Detection of toxigenic M1UK lineage group A Streptococcus clones in Taiwan

BACKGROUND

A new sublineage of emm1 group A Streptococcus (GAS), M1UK, has emerged in Europe, North America, and Australia. Notably, a significant portion of emm1 isolates in Asia, particularly in Hong Kong and mainland China, acquired scarlet fever-associated prophages following the 2011 Hong Kong scarlet fever outbreak. However, the presence of the M1UK sublineage has not yet been detected in Asia.

METHODS

This study included 181 GAS isolates (2011-2021). The emm type of these isolates were determined, and 21 emm1 isolates from blood or pleural fluid (2011-2021) and 10 emm1 isolates from throat swabs (2016-2018) underwent analysis. The presence of the scarlet fever-associated prophages and the specific single nucleotide polymorphisms of the M1UK clone were determined by polymerase chain reaction and the genome sequencing.

RESULTS

The M1UK lineage strains from throat swab and blood samples were identified. One of the M1UK strain in Taiwan carried the scarlet fever-associated prophage and therefore acquired the ssa, speC, and spd1 toxin repertoire. Nonetheless, the increase of M1UK was not observed until 2021, and there was a reduction in the diversity of emm types in 2020-2021, possibly due to the COVID-19 pandemic restriction policies in Taiwan.

CONCLUSIONS

Our results suggested that the M1UK lineage clone has introduced in Taiwan. In Taiwan, the COVID-19 restrictions were officially released in March 2023; therefore, it would be crucial to continuously monitor the M1UK expansion and its related diseases in the post COVID-19 era.

Phage transcriptional regulator X (PtrX)-mediated augmentation of toxin production and virulence in Clostridioides difficile strain R20291

Clostridioides difficile is a Gram-positive, anaerobic, and spore-forming bacterial member of the human gut microbiome. The primary virulence factors of C. difficile are toxin A and toxin B. These toxins damage the cell cytoskeleton and cause various diseases, from diarrhea to severe pseudomembranous colitis. Evidence suggests that bacteriophages can regulate the expression of the pathogenicity locus (PaLoc) genes of C. difficile. We previously demonstrated that the genome of the C. difficile RT027 strain NCKUH-21 contains a prophage-like DNA sequence, which was found to be markedly similar to that of the φCD38-2 phage. In the present study, we investigated the mechanisms underlying the φNCKUH-21-mediated regulation of the pathogenicity and the PaLoc genes expression in the lysogenized C. difficile strain R20291. The carriage of φNCKUH-21 in R20291 cells substantially enhanced toxin production, bacterial motility, biofilm formation, and spore germination in vitro. Subsequent mouse studies revealed that the lysogenized R20291 strain caused a more severe infection than the wild-type strain. We screened three φNCKUH-21 genes encoding DNA-binding proteins to check their effects on PaLoc genes expression. The overexpression of NCKUH-21_03890, annotated as a transcriptional regulator (phage transcriptional regulator X, PtrX), considerably enhanced toxin production, biofilm formation, and bacterial motility of R20291. Transcriptome analysis further confirmed that the overexpression of ptrX led to the upregulation of the expression of toxin genes, flagellar genes, and csrA. In the ptrX-overexpressing R20291 strain, PtrX influenced the expression of flagellar genes and the sigma factor gene sigD, possibly through an increased flagellar phase ON configuration ratio.

Haemolysin Ahh1 secreted from Aeromonas dhakensis activates the NLRP3 inflammasome in macrophages and mediates severe soft tissue infection

Severe soft tissue infections caused by Aeromonas dhakensis, such as necrotizing fasciitis or cellulitis, are prevalent in southern Taiwan and around the world. However, the mechanism by which A. dhakensis causes tissue damage remains unclear. Here, we found that the haemolysin Ahh1, which is the major virulence factor of A. dhakensis, causes cellular damage and activates the NLR family pyrin domain containing 3 (NLRP3) inflammasome signalling pathway. Deletion of ahh1 significantly downregulated caspase-1, the proinflammatory cytokine interleukin 1β (IL-1β) and gasdermin D (GSDMD) and further decreased the damage caused by A. dhakensis in THP-1 cells. In addition, we found that knockdown of the NLRP3 inflammasome confers resistance to A. dhakensis infection in both THP-1 NLRP3-/- cells and C57BL/6 NLRP3-/- mice. In addition, we demonstrated that severe soft-tissue infections treated with antibiotics combined with a neutralizing antibody targeting IL-1β significantly increased the survival rate and alleviated the degree of tissue damage in model mice compared control mice. These findings show that antibiotics combined with therapies targeting IL-1β are potential strategies to treat severe tissue infections caused by toxin-producing bacteria.

RopB-regulated SpeB cysteine protease degrades extracellular vesicles-associated streptolysin O and bacterial proteins from group A Streptococcus

Extracellular vesicles (EVs) can be released from gram-positive bacteria and would participate in the delivery of bacterial toxins. Streptococcus pyogenes (group A Streptococcus, GAS) is one of the most common pathogens of monomicrobial necrotizing fasciitis. Spontaneous inactivating mutation in the CovR/CovS two-component regulatory system is related to the increase of EVs production via an unknown mechanism. This study aimed to investigate whether the CovR/CovS-regulated RopB, the transcriptional regulator of GAS exoproteins, would participate in regulating EVs production. Results showed that the size, morphology, and number of EVs released from the wild-type strain and the ropB mutant were similar, suggesting RopB is not involved in controlling EVs production. Nonetheless, RopB-regulated SpeB protease degrades streptolysin O and bacterial proteins in EVs. Although SpeB has crucial roles in modulating protein composition in EVs, the SpeB-positive EVs failed to trigger HaCaT keratinocytes pyroptosis, suggesting that EVs did not deliver SpeB into keratinocytes or the amount of SpeB in EVs was not sufficient to trigger cell pyroptosis. Finally, we identified that EV-associated enolase was resistant to SpeB degradation, and therefore could be utilized as the internal control protein for verifying SLO degradation. This study revealed that RopB would participate in modulating protein composition in EVs via SpeB-dependent protein degradation and suggested that enolase is a potential internal marker for studying GAS EVs.

Age and prior vaccination determine the antibody level in children with primary SARS-CoV-2 Omicron infection

BACKGROUND

Protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfection relies on immunity generated after primary infection. However, humoral immunity following primary infection with the Omicron variant is not well understood.

METHODS

We prospectively recruited children <19 years with virologically-confirmed SARS-CoV-2 infection at National Cheng Kung University Hospital from February 2022 to September 2022 during the first wave of Omicron BA.2 outbreak in Taiwan. Serum samples were collected one month after acute infection to measure anti-spike protein receptor binding domain antibody levels and surrogate virus neutralizing antibody (NAb) levels against wild type disease and variants.

RESULTS

Of the 164 patients enrolled, most were under 5 years (65.2%) with a diagnosis of upper respiratory tract infection. Children under 6 months with maternal coronavirus disease 2019 (COVID-19) vaccination had higher levels of both anti-SARS-CoV-2 spike antibody (119.0 vs 27.4 U/ml, p < 0.05) and anti-wild type NAb (56.9% vs 27.6% inhibition, p = 0.001) than those without. Children aged 5-12 years with prior vaccination had higher anti-spike antibody, anti-wild type, and anti-Omicron BA.2 NAb levels than those without (all p < 0.05). In previously naïve children without maternal or self-vaccination, those 6 months to 2 years had the highest antibody levels. Multivariable linear regression analysis showed age was the only independent factor associated with antibody level.

CONCLUSIONS

In our study, children aged 6 months to 2 years have the highest antibody responses to SARS-CoV-2 Omicron variant infection. Age and prior vaccination are the main factors influencing the immunogenicity of SARS-CoV-2 infection.

Phosphate burden induces vascular calcification through a NLRP3-caspase-1-mediated pyroptotic pathway

AIMS

The aim of this study is to clarify the role of NLRP3 inflammasome in phosphate burden-induced vascular smooth muscle cell (VSMC) calcification.

