Colonization sites in carriers of ESBL-producing Gram-negative bacteria

The distribution of Extended-Spectrum Beta-Lactamase-producing Gram-negative bacteria(ESBL-GNB) colonizationsites is relevant for infection control guidelines on detection and follow-up of colonization. We questioned whether it is possible to rely solely on rectal swab culture for follow-up of ESBL-GNB colonization. We retrospectively assessed ESBL-GNB colonizationsites in patients in a tertiary hospital in the Netherlands. The Laboratory Information Management System was queried for all bacterial cultures obtained between January 2012 and August 2016. All patients with one or more cultures positive for ESBL-GNB were identified and the distribution of ESBL-GNB positive sample sites was assessed. A subgroup analysiswas performed on patients for whom at least one rectal swab specimen was available. We identified 1011 ESBL-GNB carriers with 16,578 specimens for analysis. ESBL-GNB were most frequently isolated from the rectum(506/1011), followed by the urogenital (414/1011) and respiratory tract (142/1011), and pus (136/1011). For 588 patients at least one rectal swab specimen was available. In this subgroup, ESBL-GNB colonizationwas detected only in the rectumin 55.4% (326/588) of patients, in 30.6% (180/588) in the rectumand a different culture site, and in 13.9% (82/588) no rectal colonizationwas detected. Rectal colonizationwith ESBL-GNB was detected in 86% of ESBL-GNB carriers. However, in 14% of ESBL-GNB carriers we did not detect rectal colonization. Therefore, samples taken for follow-up of colonizationwith multi-drug resistant Gram-negative bacteria(MDR-GNB) should ideally also include samples from the site where the MDR-GNB was initially found.