Intestinal epithelial cells of Japanese flounder (Paralichthys olivaceus) as an in vitro model for studying intestine immune function based on transcriptome analysis

Japanese flounder (Paralichthys olivaceus) is an economically crucial marine species, but diseases like hemorrhagic septicemia caused by Edwardsiella tarda have resulted in significant economic losses. E. tarda infects various hosts, and its pathogenicity in fish is not fully understood. Lipopolysaccharides (LPS) are components of the outer membrane of Gram-negative bacteria and are representative of typical PAMP molecules that cause activation of the immune system. The PoIEC cell line is a newly established intestinal epithelial cell line from P. olivaceus. In order to investigate whether it can be used as an in vitro model for studying the pathogenesis of E. tarda and LPS stimulation, we conducted RNA-seq experiments for the PoIECs model of E. tarda infection and LPS stimulation. In this study, transcriptome sequencing was carried out in the PoIEC cell line after treatment with LPS and E. tarda. A total of 62.52G of high-quality data from transcriptome sequencing results were obtained in nine libraries, of which an average of 87.96% data could be aligned to the P. olivaceus genome. Data analysis showed that 283 and 414 differentially expressed genes (DEGs) in the LPS versus Control (LPS-vs-Con) and E. tarda versus Control groups (Et-vs-Con), respectively, of which 60 DEGs were shared in two comparation groups. The GO terms were predominantly enriched in the extracellular space, inflammatory response, and cytokine activity in the LPS-vs-Con group, whereas GO terms were predominantly enriched in nucleus and positive regulation of transcription by RNA polymerase II in the Et-vs-Con group. KEGG analysis revealed that three immune-related pathways were co-enriched in both comparison groups, including the Toll-like receptor signaling pathway, C-type lectin receptor signaling pathway, and Cytokine-cytokine receptor interaction. Five genes were randomly screened to confirm the validity and accuracy of the transcriptome data. These results suggest that PoIEC cell line can be an ideal in vitro model for studies of marine fish gut immunity and pathogenesis of Edwardsiellosis.

The cyclic AMP (cAMP) phosphodiesterase CpdA required for growth, biofilm formation, motility and pathogenicity of Edwardsiella piscicida

Edwardsiella piscicida is a severe fish pathogen with wide host range, causing the huge economic losses in the aquaculture industry. Cyclic adenosine monophosphate (cAMP) as an important second messenger regulates the physiological and behavioral responses to environmental cues in eukaryotic and prokaryotic. The intracellular level of cAMP for effective activity is tightly controlled by the synthesis of adenylate cyclase, excretion and degradation of phosphodiesterase. In this study, we identified and characterized a class III cAMP phosphodiesterase, named as CpdA, in the E. piscicida. To investigate the role of CpdA in the physiology and pathogenicity, we constructed the in-frame deletion mutant of cpdA of E. piscicida, TX01ΔcpdA. The results showed that TX01ΔcpdA accumulated the higher intracellular cAMP concentration than TX01, indicating that CpdA exerted the hydrolysis of cAMP. In addition, compared to the TX01, the TX01ΔcpdA slowed growth rate, diminished biofilm formation and lost motility. More importantly, pathogenicity analysis confirmed that TX01ΔcpdA significantly impaired the ability of invading the epithelial cells, reproduction in macrophages, tissues dissemination and lethality for healthy tilapias. The most of lost properties of TX01ΔcpdA were restored partially or fully by the introduction of cpdA gene. These results suggest that cpdA is required for regulation of the physiology and virulence of E. piscicida.

Type III secretion system effector YfiD inhibits the activation of host poly(ADP-ribose) polymerase-1 to promote bacterial infection

Modulation of cell death is a powerful strategy employed by pathogenic bacteria to evade host immune clearance and occupy profitable replication niches during infection. Intracellular pathogens employ the type III secretion system (T3SS) to deliver effectors, which interfere with regulated cell death pathways to evade immune defenses. Here, we reveal that poly(ADP-ribose) polymerase-1 (PARP1)-dependent cell death restrains Edwardsiella piscicida's proliferation in mouse monocyte macrophages J774A.1, of which PARP1 activation results in the accumulation of poly(ADP-ribose) (PAR) and enhanced inflammatory response. Moreover, E. piscicida, an important intracellular pathogen, leverages a T3SS effector YfiD to impair PARP1's activity and inhibit PAR accumulation. Once translocated into the host nucleus, YfiD binds to the ADP-ribosyl transferase (ART) domain of PARP1 to suppress its PARylation ability as the pharmacological inhibitor of PARP1 behaves. Furthermore, the interaction between YfiD and ART mainly relies on the complete unfolding of the helical domain, which releases the inhibitory effect on ART. In addition, YfiD impairs the inflammatory response and cell death in macrophages and promotes in vivo colonization and virulence of E. piscicida. Collectively, our results establish the functional mechanism of YfiD as a potential PARP1 inhibitor and provide more insights into host defense against bacterial infection.

Notch2 with retinoic acid license IL-23 expression by intestinal EpCAM+ DCIR2+ cDC2s in mice

Despite the importance of IL-23 in mucosal host defense and disease pathogenesis, the mechanisms regulating the development of IL-23-producing mononuclear phagocytes remain poorly understood. Here, we employed an Il23aVenus reporter strain to investigate the developmental identity and functional regulation of IL-23-producing cells. We showed that flagellin stimulation or Citrobacter rodentium infection led to robust induction of IL-23-producing EpCAM+ DCIR2+ CD103- cDC2s, termed cDCIL23, which was confined to gut-associated lymphoid tissues, including the mesenteric lymph nodes, cryptopatches, and isolated lymphoid follicles. Furthermore, we demonstrated that Notch2 signaling was crucial for the development of EpCAM+ DCIR2+ cDC2s, and the combination of Notch2 signaling with retinoic acid signaling controlled their terminal differentiation into cDCIL23, supporting a two-step model for the development of gut cDCIL23. Our findings provide fundamental insights into the developmental pathways and cellular dynamics of IL-23-producing cDC2s at steady state and during pathogen infection.

A two-step activation mechanism enables mast cells to differentiate their response between extracellular and invasive enterobacterial infection

Mast cells localize to mucosal tissues and contribute to innate immune defense against infection. How mast cells sense, differentiate between, and respond to bacterial pathogens remains a topic of ongoing debate. Using the prototype enteropathogen Salmonella Typhimurium (S.Tm) and other related enterobacteria, here we show that mast cells can regulate their cytokine secretion response to distinguish between extracellular and invasive bacterial infection. Tissue-invasive S.Tm and mast cells colocalize in the mouse gut during acute Salmonella infection. Toll-like Receptor 4 (TLR4) sensing of extracellular S.Tm, or pure lipopolysaccharide, causes a modest induction of cytokine transcripts and proteins, including IL-6, IL-13, and TNF. By contrast, type-III-secretion-system-1 (TTSS-1)-dependent S.Tm invasion of both mouse and human mast cells triggers rapid and potent inflammatory gene expression and >100-fold elevated cytokine secretion. The S.Tm TTSS-1 effectors SopB, SopE, and SopE2 here elicit a second activation signal, including Akt phosphorylation downstream of effector translocation, which combines with TLR activation to drive the full-blown mast cell response. Supernatants from S.Tm-infected mast cells boost macrophage survival and maturation from bone-marrow progenitors. Taken together, this study shows that mast cells can differentiate between extracellular and host-cell invasive enterobacteria via a two-step activation mechanism and tune their inflammatory output accordingly.