MAIN METHODS

VSMC calcification was induced using a high concentration of inorganic phosphate. After pharmacological inhibition or genetic silencing of the NLRP3 inflammasome, pyroptosis, or potassium efflux, the cells were examined by RT-qPCR, immunofluorescence, and western blotting to identify the NLRP3-mediated pathway for VSMC calcification.

KEY FINDINGS

Calcified VSMCs with α-smooth muscle actin (α-SMA) disarray presented features of pyroptosis, including caspase-1 maturation, cleaved gasdermin D (GSDMD), and a high supernatant level of lactate dehydrogenase A. Pharmacological inhibitions of caspase-1 and pyroptosis attenuated VSMC calcification, whereas interleukin-1β receptor antagonism did not. Unlike canonical NLRP3 activation, osteogenic VSMCs did not upregulate NLRP3 expression. However, NLRP3 genetic silencing or inhibitions, which targets different domains of the NLRP3 protein, could ameliorate VSMC calcification by aborting caspase-1 and GSDMD activation. Furthermore, potassium efflux through the inward-rectifier potassium channel, and not through the P2X7 receptor, triggered NLRP3 inflammasome activation and VSMC calcification.

SIGNIFICANCE

In the present study, we identified a potassium efflux-triggered NLRP3-caspase-1-mediated pyroptotic pathway for VSMC calcification that is unique and different from the canonical NLRP3 inflammasome activation. Therefore, targeting this pathway may serve as a novel therapeutic strategy for vascular calcification.

NSUN2 is a glucose sensor suppressing cGAS/STING to maintain tumorigenesis and immunotherapy resistance

Glucose metabolism is known to orchestrate oncogenesis. Whether glucose serves as a signaling molecule directly regulating oncoprotein activity for tumorigenesis remains elusive. Here, we report that glucose is a cofactor binding to methyltransferase NSUN2 at amino acid 1-28 to promote NSUN2 oligomerization and activation. NSUN2 activation maintains global m5C RNA methylation, including TREX2, and stabilizes TREX2 to restrict cytosolic dsDNA accumulation and cGAS/STING activation for promoting tumorigenesis and anti-PD-L1 immunotherapy resistance. An NSUN2 mutant defective in glucose binding or disrupting glucose/NSUN2 interaction abolishes NSUN2 activity and TREX2 induction leading to cGAS/STING activation for oncogenic suppression. Strikingly, genetic deletion of the glucose/NSUN2/TREX2 axis suppresses tumorigenesis and overcomes anti-PD-L1 immunotherapy resistance in those cold tumors through cGAS/STING activation to facilitate apoptosis and CD8+ T cell infiltration. Our study identifies NSUN2 as a direct glucose sensor whose activation by glucose drives tumorigenesis and immunotherapy resistance by maintaining TREX2 expression for cGAS/STING inactivation.

The composition of the maternal breastmilk microbiota influences the microbiota network structure during early infancy

BACKGROUND/PURPOSE(S)

Human breastmilk (BM) is important for microbiome maturation in infants across different body sites. Streptococcus and Staphylococcus are considered universally predominant genera in the BM microbiota. However, whether the differential abundance of Streptococcus and Staphylococcus in BM can differentially affect microbiome maturation in infants remains unclear.

METHODS

We recruited exclusively breastfeeding mothers from among the donors of the human milk bank established at National Cheng-Kung University Hospital. The donor mothers provided 35 BM samples at three months (3 M; before introducing children to complementary feeding) and 23 BM samples at six months (6 M; after introducing children to complementary feeding) postpartum. At both time points, samples from different body sites, including nasal swabs, oral swabs and stool, were collected from the mothers and their infants.

RESULTS

Maternal BMI was inversely associated with coagulase-negative Staphylococcus (CoNS) abundance in breastmilk. Staphylococcus caprae representation in BM CoNS showed a negative correlation with Streptococcus abundance. Network analysis revealed that infants fed Staphylococcus-dominated BM had better gut and nasal microbiota networks than infants fed Streptococcus-abundant BM during early infancy.

CONCLUSION

Our work suggests that maternal metabolic status plays a crucial role in Staphylococcus/Streptococcus competition in BM, which in turn can impact the development of the infant microbiota. Our microbiota co-occurrence network analysis might serve as a helpful bioinformatic tool to monitor microbiota maturation during early infancy.

NLRP3 inflammasome activation, metabolic danger signals, and protein binding partners

The NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is an oligomeric complex that assembles in response to exogenous signals of pathogen infection and endogenous danger signals of non-microbial origin. When NLRP3 inflammasome assembly activates caspase-1, it promotes the maturation and release of the inflammatory cytokines interleukin-1B and IL-18. Aberrant activation of the NLRP3 inflammasome has been implicated in various diseases, including chronic inflammatory, metabolic, and cardiovascular diseases. The NLRP3 inflammasome can be activated through several principal mechanisms, including K+ efflux, lysosomal damage, and the production of mitochondrial reactive oxygen species. Interestingly, metabolic danger signals activate the NLRP3 inflammasome to induce metabolic diseases. NLRP3 contains three crucial domains: an N-terminal pyrin domain, a central nucleotide-binding domain, and a C-terminal leucine-rich repeat domain. Protein-protein interactions act as a 'pedal or brake' to control the activation of the NLRP3 inflammasome. In this review, we present the mechanisms underlying NLRP3 inflammasome activation after induction by metabolic danger signals or via protein-protein interactions with NLRP3 that likely occur in metabolic diseases. Understanding these mechanisms will enable the development of specific inhibitors to treat NLRP3-related metabolic diseases.

Pre-existing humoral immunity and CD4+ T cell response correlate with cross-reactivity against SARS-CoV-2 Omicron subvariants after heterologous prime-boost vaccination

BACKGROUND

Information regarding the heterologous prime-boost COVID vaccination has been fully elucidated. The study aimed to evaluate both humoral, cellular immunity and cross-reactivity against variants after heterologous vaccination.

METHODS

We recruited healthcare workers previously primed with Oxford/AstraZeneca ChAdOx1-S vaccines and boosted with Moderna mRNA-1273 vaccine boost to evaluate the immunological response. Assay used: anti-spike RBD antibody, surrogate virus neutralizing antibody and interferon-γ release assay.

RESULTS

All participants exhibited higher humoral and cellular immune response after the booster regardless of prior antibody level, but those with higher antibody level demonstrated stronger booster response, especially against omicron BA.1 and BA.2 variants. The pre-booster IFN-γ release by CD4⁺ T cells correlates with post-booster neutralizing antibody against BA.1 and BA.2 variant after adjustment with age and gender.

CONCLUSIONS

A heterologous mRNA boost is highly immunogenic. The pre-existing neutralizing antibody level and CD4⁺ T cells response correlates with post-booster neutralization reactivity against the Omicron variant.

Inguinal Fat Compensates Whole Body Metabolic Functionality in Partially Lipodystrophic Mice with Reduced PPARγ Expression

Peroxisome proliferator-activated receptor γ (PPARγ) gene mutations in humans and mice lead to whole-body insulin resistance and partial lipodystrophy. It is unclear whether preserved fat depots in partial lipodystrophy are beneficial for whole-body metabolic homeostasis. We analyzed the insulin response and expression of metabolic genes in the preserved fat depots of PpargC/- mice, a familial partial lipodystrophy type 3 (FPLD3) mouse model resulting from a 75% decrease in Pparg transcripts. Perigonadal fat of PpargC/- mice in the basal state showed dramatic decreases in adipose tissue mass and insulin sensitivity, whereas inguinal fat showed compensatory increases. Preservation of inguinal fat metabolic ability and flexibility was reflected by the normal expression of metabolic genes in the basal or fasting/refeeding states. The high nutrient load further increased insulin sensitivity in inguinal fat, but the expression of metabolic genes became dysregulated. Inguinal fat removal resulted in further impairment of whole-body insulin sensitivity in PpargC/- mice. Conversely, the compensatory increase in insulin sensitivity of the inguinal fat in PpargC/- mice diminished as activation of PPARγ by its agonists restored insulin sensitivity and metabolic ability of perigonadal fat. Together, we demonstrated that inguinal fat of PpargC/- mice plays a compensatory role in combating perigonadal fat abnormalities.

