ObjectiveTo investigate the intervention mechanism of the traditional Chinese medicine Number 2 Feibi recipe （N2FBR） in idiopathic pulmonary fibrosis （IPF）， focusing on its effects on endoplasmic reticulum （ER） stress， apoptosis， stemness maintenance， and regenerative capacity of alveolar type Ⅱ epithelial cells （AT2 cells）， and to validate the modern translational pathway of the theory of "deficiency of Zong Qi leading to pulmonary atelectasis and atrophy". MethodsA mouse model of pulmonary fibrosis was induced by bleomycin （BLM）. Mice were randomly divided into blank control， model， low-， and high-dose N2FBR intervention groups （9.1， 18.2 g·kg^-1）， and prednisolone intervention group （6.5 mg·kg^-1）. Pulmonary histopathological changes and collagen deposition were evaluated using hematoxylin-eosin （HE） and Masson's trichrome staining. Hydroxyproline （HYP） content was measured by the alkaline hydrolysis method. Lung coefficient and pulmonary function parameters were evaluated. The mRNA expression levels of fibrosis-related factors， including collagen type Ⅰ alpha 1 chain （ColIa1）， alpha-smooth muscle actin （α-SMA）， and tissue inhibitor of metalloproteinase 1 （Timp1）， were detected by real-time polymerase chain reaction （Real-time PCR）. Cell apoptosis was assessed using the terminal deoxynucleotidyl transferase dUTP nick-end labeling （TUNEL） assay. Apoptosis of AT2 cells was further evaluated by double immunofluorescence staining for surfactant protein C （SPC） and cysteine-aspartic protease-3 （Caspase-3）. Endoplasmic reticulum （ER） stress in AT2 cells was examined by double staining for SPC and protein kinase R-like endoplasmic reticulum kinase （PERK）. Ultrastructural changes of ER and lamellar bodies in AT2 cells were observed by transmission electron microscopy （TEM）. The expression levels of key proteins involved in ER stress and apoptosis pathways， including PERK， activating transcription factor 4 （ATF4）， and Caspase-3， were detected by Western blot. Double immunofluorescence staining of SPC and Ki-67 antigen （Ki-67） was performed to evaluate the proliferative capacity of AT2 cells. Lineage tracing technology （labeling AT2 cells with GFP） combined with Krt8 labeling was used to evaluate intermediate differentiation states， and morphological transformation of AT2 cells into alveolar type Ⅰ epithelial cells （AT1） was observed. ResultsBLM-induced mice exhibited significant structural disruption of lung tissue， increased collagen deposition， elevated lung coefficient， decreased pulmonary function， and upregulation of fibrosis-related factors （P<0.01）. High-dose N2FBR treatment significantly ameliorated lung tissue damage and dysfunction， significantly reduced HYP content （P<0.01）， and significantly downregulated ColIa1， α-SMA， and Timp1 expression （P<0.01）. Apoptosis analysis showed increased TUNEL-positive and Caspase-3-positive AT2 cells in the model group， which was significantly reduced by high-dose N2FBR treatment. TEM revealed swollen ER structures in AT2 cells of the model group， which tended to return to normal following treatment. PERK protein staining analysis showed evident ER stress in AT2 cells of the model group， which were markedly alleviated in the treatment group. The expression levels of ER stress-related proteins PERK and ATF4， as well as the apoptosis-related protein Caspase-3， were elevated in the model group and significantly reduced after treatment. TEM also revealed disrupted lamellar body structures in the model group， which tended to recover in the treatment group. Regarding the proliferative capacity of AT2 cells， the proportion of Ki-67⁺SPC⁺ AT2 cells significantly increased in the treatment group （P<0.01）. Lineage tracing showed that the proportion of keratin 8-positive green fluorescent protein-positive （Krt8⁺GFP⁺） cells increased in the model group， indicating differentiation arrest. This proportion was significantly reduced in the treatment group， and the morphology of GFP⁺ cells exhibited a flattened， extended shape， suggesting restored differentiation toward AT1 cells. ConclusionN2FBR alleviates ER stress in AT2 cells， reduces AT2 cell apoptosis， restores lamellar body structure and function， enhances proliferation activity， and alleviates differentiation arrest to promote differentiation into AT1 cells， thereby repairing the alveolar epithelium and effectively blocking the progression of pulmonary fibrosis. Its traditional Chinese medicine mechanism of "replenishing Zong Qi， harmonizing Qi and blood， and unblocking pulmonary meridians" closely aligns with the modern regulatory pathway of AT2 stem cells， providing a novel theoretical basis and experimental evidence for the intervention of IPF with traditional Chinese medicine.

