Identification and biological characteristics of Enterococcus casseliflavus TN-47 isolated from Monochamus alternatus.

With the widespread use of antibiotics, the incidence of antibiotic resistance in microorganisms has increased. Monochamus alternatus is a trunk borer of pine trees. This study aimed to investigate the in vitro antimicrobial and biological characteristics of Enterococcus casseliflavus TN-47 (PP411196), isolated from the gastrointestinal tract of M. alternatus in Jilin Province, PR China. Among 13 isolates obtained from the insects, five were preliminarily screened for antimicrobial activity. E. casseliflavus TN-47, which exhibited the strongest antimicrobial activity, was identified. E. casseliflavus TN-47 possessed antimicrobial activity against Staphylococcus aureus USA300 and Salmonella enterica serovar Pullorum ATCC 19945. Furthermore, E. casseliflavus TN-47 was sensitive to tetracyclines, penicillins (ampicillin, carbenicillin, and piperacillin), quinolones and nitrofuran antibiotics, and resistant to certain beta-lactam antibiotics (oxacillin, cefradine and cephalexin), macrolide antibiotics, sulfonamides and aminoglycosides. E. casseliflavus TN-47 could tolerate low pH and pepsin-rich conditions in the stomach and grow in the presence of bile acids. E. casseliflavus TN-47 retained its strong auto-aggregating ability and hydrophobicity. This strain did not exhibit any haemolytic activity. These results indicate that E. casseliflavus TN-47 has potential as a probiotic. This study provides a theoretical foundation for the future applications of E. casseliflavus TN-47 and its secondary metabolites in animal nutrition and feed.

STING-dependent trained immunity contributes to host defense against Clostridium perfringens infection via mTOR signaling.

Clostridium perfringens (C. perfringens) infection is recognized as one of the most challenging issues threatening food safety and perplexing agricultural development. To date, the molecular mechanisms of the interactions between C. perfringens and the host remain poorly understood. Here, we show that stimulator of interferon genes (STING)-dependent trained immunity protected against C. perfringens infection through mTOR signaling. Heat-killed Candida albicans (HKCA) training elicited elevated TNF-α and IL-6 production after LPS restimulation in mouse peritoneal macrophages (PM). Although HKCA-trained PM produced decreased levels of TNF-α and IL-6, the importance of trained immunity was demonstrated by the fact that HKCA training resulted in enhanced bacterial phagocytic ability and clearance in vivo and in vitro during C. perfringens infection. Interestingly, HKCA training resulted in the activation of STING signaling. We further demonstrate that STING agonist DMXAA is a strong inducer of trained immunity and conferred host resistance to C. perfringens infection in PM. Importantly, corresponding to higher bacterial burden, reduction in cytokine secretion, phagocytosis, and bacterial killing were shown in the absence of STING after HKCA training. Meanwhile, the high expression levels of AKT/mTOR/HIF1α were indeed accompanied by an activated STING signaling under HKCA or DMXAA training. Moreover, inhibiting mTOR signaling with rapamycin dampened the trained response to LPS and C. perfringens challenge in wild-type (WT) PM after HKCA training. Furthermore, STING­deficient PM presented decreased levels of mTOR signaling-related proteins. Altogether, these results support STING involvement in trained immunity which protects against C. perfringens infection via mTOR signaling.

Dihydroartemisinin is an inhibitor of trained immunity through Akt/mTOR/HIF1α signaling pathway.

Trained immunity is mechanistically defined as the metabolically and epigenetically mediated long-term functional adaptation of the innate immune system, characterized by a heightened response to a secondary stimulation. Given appropriate activation, trained immunity represents an attractive anti-infective therapeutic target. Nevertheless, excessive immune response and subsequent inflammatory cascades may contribute to pathological tissue damage, indicating that the negative impacts of trained immunity appear to be significant. In this study, we show that innate immune responses such as the production of extracellular traps, pro-inflammatory cytokines, and autophagy-related proteins were markedly augmented in trained BMDMs. Furthermore, heat-killed C. albicans priming promotes the activation of the AIM2 inflammasome, and AIM2-/- mice exhibit impaired memory response induced by heat-killed C. albicans. Therefore, we establish that the AIM2 inflammasome is involved in trained immunity and emerges as a promising therapeutic target for potentially deleterious effects. Dihydroartemisinin can inhibit the memory response induced by heat-killed C. albicans through modulation of mTOR signaling and the AIM2 inflammasome. The findings suggest that dihydroartemisinin can reduce the induction of trained immunity by heat-killed C. albicans in C57BL/6 mice. Dihydroartemisinin is one such therapeutic intervention that has the potential to treat of diseases characterized by excessive trained immunity.