Structural basis underlying the synergism of NADase and SLO during group A Streptococcus infection

Group A Streptococcus (GAS) is a strict human pathogen possessing a unique pathogenic trait that utilizes the cooperative activity of NAD+-glycohydrolase (NADase) and Streptolysin O (SLO) to enhance its virulence. How NADase interacts with SLO to synergistically promote GAS cytotoxicity and intracellular survival is a long-standing question. Here, the structure and dynamic nature of the NADase/SLO complex are elucidated by X-ray crystallography and small-angle scattering, illustrating atomic details of the complex interface and functionally relevant conformations. Structure-guided studies reveal a salt-bridge interaction between NADase and SLO is important to cytotoxicity and resistance to phagocytic killing during GAS infection. Furthermore, the biological significance of the NADase/SLO complex in GAS virulence is demonstrated in a murine infection model. Overall, this work delivers the structure-functional relationship of the NADase/SLO complex and pinpoints the key interacting residues that are central to the coordinated actions of NADase and SLO in the pathogenesis of GAS infection.

Association of Single Nucleotide Polymorphisms in Nucleotide-Binding Domain Leucine-Rich Repeat Protein 1 with Clostridioides difficile Colonization or Infection

Introduction

Nucleotide-binding domain leucine-rich repeat protein (NLRP) is critical in the inflammasome-activation pathway, which is important for host survival and the clearance of Clostridioides difficile. Therefore, the influence of NLRP1 polymorphisms on C. difficile colonization (CdC) or infection (CDI) was analyzed.

Materials and Methods

A prospective cohort study consisted of hospitalized adults was conducted from January 2011 to January 2013. Single nucleotide polymorphisms (SNPs) of NLRP1, including rs12150220, rs2670660, rs6502867, rs878329, rs8182352, rs3744717, and rs11078571, were incorporating in analyses. The episodes of CdC and CDI were the primary and secondary outcome, respectively.

Results

Of the total of 509 eligible patients, 376 (73.9%) had neither CdC nor CDI, 104 (21.8%) had CdC without developing CDI, and 29 (4.3%) developed CDI during the study period. Through multivariate analyses, comorbid diabetes mellitus (adjusted odds ratio [AOR] 1.59, P=0.04) and CC genotype in NLRP1 rs3744717 (AOR 1.70, P=0.02) were recognized as the risk factor of CdC. After adjusting the independent predictors of CDI, in terms of comorbid diabetes mellitus (AOR 3.18, P=0.005) and prior exposure to ceftazidime/ceftriaxone (AOR 2.87, P=0.04) or proton pump inhibitors (AOR 3.86, P=0.001), patients with CC+GC genotype in NLRP1, rs878329 (AOR 2.39, P=0.03) remained a higher risk of CDI.

Conclusion

For hospitalized adults, the association of CC genotype in NLRP1 rs3744717 and CdC as well as the CC+GC genotype in NLRP1 rs878329 and CDI was respectively evidenced. We believed the prompt identification of patients having specific genotype in NLRP1 would prevent and improve the quality of care in CDI.

Peroxisome proliferator-activated receptor-γ as the gatekeeper of tight junction in Clostridioides difficile infection

Clostridioides difficile is a major causative pathogen of nosocomial antibiotic-associated diarrhea and severe colitis. Despite the use of vancomycin and fidaxomicin as standard drugs for the treatment of C. difficile infection (CDI), clinical relapse rates remain high. Therefore, new alternative therapeutics to treat CDI are urgently required. The nuclear receptor, peroxisome proliferator-activated receptor-γ (PPAR-γ), is mainly expressed in the adipose tissue and modulates lipid metabolism and insulin sensitization. Previous studies have shown that PPAR-γ is highly expressed in colonic tissues and regulates tight junction function in epithelial cells. However, the role of PPAR-γ in CDI pathogenesis remains unclear. In this study, we used a mouse model of CDI and found that both expression levels of PPAR-γ and the tight junction protein, occludin, were decreased in colonic tissues. Furthermore, to investigate the role of PPAR-γ in CDI, we used PPAR-γ defective mice and found that intestinal permeability and bacterial dissemination in these mice were significantly higher than those in wild-type mice during CDI. Administration of the PPAR-γ agonist, pioglitazone, to activate PPAR-γ activity improved the phenotypes of CDI, including bodyweight loss, inflammation, and intestinal integrity. Taken together, these results demonstrate that PPAR-γ is a potential therapeutic target in CDI, as it modulates colonic inflammation and integrity.

Risk Factors and Clinical Impact of Carbapenem-Resistant Enterobacterales Coinfections Among Hospitalized Patients with Clostridioides difficile Infection

Introduction

The risk factors and clinical impact of carbapenem-resistant Enterobacterales (CRE) coinfection among hospitalized patients with Clostridioides difficile infection (CDI) were analyzed in this study.

Materials and Methods

A clinical study was performed at the medical wards of Tainan Hospital, Ministry of Health and Welfare in southern Taiwan. Patients with CDI between January 2013 and April 2020 were included.

Results

Among 238 patients included for analysis, 22 (9.2%) patients developed CRE coinfections within 14 days before or after the onset of CDI. CDI patients with CRE coinfection had longer hospitalization stays (103.0 ± 97.0 days vs 42.5 ± 109.6 days, P = 0.01) than those without CRE coinfection. In the multivariate analysis, age (odds ratio [OR] 1.05, 95% confidence interval [CI] 1.01–1.10, P = 0.02) was independently associated with CRE coinfection. In contrast, underlying old stroke (OR 0.15, 95% CI 0.03–0.70, P = 0.02) was negatively linked to CRE coinfection.

Conclusion

Among patients with CDI, CRE coinfections were associated with prolonged hospitalization for CDI. Age was an independent risk factor for CRE coinfection among patients with CDI.

Hypervirulent Clostridioides difficile RT078 lineage isolates from the river: A potential reservoir for environmental transmission

This is the first report to discover Clostridiodes difficile (C. difficile) ribotype RT126 and RT598 (both ribotypes belong to RT078-lineage) in a river water system in southern Taiwan. Fluoroquinolone resistance was also found. The connection between clinical isolates and those from the environment needs further investigation.

The emergence of Clostridioides difficile PCR ribotype 127 at a hospital in northeastern Taiwan

BACKGROUND

Several studies have highlighted the incidence of Clostridioides difficile infections (CDIs) in Taiwan and certain ribotypes have been related to severe clinical diseases. A study was conducted to investigate the polymerase chain reaction (PCR) ribotypes and genetic relatedness of clinical C. difficile strains collected from January 2009 to December 2015 at a hospital in northeastern Taiwan.

MATERIAL AND METHODS

A modified two-step typing algorithm for C. difficile was used by combining a modified 8-plex and 3'-truncated tcdA screening PCR. In addition, MLVA typing was adopted for investigation of bacterial clonality and transmission.

RESULTS

Among a total of 86 strains, 24 (28%) were nontoxigenic and 62 (72%) had both tcdA and tcdB (A + B+). No tcdA-negative and tcdB-positive (A^-B⁺) strains were identified. Binary toxin (CDT)-producing (cdtA+/cdtB+) strains were started to be identified in 2013. The 21 (34%) A⁺B⁺ clinical strains with binary toxin and tcdC deletion were identified as RT127 strains, which contained both RT078-lineage markers and fluoroquinolone (FQ)-resistant mutations (Thr82Ile in gyrA). Multiple loci variable-number tandem repeat analysis (MLVA) for phylogenetic relatedness of RT127 strains indicated that 20 of 21 strains belonged to a clonal complex that was identical to a clinical strain collected from southern Taiwan in 2011, suggestive of a clonal expansion in Taiwan.

