Evaluation of a novel chromogenic screening method for detection of carbapenem-resistant Escherichia coli

Introduction. Early detection of carbapenem-resistant Escherichia coli (CREco), categorized as a critical priority pathogen by the World Health Organization (WHO), is crucial in optimizing therapeutic options and to thwart outbreaks in clinical settings. Gap statement. The need of the hour is a diagnostic method that can detect carbapenem resistance conferred by intrinsic or acquired carbapenem resistance mechanisms or both. Aim. The study investigates the performance of a novel screening chromogenic method for detection of CREco. Methodology. Carbapenem-susceptible (n=23) and non-susceptible (n=90) E. coli were used to investigate the efficiency of the blue chromogenic test. All of the isolates were received from a tertiary referral hospital in Silchar, India and subjected to the blue chromogenic test and observed for colour change. A colour change from colourless to blue is interpreted as a positive result. The test results were further compared with available methods for detection of carbapenem resistance conferred by carbapenemase production or other carbapenem resistance mechanisms. Results. The blue chromogenic test generated 100 % (CI: 95.98–100 %) sensitive and 100 % (CI: 85.75–100 %) specific results for the detection of CREco with no false-positive or false-negative results. Within 3 h after incubation, the test detects all CREco with carbapenemase activity. Additionally, the blue chromogenic test also positively detected E. coli harbouring carbapenemase variants and with efflux and porin activity, compared to other phenotypic-based approaches. Conclusion. The study highlights a novel method that is highly sensitive and specific, inexpensive, rapid and user-friendly for the detection of CREco. With the surge and expansion of CREco, this sensitive, specific, user-friendly and inexpensive method can be used in laboratories with limited facilities for early detection of CREco, thereby improving infection control along with averting future outbreaks.