Trained immunity in recurrent Staphylococcus aureus infection promotes bacterial persistence.

Bacterial persister cells, a sub-population of dormant phenotypic variants highly tolerant to antibiotics, present a significant challenge for infection control. Investigating the mechanisms of antibiotic persistence is crucial for developing effective treatment strategies. Here, we found a significant association between tolerance frequency and previous infection history in bovine mastitis. Previous S. aureus infection led to S. aureus tolerance to killing by rifampicin in subsequent infection in vivo and in vitro. Actually, the activation of trained immunity contributed to rifampicin persistence of S. aureus in secondary infection, where it reduced the effectiveness of antibiotic treatment and increased disease severity. Mechanically, we found that S. aureus persistence was mediated by the accumulation of fumarate provoked by trained immunity. Combination therapy with metformin and rifampicin promoted eradication of persisters and improved the severity of recurrent S. aureus infection. These findings provide mechanistic insight into the relationship between trained immunity and S. aureus persistence, while providing proof of concept that trained immunity is a therapeutic target in recurrent bacterial infections involving persistent pathogens.

Efficacy and safety of ilioinguinal neurectomy in open tension-free inguinal hernia repair: A meta-analysis of randomized controlled trials.

BACKGROUND: There is still controversy surrounding routine ilioinguinal neurectomy in open tension-free inguinal hernia repair. METHOD: PubMed, Cochrane Library and EMBASE databases were searched for randomized controlled trials of ilioinguinal neurectomy in open tension-free inguinal hernia repair. Revman 5.3 software was used for meta-analysis. RESULT: Meta-analysis revealed that the incidence of severe pain on the first postoperative day was lower in the ilioinguinal neurectomy group (ING) than in the ilioinguinal nerve preservation group (INPG) [P < 0.0001]. The incidence of no pain in the first month postoperatively [P = 0.0004], the incidence of no pain in the sixth months postoperatively [P < 0.00001], and the numbness incidence in the first month postoperatively [P = 0.001] in the ING was higher than that in the INPG. There was no significant difference in the incidence of severe pain in the first month postoperatively [P = 0.20], the numbness incidence in the sixth postoperative month [P = 0.05], the hypoesthesia incidence in the first [P = 0.15] and sixth [P = 0.85] postoperative months between the two groups. CONCLUSION: Ilioinguinal neurectomy in open tension-free inguinal hernia repair can better prevent postoperative pain.

Culturing the Chicken Intestinal Microbiota and Potential Application as Probiotics Development.

Pure cultures of chicken intestinal microbial species may still be crucial and imperative to expound on the function of gut microbiota, and also contribute to the development of potential probiotics and novel bioactive metabolites from gut microbiota. In this study, we isolated and identified 507 chicken intestinal bacterial isolates, including 89 previously uncultured isolates. Among these, a total of 63 Lactobacillus strains, belonging to L. vaginalis, L. crispatus, L. gallinarum, L. reuteri, L. salivarius, and L. saerimneri, exhibited antibacterial activity against S. Pullorum. Acid tolerance tests showed Limosilactobacillus reuteri strain YPG14 (L. reuteri strain YPG14) has a particularly strong tolerance to acid. We further characterized other probiotic properties of L. reuteri strain YPG14. In simulated intestinal fluid, the growth of L. reuteri strain YPG14 remained stable after incubation for 4 h. The auto-aggregation test showed the auto-aggregation percentage of L. reuteri strain YPG14 was recorded as 15.0 ± 0.38%, 48.3 ± 2.51%, and 75.1 ± 4.44% at 3, 12, and 24 h, respectively. In addition, the mucin binding assay showed L. reuteri strain YPG14 exhibited 12.07 ± 0.02% adhesion to mucin. Antibiotic sensitivity testing showed that L. reuteri strain YPG14 was sensitive to the majority of the tested antibiotics. The anti-Salmonella Pullorum (S. Pullorum) infection effect in vivo revealed that the consumption of L. reuteri strain YPG14 could significantly improve body weight loss and survival rate of chicks infected by S. Pullorum; reduce the loads of S. Pullorum in the jejunum, liver, spleen, and feces; and alleviate the jejunum villi morphological structure damage, crypt loss, and inflammatory cell infiltration caused by S. Pullorum. Overall, this study may help us to understand the diversity of chicken intestinal microflora and provide some insights for potential probiotic development from gut microbiota and may find application in the poultry industry.