ObjectiveTo investigate the intervention mechanism of the traditional Chinese medicine Number 2 Feibi recipe （N2FBR） in idiopathic pulmonary fibrosis （IPF）， focusing on its effects on endoplasmic reticulum （ER） stress， apoptosis， stemness maintenance， and regenerative capacity of alveolar type Ⅱ epithelial cells （AT2 cells）， and to validate the modern translational pathway of the theory of "deficiency of Zong Qi leading to pulmonary atelectasis and atrophy". MethodsA mouse model of pulmonary fibrosis was induced by bleomycin （BLM）. Mice were randomly divided into blank control， model， low-， and high-dose N2FBR intervention groups （9.1， 18.2 g·kg^-1）， and prednisolone intervention group （6.5 mg·kg^-1）. Pulmonary histopathological changes and collagen deposition were evaluated using hematoxylin-eosin （HE） and Masson's trichrome staining. Hydroxyproline （HYP） content was measured by the alkaline hydrolysis method. Lung coefficient and pulmonary function parameters were evaluated. The mRNA expression levels of fibrosis-related factors， including collagen type Ⅰ alpha 1 chain （ColIa1）， alpha-smooth muscle actin （α-SMA）， and tissue inhibitor of metalloproteinase 1 （Timp1）， were detected by real-time polymerase chain reaction （Real-time PCR）. Cell apoptosis was assessed using the terminal deoxynucleotidyl transferase dUTP nick-end labeling （TUNEL） assay. Apoptosis of AT2 cells was further evaluated by double immunofluorescence staining for surfactant protein C （SPC） and cysteine-aspartic protease-3 （Caspase-3）. Endoplasmic reticulum （ER） stress in AT2 cells was examined by double staining for SPC and protein kinase R-like endoplasmic reticulum kinase （PERK）. Ultrastructural changes of ER and lamellar bodies in AT2 cells were observed by transmission electron microscopy （TEM）. The expression levels of key proteins involved in ER stress and apoptosis pathways， including PERK， activating transcription factor 4 （ATF4）， and Caspase-3， were detected by Western blot. Double immunofluorescence staining of SPC and Ki-67 antigen （Ki-67） was performed to evaluate the proliferative capacity of AT2 cells. Lineage tracing technology （labeling AT2 cells with GFP） combined with Krt8 labeling was used to evaluate intermediate differentiation states， and morphological transformation of AT2 cells into alveolar type Ⅰ epithelial cells （AT1） was observed. ResultsBLM-induced mice exhibited significant structural disruption of lung tissue， increased collagen deposition， elevated lung coefficient， decreased pulmonary function， and upregulation of fibrosis-related factors （P<0.01）. High-dose N2FBR treatment significantly ameliorated lung tissue damage and dysfunction， significantly reduced HYP content （P<0.01）， and significantly downregulated ColIa1， α-SMA， and Timp1 expression （P<0.01）. Apoptosis analysis showed increased TUNEL-positive and Caspase-3-positive AT2 cells in the model group， which was significantly reduced by high-dose N2FBR treatment. TEM revealed swollen ER structures in AT2 cells of the model group， which tended to return to normal following treatment. PERK protein staining analysis showed evident ER stress in AT2 cells of the model group， which were markedly alleviated in the treatment group. The expression levels of ER stress-related proteins PERK and ATF4， as well as the apoptosis-related protein Caspase-3， were elevated in the model group and significantly reduced after treatment. TEM also revealed disrupted lamellar body structures in the model group， which tended to recover in the treatment group. Regarding the proliferative capacity of AT2 cells， the proportion of Ki-67⁺SPC⁺ AT2 cells significantly increased in the treatment group （P<0.01）. Lineage tracing showed that the proportion of keratin 8-positive green fluorescent protein-positive （Krt8⁺GFP⁺） cells increased in the model group， indicating differentiation arrest. This proportion was significantly reduced in the treatment group， and the morphology of GFP⁺ cells exhibited a flattened， extended shape， suggesting restored differentiation toward AT1 cells. ConclusionN2FBR alleviates ER stress in AT2 cells， reduces AT2 cell apoptosis， restores lamellar body structure and function， enhances proliferation activity， and alleviates differentiation arrest to promote differentiation into AT1 cells， thereby repairing the alveolar epithelium and effectively blocking the progression of pulmonary fibrosis. Its traditional Chinese medicine mechanism of "replenishing Zong Qi， harmonizing Qi and blood， and unblocking pulmonary meridians" closely aligns with the modern regulatory pathway of AT2 stem cells， providing a novel theoretical basis and experimental evidence for the intervention of IPF with traditional Chinese medicine.

