Detection of Lactococcus lactis phage P680, a heat resistant member of the 936 group of phages, by loop-mediated isothermal amplification (LAMP)

The loop-mediated isothermal amplification- (LAMP-) method was adapted for fast and easy detection of phage P680, a heat resistant member of the 936 group of Lactococcus lactis phages. A set of LAMP-primers targeting the major tail protein gene (mtp) were custom designed. The LAMP method for phage P680 detection was tested in water, in native (pH 6.55) and in acid whey (pH 4.60). DNA extraction from whey was optimised by inclusion of Chelex-100™ and a reliable detection of less than 10³ plaque-forming units mL−1 in the complex whey matrix could thus be achieved. By adding SYBR® Safe to the reaction mixture at the end of incubation, a simple visual evaluation of the result as either positive or negative was made possible. Besides the low detection limit, the advantages of LAMP include: (i) an easy to use protocol, (ii) inexpensive equipment, and (iii) a comparably short detection time.