CONCLUSION

A two-step typing method could rapidly confirm species identification and define the toxin gene profile of C. difficile isolates. The clonal expansion of RT127 strains in Taiwan indicates monitoring and surveillance of toxigenic C. difficile isolates from human, animal, and environment are critical to develop One Health prevention strategies.

Akt: a key transducer in cancer

Growth factor signaling plays a pivotal role in diverse biological functions, such as cell growth, apoptosis, senescence, and migration and its deregulation has been linked to various human diseases. Akt kinase is a central player transmitting extracellular clues to various cellular compartments, in turn executing these biological processes. Since the discovery of Akt three decades ago, the tremendous progress towards identifying its upstream regulators and downstream effectors and its roles in cancer has been made, offering novel paradigms and therapeutic strategies for targeting human diseases and cancers with deregulated Akt activation. Unraveling the molecular mechanisms for Akt signaling networks paves the way for developing selective inhibitors targeting Akt and its signaling regulation for the management of human diseases including cancer.

Impacts of Corticosteroid Therapy at Acute Stage of Hospital-Onset Clostridioides difficile Infections

Introduction

The influence of corticosteroid therapy before or after the onset of Clostridioides difficile infections (CDIs) on the clinical outcomes of adults with hospital-onset CDIs was investigated.

Materials and Methods

A clinical study was conducted on the medical wards of a teaching hospital between January 2013 and April 2020. Adults (aged ≥ 20 years) with hospital-onset CDIs (ie, symptom onset at least 48 hours after hospitalization) were included. "Corticosteroid therapy during acute CDIs" was defined as the receipt of a corticosteroid at the prednisolone equivalent (PE) dose of ≥10 mg for at least 48 hours within one week after the CDI diagnosis. "Prior corticosteroid exposure" was defined as the receipt of a corticosteroid at the PE dose of ≥5 mg PE for at least 48 hours within one month before the CDI diagnosis.

Results

Of the 243 adults with hospital-onset CDIs, patients (44, 18.1%) who received corticosteroid therapy during acute CDIs were more likely to have prior corticosteroid exposure (86.4% vs 11.9%, P <0.001) and CDI episodes in intensive care units (31.8% vs 10.8%, P =0.001). Of note, a crucial association between corticosteroid therapy during acute CDIs and CDI recurrence was evidenced (13.6% vs 1.5%, P =0.002). Prior corticosteroid exposure was not associated with favorable CDI outcomes in terms of successful treatment (78.3% vs 74.9%, P =0.89), in-hospital crude mortality (17.4% vs 24.0%, P =0.61), or CDI recurrence (4.3% vs 5.3%, P = 1.00). However, for 177 patients without prior corticosteroid exposure, corticosteroid therapy during acute CDIs was linked to a higher proportion of CDI recurrence (33.3% vs 5.3%, P =0.046).

Conclusion

Corticosteroid therapy during acute CDIs might impact the recurrence of CDIs, particularly in those with a lack of prior corticosteroid exposure.

Reappraisal of the clinical role of metronidazole therapy for Clostridioides difficile infection in Taiwan: A multicenter prospective study

BACKGROUND/PURPOSE

Although metronidazole is not recommended to treat Clostridioides difficile infection (CDI) in Western countries, it was still to be recommended for the treatment of non-severe CDI among Taiwanese adults in 2020. This controversy in the clinical role of metronidazole therapy for CDI was examined in a prospective clinical study.

METHODS

The study was conducted from January 2015 to December 2016 in three hospitals in Taiwan. Metronidazole treatment failure (MTF) was defined as the persistence of diarrhea after six days of treatment, medication modification (shifting to oral vancomycin), or death after five days of therapy.

RESULTS

Overall, 325 patients receiving metronidazole for CDI were included. The overall MTF rate was 48.6% (158 patients). Leukocyte counts of >15,000 cells/mL in peripheral blood (odd ratio [OR] 1.81; P = 0.04) and congestive heart failure (OR 3.26; P = 0.02) were independently associated with MTF. The MTF rate for patients with leukocyte counts of ≤15,000 cells/mL and no congestive heart failure, leukocyte counts of >15,000 cells/mL and no congestive heart failure, leukocyte counts of ≤15,000 cells/mL and congestive heart failure, and leukocyte counts of >15,000 cells/mL and congestive heart failure were 44.2%, 51.8%, 73.3%, and 66.7%, respectively. Of note, patients who experienced MTF had a higher recurrence rate of CDI than those with metronidazole treatment success (13.9% vs. 6.0%, P = 0.02).

CONCLUSION

For Taiwanese adults with CDI, the failure rate of metronidazole therapy approached 50%, which suggests the reappraisal of the therapeutic role of metronidazole therapy, especially for patients with leukocytosis or underlying congestive heart failure.

Clostridium butyricum therapy for mild-moderate Clostridioides difficile infection and the impact of diabetes mellitus

The therapeutic effect of Clostridium butyricum for adults with Clostridioides difficile infection (CDI) was investigated. A retrospective study was conducted in medical wards of Tainan Hospital, Ministry of Health and Welfare, between January 2013 and April 2020. The disease severity of CDI was scored based on the Clinical Practice Guidelines of the IDSA/SHEA. Treatment success was defined as the resolution of diarrhea within six days of a therapeutic intervention without the need to modify the therapeutic regimen. In total, 241 patients developed CDI during hospitalization in the study period. The treatment success rates for the 99 patients with mild-moderate CDI among them were as follows: metronidazole, 69.4%; C. butyricum, 68.2%; metronidazole plus C. butyricum, 66.7%; and oral vancomycin, 66.7% (p=1.00). Patients with treatment success were less likely to have diabetes mellitus than those with treatment failure (38.2% vs. 61.3%, p=0.05). Patients treated with C. butyricum alone or in combination with metronidazole had shorter durations of diarrhea than those treated with metronidazole alone (3.1 ± 2.0 days or 3.5 ± 2.4 days vs. 4.2 ± 3.5 days; p=0.43 or 0.71), although the differences were not statistically significant. In conclusion, the treatment success rate of C. butyricum alone or in combination with metronidazole for patients with CDI was non inferior to that of metronidazole alone. The presence of diabetes mellitus in affected individuals is a risk factor for treatment failure.

Neutrophil Ratio of White Blood Cells as a Prognostic Predictor of Clostridioides difficile Infection

Introduction

A leukocyte count ≥15,000 cells/mL and serum creatinine of >1.5 mg/dL have been reported as two important predictors of severe CDI. However, the association of the differential ratios of blood leukocytes, and the prognosis of Clostridioides difficile infection (CDI) is not clear.

Materials and Methods

A clinical study was conducted at medical wards of Tainan Hospital, Ministry of Health and Welfare in southern Taiwan between January 2013 and April 2020. Hospitalized adults (aged ≥20 years) with hospital-onset CDI (ie, symptom onset after at least 48 hours of admission) were included.

Results

A total of 235 adults with an average age of 75.7 years and female predominance (51.5%), including 146 (62%) adults with non-severe CDI and 87 (38%) severe CDI, were included for analysis. Patients with severe CDI had a higher crude in-hospital mortality rate than patients with non-severe CDI (35.6% vs 18.5%, P = 0.005). Multivariate analysis revealed no association between a leukocyte count >15,000 cell/mL at the onset of CDI and in-hospital mortality (odds ratio [OR] 1.66, P = 0.21). In contrast, a neutrophil ratio >75% (OR 2.65, P = 0.02), serum creatinine >1.5 mg/L (OR 3.42, P = 0.03), and CDI caused by isolates harboring the tcdC gene (OR 3.54, P = 0.02) were independently associated with in-hospital mortality. Patients with a neutrophil ratio >85%, 80–85%, or 75–80% of serum leukocytes had a higher mortality rate (34.8%, 30.3%, or 34.4%, respectively) than patients with a neutrophil ratio of 70–75% or ≤75% (12.5% or 13.9%, respectively).