Objective To examine the impact of extreme temperature and drought stress on the survival of Bulinus globosus, so as to provide the theoretical evidence for the genomic research of Bulinus in absence of reference genes. Methods B. globosus snail samples were collected from Kiwani Shehia in Pemba Island, Zanzibar, Tanzania, and offspring snails were obtained through laboratory breeding and reproduction. A total of 120 10-week-old B. globosus snails from the same generation were selected and randomly assigned into four groups, including the high-temperature drought (HD) group, normal temperature drought (D) group, low-temperature drought (LD) group, and the control (C) group, of 30 snails in each group. Snails in HD, D, and LD groups were placed in beakers containing dry soil at the bottom and subsequently housed in climate chambers at 35, 26 ℃, and 10 ℃, respectively, while snails in Group C were maintained in 500 mL petri dishes containing dechlorinated tap water at 26 ℃. Following 3 days of breeding, living snails in each group were collected, and soft tissues were dissected and isolated. Total RNA was extracted from snail soft tissues for library construction, followed by high-throughput sequencing on the Illumina HiSeq 4000 sequencing system. De novo transcriptome assembly was performed using the Trinity software, and the longest transcripts were selected as unigenes. Gene functional annotations of unigenes were conducted using the Diamond software against Gene Ontology (GO) knowledgebase, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database, NCBI non-redundant (NR) protein sequences database, Protein Family (Pfam) database, and UniProtKB/Swiss-Prot (Swiss-Prot) knowledgebase. GO and KEGG enrichment analyses of differentially expressed genes (DEGs) were performed using the topGO and clusterProfiler software, respectively. In addition, four relevant genes were selected for validation using a real-time quantitative PCR (qRT-PCR) assay to verify the reliability of transcriptome sequencing results. Results Following 3 days of breeding, there were 7, 20, 28, and 30 survival B. globosus snails in HD, LD, D, and C groups, with corresponding survival rates of 23.33% (7/30), 66.67% (20/30), 93.33% (28/30), and 100.00% (30/30), respectively (χ² = 52.72, P < 0.001). De novo transcriptome assembly generated 176 942 unigenes, with annotation rates of 0.98%, 13.49%, 26.46%, 12.48%, and 14.39% against GO knowledgebase, KEGG pathway database, NR protein sequences database, Pfam database, and Swiss-Prot knowledgebase, respectively. There were 33 up-regulated and 72 down-regulated genes in Group D, 483 up-regulated and 815 down-regulated genes in Group HD, and 245 up-regulated and 172 down-regulated genes in Group LD relative to in Group C. Following removal of overlapping genes across groups and unmatched genes, 11 candidate genes were identified. GO and KEGG analyses revealed 3 heat shock protein (HSP)-related DEGs in these 11 candidate genes, which were annotated as HSP12.2, HSP70, and HSP20 genes and were all significantly up-regulated in each treatment group. Three immune and nervous system-related DEGs were identified, and were all significantly down-regulated in each treatment group, which were involved in the neural cell adhesion molecule L1-like protein pathway, fibrinogen binding protein pathway, and leukocyte elastase inhibitor-like protein pathway. qRT-PCR assay quantified that the expression trends of four genes related to temperature and drought stress across different treatment groups were highly consistent with transcriptome sequencing data. Conclusion The survival rate of B. globosus significantly reduces under combined stresses of extreme temperature and drought, possibly due to an imbalance in its cellular homeostasis regulatory system.

