Molecular characterization and genetic variability at κ-casein gene (CSN3) in camels.

κ-casein is a glycosilated protein belonging to a family of phosphoproteins (αs1, ß, αs2, κ) that represent the major protein component in mammalian milk. κ-casein plays an essential role in the casein micelle stabilization, determining the size and the specific function. In the present paper, we report for the first time the characterization of the nucleotide sequence of the whole κ-casein-encoding gene (CSN3) plus 1045 nucleotides at the 5' flanking region in Camelus dromedarius. The promoter region and the complete cDNA were also provided for the first time in Camelus bactrianus. The gene is spread over 9.3kb and consists of 5 exons varying in length from 33bp (exon 3) to 494bp (exon 4), and 4 introns from 1200bp (intron 3) to 2928bp (intron 2). Highly conserved sequences, located in the 5' flanking region, have been found. The regulatory regions of camels seems to be more related to equids than to other compared species. 17 polymorphic sites have been detected, one of these (g.1029T>C) is responsible for the creation of a new putative consensus sequence for the transcription factor HNF-1. In general, these SNPs are the first reported in camels for casein loci. Finally, seven interspersed repeated elements were also identified at intronic level.

Phenotypic and genotypic characterization of Staphylococcus aureus isolated from raw camel milk samples.

In the present study 320 milk samples collected from 160 apparently healthy camels of three different locations in Sudan were investigated for the presence of Staphylococcus aureus resulting in the isolation of this bacterial pathogen from 28 milk samples from 24 camels. Twenty-five S. aureus were identified phenotypically and by PCR mediated amplification of species-specific genes or gene segments. Investigation of the S. aureus for toxinogenic potential revealed that three S. aureus strains were positive for the enterotoxin encoding gene sec and the genes seg, sei, sem, sen and seo, representing the egc gene cluster. In addition all 25 S. aureus were positive for the superantigen-like encoding gene ssl7 (set1). Partial sequencing of gene sec of the three S. aureus strains yielded an almost complete sequence identity to the sequence of the sec variant sec2. However, all three sec2 genes of the present study showed a deletion of one base causing a frame shift and a corresponding earlier stop codon. According to the present results, the raw camel milk collected from three locations in Sudan seems to be, at least at this stage, of minor importance as vector causing staphylococcal food poisoning.