Abstract
The extraintestinal pathogenic Escherichia coli (ExPEC) is a typical facultative intracellular bacterial pathogen. Sensing the environmental stimuli and undertaking adaptive change are crucial for ExPEC to successfully colonize in specific extraintestinal niches. The previous studies show that pathogens exploit two-component systems (TCSs) in response to the host environments during its infection. The PhoP/PhoQ is a typical TCS which is ubiquitous in Gram-negative bacteria. However, there is an incompletely understanding about critical regulatory roles of PhoP/PhoQ in ExPEC pathogenesis. Conjugative ColV-related plasmids are responsible for ExPEC virulence, which is associated with ExPEC zoonotic risk. In this study, the molecular characteristics of HlyF, Mig-14 ortholog (Mig-14p), and OmpT variant (OmpTp) encoded by ColV plasmids were identified. Mig-14p and OmpTp played important roles in conferring ExPEC resistance to cationic antimicrobial peptides (CAMPs) during the infection. Moreover, HlyF and Mig-14p acted as intracellular survival factors to promote ExPEC resistance to macrophages killing. The hlyF and Mig-14p formed an operon in ExPEC ColV plasmid, and PhoP acted as a transcriptional activator of hlyF operon by directly binding to the PhlyF promoter. The acidic pH and CAMPs could additively stimulate ExPEC PhoQ/PhoP activities to upregulate the expression of HlyF and Mig-14p. Our studies revealed that the novel PhoP/PhoQ-HlyF signaling pathway directly upregulates the production of ExPEC outer membrane vesicles. Furthermore, our study first clarified that this PhoP/PhoQ-HlyF pathway was essential for ExPEC intracellular survival in macrophages. It was required to prevent the fusion of ExPEC-containing phagosomes with lysosomes. Moreover, PhoP/PhoQ-HlyF pathway facilitated the inhibition of the phagolysosomal acidification and disruption of the phagolysosomal membranes. In addition, this pathway might promote the formation of ExPEC-containing autophagosome during ExPEC replication in macrophages. Collectively, our studies suggested that PhoP/PhoQ system and CloV plasmids could facilitate ExPEC survival and replication within macrophages.
Highlights
Extraintestinal pathogenic Escherichia coli (ExPEC) has the selective advantages over intestinal pathogenic E. coli (IPEC) to get access to extraintestinal niches, followed by efficient adaption/ colonization in the host
The sequence alignment showed ColV plasmid-encoded Mig-14 ortholog (Mig-14p) shared about 57% identity with Salmonella Mig-14; while OmpT variant (OmpTp) shares approximately 73% homology to E. coli chromosomeencoding OmpT (Figure S1 in Supplementary Material). qRTPCR results showed that the in vitro transcriptional levels of hlyF, Mig-14p, and OmpTp were close to that of ExPEC housekeeping gene dnaE under routine condition
RNA levels of hlyF, Mig-14p, and OmpTp were significantly enhanced about 44.5, 34.9, and 10.1-fold in FY26-infected HD11 macrophages relative to those under routine condition, and similar results were detected in FY26-infected U937 cells (Figure 1B)
Summary
Extraintestinal pathogenic Escherichia coli (ExPEC) has the selective advantages over intestinal pathogenic E. coli (IPEC) to get access to extraintestinal niches, followed by efficient adaption/ colonization in the host. ExPECs cause systemic disease among birds, humans, and mammals with typical extraintestinal pathology, including persistent bacteriuria in urinary tract infection, human septicemia or meningitis in newborns [1,2,3,4]. Compared with IPECs, ExPEC possesses certain-specific virulence/fitness factors to facilitate its extraintestinal infection. These virulence factors are involved in the adhesion, invasion, tolerance to and subversion of host immune defense [10,11,12]. Many studies confirm that APEC contaminates poultry meat or eggs, causing human extraintestinal diseases. The studies on animal models mimicking human ExPEC infection showed that APEC/ExPEC isolates originated from poultry can cause bacteremia, sepsis, urinary tract infection, and meningitis. Humans may be infected by these ExPEC isolates through consumption of unhygienic poultry food, adding another concern about poultry food safety [13, 14]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