CRISPR/Cas9-mediated knockout of tnf-α1 in zebrafish reduces disease resistance after Edwardsiella piscicida bacterial infection

Tumor necrosis factor (TNF) is an important cytokine involved in immune responses to bacterial infections in vertebrates, including fish. Although Tnf-α is a well-studied cytokine, there are contradictory findings about Tnf-α function following bacterial infection. In this study, we analyzed the expression and function of the Tnf-α-type I isoform (Tnf-α1) in zebrafish by knockout experiments using the CRISPR/Cas9 gene-editing tool. The open reading frame of tnf-α1 encodes a 25.82 kDa protein with 234 amino acids (aa). The expression of tnf-α1 in the early stages of zebrafish was observed from the 2-cell stage. Adult zebrafish spleens showed the highest expression of tnf-α1. To evaluate the function of Tnf-α1, an 8 bp deletion in the target region, resulting in a short truncated protein of 55 aa, was used to create the tnf-α1 knockout mutant. The pattern of downstream gene expression in 7-day larvae in wild-type (WT) and tnf-α1 knockout fish was examined. We also verified the fish mortality rate after Edwardsiella piscicida challenge and found that it was much higher in tnf-α1 knockout fish than in WT fish. Additionally, downstream gene expression analyses after E. piscicida exposure revealed a distinct expression pattern in tnf-α1 knockout fish compared to that in WT fish. Overall, our study using tnf-α1 deletion in zebrafish confirmed that Tnf-α1 is critical for immune regulation during bacterial infection.

Characterization of Type VI secretion system in Edwardsiella ictaluri

Edwardsiella ictaluri is a Gram-negative facultative intracellular fish pathogen causing enteric septicemia of catfish (ESC). While various secretion systems contribute to E. ictaluri virulence, the Type VI secretion system (T6SS) remains poorly understood. In this study, we constructed 13 E. ictaluri T6SS mutants using splicing by overlap extension PCR and characterized them, assessing their uptake and survival in channel catfish (Ictalurus punctatus) peritoneal macrophages, attachment and invasion in channel catfish ovary (CCO) cells, in vitro stress resistance, and virulence and efficacy in channel catfish. Among the mutants, EiΔevpA, EiΔevpH, EiΔevpM, EiΔevpN, and EiΔevpO exhibited reduced replication inside peritoneal macrophages. EiΔevpM, EiΔevpN, and EiΔevpO showed significantly decreased attachment to CCO cells, while EiΔevpN and EiΔevpO also displayed reduced invasion of CCO cells (p < 0.05). Overall, T6SS mutants demonstrated enhanced resistance to oxidative and nitrosative stress in the nutrient-rich medium compared to the minimal medium. However, EiΔevpA, EiΔevpH, EiΔevpM, EiΔevpN, and EiΔevpO were susceptible to oxidative stress in both nutrient-rich and minimal medium. In fish challenges, EiΔevpD, EiΔevpE, EiΔevpG, EiΔevpJ, and EiΔevpK exhibited attenuation and provided effective protection against E. ictaluri wild-type (EiWT) infection in catfish fingerlings. However, their attenuation and protective efficacy were lower in catfish fry. These findings shed light on the role of the T6SS in E. ictaluri pathogenesis, highlighting its significance in intracellular survival, host cell attachment and invasion, stress resistance, and virulence. The attenuated T6SS mutants hold promise as potential candidates for protective immunization strategies in catfish fingerlings.

HOIL1 Regulates Group 3 Innate Lymphoid Cells in the Colon and Protects against Systemic Dissemination, Colonic Ulceration, and Lethality from Citrobacter rodentium Infection

Heme-oxidized IRP2 ubiquitin ligase-1 (HOIL1)-deficient patients experience chronic intestinal inflammation and diarrhea as well as increased susceptibility to bacterial infections. HOIL1 is a component of the linear ubiquitin chain assembly complex that regulates immune signaling pathways, including NF-κB-activating pathways. We have shown previously that HOIL1 is essential for survival following Citrobacter rodentium gastrointestinal infection of mice, but the mechanism of protection by HOIL1 was not examined. C. rodentium is an important murine model for human attaching and effacing pathogens, enteropathogenic and enterohemorrhagic Escherichia coli that cause diarrhea and foodborne illnesses and lead to severe disease in children and immunocompromised individuals. In this study, we found that C. rodentium infection resulted in severe colitis and dissemination of C. rodentium to systemic organs in HOIL1-deficient mice. HOIL1 was important in the innate immune response to limit early replication and dissemination of C. rodentium. Using bone marrow chimeras and cell type-specific knockout mice, we found that HOIL1 functioned in radiation-resistant cells and partly in radiation-sensitive cells and in myeloid cells to limit disease, but it was dispensable in intestinal epithelial cells. HOIL1 deficiency significantly impaired the expansion of group 3 innate lymphoid cells and their production of IL-22 during C. rodentium infection. Understanding the role HOIL1 plays in type 3 inflammation and in limiting the pathogenesis of attaching and effacing lesion-forming bacteria will provide further insight into the innate immune response to gastrointestinal pathogens and inflammatory disorders.

Edwardsiella ictaluri T3SS effector EseN is a phosphothreonine lyase that inactivates ERK1/2, p38, JNK, and PDK1 and modulates cell death in infected macrophages

IMPORTANCE

This work has global significance in the catfish industry, which provides food for increasing global populations. E. ictaluri is a leading cause of disease loss, and EseN is an important player in E. ictaluri virulence. The E. ictaluri T3SS effector EseN plays an essential role in establishing infection, but the specific role EseN plays is not well characterized. EseN belongs to a family of phosphothreonine lyase effectors that specifically target host mitogen activated protein kinase (MAPK) pathways important in regulating host responses to infection. No phosphothreonine lyase equivalents are known in eukaryotes, making this family of effectors an attractive target for indirect narrow-spectrum antibiotics. Targeting of major vault protein and PDK1 kinase by EseN has not been reported in EseN homologs in other pathogens and may indicate unique functions of E. ictaluri EseN. EseN targeting of PDK1 is particularly interesting in that it is linked to an extraordinarily diverse group of cellular functions.

Early coronavirus disease 2019 (COVID-19) pandemic effects on individual-level risk for healthcare-associated infections in hospitalized patients

OBJECTIVE

We compared the individual-level risk of hospital-onset infections with multidrug-resistant organisms (MDROs) in hospitalized patients prior to and during the coronavirus disease 2019 (COVID-19) pandemic. We also quantified the effects of COVID-19 diagnoses and intrahospital COVID-19 burden on subsequent MDRO infection risk.

DESIGN

Multicenter, retrospective, cohort study.

SETTING

Patient admission and clinical data were collected from 4 hospitals in the St. Louis area.

PATIENTS

Data were collected for patients admitted between January 2017 and August 2020, discharged no later than September 2020, and hospitalized ≥48 hours.

METHODS

Mixed-effects logistic regression models were fit to the data to estimate patients' individual-level risk of infection with MDRO pathogens of interest during hospitalization. Adjusted odds ratios were derived from regression models to quantify the effects of the COVID-19 period, COVID-19 diagnosis, and hospital-level COVID-19 burden on individual-level hospital-onset MDRO infection probabilities.

RESULTS

We calculated adjusted odds ratios for COVID-19-era hospital-onset Acinetobacter spp., P. aeruginosa and Enterobacteriaceae spp infections. Probabilities increased 2.64 (95% confidence interval [CI], 1.22-5.73) times, 1.44 (95% CI, 1.03-2.02) times, and 1.25 (95% CI, 1.00-1.58) times relative to the prepandemic period, respectively. COVID-19 patients were 4.18 (95% CI, 1.98-8.81) times more likely to acquire hospital-onset MDRO S. aureus infections.

CONCLUSIONS

Our results support the growing body of evidence indicating that the COVID-19 pandemic has increased hospital-onset MDRO infections.

Adjuvant effect of allogeneic blood in vaccines against edwardsiellosis in ginbuna crucian carp Carassius auratus langsdorfii

Edwardsiella tarda (E. tarda), an intracellular pathogen, has caused severe economic losses in aquaculture. Effective vaccine development for E. tarda prevention is urgently needed. A previous study indicates that cell-mediated immunity (CMI) might play an important role in E. tarda infection. We believe that the involvement of allograft rejection and CMI has now been well documented in mammals and some fishes. However, there is still little research on the application of blood allograft rejection in vaccine development. In the current study, we investigate the immune response and vaccine effect in fish vaccinated with allogeneic blood + formalin-killed cells vaccine (FKC), allogeneic blood + phosphate-buffered saline (PBS), PBS + FKC and PBS + PBS. In the challenge test, the relative percentage survival (RPS) of the allogeneic + FKC, the allogeneic blood + PBS and the PBS + FKC group was 61.46, 35.41, and 30.63 % respectively. The up-regulated expression of Th1-related genes IFN-γ 1, IFN-γ 1rel2, IL-12p35 and T-bet suggests the protection is via CMI induction. Only in the allogeneic + FKC group, gene expression of IFN-γ 1, IL-12p35 and T-bet is significantly higher, indicating synergy between the two substances. Furthermore, among the fish injected with the allogeneic blood cells, syngeneic blood cells and PBS group, only in the fish of the allogenic blood cells injection group, did expression of IFN-γ 1, IFN-γ 2 and IFN-γ rel2 gene expression significantly increased. The results indicate that the rejection was induced by allogeneic components. Thus, our findings might provide essential information and insights into vaccine development in aquaculture.