Erratum: Mixed lineage kinase-like protein protects against Clostridium perfringens infection by enhancing NLRP3 inflammasome-extracellular traps axis.

[This corrects the article DOI: 10.1016/j.isci.2022.105121.].

IFI204 protects host defense against Staphylococcus aureus-induced pneumonia by promoting extracellular traps formation.

Interferon-inducible protein 204 (IFI204) is an intracellular DNA receptor that can recognize DNA viruses and intracellular bacteria. Extracellular traps (ETs) have been recognized as an indispensable antimicrobial barrier that play an indispensable role in bacterial, fungal, parasitic, and viral infections. However, how ETs form and the mechanisms by which IFI204 function in Staphylococcus aureus pneumonia are still unclear. Moreover, by in vitro experiments, we proved that IFI204 deficiency decreases the formation of ETs induced by Staphylococcus aureus in a NOX-independent manner. More importantly, Deoxyribonuclease I (DNase I) treatment significantly inhibited the formation of ETs. IFI204 contributed to ETs formation by promoting citrullination of histone H3 and the expression of PAD4 (peptidylarginine deiminase 4). Altogether, these findings highlight the potential importance of IFI204 for host defense against S. aureus USA300-TCH1516 infection.

Effects of enteral nutrition with different energy supplies on metabolic changes and organ damage in burned rats.

Background: Enteral nutrition (EN) is an important treatment for burn patients. However, severe gastrointestinal damage caused by major burns often leads to EN intolerance. Trophic EN solves this problem basically, but how to transition from trophic EN to standard EN smoothly is still a challenge in burn clinical nutrition. The aim of this study is to investigate the effects of EN with different energy supplies on metabolic changes, organ damage and prognosis in burned rats. Methods: Different feeding regimens were designed based on the continuous monitoring of resting energy expenditure in rats. Thirty-two Sprague-Dawley rats were randomly divided into a normal control group, burn +50% REE group, burn +75% REE group and burn +100% REE group. At the end of a nutritional treatment cycle (14th day), nuclear magnetic resonance spectroscopy, blood biochemistry analysis and quantification of subscab bacteria were performed to explore the differences in metabolic changes, degrees of organ damage and prognoses between the groups. Results: Sixteen metabolites involving seven metabolic pathways were identified from the different energy supply groups. After burn injury, resting energy consumption and body weight loss increased obviously. Meanwhile, weight loss was inversely related to energy supply. The greatest changes in the degree of organ damage, the level of plasma proteins, lipids and endotoxins, as well as the quantification of subscab bacteria were observed in the 50% REE group, followed by the 75 and 100% groups. Conclusions: Achieving an early balance between energy supply and expenditure is conducive to mitigating metabolic disorders and improving prognosis after burn injury.

Mixed lineage kinase-like protein protects against Clostridium perfringens infection by enhancing NLRP3 inflammasome-extracellular traps axis.

Despite intense research in understanding Clostridium perfringens (C. perfringens) pathogenesis, the mechanisms by which it is cleared from the host are largely unclarified. In C. perfringens gas gangrene and enterocolitis model, Mlkl -/- mice, lacking mixed lineage kinase-like protein (MLKL), are more susceptible to C. perfringens infection. Mlkl deficiency results in a defect in inflammasome activation, and IL-18 and IL-1ß releases. Exogenous administration of recombinant IL-18 is able to rescue the susceptibility of Mlkl -/- mice. Notably, K+ efflux-dependent NLRP3 inflammasome signaling downstream of active MLKL promotes bacterial killing and clearance. Interestingly, the defect of bactericidal activity is also mediated by decreased classical extracellular trap formation in the absence of Mlkl. Our results demonstrate that MLKL mediates extracellular trap formation in a NLRP3 inflammasome-dependent manner. These findings highlight the requirement of MLKL for host defense against C. perfringens infection through enhancing NLRP3 inflammasome-extracellular traps axis.

