spv locus aggravates Salmonella infection of zebrafish adult by inducing Th1/Th2 shift to Th2 polarization.

Salmonella enterica serovar typhimurium (S. typhimurium) are facultative intracellular enteric pathogens causing disease with a broad range of hosts. It was known that Th1-type cytokines such as IFN-γ, IL-12, and TNF-α etc. could induce protective immunity against intracellular pathogens, while Th2-type cytokines such as IL-4, IL-10, and IL-13 etc. are proved to help pathogens survive inside hosts and cause severe infection. One of the critical virulence factor attributes to the pathogenesis of S. typhimurium is Salmonella plasmid virulence genes (spv). Until now, the interaction between spv locus and the predictable generation of Th1 or Th2 immune responses to Salmonella has not been identified. In this study, zebrafish adults were employed to explore the effect of spv locus on Salmonella pathogenesis as well as host adaptive immune responses especially shift of Th1/Th2 balance. The pathological changes of intestines and livers in zebrafish were observed by hematoxylin-eosin (HE) staining and electron microscopy. Levels of the transcription factors of Th1 (Tbx21) and Th2 (GATA3) were measured by real-time quantitative PCR (RT-qPCR). Expression of cytokines were determined by using RT-qPCR and ELISA, respectively. Results showed that spv operon aggravates damage of zebrafish. Furthermore, it demonstrated that spv locus could inhibit the transcription of tbx21 gene and suppress the expression of cytokines IFN-γ, IL-12 and TNF-α. On the contrary, the transcription of gata3 gene could be promoted and the expression of cytokines IL-4, IL-10 and IL-13 were enhanced by spv locus. Taken together, our data revealed that spv locus could aggravate Salmonella infection of zebrafish adult by inducing an imbalance of Th1/Th2 immune response and resulting in a detrimental Th2 bias of host.

Salmonella plasmid virulence gene spvB enhances bacterial virulence by inhibiting autophagy in a zebrafish infection model.

Salmonella enterica serovar typhimurium (S. typhimurium) is a facultative intracellular pathogen that can cause gastroenteritis and systemic infection in a wide range of hosts. Salmonella plasmid virulence gene spvB is closely related to bacterial virulence in different cells and animal models, and the encoded protein acts as an intracellular toxin required for ADP-ribosyl transferase activity. However, until now there is no report about the pathogenecity of spvB gene on zebrafish. Due to the outstanding advantages of zebrafish in analyzing bacteria-host interactions, a S. typhimurium infected zebrafish model was set up here to study the effect of spvB on autophagy and intestinal pathogenesis in vivo. We found that spvB gene could decrease the LD50 of S. typhimurium, and the strain carrying spvB promoted bacterial proliferation and aggravated the intestinal damage manifested by the narrowed intestines, fallen microvilli, blurred epithelium cell structure and infiltration of inflammatory cells. Results demonstrated the enhanced virulence induced by spvB in zebrafish. In spvB-mutant strain infected zebrafish, the levels of Lc3 turnover and Beclin1 expression increased, and the double-membraned autophagosome structures were observed, suggesting that spvB can inhibit autophagy activity. In summary, our results indicate that S. typhimurium strain containing spvB displays more virulence, triggering an increase in bacterial survival and intestine injuries by suppressing autophagy for the first time. This model provides novel insights into the role of Salmonella plasmid virulence gene in bacterial pathogenesis, and can help to further elucidate the relationship between bacteria and host immune response.

Salmonella spv locus suppresses host innate immune responses to bacterial infection.

Salmonella enterica serovar typhimurium (S. typhimurium) is globally distributed and causes massive morbidity and mortality in humans and animals. S. typhimurium carries Salmonella plasmid virulence (spv) locus, which is highly conserved and closely related to bacterial pathogenicity, while its exact role in host immune responses during infection remains to be elucidated. To counteract the invaders, the host has evolved numerous strategies, among which the innate immunity and autophagy act as the first defense. Recently, zebrafish has been universally accepted as a valuable and powerful vertebrate model in analyzing bacteria-host interactions. To investigate whether spv locus enhances the virulence of Salmonella by exerting an effect on the host early defense, zebrafish larvae were employed in this study. LD50 of S. typhimurium to zebrafish larvae and bacterial dissemination were analyzed. Sudan black B and neutral red staining were performed to detect the responses of neutrophils and macrophages to Salmonella infection. Autophagy agonist Torin1 and inhibitor Chloroquine were used to interfere in autophagic flux, and the protein level of Lc3 and p62 were measured by western blotting. Results indicated that spv locus could decrease the LD50 of S. typhimurium to zebrafish larvae, accelerate the reproduction and dissemination of bacteria by inhibiting the function of neutrophils and macrophages. Moreover, spv locus restrained the formation of autophagosomes in the earlier stage of autophagy. These findings suggested the virulence of spv locus involving in suppressing host innate immune responses for the first time, which shed new light on the role of spv operon in Salmonella pathogenicity.

Prevalence and antimicrobial resistance of Mycoplasmas and Chlamydiae in patients with genital tract infections in Shanghai, China.

