Incidence of Chryseobacterium spp. in raw milk and some dairy products

Abstract

A total of 225 random samples of raw cow milk (150), Kareish cheese, Domiati cheese and butter (25 samples each), were collected from various farmers’ houses, dairy shops, street vendors and supermarkets located at Aswan city, Egypt, to be examined by culture and molecular methods in which 16S rRNA gene was used; the obtained PCR product was then purified and sequenced to detect the existence of Chryseobacterium spp. All cheese and butter samples didn’t show the characteristic colonies of Chryseobacterium spp., while two raw cow milk samples exhibited the characteristic Chryseobacterium colonies. The suspected Chryseobacterium spp. were confirmed by PCR and DNA sequencing and comparing the sequenced DNA with those on GenBank using the BLAST tool on GenBank, underlining its occurrence in raw cow milk samples with an incidence of 1.3%. The isolated strains showed the highest similarity with Chryseobacterium jip 108/83 (100%). According to obtained data and our knowledge, it is the first time to isolate Chryseobacterium spp. from raw milk in Egypt. The isolated strains were registered on the GenBank with the proposed names Chryseobacterium Egyam strain AM1 (Accession No. MK059947) and Chryseobacterium Egyam strain AM2 (Accession No. MK059948). A constructed phylogenetic tree by using the neighbour-joining method was applied to detect the exact taxonomic position of the obtained strains.