Objective: To evaluate the diagnostic performance of magnetic resonance spectroscopy (MRS) in discriminating fumarate hydratase-deficient (FH-d) uterine leiomyomas (ULs) from FH-preserved ULs. Materials and Methods: This study consisted of three stages, with independent cohorts recruited for each stage: 1) sample-size estimation was retrospectively performed on UL specimens (diameter ≥3 cm; age, 20–40 years) from our database with immunohistochemistry (IHC) for 2-succinocysteine (2-SC) as the reference, without genetic testing, 2) MRS sequence optimization in confirmed FH germline mutation participants with ultrasound-detected ULs (diameter ≥3 cm), without IHC analysis, and 3) prospective diagnostic test accuracy was evaluated in consecutive participants with ultrasound-detected ULs (diameter ≥3 cm;age, 20–40 years), using IHC for 2-SC for determining the FH status and subsequent genetic testing in those with positive 2-SC results to identify whether FH mutations were germline or somatic in origin. The choline and fumarate peaks in MRS were classified as positive, negative, or technical failure (TF). TFs were analyzed separately and excluded from the primary diagnostic accuracy calculations. T1-, T2-, and diffusion-weighted images were interpreted as hyperintense or hypointense. The enhancement rate and apparent diffusion coefficient were also acquired. Diagnostic performance was compared between MRS and various magnetic resonance imaging (MRI) features. Results: The optimal MRS parameters for the fumarate peak were echo time (TE) = 140 ms and an average of 256. Among the 360 prospective participants, 37 were confirmed to have FH-dULs. MRS showed positive fumarate peaks in 35 of 37 FH-dULs.After excluding six TFs, the positive fumarate peak on MRS showed 94.6% (35/37) sensitivity, 99.7% (316/317) specificity, and 99.2% (351/354) accuracy, all of which were significantly superior to those of other MRI features (P ≤ 0.002). Conclusion A positive fumarate peak on MRS may be a useful imaging biomarker for diagnosing FH-dULs.

Plant-derived extracellular vesicles (PDEVs) are nanoscale extracellular vesicles secreted by plant cells, characterized by a lipid bilayer structure. These vesicles carry a variety of bioactive molecules, including proteins, nucleic acids, and lipids, and play essential roles in intercellular communication and physiological regulation in plants. Compared to animal-derived extracellular vesicles, PDEVs offer several advantages, such as a broad range of sources, high biocompatibility, low immunogenicity, and low production costs. Furthermore, PDEVs have demonstrated remarkable potential as natural nanocarriers for drug delivery, due to their ability to efficiently traverse biological barriers, such as the blood-brain barrier, making them promising candidates for drug delivery systems. This review systematically elaborates on the complex composition of PDEVs, which consists of lipids, proteins, and nucleic acids, the typical structural characteristics of their lipid bilayers ranging from 30 to 150 nm, and their versatile loading capabilities as drug carriers, efficiently encapsulating various types of therapeutic agents such as hydrophilic small molecules, hydrophobic drugs, nucleic acids, and proteins. We systematically summarize the recent advancements in strategies for enhancing the loading efficiency of PDEVs, which include methods such as co-incubation, ultrasound-assisted loading, electroporation, freeze-thaw cycles, and microfluidic technology. These techniques are evaluated based on their underlying principles, suitable drug types, and their respective advantages. In addition to loading strategies, we focus on the engineered approaches to achieve targeted delivery using PDEVs, such as genetic engineering modifications, chemical ligand conjugation, membrane fusion technology, and polyethylene glycol (PEG) modification. We discuss the mechanisms of these strategies in enhancing targeting efficiency, prolonging in vivo circulation time, and improving therapeutic efficacy. Further, this review highlights the application of PDEVs in various disease models, including tumor, skin inflammation, metabolic disorders, and neurodegenerative diseases, showcasing their therapeutic potential as multifunctional delivery platforms. The ability of PDEVs to encapsulate diverse therapeutic agents and target specific tissues or cells opens up new avenues for the treatment of complex diseases, offering advantages over conventional drug delivery systems. However, despite the promising applications of PDEVs, several challenges remain in their development and clinical translation. These challenges include variability in source materials, standardization of preparation processes, quality control, scalability of production, and the need for clinical validation. To overcome these obstacles, the integration of advanced technologies such as artificial intelligence-assisted design and multi-omics analysis is proposed as a way to facilitate the precise development of PDEVs. These emerging technologies hold the potential to further enhance the precision and effectiveness of plant-based drug delivery systems, ultimately advancing the field of precision medicine. In conclusion, the use of PDEVs as a platform for drug delivery represents a promising area of research with the potential to revolutionize therapeutic strategies. Their ability to encapsulate and deliver a wide variety of bioactive molecules, along with their inherent advantages in biocompatibility and versatility, makes them a valuable tool in the development of more efficient and targeted therapeutic interventions. Continued research and innovation in this field will pave the way for the clinical implementation of PDEVs in the treatment of various diseases, offering new hope for more effective and sustainable therapeutic options.

