[Antibacterial activity of silver nanoparticles against multiple drug resistant strains].

Objective: The objective of the study was to assess the antimicrobial activity of silver nanoparticles (AgNPs) against multiple drug resistant strains. Methods: Minimal inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of AgNPs against three model microbes, namely Escherichia coli, Staphylococcus aureus, Candida albicans were measured by microdilution broth method. Time-kill curve within 24 h was made according to colony count method after three model microbes were treated with a series concentration of AgNPs. Post-antibiotic effect was tested by colony count method. Finally, we determined the antimicrobial efficacy against multiple drug resistant strains in biological safety laboratory grade 2 (BSL-2). Results: AgNPs with a diameter of 5 nm to 30 nm were synthesized by the biological method. The zeta potential was -19.5 mV. The time-kill curve of the three model microbes showed time-dependent antibacterial activity. The effect of AgNPs on E. coli and C. albicans after "antibiotic effect" increased with time, there was no obvious "post-antibiotic effect" on S. aureus. Both MIC values and MBC values of AgNPs for the three model microbes were between 1 µg/mL and 4 µg/mL. However, the MIC value of AgNPs for the three human multidrug-resistant strains was 6 µg/mL to 26 µg/mL and MBC value of AgNPs was 10 µg/mL to 32 µg/mL. The MIC values of AgNPs for 14 animal multi-drug resistant strains were between 4 µg/mL and 10 µg/mL, and the MBC values were between 8 µg/mL and 16 µg/mL. The MBC/MIC values of all the tested strains were less than 2. Conclusion: AgNPs is a time-dependent antimicrobial agent with different "post-antibiotic effect", which can inhibit both human and animal-derived multi-drug resistant bacteria.

Impact of Predator Cues on Responses to Silver Nanoparticles in Daphnia carinata.

The past decades have witnessed a boom in nanotechnology that has led to increasing production and application of silver nanoparticles (AgNPs) in the textile industry due to their antimicrobial properties. Increase in the manufacture and use of NPs inevitably has resulted in their increased release into aquatic environments resulting in the exposure of organisms living in these environments. Recently, the risk of exposure to NPs and the potential interaction with biological systems has received increasing attention. The present study investigated the potential effects of predator cues on the toxicity of environmentally relevant concentrations of AgNPs in Daphnia carinata at organismal and biochemical levels. The results of this study show that exposure to environmentally relevant concentrations of AgNPs can result in adverse effects on daphnids with 24- and 48-h LC50 values of 3.56 and 1.75 µg/L, respectively. Furthermore, significant inhibition of reproduction was observed at concentrations as low as 0.5 µg/L. Exposure to predator cues alone resulted in an increase in reproduction and inhibition of superoxide dismutase activity in daphnids. However, coexposure to predator cues interacted in an antagonistic manner with AgNPs with a 24-h LC50 value of 10.81 µg/L compared with 3.56 µg/L for AgNPs alone. In summary, AgNPs could pose risks to aquatic invertebrates at environmentally relevant concentrations. Interestingly, the presence of other factors, such as predator cues, moderated the effects of exposure to AgNPs. Therefore, there is a need to further investigate the potential interactions between NPs and biological factors that can modulate toxicity of NPs for application to the risk assessment of aquatic invertebrates.

Characterization of Shiga toxin-producing Escherichia coli isolated from healthy pigs in China.

BACKGROUND: Shiga toxin-producing Escherichia coli (STEC) is recognized as an important human diarrheal pathogen. Swine plays an important role as a carrier of this pathogen. In this study we determined the prevalence and characteristics of STEC from healthy swine collected between May 2011 and August 2012 from 3 cities/provinces in China. RESULTS: A total of 1003 samples, including 326 fecal, 351 small intestinal contents and 326 colon contents samples, was analyzed. Two hundred and fifty five samples were stx-positive by PCR and 93 STEC isolates were recovered from 62 stx-positive samples. Twelve O serogroups and 19 O:H serotypes including 6 serotypes (O100:H20/[H20], O143:H38/[H38], O87:H10, O172:H30/[H30], O159:H16, O9:H30/[H30]) rarely found in swine and ruminants were identified. All 93 STEC isolates harbored stx2 only, all of which were stx2e subtype including 1 isolate being a new variant of stx2e. 53.76%, 15.05% and 2.15% STEC isolates carried astA, hlyA and ehxA respectively. Four STEC isolates harbored the high-pathogenicity island. Of the 15 adherence-associated genes tested, 13 (eae, efa1, iha, lpfAO113, lpfAO157/OI-154, lpfAO157/OI-141, toxB, saa, F4, F5, F6, F17 or F41) were all absent while 2 (paa and F18) were present in 7 and 4 STEC isolates respectively. The majority of the isolates were resistant to tetracycline (79.57%), nalidixic acid (78.49%), trimethoprim-sulfamethoxazole (73.12%) and kanamycin (55.91%). The STEC isolates were divided into 63 pulsed-field gel electrophoresis patterns and 21 sequence types (STs). Isolates of the same STs generally showed the same or similar drug resistance patterns. A higher proportion of STEC isolates from Chongqing showed multidrug resistance with one ST (ST3628) resistant to 14 antimicrobials. CONCLUSIONS: Our results indicate that swine is a significant reservoir of STEC strains in China. Based on comparison by serotypes and sequence types with human strains and presence of virulence genes, the swine STEC may have a low potential to cause human disease.