TRPV1 controls innate immunity during Citrobacter rodentium enteric infection

Mucosal immunity is critical to host protection from enteric pathogens and must be carefully controlled to prevent immunopathology. Regulation of immune responses can occur through a diverse range of mechanisms including bi-directional communication with neurons. Among which include specialized sensory neurons that detect noxious stimuli due to the expression of transient receptor potential vanilloid receptor 1 (TRPV1) ion channel and have a significant role in the coordination of host-protective responses to enteric bacterial pathogens. Here we have used the mouse-adapted attaching and effacing pathogen Citrobacter rodentium to assess the specific role of TRPV1 in coordinating the host response. TRPV1 knockout (TRPV1-/-) mice had a significantly higher C. rodentium burden in the distal colon and fecal pellets compared to wild-type (WT) mice. Increased bacterial burden was correlated with significantly increased colonic crypt hyperplasia and proliferating intestinal epithelial cells in TRPV1-/- mice compared to WT. Despite the increased C. rodentium burden and histopathology, the recruitment of colonic T cells producing IFNγ, IL-17, or IL-22 was similar between TRPV1-/- and WT mice. In evaluating the innate immune response, we identified that colonic neutrophil recruitment in C. rodentium infected TRPV1-/- mice was significantly reduced compared to WT mice; however, this was independent of neutrophil development and maturation within the bone marrow compartment. TRPV1-/- mice were found to have significantly decreased expression of the neutrophil-specific chemokine Cxcl6 and the adhesion molecules Icam1 in the distal colon compared to WT mice. Corroborating these findings, a significant reduction in ICAM-1 and VCAM-1, but not MAdCAM-1 protein on the surface of colonic blood endothelial cells from C. rodentium infected TRPV1-/- mice compared to WT was observed. These findings demonstrate the critical role of TRPV1 in regulating the host protective responses to enteric bacterial pathogens, and mucosal immune responses.

Zebrafish nos2a benefits bacterial proliferation via suppressing ROS and inducing NO production to impair the expressions of inflammatory cytokines and antibacterial genes

The enzyme nitric oxide synthase 2 or inducible NOS (NOS2), reactive oxygen species (ROS) and nitric oxide (NO) are important participants in various inflammatory and immune responses. However, the functional significances of the correlations among piscine NOS2, ROS and NO during pathogen infection remain unclear. In teleost, there are two nos2 genes (nos2a and nos2b). It has been previously reported that zebrafish nos2a behaves as a classical inducible NOS, and nos2b exerts some functions similar to mammalian NOS3. In the present study, we reported the functional characterization of zebrafish nos2a during bacterial infection. We found that zebrafish nos2a promoted bacterial proliferation, accompanied by an increased susceptibility to Edwardsiella piscicida infection. The nagative regulation of zebrafish nos2a during E. piscicida infection was characterized by the impaired ROS levels, the induced NO production and the decreased expressions of proinflammatory cytokines, antibacterial genes and oxidant factors. Furthermore, although both inducing ROS and inhibiting NO production significantly inhibited bacterial proliferation, only inhibiting NO production but not inducing ROS significantly increased resistance to E. piscicida infection. More importantly, ROS supplementation and inhibition of NO completely abolished this detrimental consequence mediated by zebrafish nos2a during E. piscicida infection. All together, these results firstly demonstrate that the innate response mediated by zebrafish nos2a in promoting bacterial proliferation is dependent on the lower ROS level and higher NO production. The present study also reveals that inhibition of NO can be effective in the protection against E. piscicida infection.

ESBL-producing Enterobacteriaceae in a rural Rwandan community: Carriage among community members, livestock, farm products and environment

OBJECTIVES

Extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-PE) are spreading globally. However, respective data from African communities including livestock and environmental specimens are rare. In a rural community of southern Rwanda, we assessed intestinal carriage of ESBL-PE among residents and livestock as well as presence in household specimens and examined associated factors.

METHODS

Samples of humans and livestock (both rectal swabs), soil, water, vegetables and animal products were collected within 312 community households in Sovu, Southern Rwanda. Specimens were screened for ESBL-PE on chromogenic agar, and susceptibility to common antibiotics was determined by disc diffusion assays. Socio-demographic information was collected with questionnaires focusing on the socio-economic background, alimentation, living conditions, hygiene measures and medical history of the participants.

RESULTS

Data and specimens from 312 randomly selected households including 617 human beings, 620 livestock and of approximately each 300 kitchen vegetables, animal products, soil and drinking water were analysed. Overall, 14.8% of 2508 collected samples were positive for ESBL-PE; figures were highest for humans (37.9%) and livestock (15.6%), lower for vegetables (3.8%) and animal products (3.3%), and lowest for soil (1.6%) and water (0.6%). Most detected ESBL-PE were Escherichia coli (93.5%) in addition to Klebsiella pneumoniae (6.5%). Cross-resistance to ampicillin-sulbactam, ciprofloxacin and co-trimoxazole was common. Logistic regression identified increasing age, another ESBL-PE positive household member, prolonged time for fetching water, current diarrhoea and the ability to pay school fees as independent predictors of intestinal ESBL-PE carriage among community members.

CONCLUSIONS

ESBL-PE carriage is common in a rural Rwandan farming community. Carriage in livestock is not associated with human carriage. Associated factors suggest few addressable risk factors. The data indicate that in southern Rwanda, ESBL-PE are no longer primarily hospital-based but circulate in the community.

Aspartate metabolic flux promotes nitric oxide to eliminate both antibiotic-sensitive and -resistant Edwardsiella tarda in zebrafish

Introduction

Metabolic reprogramming potentiates host protection against antibiotic-sensitive or -resistant bacteria. However, it remains unclear whether a single reprogramming metabolite is effective enough to combat both antibiotic-sensitive and -resistant bacteria. This knowledge is key for implementing an antibiotic-free approach.

Methods

The reprogramming metabolome approach was adopted to characterize the metabolic state of zebrafish infected with tetracycline-sensitive and -resistant Edwardsiella tarda and to identify overlapping depressed metabolite in dying zebrafish as a reprogramming metabolite.

Results

Aspartate was identify overlapping depressed metabolite in dying zebrafish as a reprogramming metabolite. Exogenous aspartate protects zebrafish against infection caused by tetracycline-sensitive and -resistant E. tarda. Mechanistically, exogenous aspartate promotes nitric oxide (NO) biosynthesis. NO is a well-documented factor of promoting innate immunity against bacteria, but whether it can play a role in eliminating both tetracycline-sensitive and -resistant E. tarda is unknown. Thus, in this study, aspartate was replaced with sodium nitroprusside to provide NO, which led to similar aspartate-induced protection against tetracycline-sensitive and -resistant E. tarda.

Discussion

These findings support the conclusion that aspartate plays an important protective role through NO against both types of E. tarda. Importantly, we found that tetracycline-sensitive and -resistant E. tarda are sensitive to NO. Therefore, aspartate is an effective reprogramming metabolite that allows implementation of an antibiotic-free approach against bacterial pathogens.

The occurrence and genomic characteristics of the blaIMI-1 carbapenemase-producing Enterobacter cloacae complex retrieved from natural water sources in central Thailand

AIM

Carbapenem resistance among Enterobacteriaceae is a serious threat to humans worldwide. This study aims to evaluate the phenotypic and genotypic characterization of carbapenemase-producing Enterobacter cloacae complex (ECC) retrieved from water sources in the central part of Thailand.

