A validated simple and rapid method for the simultaneous detection of both Cronobacter spp. and Salmonella spp. for infant formula quality control

Abstract

The presence of Cronobacter or Salmonella in powdered infant formulae represents a serious health risk when fed to newborn infants. The detection of these pathogens by standard food analysis methods takes around 3–6 days to provide an accurate result. In order to reduce the time of analysis to less than 24 h, a real-time PCR-based method for the simultaneous detection of both Cronobacter spp. and Salmonella spp. in powdered infant formula was designed combining two existing primer-probe sets, and included an internal amplification control to validate the negative results. Inclusivity and exclusivity of the PCR were tested with 70 strains of Cronobacter, 13 strains of Salmonella enterica, and 75 non-Cronobacter non-Salmonella strains. The method was validated against the reference standard methods ISO/TS 22964: 2006 for Cronobacter and ISO 6579: 2002 for Salmonella using powdered infant formula samples, but also with other powdered products which could represent a health risk for infants younger than 6 months, such as follow-up formulae and hydrolyzed cereals. The detection limit of the new method was set at 1 cfu in 10 g of food for Cronobacter and 1 cfu in 25 g of food for Salmonella after 18 h enrichment in buffered peptone water, fulfilling the requirements of the European Commission.