[Silver nanoparticles-resistance of HeLa cell associated with its unusually high concentration of α-ketoglutarate and glutathione].

Silver nanoparticles (AgNPs) is known as one of the most valuable metal nanoparticles in antibacterial and anticancer application. AgNPs-resistant bacteria has been documented, but it is unclear whether cancer cells can also escape the anti-cancer effect of AgNPs. In this study, we aimed to investigate this phenomenon and its underlying mechanism. The antibacterial activity and cytotoxicity of AgNPs were measured in the presence of HeLa cell metabolites. The status of AgNPs in the system associated with metabolites were characterized by UV-Vis, Zetasizer Nano ZS, and transmission electron microscopy. Non-targeted metabolomics was used to reveal the metabolites components that bind with AgNPs. HeLa cells were injected intraperitoneally to establish the tumor-bearing mice model, and the stability of AgNPs in mice serum was analyzed. The results manifested that HeLa cell metabolites inhibited the anticancer and antibacterial effects of AgNPs in a dose-dependent manner by causing AgNPs aggregation. Effective metabolites that inhibited the biological activity of AgNPs were stable in 100 ℃, insoluble in chloroform, containing sulfur elements, and had a molecular weight less than 1 kDa in molecular weight. There were 115 compounds bound with AgNPs. In vitro experiments showed that AgNPs aggregation occurred only when the concentration of α-ketoglutarate (AKG) and glutathione (GSH) together reached a certain threshold. Interestingly, the concentration of AKG and GSH in HeLa cellular metabolites was 10 and 6 times higher than that in normal cervical epithelial cells, respectively, which explained why the threshold was reached. Furthermore, the stability of AgNPs in the serum of tumor-bearing mice decreased by 20% (P < 0.05) compared with the healthy mice. In conclusion, our study demonstrates that HeLa cells escaped the anti-cancer effect of AgNPs through the synergistic effect of AKG and GSH, suggesting the need to develop strategies to overcome this limitation.

Dietary Lactobacillus reuteri SL001 Improves Growth Performance, Health-Related Parameters, Intestinal Morphology and Microbiota of Broiler Chickens.

It was assumed that dietary inclusion of Lactobacillus reuteri SL001 isolated from the gastric contents of rabbits could act as an alternative to feed antibiotics to improve the growth performance of broiler chickens. We randomly assigned 360 one-day-old AA white-feathered chicks in three treatments: basal diet (control), basal diet plus zinc bacitracin (antibiotic), and basal diet plus L. reuteri SL001 (SL001) treatment. The results showed the total BW gain and average daily gain (ADG) of broilers in SL001 treatment increased significantly (p < 0.05, respectively) compared with the control group from day 0 to 42. Moreover, we observed higher levels of immune globulins in both the SL001 group and the antibiotic group. Total antioxidant capacity and levels of antioxidant factors were also significantly increased (p ≤ 0.05, respectively) in the SL001 treatment group, while the interleukin 6, interleukin 4, creatinine, uric acid, total cholesterol, triglyceride, VLDL, LDL and malondialdehyde were remarkably decreased (p < 0.05, respectively). In the ileum of SL001 treatment broilers, the height of villi and the ratio of villi height to crypt depth were significantly increased (p < 0.05). Meanwhile, the crypt depth reduced (p < 0.01) and the ratio of villi height to crypt depth increased (p < 0.05) in the jejunum compared to the control. The abundance of microbiota increased in the gut of broilers supplemented with SL001. Dietary SL001 significantly increased the relative abundance of Actinobacteria in the cecal contents of broilers (p < 0.01) at the phylum level. In conclusion, L. reuteri SL001 supplementation promotes the growth performance of broiler chickens and exhibits the potential application value in the industry of broiler feeding.