METHODS AND RESULTS

Samples were collected from water bodies surrounding farms and communities in central Thailand. The species were identified by using MALDI-TOF MS. The minimum inhibitory concentration (MIC) and antibiotic susceptibility were determined. The carbapenemase-producing genes were detected by PCR and whole genome sequencing (WGS). ECC with chromosome-encoded blaIMI-1 carbapenemase were detected. These isolates were resistant to last-resort antibiotics such as carbapenems and colistin as well as penicillin. In addition, all blaIMI-1 genes isolated from this study were found to be associated with chromosomally integrated Xer-dependent integrative mobile elements (IMEXs).

CONCLUSION

These findings highlight the diversity and dissemination of carbapenemases-producing Enterobacterales in environmental sources. With the increasing detection of carbapenemase genes worldwide, we should be aware of the blaIMI-producing E. cloacae complex with a high resistance profile and the ability to mobilize within the environment.

Nutrition impact on ILC3 maintenance and function centers on a cell-intrinsic CD71-iron axis

Iron metabolism is pivotal for cell fitness in the mammalian host; however, its role in group 3 innate lymphoid cells (ILC3s) is unknown. Here we show that transferrin receptor CD71 (encoded by Tfrc)-mediated iron metabolism cell-intrinsically controls ILC3 proliferation and host protection against Citrobacter rodentium infection and metabolically affects mitochondrial respiration by switching of oxidative phosphorylation toward glycolysis. Iron deprivation or Tfrc ablation in ILC3s reduces the expression and/or activity of the aryl hydrocarbon receptor (Ahr), a key ILC3 regulator. Genetic ablation or activation of Ahr in ILC3s leads to CD71 upregulation or downregulation, respectively, suggesting Ahr-mediated suppression of CD71. Mechanistically, Ahr directly binds to the Tfrc promoter to inhibit transcription. Iron overload partially restores the defective ILC3 compartment in the small intestine of Ahr-deficient mice, consistent with the compensatory upregulation of CD71. These data collectively demonstrate an under-appreciated role of the Ahr-CD71-iron axis in the regulation of ILC3 maintenance and function.

Enteric Aeromonas Infection: a Common Enteric Bacterial Infection with a Novel Infection Pattern Detected in an Australian Population with Gastroenteritis

Aeromonas species are emerging human enteric pathogens. However, they are currently not routinely detected in many diagnostic laboratories, and information regarding Aeromonas enteric infections detected using molecular methods is lacking. Here, we investigated the detection of Aeromonas species and four other enteric bacterial pathogens in 341,330 fecal samples from patients with gastroenteritis processed in a large Australian diagnostic laboratory between 2015 and 2019. These enteric pathogens were detected using quantitative real-time PCR (qPCR) methods. Furthermore, we compared the qPCR cycle threshold (CT) values obtained from fecal samples that tested positive for Aeromonas only by molecular detection with those of samples that tested positive by both molecular detection and bacterial isolation methods. Aeromonas species were found to be the second most common bacterial enteric pathogens among patients with gastroenteritis. We observed a unique pattern of three infection peaks for Aeromonas, which correlated with the age of the patients. Aeromonas species were the most common enteric bacterial pathogens in children younger than 18 months. Fecal samples that tested positive for Aeromonas only by molecular detection had significantly higher CT values than fecal samples that tested positive by both molecular detection and bacterial culture. In conclusion, our findings reveal that Aeromonas enteric pathogens exhibit an age-related three-peak infection pattern, distinguishing them from other enteric bacterial pathogens. Moreover, the high rate of Aeromonas enteric infection discovered in this study suggests that Aeromonas species should be routinely tested in diagnostic laboratories. Our data also show that combining qPCR with bacterial culture can enhance the detection of enteric pathogens. IMPORTANCE Aeromonas species are emerging human enteric pathogens. However, these species are currently not routinely detected in many diagnostic laboratories, and no studies have reported the detection of Aeromonas enteric infection using molecular methods. We investigated the presence of Aeromonas species and four other enteric bacterial pathogens in 341,330 fecal samples from patients with gastroenteritis using quantitative real-time PCR (qPCR) methods. Interestingly, we discovered that Aeromonas species were the second most common bacterial enteric pathogens in patients with gastroenteritis, exhibiting a novel infection pattern compared to those of other enteric pathogens. Furthermore, we found that Aeromonas species were the most prevalent enteric bacterial pathogens in children aged 6 to 18 months. Our data also revealed that qPCR methods exhibit higher sensitivity in detecting enteric pathogens compared to that of bacterial culture alone. Moreover, combining qPCR with bacterial culture enhances the detection of enteric pathogens. These findings emphasize the importance of Aeromonas species in public health.

Helicobacter spp. are prevalent in wild mice and protect from lethal Citrobacter rodentium infection in the absence of adaptive immunity

Transfer of the gut microbiota from wild to laboratory mice alters the host's immune status and enhances resistance to infectious and metabolic diseases, but understanding of which microbes and how they promote host fitness is only emerging. Our analysis of metagenomic sequencing data reveals that Helicobacter spp. are enriched in wild compared with specific-pathogen-free (SPF) and conventionally housed mice, with multiple species commonly co-colonizing their hosts. We create laboratory mice harboring three non-SPF Helicobacter spp. to evaluate their effect on mucosal immunity and colonization resistance to the enteropathogen Citrobacter rodentium. Our experiments reveal that Helicobacter spp. interfere with C. rodentium colonization and attenuate C. rodentium-induced gut inflammation in wild-type (WT) mice, even preventing lethal infection in Rag2-/- SPF mice. Further analyses suggest that Helicobacter spp. interfere with tissue attachment of C. rodentium, putatively by reducing the availability of mucus-derived sugars. These results unveil pivotal protective functions of wild mouse microbiota constituents against intestinal infection.

Cooperation between physiological defenses and immune resistance produces asymptomatic carriage of a lethal bacterial pathogen

Animals evolved two defense strategies to survive infections. Antagonistic strategies include immune resistance mechanisms that operate to kill invading pathogens. Cooperative or physiological defenses mediate host adaptation to the infected state, limiting physiological damage and disease, without killing the pathogen, and have been shown to cause asymptomatic carriage and transmission of lethal pathogens. Here, we demonstrate that physiological defenses cooperate with the adaptive immune response to generate long-term asymptomatic carriage of the lethal enteric murine pathogen, Citrobacter rodentium. Asymptomatic carriage of genetically virulent C. rodentium provided immune resistance against subsequent infections. Immune protection was dependent on systemic antibody responses and pathogen virulence behavior rather than the recognition of specific virulent antigens. Last, we demonstrate that an avirulent strain of C. rodentium in the field has background mutations in genes that are important for LPS structure. Our work reveals insight into how asymptomatic infections can arise mechanistically with immune resistance, mediating exclusion of phenotypically virulent enteric pathogen to promote asymptomatic carriage.

Effects of TLR2/4 signalling pathway in western mosquitofish (Gambusia affinis) after Edwardsiella tarda infection

Gambusia affinis is regarded as an important animal model. Edwardsiella tarda is one of the most serious pathogens affecting aquaculture. The study explores the effects of TLR2/4 partial signalling pathway in G. affinis of E. tarda infection. The study collected the brain, liver, and intestine after E. tarda LD₅₀ and 0.85% NaCl solution challenge at different times (0 h, 3 h, 9 h, 18 h, 24 h, and 48 h). In these three tissues, the mRNA levels of PI3K, AKT3, IRAK4, TAK1, IKKβ, and IL-1β were substantially enhanced (p < .05) then returned to normal levels. Additionally, Rac1 and MyD88 in liver had different trend with other genes in brain and intestine, which displayed significantly indifference. The overexpression of IKKβ, and IL-1β indicated that E. tarda also caused immune reaction in intestine and liver, which would be consistent with delayed edwardsiellosis, which causes intestinal lesions and liver and kidney necrosis. Additionally, MyD88 plays a smaller role than IRAK4 and TAK1 in this signalling pathways. This study could enrich the understanding of the immune mechanism of the TLR2/4 signalling pathway in fish and might help to prescribe preventive measures against E. tarda to prevent infectious diseases in fish.

