Characterization and application of antimicrobials produced by Enterococcus faecium S6 isolated from raw camel milk.

The emergence of antimicrobial resistance in the food chain and the consumer's demand for safe food without chemical preservatives have generated much interest in natural antimicrobials. Thus, our main goal was to study the mode of action of the crude extract, the enterocins, and the organic acid produced by a bacteriocinogenic Enterococcus faecium strain S6 previously isolated from raw camel milk. Then, we aimed to evaluate their potential application in a food system. These antimicrobials exhibited antimicrobial activity against Listeria monocytogenes, Salmonella enterica, and Escherichia coli. The enterocins were synthesized as primary metabolites beginning at the lag phase, with optimal production at the exponential and stationary phases. The antimicrobials had a direct effect in extending the lag phase of L. monocytogenes, along with a significant inhibitory activity. The organic acid, in particular, inhibited both L. monocytogenes and S. enterica by inducing a total lysis and damage of the cell wall. The enterocins acted on disrupting the cell wall with pore formation, leading to cell death. Moreover, the crude extract revealed a combined inhibitory activity between enterocins and organic acid. Furthermore, the antimicrobials showed promising results through inhibiting L. monocytogenes cells in milk samples up to 1 wk at 4°C.

Characterization of semipurified enterocins produced by Enterococcus faecium strains isolated from raw camel milk.

Food safety has become an issue of great interest worldwide. Listeria monocytogenes is a food-borne pathogen that causes listeriosis and is difficult to control in the dairy industry. The use of lactic acid bacteria (LAB) and their antimicrobial substances against Listeria is promising in food applications. Here, we report the isolation from raw camel milk of LAB displaying antilisterial activity. Two isolates were selected for their secretion of bacteriocin(s) and identified by 16S rRNA sequencing as Enterococcus faecium S6 and R9. The produced bacteriocins were partially purified by ammonium sulfate precipitation and then biochemically characterized. Antimicrobial activity was estimated to be 6,400 and 400 AU (arbitrary units)/mL for E. faecium S6 and R9, respectively. The proteinaceous nature of the bacteriocins was confirmed via enzymatic reactions. Moreover, lipolytic and glycolytic enzymes completely inactivated the antimicrobial effect of the bacteriocins. These bacteriocins were heat-resistant and stable over a wide range of pH (2.0 to 10.0). To confirm its inactivation by lipolytic and glycolytic enzymes, the bacteriocin of E. faecium S6 was further purified by gel filtration, which suggested the existence of carbohydrate and lipid moieties. In addition, enterocin-coding genes were identified by PCR, showing DNA fragments corresponding in size to enterocins A, B, and P for E. faecium S6 and to enterocins B and P for E. faecium R9. In conclusion, these results indicate that partially purified bacteriocins from E. faecium S6 and R9 may be beneficial in controlling Listeria in the dairy industry.

Data on microbial diversity of camel milk microbiota determined by 16S rRNA gene sequencing.

Raw camel milk samples were collected from three geographical locations (south, north and middle Kuwait) during two seasons. Next generation sequencing of the V3-V4 regions of the 16S rRNA gene was used to analyze the bacterial community in camel milk. DNA was extracted from one hundred thirty-three samples, and libraries were prepared using custom fusion primers of the 16S rRNA gene and sequenced on Illumina HiSeq 2500 platform. 16S rRNA gene sequences were aligned against the SILVA database SSU release 138. The high-throughput sequencing data are available at the NCBI database under the Bioproject PRJNA814013. This work describes camel milk's bacterial diversity among different geographical locations and seasons. The distribution of alpha diversity measures among camel milk sample groups collected from different geographical locations and seasons is presented. A significant effect of these parameters on camel milk's bacterial diversity was shown. Linear discriminant analysis (LefSe) showed significant differentially abundant bacteria at the phylum, class, order, family and genus level among the three locations and seasons. LefSe identified a total of 83 and 40 differentially abundant genera in the different geographical locations and seasons, respectively. More details about the bacterial composition of raw camel milk at the phylum and genus level can be found in research article [1]. These data can be used to compare the diversity of milk bacterial community between different milk producing species and camels from different parts of the world. Besides, these findings will contribute to our understanding of the camel microbiome structure and might be useful for designing an appropriate control program in the camel dairy herd. The data described in this article are available in Mendeley Data [2].

Camel milk microbiota: A culture-independent assessment.

Camel milk is renowned for its nutritional value and its therapeutic properties. It is considered a promising alternative to bovine milk due to its higher nutritional benefits, hypoallergenic characteristics and greater digestibility in the human gastrointestinal system. This study reports camel milk's bacterial and fungal microbiota, and the effect of geographical location and season on its bacterial community. We sequenced the V3-V4 regions of the16S rRNA gene for bacteria and the internal transcribed spacer (ITS) for fungi. A total of 134 samples of dromedary raw camel milk were collected from south, north and middle Kuwait during two seasons. Raw camel milk showed a diversified bacterial community, with 1196 genera belonging to 33 phyla. The four most predominant phyla of bacteria were Proteobacteria, Firmicutes, Actinobacteria and Bacteroidota. The core microbiota of raw camel milk, represented by the dominant genera shared by the majority of samples, was constituted by the genera Schlegelella, Paenibacillus, Lactobacillus, unclassified Comamonadaceae, Pediococcus, Moraxella, Acinetobacter, Staphylococcus, Enterococcus, Pseudomonas, Streptococcus, unclassified Micrococcaceae, Rothia, unclassified Sphingomonadaceae, unclassified Neisseriaceae and Sphingomonas. The fungal population was assessed in 14 raw camel milk samples, and comprised 87 genera belonging to 3 phyla. The genera Penicillium, Cladosporium, Candida, Aspergillus, Alternaria and Fusarium, dominated the fungal community. These findings shed light on raw camel milk's core bacterial and fungal microbiome. The geographical location and the season had a significant impact on the diversity and composition of camel milk microbiome.

Bayesian estimation of ELISA and gamma interferon test accuracy for the detection of bovine tuberculosis in caudal fold test-negative dairy cattle in Kuwait.

Bovine tuberculosis (TB) is endemic in Kuwait; cattle identified as TB-positive using the caudal fold test (CFT) are culled. We used a Bayesian approach to estimate the sensitivity (Se) and specificity (Sp) of the IFNγ assay and ELISA, which are not routinely used in Kuwait in CFT-negative dairy cattle. Blood samples from CFT-negative cattle ( n = 384) collected from 38 dairy farms were tested by IFNγ assay and ELISA. The Se and Sp (95% CI) of the IFNγ were 85.0% (67.6-95.3%) and 90.4% (86.7-95.3%), respectively, whereas estimates for the ELISA were 61.1% (33.1-84.6%) and 85.4% (81.7-88.8%). TB prevalence (95 CI%) in CFT-negative cattle was estimated as 2.6% (0.5-9.5%). The IFNγ assay may play a role as an ancillary test for the identification of Mycobacterium bovis-infected cattle that are undetected by CFT.