Serum protein coating enhances the antisepsis efficacy of silver nanoparticles against multidrug-resistant Escherichia coli infections in mice.

Antimicrobial resistance poses a significant threat to public health and social development worldwide. This study aimed to investigate the effectiveness of silver nanoparticles (AgNPs) in treating multidrug-resistant bacterial infections. Eco-friendly spherical AgNPs were synthesized using rutin at room temperature. The biocompatibility of both polyvinyl pyrrolidone (PVP) and mouse serum (MS)-stabilized AgNPs was evaluated at 20 µg/mL and showed a similar distribution in mice. However, only MS-AgNPs significantly protected mice from sepsis caused by the multidrug-resistant Escherichia coli (E. coli) CQ10 strain (p = 0.039). The data revealed that MS-AgNPs facilitated the elimination of Escherichia coli (E. coli) in the blood and the spleen, and the mice experienced only a mild inflammatory response, as interleukin-6, tumor necrosis factor-α, chemokine KC, and C-reactive protein levels were significantly lower than those in the control group. The results suggest that the plasma protein corona strengthens the antibacterial effect of AgNPs in vivo and may be a potential strategy for combating antimicrobial resistance.

Multi-omics reveals 2-bromo-4,6-dinitroaniline (BDNA)-induced hepatotoxicity and the role of the gut-liver axis in rats.

2-Bromo-4, 6-dinitroaniline (BDNA) is a widespread azo-dye-related hazardous pollutant. However, its reported adverse effects are limited to mutagenicity, genotoxicity, endocrine disruption, and reproductive toxicity. We systematically assessed the hepatotoxicity of BDNA exposure via pathological and biochemical examinations and explored the underlying mechanisms via integrative multi-omics analyses of the transcriptome, metabolome, and microbiome in rats. After 28 days of oral administration, compared with the control group, 100 mg/kg BDNA significantly triggered hepatotoxicity, upregulated toxicity indicators (e.g., HSI, ALT, and ARG1), and induced systemic inflammation (e.g., G-CSF, MIP-2, RANTES, and VEGF), dyslipidemia (e.g., TC and TG), and bile acid (BA) synthesis (e.g., CA, GCA, and GDCA). Transcriptomic and metabolomic analyses revealed broad perturbations in gene transcripts and metabolites involved in the representative pathways of liver inflammation (e.g., Hmox1, Spi1, L-methionine, valproic acid, and choline), steatosis (e.g., Nr0b2, Cyp1a1, Cyp1a2, Dusp1, Plin3, arachidonic acid, linoleic acid, and palmitic acid), and cholestasis (e.g., FXR/Nr1h4, Cdkn1a, Cyp7a1, and bilirubin). Microbiome analysis revealed reduced relative abundances of beneficial gut microbial taxa (e.g., Ruminococcaceae and Akkermansia muciniphila), which further contributed to the inflammatory response, lipid accumulation, and BA synthesis in the enterohepatic circulation. The observed effect concentrations here were comparable to the highly contaminated wastewaters, showcasing BDNA's hepatotoxic effects at environmentally relevant concentrations. These results shed light on the biomolecular mechanism and important role of the gut-liver axis underpinning BDNA-induced cholestatic liver disorders in vivo.

Systems-level analysis of Escherichia coli response to silver nanoparticles: the roles of anaerobic respiration in microbial resistance.

Despite extensive use of silver nanoparticles for antimicrobial applications, cellular mechanisms underlying microbial response to silver nanoparticles remain to be further elucidated at the systems level. Here, we report systems-level response of Escherichia coli to silver nanoparticles using transcriptome-based biochemical and phenotype assays. Notably, we provided the evidence that anaerobic respiration is induced upon exposure to silver nanoparticles. Further we showed that anaerobic respiration-related regulators and enzymes play an important role in E. coli resistance to silver nanoparticles. In particular, our results suggest that arcA is essential for resistance against silver NPs and the deletion of fnr, fdnH and narH significantly increases the resistance. We envision that this study offers novel insights into modes of antimicrobial action of silver nanoparticles, and cellular mechanisms contributing to the development of microbial resistance to silver nanoparticles.

[Influence of Lactobacillus reuteri SL001 on intestinal microbiota in AD model mice and C57BL/6 mice].

