Genome-wide comparative analysis of CC1 Staphylococcus aureus between colonization and infection

Abstract

Background: Staphylococcus aureus is one of the most important bacteria in human colonization and infection. Clonal complex1 (CC1) is one of the largest and most important S. aureus CCs, and it is a predominant clone in S. aureus colonization and can cause a series of S. aureus infections including bloodstream infections. No studies on the relationship of CC1 S. aureus between colonization and infection have been published.

Methods: To figure out if there are some significant factors in CC1 S. aureus help its colonization or infection, 15 CC1 S. aureus isolates including ten from colonization and five from bloodstream infections were enrolled in this study. Whole-genome sequencing and bioinformatics analysis were performed.

Results: Virulence factor regulators XdrA, YSIRK signal peptide, CPBP family and OmpR family specifically found in infection isolates can promote virulence factors and enhance the pathogenicity of S. aureus. In addition, some significant differences in metabolism and human diseases were discovered between colonization and infection. Fst family of type I toxin-antitoxin system that mainly maintains stable inheritance was specifically found in CC1 S. aureus colonization isolates and might help S. aureus survive for colonization. No significant differences in genomic evolutionary relationship were found among CC1 S. aureus isolates between colonization and infection.

Conclusions: Virulence factor regulators and metabolic state can promote CC1 S. aureus pathogenic process compared with colonization, and it seems that the strains of colonization origin cannot have pathogenic potential. Experimental confirmation and a bigger number of CC1 S. aureus strains are necessary for further study about the details and mechanism between colonization and infection.

Keywords: Staphylococcus aureus; CC1; Colonization; Genome; Infection.

Fig. 1

The tree shows an evolutionary of 15 CCI S. aureus isolates based on 27 housekeeping genes, in which each branch represents one isolate, and the length of the branch is the evolutionary distance between two isolates

Fig. 2

Estimation of pan and core-genome size with the number of genomes. a Pan-genome; b core-genome. The abscissa is the number of genomes, the ordinate is the size of pan or core-genome. The equation for estimating pan and core-genome size according to PGAP is given with the respective graphs

Fig. 3

The ellipse or petal of each color in the figure represents a group, the number of crossed petals indicates the number of shared homologous genes, and the number of individual petals indicates the number of homologous genes specific to the group. a GBSI and GCOL; b G2014, G2019 and GBSI

Fig. 4

The horizontal and vertical coordinates represent the two selected principal components, and the percentage represents the contribution value of the principal component to the difference in sample composition. The scale of horizontal and vertical axes is relative distance and has no practical significance. Points with different colors or shapes represent isolates of different groups. The closer the two isolate points are, the more similar the two isolates are. a PCA-COG; b PCA-KEGG; c PCoA-COG; d PCoA-KEGG

Fig. 5

The right and lower sides are isolate names, the left and upper sides are isolate clustering, and squares of different colors represent the correlation between the two isolates. The closer the color is to 1, the better the correlation between the two isolates is. a Correlation heat-map based on COG; b correlation heat-map based on KEGG