The infections of Mycoplasmas and Chlamydiae are still severe in patients with genital tract diseases and antimicrobial resistance for these organisms has been changing in recent years. In this study, we reported the prevalence status of Ureaplasma urealyticum, Mycoplasma hominis and Chlamydia trachomatis in 965 patients with genital tract infection in Shanghai from January 2011 to December 2014 and analyzed the antimicrobial resistance of U. urealyticum and M. hominis to 12 kinds of antimicrobial drugs by using commercial kits and SPSS13.0 software. Here, we found the infection of U. urealyticum was the most frequent among these three organisms. The total infection rate for containing any organisms of them was 49.5%, and it has been increasing in recent 4 years. Positive rate in female (53.3%) was higher than male's (34.8%), and the high risk population was 20-39 years old (56.7%). Besides, U. urealyticum and M. hominis displayed relative lower resistance rates to minocycline, doxycycline, josamycin and gatifloxacin (6.5%, 7.2%, 13.5% and 8.6%, respectively). However, for erythromycin, roxithromycin, thiamphenicol and clindamycin, the resistance rates were relatively high (41.9%, 47.2%, 62.3% and 74.9%, respectively). U. urealyticum and M. hominis displayed a declined trend of the antimicrobial resistance to 12 kinds of drugs detected in this study. In total, these preliminary data showed the prevalence of Mycoplasmas and Chlamydiae in patients and the antimicrobial resistance status of Mycoplasmas, which has use for reference on both prevention and treatment of diseases caused by them.

Enhanced photocatalytic activity of 3D hierarchical RP/BP/BiOCOOH via oxygen vacancies and double heterojunctions.

A 3D hierarchical RP/BP/BiOCOOH double heterostructures with abundant oxygen vacancies (OVs) was obtained by hydrothermal process and its photocatalytic activity was investigated by degradation of TC-HCl with different light sources and various natural water. The physicochemical characteristics of RP/BP/BiOCOOH heterojunctions were systematically characterized via TEM, XPS, EPR, EIS et al. Compared with BiOCOOH, the photocatalytic activity of RP/BP/BiOCOOH was obviously enhanced. Under simulated solar light irradiation, 60.5% of TC-HCl was removed by 3%RP/BP/BiOCOOH. And the rate constant of 3%RP/BP/BiOCOOH was 2.95 times than that of BiOCOOH. Traces of small molecular organics were beneficial to improve photocatalytic efficiency. The process of photocatalytic degradation and the cytotoxicity of intermedia products of TC-HCl were discussed via HPLC-MS, 3D-EEM, and antibacterial properties test. Based on the results of trapping experiments and ESR tests, •OH and •O2- were the most significant reactive oxygen species. The enhanced photocatalytic activity was ascribed to two reasons: 1 double heterojunctions structure enhanced the separation efficiency of carriers, 2 the introduction of OVs and BP/RP expanded the response range of light. This work provides a feasible strategy that non-metallic element semiconductor is used to modify the wide band gap semiconductor to enhance the photocatalytic efficiency.

Morphological Reconstruction-Based Image-Guided Fuzzy Clustering with a Novel Impact Factor.

The guided filter is a novel explicit image filtering method, which implements a smoothing filter on "flat patch" regions and ensures edge preserving on "high variance" regions. Recently, the guided filter has been successfully incorporated into the process of fuzzy c-means (FCM) to boost the clustering results of noisy images. However, the adaptability of the existing guided filter-based FCM methods to different images is deteriorated, as the factor ε of the guided filter is fixed to a scalar. To solve this issue, this paper proposes a new guided filter-based FCM method (IFCM_GF), in which the guidance image of the guided filter is adjusted by a newly defined influence factor ρ. By dynamically changing the impact factor ρ, the IFCM_GF acquires excellent segmentation results on various noisy images. Furthermore, to promote the segmentation accuracy of images with heavy noise and simplify the selection of the influence factor ρ, we further propose a morphological reconstruction-based improved FCM clustering algorithm with guided filter (MRIFCM_GF). In this approach, the original noisy image is reconstructed by the morphological reconstruction (MR) before clustering, and the IFCM_GF is performed on the reconstructed image by utilizing the adjusted guidance image. Due to the efficiency of the MR to remove noise, the MRIFCM_GF achieves better segmentation results than the IFCM_GF on images with heavy noise and the selection of the influence factor for the MRIFCM_GF is simple. Experiments demonstrate the effectiveness of the presented methods.

A novel contribution of spvB to pathogenesis of Salmonella Typhimurium by inhibiting autophagy in host cells.

Salmonella plasmid virulence genes (spv) are highly conserved in strains of clinically important Salmonella serovars. It is essential for Salmonella plasmid-correlated virulence, although the exact mechanism remains to be elucidated. Autophagy has been reported to play an important role in host immune responses limiting Salmonella infection. Our previous studies demonstrated that Salmonella conjugative plasmid harboring spv genes could enhance bacterial cytotoxicity by inhibiting autophagy. In the present study, we investigated whether spvB, which is one of the most important constituents of spv ORF could intervene in autophagy pathway. Murine macrophage-like cells J774A.1, human epithelial HeLa cells, and BALB/c mice infected with Salmonella Typhimurium wild type, mutant and complementary strains (carrying or free spvB or complemented only with ADP-ribosyltransferase activity of SpvB) were used in vitro and in vivo assay, respectively. To further explore the molecular mechanisms, both SpvB ectopic eukaryotic expression system and cells deficient in essential autophagy components by siRNA were generated. Results indicated that spvB could suppress autophagosome formation through its function in depolymerizing actin, and aggravate inflammatory injury of the host in response to S. Typhimurium infection. Our studies demonstrated virulence of spvB involving in inhibition of autophagic flux for the first time, which could provide novel insights into Salmonella pathogenesis, and have potential application to develop new antibacterial strategies for Salmonellosis.