Possible roles of LysR-type transcriptional regulator (LTTR) homolog as a global regulator in Cronobacter sakazakii ATCC 29544

Cronobacter sakazakii is a Gram-negative opportunistic pathogen that causes necrotizing enterocolitis, sepsis, and meningitis in premature infants. The genetic basis of C. sakazakii virulence is poorly understood. In this study, the putative LysR-type transcriptional regulator (LTTR) gene (ESA_01081 homolog) was characterized as a possible regulator for C. sakazakii pathogenesis. An in-frame deletion mutant of the ESA_01081 homolog and its cognate complementation strain were constructed and characterized for pathogenesis (adhesion/invasion potentials to human intestinal cells and in vivo rat pup challenge assay), biofilm formation, resistance to oxidative stress and induction of IL-8 secretion. LTTR-deficient C. sakazakii ATCC 29544 exhibits significantly attenuated phenotypes in all the properties tested, except adhesion. Our data strongly suggest that the putative gpESA_01081 homolog, plays an important regulatory role in diverse biological processes including the virulence of C. sakazakii. This is the first report of a functional global regulator in C. sakazakii.