Detection of Helicobacter pylori in raw bovine milk by fluorescence in situ hybridization (FISH)

The transmission pathways of Helicobacter pylori in humans have not been fully elucidated. Research in the last decade has proposed that foodborne transmission, among others, may be a plausible route of human infection. Owing to the organism's fastidious growth characteristics and its ability to convert to viable, yet unculturable states upon exposure to stress conditions, the detection of H. pylori in foods via culture-dependent methods has been proven to be laborious, difficult and in most cases unsuccessful. Hence, nucleic acid-based methods have been proposed as alternative methods but, to date, only PCR-based methods have been reported in the literature. In the current study, fluorescence in situ hybridization (FISH) was used for the detection of H. pylori in raw, bulk-tank bovine milk. After repeated milk centrifugation and washing steps, the bacterial flora of raw milk was subjected to fixation and permeabilization and H. pylori detection was conducted by FISH after hybridization with an H. pylori-specific 16S rRNA-directed fluorescent oligonucleotide probe. Using this protocol, H. pylori was detected in four out of the twenty (20%) raw milk samples examined. The data presented in this manuscript indicate that FISH can serve as an alternative molecular method for screening raw bovine milk for the presence of H. pylori.