Akkermansia muciniphila Suppresses High-Fat Diet-Induced Obesity and Related Metabolic Disorders in Beagles.

Obesity is one of the prevalent chronic diseases in human and companion animals usually associated with several metabolic disorders. The gut commensal bacterium Akkermansia muciniphila (A. muciniphila) is known for its therapeutic effects on metabolic disorders and inflammations. Here, we isolated the A. muciniphila AKK2 strain from the feces of interferon-inducible protein 204-/- (IFI204-/-) mice and further evaluated its anti-obesity effects on high-fat diet (HFD)-fed C57BL/6J mice and beagles. The results showed that it effectively controlled weight gain. Microbiome analysis using 16S rRNA gene sequencing revealed that HFD alters gut microbiota composition and A. muciniphila AKK2 increases the Firmicutes/Bacteroidetes (F/B) ratio in beagles. Furthermore, we prepared microcapsules containing A. muciniphila AKK2, and tolerance tests showed the encapsulation maintained high viability and stability in an aerobic environment and simulated the secretion of gastrointestinal fluids. Overall, this study widens the spectrum of A. muciniphila applications to prevent obesity.

[Comparison of vesselplasty and percutanous kyphoplasty in the treatment of Kümmell disease].

OBJECTIVE: To compare the efficacy between vesselplasty and percutanous kyphoplasty (PKP) in the treatment of Kümmell disease. METHODS: The clinical data of patients with Kümmell disease from July 2018 to December 2019 were retrospectively analyzed. According to the different therapeutic methods, the patients were divided into vesselplasty group and PKP group. There were 20 patients in vesselplasty group, including 2 males and 18 females, aged from 54 to 83 years with an average of (67.40±7.44)years, 1 case of T10 fracture, 3 cases of T12 fracture, 9 cases of L1 fractures, 5 cases of L2 fractures and 2 cases of L3 fractures. There were 20 patients in PKP group, including 3 males and 17 females, aged from 56 to 81 with an average of(67.20±7.01) years, 2 cases of T10 fracture, 1 case of T11 fracture, 6 cases of T12 fracture, 10 cases of L1 fracture and 1 case of L3 fracture. Visual analogue scale(VAS), Cobb angle, anterior vertebral height were recorded before operation, 1 day after operation and 1 year after operation. Oswestry Disability Index(ODI) was recorded before operation, 1 month after operation and 1 year after operation. And bone cement leakage rate was compared between two groups after operation. RESULTS: All the patient were followed up for more than 1 year. In vesselplasty group, VAS score was 1.20±0.41, ODI was(13.50±3.10)%, Cobb angle was(17.20±3.12)° and anterior vertebral height was(20.20±1.35) mm at 1 year after operation. In PKP group, VAS score was 1.15±0.40, ODI was (13.20±3.00)%, Cobb angle was (17.10±3.19)° and anterior vertebral height was (20.10±1.37) mm at 1 year after operation. These index was significantly better than pre-operation through intra-group comparison(P<0.05), and there was no statistically difference between the two groups(P>0.05). There were 20 cases (20 vertebrae) in vesselplasty group, of which 1 case had bone cement leakage at the upper endplate, with a leakage rate of 5%(1/20). In PKP group, there were 20 cases (20 vertebrae), 3 cases of upward endplate leakage(3/7), 1 case of downward endplate leakage(1/7), 1 case of leakage to the front of the vertebral body(1/7), 2 cases of leakage to the side of the vertebral body(2/7), with a leakage rate of 35% (7/20). The difference between two groups was statistically significant(P<0.05). CONCLUSION: Vesselplasty in the treatment of Kümmell disease can better reduce leakage rate of bone cement and reduce complications.

Purification, Characterization, Mode of Action, and Application of Jileicin, a Novel Antimicrobial from Paenibacillus jilinensis YPG26.