We studied the influence of Lactobacillus reuteri SL001 (L. reuteri SL001) on the gut microbial community in Alzheimer's disease model mice (APP/PS1 double transgenic mice, ADmice) and wild type (C57BL/6) mice. The AD model mice and wild type mice were divided into test and control groups (4 in total), with 5 mice each and only male mice. The test group was fed with 0.2 mL suspension of L. reuteri SL001 at 5×10¹¹ CFU/mL. The control group received the same amount of sterile PBS daily for 45 days. Fecal samples were collected to compare and analyze the community structure and diversity of microbiota through high-throughput sequencing of the V3-V4 region of 16S rRNA gene. By sequence alignment and classification, the intestinal microbial OTUs of the 4 groups including 19 phyla, 40 classes, 64 orders, 104 families and 175 genera. The α diversity of AD model mice was greater than that of wild type mice, but the difference between the two was small. After adding L. reuteri SL001, the α diversity of both mice increased, and the increase in AD model mice was smaller. At the phyla level, the dominant phyla of the four groups of mice were Bacteroidetes, Firmicutes and Proteobacteria. The abundance of Bacteroides phylum in AD model mice was lower than that of wild type, and the abundance of chlamydomonas was higher than that of wild type. Feeding L. reuteri SL001 reduced the proportion of Firmicutes/Bacteroidetes (F/B) in mice. At the order level, the relative abundance of Bacteroidales, Lactobacillales, Bacillales and Bifidobacteriales in AD model mice was lower than that of wild type mice. At the genus level, the abundant genera were Allobaculum, Lachnospiraceae_NK4A136_group, Bacteroides and Lactobacillus. The relative abundance of Bacteroides, Lactobacillus, Bifidobacterium and Alloprevotella in AD model mice was lower than that in wild type mice. Adding L. reuteri SL001 increased the abundance of these genera and Bacteroides, Lactobacillus, Bacillus and Bifidobacteria in AD model mice. The relative abundance of Butyrivibrio in AD model mice was also lower than that in wild type, but after the feeding of L. reuteri SL001, the relative abundance was reduced in both mice. The dominant strains of wild-type mice were Lactobacillus, and no dominant flora was found in AD model mice. The results in this article provide valuable data for revealing the difference in intestinal microbial diversity between AD model mice and C57BL/6 mice, and feeding L. reuteri SL001 play positive roles in adjusting the intestinal bacterial community structure of AD model mice.

[Biological profiles of recombinant Suilysin].

OBJECTIVE: To provide insights into the role of Suilysin in the pathogenesis of Streptococcus suis by analysing the biological profiles of recombinant Suilysin (rSLY). METHODS: sly gene of S. suis strain SC22 was cloned into pET30a(+) vector and overexpressed in E. coli Rosseta, and rSLY was purified with Ni2+ affinity chromatography, anion exchange chromatography and gel filtration. The hemolytic unit of rSLY was measured with human red blood cells. The cellular toxicity of rSLY to human peripheral white blood cell and cells derived from fetal heart (HEH), liver (HEL), kidney (HEK), lung (HPL) was detected by lactate dehydrogenase (LDH) release assay. The blocking effects of water-soluble cholesterol, serum and specific antibody on the hemolytic activity of rSLY were detected. The amount of proinflammatory cytokines in the serum of mice stimulated by rSLY was measured by Luminex-100. RESULTS: The hemolytic unit of rSLY was 0.125 nmol/L, but the cellular toxicity of 1 nmol/L rSLY to human peripheral white blood cell, HEH, HEL, HEK and HPF was 20%-25%. The hemolytic activity of rSLY was blocked completely by equal molar of water-soluble cholesterol. Human serum containing 2.8 mmol/L-5.7 mmol/L of cholesterol in physical condition, could merely blocked 1 nmol/L of rSLY to lyse erythrocytes. The human serum with the addition of rabbit anti-rSLY IgG to a final concentration of 15 mg/ml decreased the hemolysis by 10 nmol/L rSLY from 77% down to 5% successfully, but hemolysis remained 60% when tested with 100 nmol/L rSLY. Although IL-1 beta and TNF-alpha didn't display any observable change, the level of interleukin -6 (IL-6) and KC were increased continually in C57BL/6 mice injected intraperitoneumly with rSLY whereas the IL-6 and KC level of mice in the control group only increased slightly and quickly decreased. CONCLUSION: The data suggest that rSLY could not only lyse cells but also induce strong inflammatory response and damage immune cells recruited to the sites of inflammation. This finding implies that serum could provide light protection against rSLY, and specific antibody show a concentration-dependent protection.

Characterization of synergistic antibacterial effect of silver nanoparticles and ebselen.

