Optimization of the methodology to enumerate Lactobacillus delbrueckii phages

EBRECHT, A. C.; GUGLIELMOTTI, D. M.; REINHEIMER, J. A.; SUÁREZ, V. B.

FOOD PROTECTION TRENDS

International Association for Food Protection

Año: 2010 p. 25 - 29

0325-3384

The influence of incubation temperature, presence of calcium cations in soft-agar (double-layer plaque titration), nature of inoculum used (from broth or reconstituted skim milk, RSM) and addition of glycine on enumeration of Lactobacillus delbrueckii phages was studied. Assays were performed on two temperate and three virulent Lactobacillus delbrueckii phages. Results showed that the diverse conditions influenced the number and definition of phage plaques. The addition of calcium to the soft-agar increased (ANOVA test, P < 0.05) by one log order the counts of all phages studied. The presence of glycine improved the definition and size of plaques for some phages, but not their counts. The origin of inoculum was important for phage Cb1/204, since plaques were more visible when an inoculum from RSM was used.Some species of lactic acid bacteria phages are fastidious for counting, and an optimized methodology can allow overcoming this problem. This study demonstrates enhanced detection of phage particles, assuring the correctness of visualization and quantification of them.