This study was aimed at investigating the immunoregulatory function of Mycobacterium tuberculosis Rv3641c gene in modulating host type Ⅰ interferon responses.The shuttle plasmid pMV261 was used to construct Rv3641c overexpression recombinant Mycobacterium smegmatis,and the biological characteristics of the recombinant bacteria were analyzed to explore the effect of Rv3641c on the growth curve,colony morphology and stress resistance of Mycobacterium.Subsequently,RAW264.7 cells were infected with Rv3641c overexpressing Mycobacterium smegmatis,and the transcriptional expression of genes related to the inhibition of type I inter-feron pathway was determined by RT-PCR.The expression level of IFN-βprotein was determined by ELISA,and the intracellular sur-vival level was determined.As a result,the recombinant rMS::pMV261-Rv3641c was successfully constructed.The results of biologi-cal characteristics analysis showed that Rv3641c did not affect the growth of mycobacteria,but significantly changed the colony mor-phology of mycobacteria and improved its resistance to H2O2.The results of recombinant bacteria infection experiments showed that Rv3641c significantly down-regulated the transcription levels of IFN-α,IFN-βand downstream ISGs genes CXCL10,IFIT2 and IL-1β in host cells,and Rv3641c significantly down-regulated the transcription levels of IFN-α,IFN-βand downstream ISGs genes CXCL10,IFIT2 and IL-1βin host cells.The results of intracellular colonization experiments showed that the intracellular mycobacte-ria in the overexpression recombinant bacteria infection group were significantly higher than those in the empty vector group,indicat-ing that Rv3641c could promote the intracellular surviv al of mycobacteria.In summary,the Rv3641c gene of M.tuberculosis can inhibit the host type I interferon response and promote the intracellular survival of M.tuberculosis,which provides a new idea for further explor-ing the immune escape function of M.tuberculosis and the discovery of new targets for anti-tuberculosis drugs.

Objective:To investigate the detection rate of human herpesvirus（HHV）in children with drug-induced hypersensitivity syndrome（DIHS）and to analyze the impact of HHV on the prognosis of DIHS.Methods:This study included a retrospective analysis of clinical data from hospitalized patients diagnosed with DIHS at the Department of Dermatology at Beijing Children's Hospital between January 2009 and December 2023 who underwent peripheral blood HHV-DNA testing.The positive rates of the following HHV types were analyzed:epstein-barr virus,cytomegalovirus,HHV-6,and HHV-7.The clinical features,disease severity,course,and prognosis were then compared between HHV-positive and HHV-negative children.Results:Of the 81 patients enrolled，46（56.8%）tested positive for at least one type of HHV-DNA.The positive detection cases of epstein-barr virus，cytomegalovirus，HHV-6，and HHV-7 were 16（19.8%）cases，9（11.1%）cases，25（30.9%）cases，and 8（9.9%）cases，respectively.Compared with the HHV-negative group,the HHV-positive group exhibited significantly higher incidences of facial/limb edema,severe disease,and a RegiSCAR score ≥6( P<0.05).Furthermore,the HHV-positive group experienced significantly longer durations of fever,skin rash,liver injury,total disease course,and treatment period ( P<0.05). Conclusion:HHV-6 is the most frequently detected herpesvirus among children with DIHS.HHV positivity is significantly associated with greater disease severity and a prolonged clinical course in pediatric DIHS patients.

