem-resistant organism despite enrichment culture and only 2 were positive when retested several months later by Check-Direct and a second PCR assay (Cepheid GeneXpert® Carba-R). A modified Ct cut-off of <35 would have resolved these apparent false-positives. 40% of patients had a risk-factor that should prompt screening and pre-emptive isolation as defined by UK CPE guidelines but only 8.1% and 20.2% of these patients had been screened and pre-emptively isolated by clinical teams, respectively. Overseas hospitalisation was the only significant risk factor for CPE carriage (p<0.001, OR 64.3, 95% CI 7.3-488.5). Conclusions This study highlights a very low carriage rate of CPE. Hospitalisation abroad is the most important risk factor to guide admission screening in this low prevalence setting.