Salmonella is the genus of Gram-negative, facultative intracellular pathogens that have the ability to infect large numbers of animal or human hosts. The S. enterica usg gene is associated with intracellular survival based on ortholog screening and identification. In this study, the λ-Red recombination system was used to construct gene deletion strains and to investigate whether the identified operon was related to intracellular survival. The pdxB-usg-truA-dedA operon enhanced the intracellular survival of S. enterica by resisting the oxidative environment and the usg and truA gene expression was induced by H2O2. Moreover, the genes in this operon (except for dedA) contributed to virulence in mice. These findings indicate that the pdxB-usg-truA-dedA operon functions in resistance to oxidative environments during intracellular survival and is required for in vivo S. enterica virulence. This study provides insight toward a better understand of the characteristics of intracellular pathogens and explores the gene modules involved in their intracellular survival.

Purpose In current studies, the role of serum Cytokeratin-19 fragments (CYFRA 21-1) in colorectal cancer (CRC) remains unclear. This study aimed to clarify the diagnostic and prognostic value of CYFRA 21-1 in CRC. Patients and Methods Data were collected for 196 stage I–III CRC patients and 50 colorectal liver metastases (CRLM) patients between January 2018 and December 2019. The serum CYFRA 21-1 levels were measured using the chemiluminescent particle immunoassay (CMIA) kit in all objects and common biomarkers such as CA19-9, CEA, HSP90α, and AFP were measured in all colorectal cancer patients. We investigated the association between CYFRA 21-1 level and clinicopathological features. In addition, we evaluated the ability of serum CRFRA21-1 to differentiate CRLM from CRC. To assess the potential prognostic value, we used Cox proportional hazard model for univariate or multivariate analyses. Results Serum CYFRA 21-1 was significantly elevated in CRLM patients compared to stage I–III CRC patients (5.85 ng/mL vs 2.29 ng/mL, p < 0.001). For all CRC patients cohort, stage I–III CRC patients cohort and CRLM patients cohort, the optimal cutoff levels of CYFRA 21-1 for overall survival (OS) were 3.47 ng/mL, 2.14 ng/mL and 7.63 ng/mL, respectively, and the optimal cutoff levels for progression-free survival (PFS) were 3.47 ng/mL, 2.56 ng/mL and 7.63 ng/mL, respectively. For CRLM patients, Kaplan–Meier analysis showed that patients with high CYFRA 21-1 level had poor OS. Multivariate analysis indicated that the CYFRA 21-1 level was an independent prognostic factor for PFS in stage I–III patients. And CYFRA 21-1 levels and age were independent prognostic factors for OS and PFS in CRLM patients. Conclusion CYFRA 21-1 can better differentiate CRLM patients from the whole CRC patients and has unique prognostic value for CRLM patients.