GATA4 controls regionalization of tissue immunity and commensal-driven immunopathology

There is growing recognition that regionalization of bacterial colonization and immunity along the intestinal tract has an important role in health and disease. Yet, the mechanisms underlying intestinal regionalization and its dysregulation in disease are not well understood. This study found that regional epithelial expression of the transcription factor GATA4 controls bacterial colonization and inflammatory tissue immunity in the proximal small intestine by regulating retinol metabolism and luminal IgA. Furthermore, in mice without jejunal GATA4 expression, the commensal segmented filamentous bacteria promoted pathogenic inflammatory immune responses that disrupted barrier function and increased mortality upon Citrobacter rodentium infection. In celiac disease patients, low GATA4 expression was associated with metabolic alterations, mucosal Actinobacillus, and increased IL-17 immunity. Taken together, these results reveal broad impacts of GATA4-regulated intestinal regionalization on bacterial colonization and tissue immunity, highlighting an elaborate interdependence of intestinal metabolism, immunity, and microbiota in homeostasis and disease.

GPR120 promotes neutrophil control of intestinal bacterial infection

G-protein coupled receptor 120 (GPR 120) has been implicated in anti-inflammatory functions. However, how GPR120 regulates the neutrophil function remains unknown. This study investigated the role of GPR120 in the regulation of neutrophil function against enteric bacteria. 16S rRNA sequencing was used for measuring the gut microbiota of wild-type (WT) mice and Gpr120-/- mice. Citrobacter rodentium infection and dextran sulfate sodium (DSS)-induced colitis models were performed in WT and Gpr120-/- mice. Mouse peritoneal-derived primary neutrophils were used to determine the neutrophil functions. Gpr120-/- mice showed altered microbiota composition. Gpr120-/- mice exhibited less capacity to clear intestinal Citrobacter rodentium and more severe intestinal inflammation upon infection or DSS insults. Depletion of neutrophils decreased the intestinal clearance of Citrobacter rodentium. GPR120 agonist, CpdA, enhanced WT neutrophil production of reactive oxygen species (ROS) and extracellular traps (NETs), and GPR120-deficient neutrophils demonstrated a lower level of ROS and NETs. CpdA-treated neutrophils showed an enhanced capacity to inhibit the growth of Citrobacter rodentium, which was abrogated by the inhibition of either NETs or ROS. CpdA promoted neutrophil inhibition of the growth of commensal bacteria Escherichia coli O9:H4 and pathobiont Escherichia coli O83:H1 isolated from a Crohn's disease patient. Mechanically, mTOR activation and glycolysis mediated GPR120 induction of ROS and NETs in neutrophils. Additionally, CpdA promoted the neutrophil production of IL-17 and IL-22, and treatment with a conditioned medium of GPR120-activated neutrophils increased intestinal epithelial cell barrier functions. Our study demonstrated the critical role of GPR120 in neutrophils in protection against enteric bacterial invasion.

A novel C1qDC (PoC1qDC) with a collagen domain in Paralichthys olivaceus mediates complement activation and against bacterial infection

Complement C1q domain containing protein (C1qDC) is a vital recognition molecule and has an important effect on immunity. The C1qDCs exhibit opsonic activity in fish, while the mechanisms of C1qDCs in activation complement still remain unclear. This study explored immunological characteristics of a C1qDC from Japanese flounder (Paralichthys olivaceus) (PoC1qDC). PoC1qDC consists of 296 amino acid residues, possessing a collagen domain and a C1q domain. According to our results, PoC1qDC was expressed in 9 diverse tissue samples and showed up-regulation after bacterial challenge. Recombinant PoC1qDC (rPoC1qDC) activated normal serum bactericidal and hemolytic activities by interaction with Japanese flounder IgM, but not enhanced the complement activity of C3-depeleted serum. rPoC1qDC was significantly bound to various bacterial species and agglutination activity against Edwardsiella piscicida and Streptococcus iniae. Furthermore, rPoC1qDC showed direct interaction with peripheral blood leucocytes while enhancing phagocytic and chemotactic activity. When PoC1qDC was overexpressed in Japanese flounder before E. piscicida infection, bacterial replication was significantly inhibited in fish tissues. Consistently, when PoC1qDC expression in Japanese flounder was knocked down, bacterial replication was significantly enhanced. The above findings first suggested the role of PoC1qDC in teleost in mediating complement activation by interaction with IgM, which can positively influence bacterial infection.

Three IRF4 paralogs act as negative regulators of type Ⅰ IFN responses in yellow catfish (Pelteobagrus fulvidraco)

IRF4 is a master member of the interferon regulatory factor (IRF) family playing vital regulatory roles in immune system development and function. Tetrapods have a single-copy IRF4 gene, while teleosts harbor duplicated IRF4 genes. This work describes three IRF4 paralogs from yellow catfish (Pelteobagrus fulvidraco), designated PfIRF4A, PfIRF4B and PfIRF4B-like. These genes all contain a typical IRF structural architecture. Phylogenic and synteny analyses indicate that they should arise from the teleost-specific whole-genome duplication. PfIRF4 genes are abundantly expressed in the immune-related tissues and upregulated by PolyI:C, LPS, and Edwardsiella ictaluri. Ectopic expression of these genes inhibits the activation of fish type Ⅰ IFN promoters and downregulates the transcription levels of IFN-responsive genes, thus allowing the efficient replication of a fish rhabdovirus, spring viremia of carp virus (SVCV). PfIRF4s possess a repressive effect on MyD88-mediated activation of IFN and NF-κB. Some differences are observed between each individual paralog. PfIRF4B is the main form expressed across the tissues and the most up-regulated one after pathogen induction. It exerts a stronger inhibitory effect on IFN antiviral response than the other two paralogs. PfIRF4A and PfIRF4B-like are primarily present in the nucleus, while PfIRF4B displays colocalization and direct associations with MyD88 in the cytoplasm. Overall, the data demonstrate that three PfIRF4 paralogs show shared and individual functional properties in the negative regulation of type Ⅰ IFN response.

Identification and functional analysis of dual-specificity phosphatases (DUSP) genes in Japanese flounder (Paralichthys olivaceus) against temperature and Edwardsiella tarda stress

Dual-specificity Phosphatases (DUSPs) are not only the key regulators of dephosphorylating and inactivating mitogen-activated protein kinases (MAPKs), but play a crucial role in the immune response. However, the role of DUSP genes in Japanese flounder (PoDUSPs) is still unclear. In this study, 28 DUSP genes in Japanese flounder were identified and classified based on the whole genome database. Phylogenetic analysis and protein structure analysis revealed that DUSPs had highly conserved domains in teleosts. Molecular evolution analysis indicated that the PoDUSP genes were conservative during evolution and were functional-constrained. Meanwhile, PoDUSP genes were found to express in different embryonic and larval stages which might play the role of sentinel in healthy organisms. Furthermore, PoDUSP genes' expression profiles after temperature stress and Edwardsiella tarda (E. tarda) infection were determined in Japanese flounder without precedent, and the results demonstrated that Podusp1, Podusp2 and Podusp16 were more respective to temperature variation whereas Podusp1 and Podusp6 were more respective to E. tarda infection. In summary, our results provide useful resources for understanding the immune responsibilities of DUSP genes in flatfish.

Subtractive genomic analysis for computational identification of putative immunogenic targets against clinical Enterobacter cloacae complex

Background

Enterobacter is a major nosocomial genus of Enterobacteriaceae responsible for a variety of nosocomial infections, particularly in prolonged hospitalized patients in the intensive care units. Since current antibiotics have failed treating colistin- and carbapenem-resistant Enterobacteriaceae, efforts are underway to find suitable alternative strategies. Therefore, this study conducted a reverse vaccinology (RV) to identify novel and putative immunogenic targets using core proteome of 20 different sequence types (STs) of clinical Enterobacter spp. Moreover, we introduced a structural-based approach for exploration of potential vaccine candidates against the Enterobacteriaceae family using their conserved domain analysis.

