An immunoliposome-based immunochromatographic strip assay for the rapid detection of Cronobacter species

Cronobacter species are foodborne pathogens that pose a high risk in infant formula and can cause fatality rates of 40-80% in infected infants. To develop a rapid and easy detection method for Cronobacter species, especially in powdered infant formula (PIF), an immunoliposome-based immunochromatographic strip assay was developed using an anti-Cronobacter immunoglobulin G (IgG)-conjugated liposome and an anti-Cronobacter IgGcoated nitrocellulose membrane. The developed assay could detect Cronobacter species in both pure culture and artificially contaminated PIF. The detection limits of the developed assay were 10(6)-10(7) colony forming units (CFU)/mL in pure culture and 10(7)-10(8) CFU/g in PIF by visual judgment, respectively. When the immunoliposome-based immunochromatographic strip assay results were analyzed using QuantiScan, the detection limit decreased to 10(5)-10(7) CFU/mL in pure culture and 10(6)-10(8) CFU/g in PIF, except for Cronobacter malonaticus. Furthermore, visual judgment showed that the developed immunochromatographic strip could not detect Cronobacter malonaticus in pure culture or PIF. However, Cronobacter malonaticus could be detected after QuantiScan analysis, and the detection limits were 10(8) CFU/mL and 10(8) CFU/g in both pure culture and PIF. This developed immunoliposome-based immunochromatographic strip assay is simple, easy, and effective method to detect Cronobacter species and thus could be widely applied in the food industry, research institutes, and even for onsite detection.