Propidium Monoazide (PMAxx)-Recombinase Polymerase Amplification Exo (RPA Exo) Assay for Rapid Detection of <i>Burkholderia cepacia</i> Complex in Chlorhexidine Gluconate (CHX) and Benzalkonium Chloride (BZK) Solutions

Abstract

Both sterile and non-sterile pharmaceutical products, which include antiseptics, have been recalled due to Burkholderia cepacia complex (BCC) contamination. Therefore, minimizing the frequency of outbreaks may be conducive to the development of a quick and sensitive approach that can distinguish between live and dead loads of BCC. We have assessed an exo probe-based recombinase polymerase amplification (RPA) with 10 µM propidium monoazide (PMAxx) for selective detection of live/dead BCC cells in various concentrations of antiseptics (i.e., chlorhexidine gluconate (CHX) and benzalkonium chloride (BZK) solutions) after 24 h. The optimized assay conducted using a set of primer–probes targeting gbpT was performed at 40 °C for 20 min and shows a detection limit of 10 pg/µL of genomic DNA from B. cenocepacia J2315, equivalent to 104 colony-forming units (CFU/mL). The specificity of a newly designed primer and probe was 80% (20 negatives out of 25). The readings for total cells (i.e., without PMAxx) from 200 µg/mL CHX using PMAxx-RPA exo assay was 310 relative fluorescence units (RFU), compared to 129 RFU with PMAxx (i.e., live cells). Furthermore, in 50–500 µg/mL BZK-treated cells, a difference in the detection rate was observed between the PMAxx-RPA exo assay in live cells (130.4–459.3 RFU) and total cells (207.82–684.5 RFU). This study shows that the PMAxx-RPA exo assay appears to be a valid tool for the simple, rapid and presumptive detection of live BCC cells in antiseptics, thereby ensuring the quality and safety of pharmaceutical products.

Keywords

• <i>Burkholderia cepacia</i> complex
• recombinase polymerase amplification exo (RPA exo)
• propidium monoazide (PMAxx)
• non-sterilized pharmaceutical products