Antimicrobial compounds from the commensal gut microbiota have gained much attention due to their multifunctionality in maintaining good health in the host and killing multidrug-resistant bacteria. Our previous study showed that Paenibacillus jilinensis YPG26 isolated from chicken intestine can antagonize multiple pathogens. Herein, we characterized a bacteriocin-like inhibitory substance, jileicin, purified from P. jilinensis YPG26. Mass spectrometry analysis revealed that jileicin was a protein consisting of 211 amino acids, which showed 88.98% identity to the SIMPL domain-containing protein. The jileicin showed a relatively broad-spectrum antibacterial ability, especially against enterococci. Additionally, the jileicin exhibited good stability after various treatments, no detectable resistance, no significant cytotoxicity, and very low levels of hemolytic activity. The mode of action against Enterococcus faecium demonstrated that jileicin could destroy cell membrane integrity, increase cell membrane permeability, and eventually lead to cell death. Furthermore, jileicin was efficient in controlling the growth of E. faecium in milk. In conclusion, jileicin, as a newly identified antibacterial agent, is expected to be a promising candidate for application in the food, pharmaceutical, and biomedical industries.

Genome mining reveals polysaccharide-degrading potential and new antimicrobial gene clusters of novel intestinal bacterium Paenibacillus jilinensis sp. nov.

BACKGROUND: Drug-resistant bacteria have posed a great threat to animal breeding and human health. It is obviously urgent to develop new antibiotics that can effectively combat drug-resistant bacteria. The commensal flora inhabited in the intestines become potential candidates owing to the production of a wide range of antimicrobial substances. In addition, host genomes do not encode most of the enzymes needed to degrade dietary structural polysaccharides. The decomposition of these polysaccharides mainly depends on gut commensal-derived CAZymes. RESULTS: We report a novel species isolated from the chicken intestine, designated as Paenibacillus jilinensis sp. nov. and with YPG26T (= CCTCC M2020899T) as the type strain. The complete genome of P. jilinensis YPG26T is made up of a single circular chromosome measuring 3.97 Mb in length and containing 49.34% (mol%) G + C. It carries 33 rRNA genes, 89 tRNA genes, and 3871 protein-coding genes, among which abundant carbohydrate-degrading enzymes (CAZymes) are encoded. Moreover, this strain has the capability to antagonize multiple pathogens in vitro. We identified putative 6 BGCs encoding bacteriocin, NRPs, PKs, terpenes, and protcusin by genome mining. In addition, antibiotic susceptibility testing showed sensitivity to all antibiotics tested. CONCLUSIONS: This study highlights the varieties of CAZymes genes and BGCs in the genome of Paenibacillus jilinensis. These findings confirm the beneficial function of the gut microbiota and also provide a promising candidate for the development of new carbohydrate degrading enzymes and antibacterial agents.

Stimulator of Interferon Genes (STING) Promotes Staphylococcus aureus-Induced Extracellular Traps Formation via the ROS-ERK Signaling Pathway.

Stimulator of interferon genes (STING) is a cytosolic DNA sensor or directly recognizes bacterial cyclic dinucleotides, which is required for the detection of microbial infection. Extracellular traps (ETs) are known to be part of the antimicrobial defense system. However, the implication of STING in ETs formation during microbial infection remains unknown. Here, we showed that STING contributed to Staphylococcus aureus (S. aureus)-induced ETs formation through the ROS-ERK signaling. STING deficiency exhibited decreased cell-free DNA (cfDNA) level, reduced expression of citrullinated histone H3 (CitH3), and diminished DNA colocalization with CitH3 and myeloperoxidase (MPO). Interestingly, NADPH oxidase-derived reactive oxygen species (ROS) promoted ETs formation, accompanied by increased activation of extracellular signal-regulated kinase 1 and 2 (ERK1/2) in S. aureus-stimulated bone marrow-derived macrophages (BMDMs). Corresponding to less ROS production, decreased ERK1/2 activation was shown in STING-/- BMDMs after S. aureus infection. Importantly, inhibiting the ROS-ERK signal reduced the ETs formation and the differences disappeared between WT and STING-/- BMDMs after S. aureus infection. Moreover, STING-/- BMDMs exhibited significantly increased levels of extracellular bacteria compared to WT BMDMs regardless of phagocytosis. In addition, such differences disappeared after DNase I treatment. DNase I treatment also facilitated pathogen colonization without affecting the inflammatory cells infiltration and pro-inflammatory factors secretion following pulmonary S. aureus infection. Furthermore, STING-/- mice presented decreased levels of cfDNA and CitH3, along with increased bacterial colonization compared to WT mice. Altogether, these findings highlighted that STING promoted ETs formation via the ROS-ERK signal for host defense against S. aureus infection.

