Laban jameed is a dried salty dairy product obtained by fermentation of milk using a complex population of lactic acid bacteria. Jameed is considered a traditional food product in most eastern Mediterranean countries and is usually made from sheep or cow milk. The aim of this study was to assess phage contamination of jameed dairy product. Two phages were isolated: one from sheep milk jameed (PPUDV) and the other from cow milk jameed (PPURV). Each of the two bacteriophages was partially characterized. The PPUDV phage was identified as a single stranded DNA virus with an approximately 20 kb genome that was resistant to RNase, whereas PPURV phage possessed a double stranded RNA genome of approximately 20 kb and was resistant to DNase. The phage bacterial strain hosts were identified as Lactobacillus helveticus and Bacillus amyloliquefaciens for PPUDV and PPURV, respectively. One step growth curve using a double layer plaque assay test was carried out to monitor the phage life cycle after host infection. PPUDV showed a latent period of about 36 h, burst period of 70 h and a burst size of about 600 Plaque Forming Units (PFU) per infected cell. PPURV phage showed a latent period of about 24 h, burst period of 47 h and a burst size of about 700 PFU per infected cell. SDS-PAGE analysis of total viral proteins showed at least three major bands (27, 40, and 45 kDa) for PPUDV. This is the first study to report the isolation of both DNA and RNA bacteriophages from laban jameed. This study adds new insights into the complexity of dairy contamination and fermentation microbiology of the jameed revealing the existence of two viral genomes in this highly dried and salty dairy product.
Aims
The gastro‐intestinal tract is a major reservoir of extended‐spectrum beta‐lactamase (ESBL) producing Escherichia coli. Bacillus spores may be used as probiotics to decrease digestive colonization by ESBL‐E. coli. Our aim was to assess the in vitro and in vivo activity of new Bacillus strains against ESBL‐E. coli.
Methods and Results
We screened the in vitro activity of 50 Bacillus strains against clinical isolates of ESBL‐E. coli and selected B. subtilis strains CH311 and S3B. Both strains decreased ESBL‐E. coli titers by 4 log10 CFU L−1 in an in vitro model of gut content, whereas the B. subtilis CU1 strain did not. In a murine model of intestinal colonization by ESBL‐E. coli, CH311 and S3B did not decrease fecal titers of ESBL‐E. coli. Ten sequences of putative antimicrobial peptides were identified in the genomes of CH311 and S3B, but not in CU1.
Conclusions
Two new B. subtilis strains showed strong in vitro activity against ESBL‐E. coli.
Significance and Impact of Study
Despite strong in vitro activities of new B. subtilis strains against ESBL‐E. coli, intestinal colonisation was not altered by curative Bacillus treatment even if their spores proved to germinate in the gut. Thus, this work underlines the importance of in vivo experiments to identify efficient probiotics. The use of potential antimicrobial compounds identified by genome sequencing remains an attractive alternative to explore.
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