Development and Multicentric Validation of a Lateral Flow Immunoassay for Rapid Detection of MCR-1-Producing

Colistin has become a last-resort antibiotic for the treatment of infections caused by highly drug-resistant Gram-negative bacteria. Moreover, it has been widely used in the livestock sector. As a consequence, colistin resistance is emerging worldwide. Among the colistin resistance mechanisms, the spread of the plasmid-encoded colistin resistance gene (mostly in ) is of particular concern due to its increased transferability compared to that of chromosome-encoded resistance. The early detection of MCR-1-producing bacteria is essential to prevent further spread and provide appropriate antimicrobial therapy. Lateral flow immunoassays (LFIAs) were manufactured with selected monoclonal antibodies. A collection of 177 human and 121 animal enterobacterial isolates was 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 min, and the results were monitored by the appearance of a specific band. 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, 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-, MCR-4-, or MCR-5-producing isolates. 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. LFIA is a major tool for the rapid detection and monitoring of MCR-1 producers in humans and animals.