Conclusion

Serum creatinine >1.5 mg/L, a high neutrophil ratio of blood leukocytes (>75%), and the causative C. difficile harboring the tcdC gene was independent prognostic predictors in hospitalized adults with CDI.

Postnatal Dexamethasone Therapy Impairs Brown Adipose Tissue Thermogenesis and Autophagy Flux in Neonatal Rat Pups

Rationale: Very preterm infants may require dexamethasone (Dex) for facilitating extubation or treating bronchopulmonary dysplasia. However, Dex may result in disturbance of metabolisms. This study was to investigate the effects of postnatal short course Dex exposure on brown adipose tissue (BAT) in neonatal rats.

Method: Neonatal rats received either three consecutive doses of daily Dex (0.2 mg/kg/day) or saline from postnatal P1 to P3. We investigated the effects of Dex on BAT including thermogenesis, mitochondrial dynamics and autophagy flux. We also compared diurnal temperature variation between preterm infants who received systemic corticosteroid and their treatment-naïve controls.

Results: Postnatal Dex treatment induced growth retardation, BAT whitening, UCP1 downregulation and cold intolerance in neonatal rats. BAT mitochondria were damaged, evident by loss of normal number, structure, and alignment of cristae. Mitochondrial fission-fusion balance was disrupted and skewed toward increased fusion, reflected by increased OPA1 and MFN2 and decreased DRP1, FIS1 and phosphorylated MFF protein levels. Autophagosome synthesis was increased but clearance was inhibited, indicated by accumulation of p62 protein after Dex treatment and no further increase of LC3-II after chloroquine co-treatment. While autophagy modulators, including chloroquine and rapamycin, did not improve UCP1 downregulation and BAT whitening, AMPK activators could partially rescue these damages. We also demonstrated that preterm infants had higher diurnal temperature variation during corticosteroid treatment.

Conclusions: Postnatal short course Dex impaired BAT mitochondrial function and autophagy flux in rat pups. AMPK activators had the potential to rescue the damage.

Assessment of the Antibacterial Mechanism of Pterostilbene against Bacillus cereus through Apoptosis-like Cell Death and Evaluation of Its Beneficial Effects on the Gut Microbiota

Foods contaminated by harmful substances such as bacteria and viruses have caused more than 200 kinds of diseases, ranging from diarrhea to cancer. Among them, Bacillus cereus (B. cereus) is a foodborne pathogen that commonly contaminates raw meat, fresh vegetables, rice, and uncooked food. The current chemical preservatives may have adverse effects on food and even human health. Therefore, natural antibacterial agents are sought after as alternative preservatives. Stilbene compounds, including pterostilbene (PT), pinostilbene (PS), and piceatannol (PIC), which have many health benefits and exhibit antibacterial activity, were tested against B. cereus. The minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of PT, PS, and PIC against B. cereus ranged from 25 to 100 μg/mL. From the time-kill curve assay, PT reduced B. cereus cell survival, increased intracellular reactive oxygen species (ROS), and induced apoptosis-like cell death (ALD) in a dose-dependent manner. The quantitative real-time polymerase chain reaction (qPCR) results confirmed that treatment with PT induced genetic changes related to ALD, such as an increase in RecA gene expression and a decrease in LexA gene expression. In addition, PT showed a beneficial effect on the gut microbiota that increased the abundance of Bacteroidetes and lowered the abundance of Firmicutes. Taken together, our results showed that PT has antibacterial effects against B. cereus via ALD and is beneficial for promoting healthy gut microbiota that is worthy for the development of antibacterial agents for the food industry.

Autophagy Drives Galectin-1 Secretion From Tumor-Associated Macrophages Facilitating Hepatocellular Carcinoma Progression

Galectin-1 (Gal-1) is a secretory lectin with pro-tumor activities and is associated strongly with hepatocellular carcinoma (HCC) development. Although Gal-1 is a well-known soluble pro-tumor factor in the tumor microenvironment (TME), the secretion mode of Gal-1 is not clearly defined. On the other hand, in addition to cancer cells, Gal-1 is widely expressed in tumor stromal cells, including tumor-associated macrophages (TAMs). TAMs are a significant component of stromal cells in TME; however, their contributions in producing Gal-1 to TME are still not explored. Here we reveal that TAMs can actively secrete Gal-1 in response to stimuli of HCC cells. Gal-1 produced by TAMs leads to an increase of the systemic level of Gal-1 and HCC tumor growth in mice. Mechanistically, TLR2-dependent secretory autophagy is found to be responsible for Gal-1 secretion from TAMs. Gal-1 acts as a cargo of autophagosomes to fuse with multivesicular bodies via Rab11 and VAMP7-mediated vesicle trafficking before being secreted. This autophagy-regulated Gal-1 secretion in TAMs correlates to poor overall survival and progression-free survival rates of HCC patients. Our findings uncover the secretion mode of Gal-1 via secretory autophagy and highlight the pathological role of TAM-produced Gal-1 in HCC progression.

The Potential of Probiotics to Eradicate Gut Carriage of Pathogenic or Antimicrobial-Resistant Enterobacterales

Probiotic supplements have been used to decrease the gut carriage of antimicrobial-resistant Enterobacterales through changes in the microbiota and metabolomes, nutrition competition, and the secretion of antimicrobial proteins. Many probiotics have shown Enterobacterales-inhibiting effects ex vivo and in vivo. In livestock, probiotics have been widely used to eradicate colon or environmental antimicrobial-resistant Enterobacterales colonization with promising efficacy for many years by oral supplementation, in ovo use, or as environmental disinfectants. In humans, probiotics have been used as oral supplements for infants to decease potential gut pathogenic Enterobacterales, and probiotic mixtures, especially, have exhibited positive results. In contrast to the beneficial effects in infants, for adults, probiotic supplements might decrease potentially pathogenic Enterobacterales, but they fail to completely eradicate them in the gut. However, there are several ways to improve the effects of probiotics, including the discovery of probiotics with gut-protection ability and antimicrobial effects, the modification of delivery methods, and the discovery of engineered probiotics. The search for multifunctional probiotics and synbiotics could render the eradication of “bad” Enterobacterales in the human gut via probiotic administration achievable in the future.

Gut Dysbiosis during COVID-19 and Potential Effect of Probiotics

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), an RNA virus of the family Coronaviridae, causes coronavirus disease 2019 (COVID-19), an influenza-like disease that chiefly infects the lungs through respiratory transmission. The spike protein of SARS-CoV-2, a transmembrane protein in its outer portion, targets angiotensin-converting enzyme 2 (ACE2) as the binding receptor for the cell entry. As ACE2 is highly expressed in the gut and pulmonary tissues, SARS-CoV-2 infections frequently result in gastrointestinal inflammation, with presentations ordinarily ranging from intestinal cramps to complications with intestinal perforations. However, the evidence detailing successful therapy for gastrointestinal involvement in COVID-19 patients is currently limited. A significant change in fecal microbiomes, namely dysbiosis, was characterized by the enrichment of opportunistic pathogens and the depletion of beneficial commensals and their crucial association to COVID-19 severity has been evidenced. Oral probiotics had been evidenced to improve gut health in achieving homeostasis by exhibiting their antiviral effects via the gut-lung axis. Although numerous commercial probiotics have been effective against coronavirus, their efficacies in treating COVID-19 patients remain debated. In ClinicalTrials.gov, 19 clinical trials regarding the dietary supplement of probiotics, in terms of Lactobacillus and mixtures of Bifidobacteria and Lactobacillus, for treating COVID-19 cases are ongoing. Accordingly, the preventive or therapeutic role of probiotics for COVID-19 patients can be elucidated in the near future.