Results

A number of 2616 core coding sequences (CDSs) were retrieved from 20 clinical strains of Enterobacter spp. with a similarity of ≥ 50%. Nine proteins with a score of ≥ 20 considered as the shortlisted proteins based on the quartile scoring method, including three TonB-dependent receptors, WP_008500981.1, WP_058690971.1 and WP_058679571.1; one YjbH domain-containing protein, WP_110108068.1; three flagellar proteins, WP_088207510.1, WP_033145204.1 and WP_058679632.1; one spore-coat U domain-containing protein, WP_039266612.1; and one DD-metalloendopeptidase family protein, WP_025912449.1. In this study, proteins WP_058690971.1 and WP_110108068.1 were detected as the top candidates with regard to immune stimulation and interactions with TLRs. However, their efficacy is remaining to be evaluated experimentally.

Conclusions

Our investigation introduced common ferrichrome porins with high sequence similarity as potential vaccine candidates against the Enterobacteriaceae family. These proteins belong to the iron acquisition system and possess all criteria of suitable vaccine targets. Therefore, they need to be specifically paid attention for vaccine development against clinically important members of Enterobacteriaceae family.

Taurine promotes Oreochromis niloticus survival against Edwardsiella tarda infection

Edwardsiella tarda represents one of the most important pathogens that infects a variety of hosts including aquatic animals and humans. The outbreak of E. tarda infection is frequently reported in aquaculture that causes huge economic loss. Due to the widespread of antibiotic resistance, available antibiotics to treat bacterial infection are limited. Therefore, enhancing aquatic animals to survive upon E. tarda infection become an urgent issue. In this study, we profiled the metabolomic change of tilapia in-between the dying and survival fish upon E. tarda infection. The dying and survival fish mounts differential metabolic response, from which we identify a key metabolite, taurine, whose abundance is increased in both the survival group and the dying group but is more significant in the survival group. Exogenous taurine increases tilapia survival rate by 37.5% upon E. tarda infection. Further quantitative PCR analysis demonstrate taurine increases the expression of immune genes in liver, spleen and head kidney. Therefore, our study shows a new strategy to enhance fish immune response against bacterial infection.

TNFR2 is a regulatory target of pol-miR-194a and promotes the antibacterial immunity of Japanese flounder Paralichthys olivaceus

MicroRNAs (miRNAs) are regulatory RNAs that modulate target gene expression after transcription. Pol-miR-194a had been reported to be a miRNA of Japanese flounder (Paralichthys olivaceus) involved in Edwardsiella tarda infection. Here, we identified tumor necrosis factor receptor 2 (TNFR2) as a target gene of pol-miR-194a. Pol-miR-194a markedly repressed the protein expression of flounder TNFR2 (PoTNFR2) via specific interaction with the 3'UTR of PoTNFR2. PoTNFR2 responded to E. tarda infection in a manner that was opposite to that of pol-miR-194a and inhibited E. tarda invasion by activating the NF-κB pathway. Consistently, dysregulation of PoTNFR2 had a significant impact on E. tarda dissemination in flounder tissues. Together, these results add new insights into the regulation mechanism and immune function of fish TNFR2 and pol-miR-194a.

Temperature induces metabolic reprogramming in fish during bacterial infection

Water temperature elevation as a consequence of global warming results in increased incidence of bacterial disease, such as edwardsiellosis, in fish farming. Edwardsiellosis is caused by the bacterial pathogen Edwardsiella tarda and affects many farmed fish including flounder (Paralichthys olivaceus). Currently, the effect of temperature on the metabolic response of flounder to E. tarda infection is unclear. In this study, we found that compared to low temperature (15°C), high temperature (23°C) enhanced E. tarda dissemination in flounder tissues. To examine the impact of temperature on the metabolism of flounder induced by E. tarda, comparative metabolomics were performed, which identified a large number of metabolites responsive to E. tarda invasion and temperature alteration. During E. tarda infection, the metabolic profile induced by elevated temperature was mainly featured by extensively decreased amino acids and TCA intermediates such as succinate, a proven immune regulator. Further, 38 potential metabolite markers of temperature effect (MMTE) in association with bacterial infection were identified. When used as exogenous supplements, two of the MMTE, i.e., L-methionine and UDP-glucose, effectively upregulated the expression of pro-inflammatory cytokines and suppressed E. tarda infection in flounder leukocytes. Taken together, the results of this study indicate an important influence of temperature on the metabolism of flounder during bacterial infection, which eventually affects the survivability of the fish.

Edwardsiella piscicida YccA: A novel virulence factor essential to membrane integrity, mobility, host infection, and host immune response

YccA is a hydrophobic protein with seven transmembrane domains. The function of YccA is largely unknown in pathogenic bacteria. Edwardsiella piscicide (formerly known as E. tarda) is an aquatic pathogen that can infect various economically important fish, including flounder (Paralichthys olivaceus) and tilapia (Oreochromis niloticus). In this study, we investigated the role of YccA in E. piscicida by the construction of a mar kerless yccA in-frame mutant strain, TX01ΔyccA. We found that (i) in comparison to the wild type TX01, TX01ΔyccA exhibited markedly compromised tolerance to high temperature and tobramycin; (ii) deletion of yccA significantly impaired the integrity of the cell membrane and retarded bacterial biofilm formation and mobility; (iii) deficiency of yccA reduced bacterial adhesion and invasion of fish cells and immune tissues, while the introduction of a trans-expressed yccA gene restored the lost virulence of TX01ΔyccA; and (iv) host immune responses induced by TX01 and TX01ΔyccA were different in terms of reactive oxygen species (ROS) levels and expression levels of cytokines. Taken together, the results of our study indicate that YccA is a novel virulence factor of E. piscicida, and YccA is essential for bacterial pathogenicity through evasion of the host's innate immune functions.

Genome-wide identification and analysis of scavenger receptors and their expression profiling in response to Edwardsiella tarda infection in Japanese flounder (Paralichthys olivaceus)

The scavenger receptors (SRs) gene family, as one of pattern recognition receptors, participates in the innate immune response in diverse lineages. However, the systematic identification, characteristics and functions of SRs family are lacking in teleost. Here, we identified all 19 SRs family members in Japanese flounder (Paralichthys olivaceus) based on the genome and transcriptome data. Phylogenetic and Ka/Ks analysis demonstrated that these SRs genes were divided into five classes and all exhibited pronounced purified selection pressures. Whole genome duplication event was found in colec12, scarb2, and lamp1. Gene structure, functional domain and motif distribution analyses indicated that SRs within the different subfamilies are severely conservative. SRs genes showed diverse expression patterns in the embryogenesis and unchanged tissues. The regulations of 14 SRs genes in blood, gill and kidney after E. tarda infection suggested their roles in innate immune response. Meanwhile, ten SRs genes were differentially expressed after E. tarda stimulation in macrophages in vitro. Then we proved that PoSCARA3 could suppress the activity of NF-κB and AP-1 in HEK 293T cells by dual-luciferase assays. In summary, this study provided valuable basis for further functional characterization and immune functions of SRs genes in P. olivaceus.

Dietary supplementation of propolis enhanced the innate immune response against Edwardsiella piscicida challenge in turbot (Scophthalmus maximus)

Propolis is non-hazardous resinous substance mixture containing bioactive ingredients such as polyphenols, flavonoids and organic acid. It has been widely used as food supplement and immune adjuvant due to its benefits in anti-microbial and immunomodulation. Edwardsiella piscicida is a kind of threatening pathogen which could cause high mortality in turbot. However, whether propolis could enhance the innate immune response against E. piscicida infection in turbot remains unknown. In this study, we found dietary propolis addition could improve the expression of anti-oxidative stress related enzymes, e.g., SOD, CAT and GPT, and relieved the histopathological changes of juvenile turbot after E. piscicida infection. Moreover, propolis addition increased the expression of cytokines such as il-1β, il-6 and tnf-α in different organs of juvenile turbot. Importantly, rescued survival and decreased bacterial loads were observed in propolis feeding group. Taken together, these findings suggest that the important roles of propolis in protecting juvenile turbot from E. piscicida infection, indicating propolis might be applied as a promising immunopotentiator candidate in aquaculture.

