Analysis of CRISPR Regions in Food-borne Listeria monocytogenes
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Abstract:
In order to find out CRISPRs in 18 lineage I (serotype1/2b, 4b) strains of food-borne Listeria monocytogens isolated from 2177 retail food samples in Hebei province, the CRISPR sequences were obtained by PCR amplification, and homology analysis was predicted using bioinformatic methods, then cluster typed by using a CRISPR-based approach. We detected three CRISPR loci in all studied strains. Loucus1 was most popular (13/18); locus2 and locus3, as two activity loci , were only detected at least one in 5 serotype 1/2b strains. Locus1, a putative remnant of a functional CRISPR ancestor, was beared unconserved repeats (DR1) and a few of spacers; locus2 and locus3, relative new functional structures, were beared conserved repeats (DR2, DR3) and fast growing number of spacers. In all, 2 strains containerd all three loci, 3 strains contained the first 2 of the three loci, as well as 8 strains only contained the first one locus, and 5 strains did not find any CRISPR structure. As the diversity of CRISPR arrays, 18 strains typed to 5 clusters (A~F), and 4 subset clusters (A1and A2, B1 and B2). CRISPR typing can be good used in differentiating serotype 1/2b strains. In other hands, the CRISPR structures, especially that beared more spacers, enhance the host's environmental adaptability, enlarged the clear difficulty in food processing, alarm the food safety. The government should reinforce the control of these kinds of L. monocytogenes.
