Multiplex PCR for detection and identification of dairy bacteriophages in milk

DEL RÍO, BEATRIZ; BINETTI, ANA; MARTÍN, M. CRUZ; FERNÁNDEZ, MARÍA; H. MAGADÁN, ALFONSO; ÁLVAREZ, MIGUEL A.

Egmond an zee (Holanda)

Simposio; VIIIth Symposium on Lactic Acid Bacteria; 2005

Bacteriophage infection of starter lactic acid bacteria (LAB) continues being a serious challenge in the dairy industry. The presence of phages causes slow acid procuction or total failure of the fermentation resulting in substantial economic losses. Therefore, it is necessary to develop fast and sensitive methods to detect and identify dairy phages in the milk or in any critical point during the manufacture process. This study describes a simple and rapid multiplex PCR method to detect, in a single reactiona, the presence of bacteriophages infecting Streptococcus thermophilus, Lactobacillus delbreuckii subsp bulgaricus and the three genetically distinct groups of Lactococcus lactis phages that are found in dairy plants, namely 936, c2 and P335 “·species”. Different regions of each bacteriophage genome were compared and the conserved regions were used to desing five pairs of primers, one of each bacteriophage “specie”. The primers were designed to generate specific PCR fragments with different sizes that allow to identify the phage specie detected. This method, that has been patented together with the company “Corporación Alimentaria Peñasanta S. A.”, can be easily incorporated in the dairy industry in order to drive contaminated milk into processes not involving sensitive bacteria or to processes with milk treatments capable of inactivating the phages.