Structural characteristics and mucosal immune response of the interbranchial lymphoid tissue in the gills of flounder (Paralichthys olivaceus)

A specialized lymphoepithelial tissue termed the interbranchial lymphoid tissue (ILT) is recently identified in several fish species. However, the structural variation and mucosal immune functions of the ILT remain largely unknown. In this study, the anti-Zap-70 MAb was firstly determined to specifically recognize ZAP-70 protein, and CD4-1⁺, CD4-2⁺ and CD8β⁺ T-cells, but not IgM⁺ B cells, in peripheral blood leucocytes of flounder (Paralichthys olivaceus). Then we found that aggregates of Zap-70⁺ cells were located in the epithelium covering the bottom of the interbranchial cleft and along the afferent and efferent edges of the filaments in a cross view, where a meshwork of epithelial cells containing diffused lymphoid cells was exhibited, confirming these structures as the ILT; In a sagittal view, Zap-70⁺ cells were situated at the base of the filaments (here named as proximal ILT, pILT) and in the interlamellar epithelium (named as distal ILT, dILT). Also, a few IgM⁺ B cells were distributed at these sites. The lymphoepithelium within pILT and dILT was very thin with a low number of Zap-70⁺ cells in premetamorphosis and postclimax larvae of flounder, and got thicker containing much more Zap-70⁺ cells in juvenile and adult individuals. The aggregates of CD4-1⁺/Zap-70⁺, CD4-2⁺/Zap-70⁺, and CD8β⁺/Zap-70⁺ T-cell subsets were identified in the ILT. Post bath vaccination with inactivated Edwardsiella tarda and then intraperitoneal injection of EdU, the amounts of EdU⁺ and Zap-70⁺ cells obviously increased at 3 d and 7 d, and co-localization of EdU⁺/Zap-70⁺ cells identified the presence of proliferative T cells; meanwhile, MHC class II-expressing cells were increased. These findings indicated that the ILT in gills of flounder was an important site for the induction of local T cell-mediated immunity, which would lead to a better understanding of mucosal immunity and defense mechanisms of teleost fish.

Transcriptome analysis and protein-protein interaction in resistant and susceptible families of Japanese flounder (Paralichthys olivaceus) to understand the mechanism against Edwardsiella tarda

Edwardsiella tarda is one of the most harmful bacterial pathogens for aquaculture flatfish. After artificial infection of 47 Japanese flounder (Paralichthys olivaceus) families, resistant and susceptible families were identified in this study. High-throughput sequencing was performed on the liver transcriptome of uninfected groups (PoRU and PoSU) and infected groups (PoRC and PoSC). Through assembly and annotation, a total of 3012 and 1386 differentially expressed genes (DEGs) were identified in PoRU vs. PoSU and PoRC vs. PoSC. The significant enrichment pathways between PoRU and PoSU were mainly in metabolic and biosynthesis pathways. A total of thirty dominant enrichment pathways between PoRC and PoSC mainly focused on some immune-related pathways, including the hematopoietic cell lineage, cytokine-cytokine receptor interaction, complement and coagulation cascades, antigen processing and presentation, the intestinal immune network for immunoglobulin A (IgA) production and T/B cell receptor signaling pathway. Under the protein-protein interaction (PPI) analysis, hub genes, including CD molecules, complement component factors and chemokines, were identified in the network, and 16 core genes were differentially expressed in resistant and sustainable families in quantitative polymerase chain reaction (qPCR) validation. This study represents the first transcriptome analysis based on resistant and susceptible families and provides resistant genes to understand the potential molecular mechanisms of antibacterial function in marine fish. The results obtained in this study provide crucial information on gene markers for resistant breeding of Japanese flounder.

A nonredundant role for T cell-derived interleukin 22 in antibacterial defense of colonic crypts

Interleukin (IL)-22 is central to immune defense at barrier sites. We examined the contributions of innate lymphoid cell (ILC) and T cell-derived IL-22 during Citrobacter rodentium (C.r) infection using mice that both report Il22 expression and allow lineage-specific deletion. ILC-derived IL-22 activated STAT3 in C.r-colonized surface intestinal epithelial cells (IECs) but only temporally restrained bacterial growth. T cell-derived IL-22 induced a more robust and extensive activation of STAT3 in IECs, including IECs lining colonic crypts, and T cell-specific deficiency of IL-22 led to pathogen invasion of the crypts and increased mortality. This reflected a requirement for T cell-derived IL-22 for the expression of a host-protective transcriptomic program that included AMPs, neutrophil-recruiting chemokines, and mucin-related molecules, and it restricted IFNγ-induced proinflammatory genes. Our findings demonstrate spatiotemporal differences in the production and action of IL-22 by ILCs and T cells during infection and reveal an indispensable role for IL-22-producing T cells in the protection of the intestinal crypts.

High rate of asymptomatic colonization with antimicrobial-resistant Escherichia coli in Australian returned travellers

Global movement of people plays a key role in the spread of antimicrobial resistant (AMR) organisms. We found that 58% of Australian travellers returning from Asia were asymptomatic carriers of AMR Escherichia coli, including resistance to critically important antibiotics. Future studies are needed to identify interventions for travellers to reduce their risk of AMR acquisition.

Development of Nano-Conjugated DNA Vaccine Against Edwardsiellosis Disease in Fish

Biotechnological advancements have paved newer avenues for developing and designing novel and effective vaccines for rendering protection from various types of infectious diseases. Use of immunogenic genes via plasmid DNA constitutes an important next-generation biotechnological approach to fish immunization. In addition, the use of nanotechnology has significantly addressed the issue of mucosal mode of DNA vaccine delivery in aquaculture. Taking together both these advance technologies, this chapter entails a detailed protocol for the development of a nano-conjugated bicistronic DNA vaccine using chitosan nanoparticles as delivery vehicle, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene of Edwardsiella tarda as antigenic gene and interferon gamma (IFN-γ) gene of Labeo rohita as molecular adjuvant.

Household Transmission of Carbapenemase-producing Enterobacterales in Ontario, Canada

BACKGROUND

Data on household transmission of carbapenemase-producing Enterobacterales (CPE) remain limited. We studied risk of CPE household co-colonization and transmission in Ontario, Canada.

METHODS

We enrolled CPE index cases (identified via population-based surveillance from January 2015 to October 2018) and their household contacts. At months 0, 3, 6, 9, and 12, participants provided rectal and groin swabs. Swabs were cultured for CPE until September 2017, when direct polymerase chain reaction (PCR; with culture of specimens if a carbapenemase gene was detected) replaced culture. CPE risk factor data were collected by interview and combined with isolate whole-genome sequencing to determine likelihood of household transmission. Risk factors for household contact colonization were explored using a multivariable logistic regression model with generalized estimating equations.

RESULTS

Ninety-five households with 177 household contacts participated. Sixteen (9%) household contacts in 16 (17%) households were CPE-colonized. Household transmission was confirmed in 3/177 (2%) cases, probable in 2/177 (1%), possible in 9/177 (5%), and unlikely in 2/177 (1%). Household contacts were more likely to be colonized if they were the index case's spouse (odds ratio [OR], 6.17; 95% confidence interval [CI], 1.05-36.35), if their index case remained CPE-colonized at household enrollment (OR, 7.00; 95% CI, 1.92-25.49), or if they had at least 1 set of specimens processed after direct PCR was introduced (OR, 6.46; 95% CI, 1.52-27.40).

CONCLUSIONS

Nine percent of household contacts were CPE-colonized; 3% were a result of household transmission. Hospitals may consider admission screening for patients known to have CPE-colonized household contacts.

Lactobacillus johnsonii Attenuates Citrobacter rodentium-Induced Colitis by Regulating Inflammatory Responses and Endoplasmic Reticulum Stress in Mice

BACKGROUND

Probiotics are beneficial in intestinal disorders. However, the benefits of Lactobacillus johnsonii in experimental colitis remain unknown.

OBJECTIVES

This study aimed to investigate the benefits of L. johnsonii against Citrobacter rodentium-induced colitis.

METHODS

Thirty-six 5-wk-old female C57BL/6J mice were randomly assigned to 3 groups (n = 12): control (Ctrl) group, Citrobacter rodentium treatment (CR) group (2 × 109 CFU C. rodentium), and Lactobacillus johnsonii and Citrobacter rodentium cotreatment (LJ + CR) group (109 CFU L. johnsonii with C. rodentium). Colon length, mucosal thickness, proinflammatory cytokine genes, and endoplasmic reticulum stress were tested.