Aim To investigate the protective effect of Vaccarin(Va)on epithelial-mesenchymal transition(EMT)in renal fibrosis model mice through regulating STAT3,and the underlying mechanism.Methods Left ureter ligation was used to establish a mouse model of unilateral ureteral obstruction(UUO);human kid-ney tubular epithelial(HK2)cells were induced to differentiate by transforming growth factor-β(TGF-β)in vitro.HE and Masson staining were used to observe the morphological changes of renal tissue;kits were used to detect the levels of BUN,Cr,IL-1β and IL-7 in mouse serum;CCK-8 was used to detect the effect of Va on the viability of HK2 cells;RT-PCR was used to detect the levels of inflammatory factors in HK2 cells;Western blot was used to detect the expression of STAT3,p-STAT3,E-cadherin,and α-SMA proteins in renal tissue and HK2 cells;to further investigate the regulation of Va on STAT3,JAK/STAT3 pathway acti-vator RO8191 was used to treat TGF-β-induced HK2 cells,and functional loss was detected.Results Va improved the pathological damage in UUO mice,inhibi-ted the levels of BUN,Cr and inflammatory factors;Va inhibited the phosphorylation of STAT3,upregulated E-cadherin,and downregulated α-SMA protein expres-sion;RO8191 counteracted the inhibitory effect of Va on the phosphorylation of STAT3.Conclusions Va inhibits the phosphorylation of STAT3 and the release of inflammatory factors,improves EMT,thus exerting an anti-renal fibrosis effect.

Non-small cell lung cancer(NSCLC)is one of the most common and deadly malignant tumors worldwide,with surgical resection being the primary treatment for early-stage NSCLC.Tumor spread through air spaces(STAS)is a novel pattern of tumor dissemination into the air spaces in the lung.Its occurrence after sublobar resection is closely associated with recurrence and distant metastasis,making its con-sideration a vital factor in surgical strategy selection and prognostic evaluation.Patients with STAS-positive status exhibit significantly higher postoperative recurrence rates than do STAS-negative patients,with molecular mechanisms involving tumor microenvironment remodeling,specific genetic mutations,and epithelial-mesenchymal transition(EMT).Imaging techniques including computed tomography(CT)and positron emission tomography/CT have shown potential for preoperative STAS prediction,although their accuracy and practicality require improvement.This paper reviews the definition,pathological characteristics,and related mechanisms of STAS,with a focus on surgical ap-proach selection for STAS-positive patients and its role in cancer recurrence after sublobar resection of early-stage NSCLC.Future research directions include optimization of preoperative diagnostic methods for STAS,exploration of molecular targeted therapies,and development of imaging-based precision prediction models.

Objective To investigate the distribution and antimicrobial resistance profiles of common pathogens isolated from cerebrospinal fluid(CSF)in CHINET program from 2015 to 2021.Methods The bacterial strains isolated from CSF were identified in accordance with clinical microbiology practice standards.Antimicrobial susceptibility test was conducted using Kirby-Bauer method and automated systems per the unified CHINET protocol.Results A total of 14 014 bacterial strains were isolated from CSF samples from 2015 to 2021,including the strains isolated from inpatients(95.3％)and from outpatient and emergency care patients(4.7％).Overall,19.6％of the isolates were from children and 80.4％were from adults.Gram-positive and Gram-negative bacteria accounted for 68.0％and 32.0％,respectively.Coagulase negative Staphylococcus accounted for 73.0％of the total Gram-positive bacterial isolates.The prevalence of MRSA was 38.2％in children and 45.6％in adults.The prevalence of MRCNS was 67.6％in adults and 69.5％in children.A small number of vancomycin-resistant Enterococcus faecium(2.2％)and linezolid-resistant Enterococcus faecalis(3.1％)were isolated from adult patients.The resistance rates of Escherichia coli and Klebsiella pneumoniae to ceftriaxone were 52.2％and 76.4％in children,70.5％and 63.5％in adults.The prevalence of carbapenem-resistant E.coli and K.pneumoniae(CRKP)was 1.3％and 47.7％in children,6.4％and 47.9％in adults.The prevalence of carbapenem-resistant Acinetobacter baumannii(CRAB)and Pseudomonas aeruginosa(CRPA)was 74.0％and 37.1％in children,81.7％and 39.9％in adults.Conclusions The data derived from antimicrobial resistance surveillance are crucial for clinicians to make evidence-based decisions regarding antibiotic therapy.Attention should be paid to the Gram-negative bacteria,especially CRKP and CRAB in central nervous system(CNS)infections.Ongoing antimicrobial resistance surveillance is helpful for optimizing antibiotic use in CNS infections.