The Role of Toll-Like Receptor-2 in Clostridioides difficile Infection: Evidence From a Mouse Model and Clinical Patients

Background

Clostridioides difficile is the leading cause of nosocomial infectious diarrhea. Toll-like receptors (TLRs) are the major components of innate immunity that sense pathogens. The relationship between TLRs and C. difficile infection (CDI) was analyzed in clinical patients and a mouse model.

Materials and Methods

A prospective investigation was conducted in medical wards of Tainan Hospital, Ministry of Health and Welfare, Tainan, Taiwan, from January 2011 to January 2013. Adult patients were followed up for the development of CDI. Single nucleotide polymorphisms (SNPs) of TLR2 and TLR4 were analyzed to assess the relationship between genetic polymorphisms and the development of CDI. A mouse model of CDI was used to investigate the pathogenic role of TLRs in CDI, TLR2 and TLR4 knockout (Tlr2-/- and Tlr4-/-) mice.

Results

In the prospective study, 556 patients were enrolled, and 6.5% (36) of patients, accounting for 3.59 episodes per 1000 patient-days, developed CDI. Of 539 patients with available blood samples, the TLR2 rs3804099 polymorphism was more often noted in those with CDI than in those without CDI (64.5% vs. 46.1%; P = 0.046) but was not significant in multivariate analysis. Because the TLR2 rs3804099 polymorphism was moderately associated with CDI, the role of TLR2 and TLR4 was further evaluated in a mouse model. Both Tlr2-/- and Tlr4-/- mice showed more severe CDI disease than wild-type mice in terms of body weight change and fecal content five days after oral challenge with C. difficile. Furthermore, Tlr2-/- mice suffered from more severe disease than Tlr4-/- mice, as evidenced by stool consistency, cecum weight, and survival rate.

Conclusion

The TLR2 rs3804099 polymorphism is marginally associated with the development of CDI, and the pathogenic role of TLR2 is further supported by a mouse model.

Inhibition of spores to prevent the recurrence of Clostridioides difficile infection - A possibility or an improbability?

Clostridioides difficile is one of the most common nosocomial gastrointestinal pathogens, and recurrence is a problematic issue because approximately 20-30% of patients experience at least one episode of recurrence, even after treatment with a therapeutic drug of choice for C. difficile infection (CDI), such as vancomycin. CDI recurrence has a multifactorial complex mechanism, in which gut microbiota disruption coincident with viable C. difficile spores, is considered the most important factor. The effectiveness of an anti-C. difficile antimicrobial agent against CDI cannot guarantee its inhibitory effect on C. difficile spores and vice versa. However, an antimicrobial agent, such as fidaxomicin, which has a good inhibitory effect on both C. difficile vegetative cells and spores is assumed to not only treat CDI but also prevent its recurrence. Prolonged adherence to the exosporium has been proposed as a possible mechanism of inhibiting spores, and as a result, redesigning anti-C. difficile antimicrobial agents with the ability to adhere to the exosporium may provide another pathway for the development of anti-C. difficile spore agents. For example, vancomycin lacks an inhibitory effect against C. difficile spores, but a vancomycin-loaded spore-targeting iron oxide nanoparticle that selectively binds to C. difficile spores has been developed to successfully delay spore germination. Some new antimicrobial agents in phase II clinical trials, including cadazolid and ridinilazole, have shown exceptional anti-C. difficile and spore-inhibiting effects that can be expected to not only treat CDI but also prevent its recurrence in the future.

Clostridioides difficile spores stimulate inflammatory cytokine responses and induce cytotoxicity in macrophages

Clostridioides difficile is a gram-positive, spore-forming anaerobic bacterium, and the leading cause of antibiotic-associated diarrhea worldwide. During C. difficile infection, spores germinate in the presence of bile acids into vegetative cells that subsequently colonize the large intestine and produce toxins. In this study, we demonstrated that C. difficile spores can universally adhere to, and be phagocytosed by, murine macrophages. Only spores from toxigenic strains were able to significantly stimulate the production of inflammatory cytokines by macrophages and subsequently induce significant cytotoxicity. Spores from the isogenic TcdA and TcdB double mutant induced significantly lower inflammatory cytokines and cytotoxicity in macrophages, and these activities were restored by pre-exposure of the spores to either toxins. These findings suggest that during sporulation, spores might be coated with C. difficile toxins from the environment, which could affect C. difficile pathogenesis in vivo.

Application of Microbiome Management in Therapy for Clostridioides difficile Infections: From Fecal Microbiota Transplantation to Probiotics to Microbiota-Preserving Antimicrobial Agents

Oral vancomycin and metronidazole, though they are the therapeutic choice for Clostridioides difficile infections (CDIs), also markedly disturb microbiota, leading to a prolonged loss of colonization resistance to C. difficile after therapy; as a result, their use is associated with a high treatment failure rate and high recurrent rate. An alternative for CDIs therapy contains the delivery of beneficial (probiotic) microorganisms into the intestinal tract to restore the microbial balance. Recently, mixture regimens containing Lactobacillus species, Saccharomyces boulardii, or Clostridium butyricum have been extensively studied for the prophylaxis of CDIs. Fecal microbiota transplantation (FMT), the transfer of (processed) fecal material from healthy donors to patients for treating CDIs, combined with vancomycin was recommended as the primary therapy for multiple recurrent CDIs (rCDIs). Either probiotics or FMT have been utilized extensively in preventing or treating CDIs, aiming at less disturbance in the microbiota to prevent rCDIs after therapy cessation. Otherwise, many newly developed therapeutic agents have been developed and aim to preserve microbiota during CDI treatment to prevent disease recurrence and might be useful in clinical patients with rCDIs in the future.

Discovery of Spoilage Markers for Chicken Eggs Using Liquid Chromatography-High Resolution Mass Spectrometry-Based Untargeted and Targeted Foodomics

The current approaches remain insufficient for measuring chicken egg spoilage or present analytical limitations. This study aimed to complement the existing analyses and identify novel markers using liquid chromatography-high resolution mass spectrometry-based foodomics strategies. In the discovery set, comparative untargeted metabolomics was utilized to identify marker candidates in microbially inoculated chicken eggs. Markers were annotated by spectral matching with authentic standards, experimental libraries, or in silico fragmentation. In the validation set, targeted metabolomics was employed to verify the markers in stored chicken eggs from five farms. Statistical differences at a p-value < 0.001 revealed increases in lactic and 3-hydroxybutyric acids and decreases in phosphocholine, LPE(O-18:1), LPC(16:0), and LPC(18:0) in stored eggs. Receiver operating characteristic curve analysis of the six combined markers yielded an AUC of 0.956 and a sensitivity and specificity of ∼90%. Four phospholipids were highlighted as a novel class of spoilage markers. Our findings may contribute to further industrial implementation, benefiting the quality assurance and food safety of poultry egg production.

PPARγ activation improves the microenvironment of perivascular adipose tissue and attenuates aortic stiffening in obesity

Background

Obesity-related cardiovascular risk, end points, and mortality are strongly related to arterial stiffening. Current therapeutic approaches for arterial stiffening are not focused on direct targeting within the vessel. Perivascular adipose tissue (PVAT) surrounding the artery has been shown to modulate vascular function and inflammation. Peroxisome proliferator-activated receptor γ (PPARγ) activation significantly decreases arterial stiffness and inflammation in diabetic patients with coronary artery disease. Thus, we hypothesized that PPARγ activation alters the PVAT microenvironment, thereby creating a favorable environment for the attenuation of arterial stiffening in obesity.

Methods

Obese ob/ob mice were used to investigate the effect of PPARγ activation on the attenuation of arterial stiffening. Various cell types, including macrophages, fibroblasts, adipocytes, and vascular smooth muscle cells, were used to test the inhibitory effect of pioglitazone, a PPARγ agonist, on the expression of elastolytic enzymes.

