Abstract
Cronobacter spp. can cause systemic infections, such as meningitis, sepsis, and necrotizing enterocolitis, in immunocompromised patients, especially neonates. Although some virulence factors have been reported previously, the pathogenesis of Cronobacter remains unclear. In this study, we compared genome sequences from different Cronobacter species, sequence types, and sources, with the virulence genes in the virulence factor database. The results showed that Cronobacter has species specificity for these virulence genes. Additionally, two gene clusters, including sfp encoding fimbriae and hly encoding hemolysin, were discovered. Through cell adhesion, cytotoxicity, and hemolysis assays, we found that the isolates possessing the two gene clusters had higher cytotoxicity and stronger hemolysis capacity than those of other isolates in this study. Moreover, analysis of type VI secretion system (T6SS) cluster and putative fimbria gene clusters of Cronobacter revealed that T6SS have species specificity and isolates with high cytotoxicity possessed more complete T6SS cluster construction than that of the rest. In conclusion, the two novel gene clusters and T6SS cluster were involved in the mechanism underlying the cytotoxicity of Cronobacter.
Highlights
Cronobacter spp. can cause systemic infections in immunocompromised patients, especially neonatal meningitis, sepsis, and necrotizing enterocolitis in neonates
There were 28 virulence genes in C. sakazakii, 11 in C. malonaticus, 15 in C. dublinensis, 9 in C. turicensis, and 10 in C. muytjensii possessed by different species (Figure 1B)
The genome sequences of the isolates in this study were submitted to CRISPRCasFinder3, and the results showed that most of the isolates, except for C. dublinensis SD69 and C. muytjensii SD92, possessed Crispr 1 (Table 1)
Summary
Cronobacter spp. can cause systemic infections in immunocompromised patients, especially neonatal meningitis, sepsis, and necrotizing enterocolitis in neonates. Seven different species of Cronobacter have been identified, namely Cronobacter sakazakii, Cronobacter malonaticus, Cronobacter turicensis, Cronobacter muytjensii, Cronobacter dublinensis, Cronobacter universalis, and Cronobacter condimenti (Joseph et al, 2012b). These bacteria were observed to adhere to different epithelial cell lines and even persist in macrophage cells (Mange et al, 2006; Townsend et al, 2008). Enterotoxin production by the bacteria was initially evaluated
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