Enhanced recovery of injured and noninjured cells of Bifidobacterium species from water and dairy products

Bifidobacterium spp. are anaerobic, Gram-positive, nonmotile bacteria that are a major component of intestinal microbiota. They are potential indicators of human fecal pollution in shellfish harvesting waters. In addition, Bifidobacterium spp. are used as supplements in dairy products. These bacteria are easily injured and it is important to have methods that will recover all cells (injured and uninjured) present in water and food samples. The objectives of this research were to develop a repair detection (RD) procedure to be used with VPI's anaerobic roll tube apparatus for improving the recovery of Bifidobacterium and to compare this method with existing enumeration methods.

Bifidobacterium adolescentis cells were injured by exposure to pond water. Cells were enumerated using a modification of Human Bifid Sorbitol Agar (MHBSA). MHBSA was modified by substituting phenyl red for bromocresol purple and adding methylene blue as an indicator of oxidation/reduction.