Extracellular trap can be trained as a memory response.

Extracellular trap (ET) appears as a double-edged sword for the host since it participates in host immune defense by entrapping pathogens, while excessive ET release also contributes to various diseases progression including atherosclerosis, cancer, and autoimmune disorders. A better understanding of ET formation and regulation will be beneficial for developing strategies for infection control and ET-associated disease treatment. There is some evidence indicating that prior infection can enhance extracellular killing. Neutrophils from cancer or sepsis are predisposed to generate ET. It is reasonable to suspect that ET may be trained to form as a memory response, just like cytokine memory response termed "trained immunity." The mice were intraperitoneally injected with heat-killed Candida albicans (HK-C. albicans), 3 days later bone marrow-derived macrophages (BMDM) were isolated and challenged with Clostridium perfringens as a second stimulation. We found that HK-C. albicans priming enhanced ET formation upon Clostridium perfringens infection, accompanied by increased extracellular killing capacity. Mannan priming also enhanced ET formation. Since ETs memory was induced in chicken PBMC, ETs memory may be evolutionarily conserved. Moreover, mTOR was required for ETs memory response. Collectively, this study showed that ETs can be trained as a memory response and indicated that memory property of ETs should be considered during the understanding of recurrent infection and ET-associated disorders.

[Application of spinal surgical robots in minimally invasive surgery for thoracolumbar fracture].

OBJECTIVE: To evaluate the safety and accuracy of Renaissance robot navigation system in minimally invasive surgery for thoracolumbar fracture. METHODS: The clinical data of patients with thoracolumbar fracture who underwent posterior minimally invasive pedicle screw internal fixation from July 2016 to July 2019 was retrospectively analyzed. And the patients were divided into robot group and artificial group. Robot navigation assisted screw placement was used in robot group, and traditional unarmed screw placement was used in artificial group. There were 20 patients in robot group, including 13 males and 7 females, aged from 23 to 69 years old with an average of(45.05±11.81)years old, one case was T11 fracture, 2 cases were T12, 10 cases were L1, 6 cases were L2 and 1 case was L3. There were 20 patients in artificial group, including 11 males and 9 females, aged from 26 to 65 years old with an average of(43.40±11.22)years old, 2 cases were T11 fractures, 7 cases were T12, 10 cases were L1, and 1 case was L3. The numbers of fluoroscopy, operation time and intraoperative blood loss were observed. The screw position was evaluated by Neo method. RESULTS: A total of 126 screws were implanted in robot group and 124 screws were implanted in artificial group. The operation time, fluoroscopy times, intraoperative blood loss were(115.75±14.26) min, (7.95±0.89) times and (132.50±29.36) ml in robot group and (129.50±10.50) min, (14.40±2.56) times and(182.50±23.14) ml in artificial group, respectively, there was significant difference between the groups(P<0.05). According to Neo classification method, there were 122 screws at grade 0, 4 screws at grade 1 in robot group, and there were 108 screws at grade 0, 9 screws at grade 1 and 7 screws at grade 2 in artificial group. The accuracy of the robot group was better than that of artificial group(P<0.05). CONCLUSION: Compared with free hand screw placement, Renaissance robot navigation system can effectively improve the accuracy of pedicle screw placement, reduce the number of fluoroscopy times and intraoperative blood loss, thereby improving the safety of operation.

Glutamine relieves the hypermetabolic response and reduces organ damage in severe burn patients: A multicenter, randomized controlled clinical trial.