Results

PPARγ activation by pioglitazone effectively attenuated arterial stiffening in ob/ob mice. This beneficial effect was not associated with the repartitioning of fat from or changes in the browning of the PVAT depot but was strongly related to improvement of the PVAT microenvironment, as evidenced by reduction in the expression of pro-inflammatory and pro-oxidative factors. Pioglitazone treatment attenuated obesity-induced elastin fiber fragmentation and elastolytic activity and ameliorated the obesity-induced upregulation of cathepsin S and metalloproteinase 12, predominantly in the PVAT. In vitro, pioglitazone downregulated Ctss and Mmp12 in macrophages, fibroblasts, and adipocytes—cell types residing within the adventitia and PVAT. Ultimately, several PPARγ binding sites were found in Ctss and Mmp12 in Raw 264.7 and 3T3-L1 cells, suggesting a direct regulatory mechanism by which PPARγ activation repressed the expression of Ctss and Mmp-12 in macrophages and fibroblasts.

Conclusions

PPARγ activation attenuated obesity-induced arterial stiffening and reduced the inflammatory and oxidative status of PVAT. The improvement of the PVAT microenvironment further contributed to the amelioration of elastin fiber fragmentation, elastolytic activity, and upregulated expression of Ctss and Mmp12. Our data highlight the PVAT microenvironment as an important target against arterial stiffening in obesity and provide a novel strategy for the potential clinical use of PPARγ agonists as a therapeutic against arterial stiffness through modulation of PVAT function.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12929-021-00720-y.

Clostridioides difficile infection in patients with hematological malignancy: A multicenter study in Taiwan

BACKGROUND

Among the individuals with hematological malignancy (HM) complicated with Clostridioides difficile infection (CDI), the variables associated with in-hospital mortality and recurrence of CDI were investigated.

MATERIAL AND METHODS

Including adults with HM and those without malignancy suffering from CDI from January 2015 to December 2016 in three hospitals in Taiwan.

RESULTS

Totally 314 patients including 77 with HM and 237 patients without malignancy were included. HM patients more often had low leukocyte counts (<500 cells/mL: 28.6% vs. 2.1%) than those without malignancy and more patients without malignancy had severe CDI than patients with HM (31.6% vs. 14.3%, P = .003), according to the severity score of IDSA/SHEA. Patients with HM had a higher recurrence rate of CDI (14.3%, 11/77 vs. 7.2%, 17/237; P = .07) and longer hospital stay (47.2 ± 40.8 days vs. 33.3 ± 37.3 days; P = .006) than those without malignancy. In the multivariate analyses for those with HM and CDI, the in-hospital mortality was associated with vancomycin-resistant Enterococcus (VRE) colonization or infection (odds ratio [OR] 7.72; P = .01), and C. difficile ribotype 078 complex infection (OR 9.22; P = .03). Moreover underlying hematological malignancy (OR 2.74; P = .04) and VRE colonization/infection (OR 2.71; P = .02) were independently associated with CDI recurrence.

CONCLUSION

Patients with HM complicated with CDI were often regarded as non-severe infection, but had a similar in-hospital mortality rate as those without malignancy. CDI due to ribotype 078 complex isolates heralded a poor prognosis among HM patients.

Inhibitory effect of PPARγ on NLRP3 inflammasome activation

Rationale: Stimulation of the NLRP3 inflammasome by metabolic byproducts is known to result in inflammatory responses and metabolic diseases. However, how the host controls aberrant NLRP3 inflammasome activation remains unclear. PPARγ, a known regulator of energy metabolism, plays an anti-inflammatory role through the inhibition of NF-κB activation and additionally attenuates NLRP3-dependent IL-1β and IL-18 production. Therefore, we hypothesized that PPARγ serves as an endogenous modulator that attenuates NLRP3 inflammasome activation in macrophages.

Methods: Mouse peritoneal macrophages with exposure to a PPARγ agonist at different stages and the NLRP3 inflammasome-reconstituted system in HEK293T cells were used to investigate the additional anti-inflammatory effect of PPARγ on NLRP3 inflammasome regulation. Circulating mononuclear cells of obese patients with weight-loss surgery were used to identify the in vivo correlation between PPARγ and the NLRP3 inflammasome.

Results: Exposure to the PPARγ agonist, rosiglitazone, during the second signal of NLRP3 inflammasome activation attenuated caspase-1 and IL-1β maturation. Moreover, PPARγ interfered with NLRP3 inflammasome formation by decreasing NLRP3-ASC and NLRP3-NLRP3 interactions as well as NLRP3-dependent ASC oligomerization, which is mediated through interaction between the PPARγ DNA-binding domain and the nucleotide-binding and leucine-rich repeat domains of NLRP3. Furthermore, PPARγ was required to limit metabolic damage-associated molecular pattern-induced NLRP3 inflammasome activation in mouse macrophages. Finally, the mature caspase-1/PPARγ ratio was reduced in circulating mononuclear cells of obese patients after weight-loss surgery, which we define as an “NLRP3 accelerating index”.

Conclusions: These results revealed an additional anti-inflammatory role for PPARγ in suppressing NLRP3 inflammasome activation through interaction with NLRP3. Thus, our study highlights that PPARγ agonism may be a therapeutic option for targeting NLRP3-related metabolic diseases.

Emergence of macrolide-resistant Streptococcus pyogenes emm12 in southern Taiwan from 2000 to 2019

BACKGROUND

Group A Streptococcus (GAS) is an important pathogen causing morbidity and mortality worldwide. Surveillance of resistance and emm type has important implication to provide helpful information on the changing GAS epidemiology and empirical treatment.

METHODS

To study the emergence of resistant GAS in children with upper respiratory tract infection (URTI), a retrospective study was conducted from 2000 to 2019 in southern Taiwan. Microbiological studies, including antibiotic susceptibility, were performed. GAS emm types and sequences were determined by molecular methods. The population was divided into two separate decades to analyze potential changes over time. The 1st decade was 2000-2009; the 2nd decade was 2010-2019. Multivariate analyses were performed to identify independent risk factors associated with macrolide resistance between these periods.

RESULTS

A total of 320 GAS from 339 children were enrolled. Most of the children (75%) were under 9 years of age. The most common diagnosis was scarlet fever (225, 66.4%), and the frequency increased from 54.8% in the 1st to 77.9% in the 2nd decade (p < 0.0001). There was a significant increase in resistance to erythromycin and azithromycin from 18.1%, 19.3% in the 1st to 58.4%, 61.0% in the 2nd decade (p < 0.0001). This was associated with clonal expansion of the GAS emm12-ST36 which carrying erm(B) and tet(M) from 3.0% in the 1st to 53.2% in the 2nd decade (p < 0.0001).

CONCLUSIONS

Significant emergence of macrolide-resistant GAS emm12-ST36 in children supports the need for continuing surveillance and investigation for the clonal virulence.

Membrane Cholesterol Is Crucial for Clostridium difficile Surface Layer Protein Binding and Triggering Inflammasome Activation

Clostridium difficile, an obligate anaerobic gram-positive bacillus, generates spores and is commonly found colonizing the human gut. Patients with C. difficile infection (CDI) often exhibit clinical manifestations of pseudomembranous colitis or antibiotic-associated diarrhea. Surface layer proteins (SLPs) are the most abundant proteins in the C. difficile cell wall, suggesting that they might involve in immune recognition. Our previous results demonstrated that C. difficile triggers inflammasome activation. Here, we found SLPs as well as C. difficile induced inflammasome activation, and in a dose-dependent manner. In addition, the cholesterol-rich microdomains on the cell membrane (also referred to as lipid rafts) are thought to be crucial for bacterial adhesion and signal transduction. We demonstrated that lipid rafts participated in C. difficile SLPs binding to the cell membrane. Fluorescence microscopy showed that membrane cholesterol depletion by methyl-β-cyclodextrin (MβCD) reduced the association of SLPs with the cell surface. The coalescence of SLPs in the cholesterol-rich microdomains was confirmed in C. difficile-infected cells. Furthermore, the inflammasome activations induced by SLPs or C. difficile were abrogated by MβCD. Our results demonstrate that SLPs recruit the lipid rafts, which may be a key step for C. difficile colonization and inducing inflammasome activation.

