Loop-mediated isothermal amplification assay detects multiple alleles of blaOXA-51-like genes in Acinetobacter baumannii and other Gram-negative bacteria despite primer-template mismatches

Abstract

The known intrinsic and polymorphic blaOXA-51-like genes of Acinetobacter baumannii were recently reported in other non-A. baumannii Gram-negative pathogens. Accurate detection of this potentially transferrable carbapenemase gene in the clinical setting is critical. This study developed a loop-mediated isothermal amplification (LAMP) assay targetting multiple alleles of blaOXA-51-like genes. Specifically, an alignment-based primer design, in silico primer screening, and in vitro assay confirmation were conducted. Both in silico and in vitro results revealed the tolerance of the LAMP assay to up to five primer-template mismatches outside the 3′-end primer regions. Within 90 min, the LAMP assay also detected the gene targets in other Gram-negative bacteria with known and novel blaOXA-51-like genes. Finally, it showed a superior limit of detection (as low as 101 CFU/mL) compared with polymerase chain reaction, and high specificity against non-targets. This study developed a highly adaptable LAMP assay to monitor blaOXA-51-like genes in the clinical setting and provided important insights into LAMP primer design and screening.

Keywords

• Acinetobacter baumannii
• Carbapenemase
• Loop-mediated isothermal amplification
• OXA-51