BACKGROUND: Severe burns can cause a hypermetabolic response and organ damage. Glutamine is a conditionally essential amino acid with various pharmacological effects. In this study, whether glutamine could alleviate the hypermetabolic response and maintain organ function after burn injury was analyzed. METHODS: A multicenter, randomized, single-blind, parallel controlled trial was conducted to evaluate the efficacy of glutamine in decreasing hypermetabolism after burn injury. Physiological and biochemical indexes, such as vital signs, metabolic hormones, metabolic rate, and organ damage, were recorded on the 7th and 14th days after treatment. RESULTS: In total, 55 adult burn patients with a total burn surface area (TBSA) of 30-70% were included in this study and randomly divided into the burn control (B, 28 patients) and burn+glutamine (B+G, 27 patients) groups. Except for the glutamine administration, the groups did not differ in the other treatments and nutrition supplements. The levels of diamine oxidase (DAO), lactulose/mannitol (L/M), ß2-microglobulin, lactate dehydrogenase (LDH), hydroxybutyrate dehydrogenase (HBD) and cardiac troponin l (cTnl) in the B+G group were significantly lower than those in the B group (p < 0.05 or 0.01). The levels of resting energy expenditure (REE), serum catecholamines, glucagon, lactate and Homeostasis model assessment (HOMA) in the B+G group were significantly lower than those in the B group (p < 0.05 or 0.01). No significant difference was found in the length of hospitalization or the mortality rate between the two groups (p > 0.05). CONCLUSIONS: Glutamine moderately alleviates the hypermetabolic response and reduces organ damage after severe burns. Therefore, the early application of glutamine, which is effective and safe, should be used as an active intervention as early as possible.

STING Contributes to Host Defense Against Staphylococcus aureus Pneumonia Through Suppressing Necroptosis.

STING (Stimulator of interferon genes) is known as an important adaptor protein or direct sensor in the detection of nucleotide originating from pathogens or the host. The implication of STING during pulmonary microbial infection remains unknown to date. Herein, we showed that STING protected against pulmonary S.aureus infection by suppressing necroptosis. STING deficiency resulted in increased mortality, more bacteria burden in BALF and lungs, severe destruction of lung architecture, and elevated inflammatory cells infiltration and inflammatory cytokines secretion. STING deficiency also had a defect in bacterial clearance, but did not exacerbate pulmonary inflammation during the early stage of infection. Interestingly, TUNEL staining and LDH release assays showed that STING-/- mice had increased cell death than WT mice. We further demonstrated that STING-/- mice had decreased number of macrophages accompanied by increased dead macrophages. Our in vivo and in vitro findings further demonstrated this cell death as necroptosis. The critical role of necroptosis was detected by the fact that MLKL-/- mice exhibited decreased macrophage death and enhanced host defense to S.aureus infection. Importantly, blocking necroptosis activation rescued host defense defect against S.aureus pneumonia in STING-/- mice. Hence, these results reveal an important role of STING in suppressing necroptosis activation to facilitate early pathogen control during pulmonary S.aureus infection.

GSDMD contributes to host defence against Staphylococcus aureus skin infection by suppressing the Cxcl1-Cxcr2 axis.

Gasdermin D (GSDMD), a member of the gasdermin protein family, is a caspase substrate, and its cleavage is required for pyroptosis and IL-1ß secretion. To date, the role and regulatory mechanism of GSDMD during cutaneous microbial infection remain unclear. Here, we showed that GSDMD protected against Staphylococcus aureus skin infection by suppressing Cxcl1-Cxcr2 signalling. GSDMD deficiency resulted in larger abscesses, more bacterial colonization, exacerbated skin damage, and increased inflammatory cell infiltration. Although GSDMD deficiency resulted in defective IL-1ß production, the critical role of IL-1ß was counteracted by the fact that Caspase-1/11 deficiency also resulted in less IL-1ß production but did not aggravate disease severity during S. aureus skin infection. Interestingly, GSDMD-deficient mice had increased Cxcl1 secretion accompanied by increased recruitment of neutrophils, whereas Caspase-1/11-deficient mice presented similar levels of Cxcl1 and neutrophils as wild-type mice. Moreover, the absence of GSDMD promoted Cxcl1 secretion in bone marrow-derived macrophages induced by live, dead, or different strains of S. aureus. Corresponding to higher transcription and secretion of Cxcl1, enhanced NF-κB activation was shown in vitro and in vivo in the absence of GSDMD. Importantly, inhibiting the Cxcl1-Cxcr2 axis with a Cxcr2 inhibitor or anti-Cxcl1 blocking antibody rescued host defence defects in the GSDMD-deficient mice. Hence, these results revealed an important role of GSDMD in suppressing the Cxcl1-Cxcr2 axis to facilitate pathogen control and prevent tissue damage during cutaneous S. aureus infection.