Comparison of four low-cost carbapenemase detection tests and a proposal of an algorithm for early detection of carbapenemase-producing Enterobacteriaceae in resource-limited settings

Abstract

Rapidly progressing antibiotic resistance is a great challenge in therapy. In particular, the infections caused by carbapenem-resistant Enterobacteriaceae (CRE) are exceedingly difficult to treat. Carbapenemase production is the predominant mechanism of resistance in CRE. Early and accurate identification of carbapenemase-producing carbapenem-resistant Enterobacteriaceae (CP-CRE) is extremely important for the treatment and prevention of such infections. In the present study, four phenotypic carbapenemase detection tests were compared and an algorithm was developed for rapid and cost-effective identification of CP-CRE. A total of 117 Enterobacteriaceae (54 CP-CRE, 3 non-CP-CRE, and 60 non-CRE) isolates were tested for carbapenemase production using modified Hodge test (MHT), modified carbapenem inactivation method (mCIM), Carba NP test (CNPt), and CNPt-direct test. The overall sensitivity/specificity values were 90.7%/92.1% for MHT, 100%/100% for mCIM, 75.9%/100% for CNPt, and 83.3%/100% for CNPt-direct. OXA-48-like enzymes were detected with 93.2% sensitivity by MHT and >77.3% sensitivity by two Carba NP tests. MHT could only detect half of the NDM carbapenemase producers. CNPt-direct exhibited enhanced sensitivity compared to CNPt (100% vs 25%) for detection of NDM producers. Considering these findings we propose CNPt-direct as the first test followed by mCIM for rapid detection of CP-CRE. With this algorithm >80% of the CP-CRE could be detected within 24 hours from the time the sample is received and 100% CP-CRE could be detected in day two. In conclusion, mCIM was the most sensitive assay for the identification of CP-CRE. CNPt-direct performed better than CNPt. An algorithm consisting CNPt-direct and mCIM allows rapid and reliable detection of carbapenemase production in resource-limited settings.

Evaluation of direct Carba-NP (CNPt) for screening of carbaenemases production in Gram negative bacilli

“…The sensitivity of the test was 100% for all carbapenemase genes except for OXA-48 (79.5%).Therefore, they concluded that the OXA-48 producers were the main cause of false negative results of direct CNPt leading to reducing the overall sensitivity of the test. No IMP genes were found in their study [22]. These results are in accordance with our results where reduced sensitivity was only found with OXA-48 and IMP (91.6% and 85.7% respectively).…”

Multimodal Interventions to Prevent and Control Carbapenem-Resistant Enterobacteriaceae and Extended-Spectrum β-Lactamase Producer-Associated Infections at a Tertiary Care Hospital in Egypt

“…The infection control team had trained, monitored and provided feedback on hand hygiene and the use of gloves and gowns [ 52 , 53 ]. In case of carriage or infection with CRE, patient and staff cohorting were applied and such patients were preferably placed in a single room [ 54 , 55 ].…”

Performance Evaluation of Diagnostic Assays for Detection and Classification of Carbapenemase-Producing Organisms

“…The Rapidec Carba-NP kit (bioMérieux, La Balme-les-Grottes, France) is a rapid biochemical test based on detecting the hydrolysis of the β-lactam ring of imipenem. The test was performed in accordance with the manufacturer’s recommendations [ 31 ]. A full loop (10 μL) of bacterial colonies from a culture plate was mixed into the well c so that the turbidity is similar to well b.…”