The average read size was used in analysis for each strain was 400 nt. De novo assembly yielded 77 and 113 contigs for A1VSSA and A2-VISA, respectively, composed of over 40 million total bases, with average read lengths of over 350 bp and a GC content of 32%.BLAST analysis of the 7MLST alleles(http://www .mlst.net/)(25)and spa repeat pattern alignment(RidomSpaServer; www.spaserver.ridom.de) confirmed that both isolates were sequencetype8(ST8)andspat008(33). In order to determine the best reference, the 454 data were remappedagainstfinishedgenomesoftwovancomycin-susceptible USA300 strains, TCH1516 (NC_010079) and FPR3757 (NC_007793) (21, 35). The sequencing data for A1-VSSA and A2-VISA (experimental strains) covered the entire genomes of bothUSA300referencesequences(averagegenome-widenucleotide coverage of 14 and 13, respectively). Both experimental strains contained the entire sequences of the two plasmids from TCH1516 (pUSA01HOU and pUSA300HOUMR) (35, 44). Sequencing coverage for the smaller plasmid was between 200 and 1,000, while the larger plasmid was covered about 90 for A1VSSA and 200 for A2-VISA. There were at least 70 putative SNPs and one indel that A1VSSA and A2-VISA shared in common compared to either reference strain. Because our strains were more related to TCH1516, this genome was used as the reference strain for further comparative analysis. The complete list of variants discovered in the experimentalstrainsandTCH1516arelistedinTableS1inthesupplemental material. Additionally, we noted that two particular regions were divergent in the experimental strains and strain TCH1516. First, an approximately 600-bp region of the chromosome overlapping two tandem lipoproteins (USA300HOU_0109 and USA300HOU_0110) was missing in both experimental strains. Second, a putative noncoding RNA region annotated as
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