Laboratory detection of carbapenam resistant enterobacteriales from rectal swabs by direct agar and broth enrichment culture techniques

Gastrointestinal tract of patients colonized with Carbapenem-resistant Enterobacteriales (CRE) constitutes a major reservoir for transmission of CRE in healthcare facilities. Rapid horizontal spread of these CRE and paucity of available treatment options, accentuates the need for a simple and sensitive screening method for rapid identification and isolation of CRE colonized patients to improve the infection control measures.
Methods: The study was conducted in the Department of Microbiology from February to July 2019. Rectal swabs from 365 patients admitted to Intensive care units were collected. Swabs were subjected to four different culture based screening protocols. All isolates presumptively identified as CRE by screening methods were subjected to modified carbapenam inactivation method detection of carbapenamase production and confirmed by multiplex PCR.
Result: The overall prevalence of colonization of CRE was 19.7% (n =72). Out
of 72 CRE 30 isolates were detected only by direct ertapenam disc method and MacConkey broth enrichment technique. Both were 100% sensitive and 98% specific. Direct ertapenam disc method require 24 hrs and enrichment method needs 48 hrs for final result.
Conclusion: Direct ertapenem disk method is a simple, sensitive, and specific protocol with short turn around time than selective enrichment methods for screening rectal swab specimens for detection of carbapenamase producing CRE.