RESULTS

The CR group had greater spleen weight, mucosal thickness, and Ki67+ cells (0.4-4.7 times), and a 23.8% shorter colon length than the Ctrl group, which in the LJ + CR group were 22.4%-77.6% lower and 30% greater than in the CR group, respectively. Relative to the Ctrl group, serum proinflammatory cytokines and immune cell infiltration were greater by 0.3-1.6 times and 6.2-8.8 times in the CR group, respectively; relative to the CR group, these were 19.9%-61.9% and 69.5%-84.2% lower in the LJ + CR group, respectively. The mRNA levels of lysozyme (Lyz) and regenerating islet-derived protein III were 22.7%-36.5% lower and 1.5-2.7 times greater in the CR group than in the Ctrl group, respectively, whereas they were 22.2%-25.7% greater and 57.2%-76.9% lower in the LJ + CR group than in the CR group, respectively. Cell apoptosis was 11.9 times greater in the CR group than in the Ctrl group, and 87.4% lower in the LJ + CR group than in the CR group. Consistently, the protein abundances of C/EBP homologous protein (CHOP), cleaved caspase 1 and 3, activating transcription factor 6α (ATF6A), and phospho-inositol-requiring enzyme 1α (P-IRE1A) were 0.3-2.1 times greater in the CR group and 31.1%-60.4% lower in the LJ + CR group. All these indexes did not differ between the Ctrl and LJ + CR groups, except for CD8+ T lymphocytes and CD11b+ and F4/80+ macrophages (1-1.5 times greater in LJ + CR) and mRNA concentration of Lyz2 (20.1% lower in LJ + CR).

CONCLUSIONS

L. johnsonii supplementation is a promising nutritional strategy for preventing C. rodentium-induced colitis in mice.

Monitoring of hospital sewage shows both promise and limitations as an early-warning system for carbapenemase-producing Enterobacterales in a low-prevalence setting

Carbapenemase-producing Enterobacterales (CPE) constitute a significant threat to healthcare systems. Continuous surveillance is important for the management and early warning of these bacteria. Sewage monitoring has been suggested as a possible resource-efficient complement to traditional clinical surveillance. It should not least be suitable for rare forms of resistance since a single sewage sample contains bacteria from a large number of individuals. Here, the value of sewage monitoring in early warning of CPE was assessed at the Sahlgrenska University Hospital in Gothenburg, Sweden, a setting with low prevalence of CPE. Twenty composite hospital sewage samples were collected during a two-year period. Carbapenemase genes in the complex samples were analyzed by quantitative PCR and the CPE loads were assessed through cultures on CPE-selective agar followed by species determination as well as phenotypic and genotypic tests targeting carbapenemases of presumed CPE. The findings were related to CPE detected in hospitalized patients. A subset of CPE isolates from sewage and patients were subjected to whole genome sequencing. For three of the investigated carbapenemase genes, bla_NDM, bla_OXA-48-like and bla_KPC, there was concordance between gene levels and abundance of corresponding CPE in sewage. For the other two analyzed genes, bla_VIM and bla_IMP, there was no such concordance, most likely due to the presence of those genes in non-Enterobacterales populating the sewage samples. In line with the detection of OXA-48-like- and NDM-producing CPE in sewage, these were also the most commonly detected CPE in patients. NDM-producing CPE were detected on a single occasion in sewage and isolated strains were shown to match strains detected in a patient. A marked peak in CPE producing OXA-48-like enzymes was observed in sewage during a few months. When levels started to increase there were no known cases of such CPE at the hospital but soon after a few cases were detected in samples from patients. The OXA-48-like-producing CPE from sewage and patients represented different strains, but they carried similar bla_OXA-48-like-harbouring mobile genetic elements. In conclusion, sewage analyses show both promise and limitations as a complement to traditional clinical resistance surveillance for early warning of rare forms of resistance. Further evaluation and careful interpretation are needed to fully assess the value of such a sewage monitoring system.

Acute Cholecystitis, Sepsis, and Disseminated Intravascular Coagulation Caused by Edwardsiella tarda in an Elderly Woman

Edwardsiella tarda is a gram-negative bacillus associated with gastrointestinal diseases. It is rarely responsible for sepsis; however, the fatality is very high. Only two cases of E. tarda infections in patients over 90 years of age have been reported; these are not cases of sepsis associated with acute cholecystitis. We report a case of acute cholecystitis, sepsis, and disseminated intravascular coagulation (DIC) caused by E. tarda in a super-elderly woman aged over 90 years. There could be a possibility for recovery from sepsis and DIC if antimicrobial treatment responsiveness is ensured in the super-elderly.

CLINICAL CASE OF EDWARDSIELLOSIS IN UKRAINE

Edwardsiellosis is a zoonotic infectious disease that caused by Edwardsiella tarda and characterized by gastroenteritis in humans. Contaminated water can also be a source of infection. Primary nutritional toxicity clinical signs may mask aquatic zoonosis caused by Edwardsiella tarda. Infectious border control should ensure that the import into Ukraine of such preservatives of food products, highly probably infected by this agent is not allowed.

[Resistance to antibiotics of clinical relevance in a hospital of Corrientes city]

Carbapenemaseproducing bacteria are involved in infections and colonizations and associated with high morbidity and mortality. Their identification facilitates the design and implementation of interventions aimed at reducing the risk of infections and deaths. The objective of this study was to determine the prevalence of carbapenemase-producing microorganisms in the main public hospital in the city of Corrientes, Argentina, and to determine their susceptibility to antibiotics commonly used in clinical practice. We analyzed 674 clinical samples from the same number of adults admitted to different inpatient units of the Hospital Escuela Gral. José Francisco de San Martín during the period September-December 2018. The bacterial identification was carried out through manual biochemical tests and the susceptibility to antimicrobials was evaluated according to the recommendations of the Clinical and Laboratory Standards Institute. We identified 115 carbapenemase-producing bacteria of the following types: KPC (90, 78%), OXA-ACI (24, 21%) and OXA-163 (≈1%). Among the microorganisms involved in infections (n = 56; 49%), most of those of the KPC type (n = 32; 57%) showed sensitivity only against amikacin (27/32; 84%), while most of those of the OXA-ACI type ( 24; 43%) showed significant sensitivity only against minocycline (17/24; 71%) and colistin (n = 19/24; 79%). This study demonstrated the presence of carbapenemase-producing microorganisms in all the investigated hospital units and a high frequency of resistance to antimicrobials commonly used in clinical practice. This information is relevant to adapt the therapeutic schemes and hygienic-sanitary measures to the local reality.

[Development and Evaluation of Screening Culture Medium for Detection of Drug-Resistant Gram Negative Rods Containing Stealth Type CPE]

There is a report that an infection by medicine resistant bacteria will be the number one cause of death in 2050 according to the recommendation of WHO, and the CPE (carbapenem-producing Enterobacteriaceae) infection is regarded as a problem in particular. When detecting CPE, it is important how to detect stealth type CPE sensitive to carbapenem series medicines. So we used the 2 types of screening culture medium, "KBM" CRE-JU culture medium ‹KOJINBAIO› (CRE-JU culture medium) and the FRPM culture medium, and tried to detect drug-resistant gram-negative bacilli such as CPE, stealth type CPE, ESBL-producing bacteria, and excess AmpC-producing bacteria (AmpC-producing bacteria), etc. in combination of this culture mediums. As a result, CRE-JU culture medium showed a difference in the growth of CPE depending on the amount of inoculated bacteria while β-lactamase non-producing strain and other strains except for high concentration ESBL-producing bacteria and AmpC-producing bacteria were un-growing. Most of the CRE, stealth type CPE, ESBL-producing bacteria and AmpC-producing bacteria grew in the FRPM culture medium while most of the β-lactamase non-producing strains with a MIC value of meropenem (MEPM) of 2 µg/mL or less were un-growing. From these results, it was suggested that when a strain grown on CRE-JU and FRPM culture mediums, it could be distinguished as CPE, and when strains grown on FRPM culture medium which were un-grown on CRE-JU culture medium, it could be distinguished as drug-resistant bacteria such as stealth type CPE, ESBL-producing bacteria, and AmpC-producing bacteria. When strains not grown on CRE-JU and FRPM culture mediums, it could be distinguished as sensitive.