Probiotics-Containing Yogurt Ingestion and H. pylori Eradication Can Restore Fecal Faecalibacterium prausnitzii Dysbiosis in H. pylori-Infected Children

This study investigated the compositional differences in fecal microbiota between children with and without H. pylori infection and tested whether probiotics-containing yogurt and bacterial eradication improve H. pylori-related dysbiosis. Ten H. pylori-infected children and 10 controls ingested probiotics-containing yogurt for 4 weeks. Ten-day triple therapy plus yogurt was given to the infected children on the 4th week. Fecal samples were collected at enrollment, after yogurt ingestion, and 4 weeks after successful H. pylori eradication for cytokines and microbiota analysis using ELISA and metagenomic sequencing of the V4 region of the 16S rRNA gene, respectively. The results showed H. pylori-infected children had significantly higher levels of fecal TGF-β1 than those who were not infected. Eight of 295 significantly altered OTUs in the H. pylori-infected children were identified. Among them, the abundance of F. prausnitzii was significantly lower in the H. pylori-infected children, and then increased after yogurt ingestion and successful bacterial eradication. We further confirmed probiotics promoted F. prausnitzii growth in vitro and in ex vivo using real-time PCR. Moreover, F. prausnitzii supernatant significantly ameliorated lipopolysaccharide-induced IL-8 in HT-29 cells. In conclusions, Probiotics-containing yogurt ingestion and H. pylori eradication can restore the decrease of fecal F. prausnitzii in H. pylori-infected children.

Loss of EGR-1 uncouples compensatory responses of pancreatic β cells

Rationale: Subjects unable to sustain β-cell compensation develop type 2 diabetes. Early growth response-1 protein (EGR-1), implicated in the regulation of cell differentiation, proliferation, and apoptosis, is induced by diverse metabolic challenges, such as glucose or other nutrients. Therefore, we hypothesized that deficiency of EGR-1 might influence β-cell compensation in response to metabolic overload.

Methods: Mice deficient in EGR-1 (Egr1^-/-) were used to investigate the in vivo roles of EGR-1 in regulation of glucose homeostasis and beta-cell compensatory responses.

Results: In response to a high-fat diet, Egr1^-/- mice failed to secrete sufficient insulin to clear glucose, which was associated with lower insulin content and attenuated hypertrophic response of islets. High-fat feeding caused a dramatic impairment in glucose-stimulated insulin secretion and downregulated the expression of genes encoding glucose sensing proteins. The cells co-expressing both insulin and glucagon were dramatically upregulated in islets of high-fat-fed Egr1^-/- mice. EGR-1-deficient islets failed to maintain the transcriptional network for β-cell compensatory response. In human pancreatic tissues, EGR1 expression correlated with the expression of β-cell compensatory genes in the non-diabetic group, but not in the diabetic group.

Conclusion: These results suggest that EGR-1 couples the transcriptional network to compensation for the loss of β-cell function and identity. Thus, our study highlights the early stress coupler EGR-1 as a critical factor in the development of pancreatic islet failure.

Nicotinamide Increases Intracellular NAD+ Content to Enhance Autophagy-Mediated Group A Streptococcal Clearance in Endothelial Cells

Group A streptococcus (GAS) is a versatile pathogen that causes a wide spectrum of diseases in humans. Invading host cells is a known strategy for GAS to avoid antibiotic killing and immune recognition. However, the underlying mechanisms of GAS resistance to intracellular killing need to be explored. Endothelial HMEC-1 cells were infected with GAS, methicillin-resistant Staphylococcus aureus (MRSA) and Salmonella Typhimurium under nicotinamide (NAM)-supplemented conditions. The intracellular NAD⁺ level and cell viability were respectively measured by NAD⁺ quantification kit and protease-based cytotoxicity assay. Moreover, the intracellular bacteria were analyzed by colony-forming assay, transmission electron microscopy, and confocal microscopy. We found that supplementation with exogenous nicotinamide during infection significantly inhibited the growth of intracellular GAS in endothelial cells. Moreover, the NAD⁺ content and NAD⁺/NADH ratio of GAS-infected endothelial cells were dramatically increased, whereas the cell cytotoxicity was decreased by exogenous nicotinamide treatment. After knockdown of the autophagy-related ATG9A, the intracellular bacterial load was increased in nicotinamide-treated endothelial cells. The results of Western blot and transmission electron microscopy also revealed that cells treated with nicotinamide can increase autophagy-associated LC3 conversion and double-membrane formation during GAS infection. Confocal microscopy images further showed that more GAS-containing vacuoles were colocalized with lysosome under nicotinamide-supplemented conditions than without nicotinamide treatment. In contrast to GAS, supplementation with exogenous nicotinamide did not effectively inhibit the growth of MRSA or S. Typhimurium in endothelial cells. These results indicate that intracellular NAD⁺ homeostasis is crucial for controlling intracellular GAS infection in endothelial cells. In addition, nicotinamide may be a potential new therapeutic agent to overcome persistent infections of GAS.

The Transcriptional Regulator Lrp Contributes to Toxin Expression, Sporulation, and Swimming Motility in Clostridium difficile

Clostridium difficile is a Gram-positive, spore-forming bacterium, and major cause of nosocomial diarrhea. Related studies have identified numerous factors that influence virulence traits such as the production of the two primary toxins, toxin A (TcdA) and toxin B (TcdB), as well as sporulation, motility, and biofilm formation. However, multiple putative transcriptional regulators are reportedly encoded in the genome, and additional factors are likely involved in virulence regulation. Although the leucine-responsive regulatory protein (Lrp) has been studied extensively in Gram-negative bacteria, little is known about its function in Gram-positive bacteria, although homologs have been identified in the genome. This study revealed that disruption of the lone lrp homolog in C. difficile decelerated growth under nutrient-limiting conditions, increased TcdA and TcdB production. Lrp was also found to negatively regulate sporulation while positively regulate swimming motility in strain R20291, but not in strain 630. The C. difficile Lrp appeared to function through transcriptional repression or activation. In addition, the lrp mutant was relatively virulent in a mouse model of infection. The results of this study collectively demonstrated that Lrp has broad regulatory function in C. difficile toxin expression, sporulation, motility, and pathogenesis.

Corrigendum: The ATP-P2X7 Signaling Axis Is an Essential Sentinel for Intracellular Clostridium difficile Pathogen-Induced Inflammasome Activation

[This corrects the article DOI: 10.3389/fcimb.2018.00084.].

Vancomycin-Loaded Nanoparticles Enhance Sporicidal and Antibacterial Efficacy for Clostridium difficile Infection

Current antibiotic treatments fail to eliminate the Clostridium difficile (C. difficile) spores and induce dysbiosis and intestinal inflammation via off-target effect, which causes refractory C. difficile infection raise an unmet need for a spore-specific antimicrobial treatment. We developed a sporicidal and antimicrobial vancomycin-loaded spore-targeting iron oxide nanoparticle (van-IONP) that selectively binds to C. difficile spores. Cryo-electron microscopy showed that vancomycin-loaded nanoparticles can target and completely cover spore surfaces. They not only successfully delayed the germination of the spores but also inhibited ∼50% of vegetative cell outgrowth after 48 h of incubation. The van-IONPs also inhibited the interaction of spores with HT-29 intestinal mucosal cells in vitro. In a murine model of C. difficile infection, the van-IONP significantly protected the mice from infected by C. difficile infection, reducing intestinal inflammation, and facilitated superior mucosal viability compared with equal doses of free vancomycin. This dual-function targeted delivery therapy showed advantages over traditional therapeutics in treating C. difficile infection.