Development and multicentric validation of a lateral flow immunoassay for the rapid detection of MCR-1-producing Enterobacteriaceae .

Background: Colistin has become a last resort antibiotic for the treatment of highly drug-resistant Gram negatives. Moreover, it has been widely used in the livestock sector. As a consequence, colistin resistance is emerging worldwide. Among colistin resistance mechanism, the spread of the plasmid-encoded colistin resistance gene mcr-1 (mostly in E. coli ) is of particular concern due to its increased transfer abilities compared to chromosome-encoded resistance. Early detection of MCR-1-producing bacteria is essential to prevent further spread and provide appropriate antimicrobial therapy. Methods: Lateral flow immunoassays (LFIAs) were manufactured with selected monoclonal antibodies. A collection of 177 human and 121 animal enterobacterial isolates were tested in a multicentric study. One bacterial colony grown on agar plates was suspended in extraction buffer and dispensed on the cassette. Migration was allowed for 15 minutes and the results were monitored by the appearance of a specific band. Results: The positive results showed a pink line resulting in an unambiguous interpretation. All MCR-1-producing isolates were found to be positive by the LFIA test and no false-negative results were observed. Three out of four MCR-2-producing isolates were also found to be positive. Our test does not detect MCR-3, -4, -5-producing isolates. Conclusions: LFIA allows the detection of MCR-1 with 100% sensitivity and 98% specificity. This test is fast, sensitive, specific, easy to use, and cost-effective and can therefore be implemented in any microbiology laboratory worldwide. The LFIA test is a major tool for rapid diagnosis and monitoring of MCR-1 producers in humans and animals.