The emerging and spreading of multi-drug resistant (MDR) bacteria have been becoming one of the most severe threats to human health. Enhancing oxidative stress as mimicking immune system was considered as a potential strategy to fight against infection of MDR bacteria. In this study, we investigated the antibacterial efficiency of such a strategy which combines silver nanoparticles (AgNPs) with ebselen. The results showed that AgNPs and ebselen combination had significant synergistic killing effects both on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in vitro, including model strains of China Veterinary Culture Collection and MDR clinical isolates, which is similar as the combination of silver ion and ebselen. AgNPs exhibited to be a strong inhibitor of bacterial thioredoxin reductase, same as a free silver ion. Ebselen mitigated the cytotoxicity of AgNPs to HeLa cells. However, in a bacteria-cell coexistence condition, the synergistic bactericidal effect was only observed on S. aureus (p<.05), while the temporary synergistic inhibitory effect on E. coli within 4 hours treatment (p<.01). In mice infection model, a combination of AgNPs and ebselen did not increase protection against the challenge of clinical E. coli CQ10 strain. Our data demonstrated that AgNPs and ebselen combination may be a promising strategy to fight against the increasingly MDR bacteria targeting bacterial thiol redox system.

Spread of Streptococcus suis sequence type 7, China.

Streptococcus suis sequence type (ST) 7 has been spreading throughout China. To determine events associated with its emergence, we tested 114 isolates. In all 106 ST7 strains responsible for human outbreaks and sporadic infections, the tetracycline-resistance gene, tetM, was detected on the conjugative transposon Tn916. Horizontal transmission of tetM is suspected.

Health implications of engineered nanoparticles in infants and children.

BACKGROUND: The nanotechnology boom and the ability to manufacture novel nanomaterials have led to increased production and use of engineered nanoparticles (ENPs). However, the increased use of various ENPs inevitably results in their release in or the contamination of the environment, which poses significant threats to human health. In recent years, extraordinary economic and societal benefits of nanoproducts as well as their potential risks have been observed and widely debated. To estimate whether ENPs are safe from the onset of their manufacturing to their disposal, evaluation of the toxicological effects of ENPs on human exposure, especially on more sensitive and vulnerable sectors of the population (infants and children) is essential. DATA SOURCES: Papers were obtained from PubMed, Web of Science, and Google Scholar. Literature search words included: "nanoparticles", "infants", "children", "exposure", "toxicity", and all relevant cross-references. RESULTS: A brief overview was conducted to 1) characterize potential exposure routes of ENPs for infants and children; 2) describe the vulnerability and particular needs of infants and children about ENPs exposure; 3) investigate the current knowledge about the potential health hazards of ENPs; and 4) provide suggestions for future research and regulations in ENP applications. CONCLUSIONS: As the manufacturing and use of ENPs become more widespread, directed and focused studies are necessary to measure actual exposure levels and to determine adverse health consequences in infants and children.

Neuropilin 1 is an entry factor that promotes EBV infection of nasopharyngeal epithelial cells.

Epstein-Barr virus (EBV) is implicated as an aetiological factor in B lymphomas and nasopharyngeal carcinoma. The mechanisms of cell-free EBV infection of nasopharyngeal epithelial cells remain elusive. EBV glycoprotein B (gB) is the critical fusion protein for infection of both B and epithelial cells, and determines EBV susceptibility of non-B cells. Here we show that neuropilin 1 (NRP1) directly interacts with EBV gB(23-431). Either knockdown of NRP1 or pretreatment of EBV with soluble NRP1 suppresses EBV infection. Upregulation of NRP1 by overexpression or EGF treatment enhances EBV infection. However, NRP2, the homologue of NRP1, impairs EBV infection. EBV enters nasopharyngeal epithelial cells through NRP1-facilitated internalization and fusion, and through macropinocytosis and lipid raft-dependent endocytosis. NRP1 partially mediates EBV-activated EGFR/RAS/ERK signalling, and NRP1-dependent receptor tyrosine kinase (RTK) signalling promotes EBV infection. Taken together, NRP1 is identified as an EBV entry factor that cooperatively activates RTK signalling, which subsequently promotes EBV infection in nasopharyngeal epithelial cells.

The genetically modified suilysin, rSLY(P353L), provides a candidate vaccine that suppresses proinflammatory response and reduces fatality following infection with Streptococcus suis.

Streptococcus suis is a persistent global hazard in the swine industry and an emerging threat to public health. The high mortality in China following outbreaks of streptococcal toxic shock syndrome (STSS) underscores the urgency for effective prevention. A limited understanding of the pathogenesis of S. suis in STSS may explain the lack of biological products for prevention. Suilysin (SLY) is an important virulence factor in the pathogenesis of S. suis. To identify a candidate vaccine for S. suis-induced STSS, we constructed a recombinant non-hemolytic mutant of SLY that has hemagglutination activity, rSLY(P353L), and evaluated its ability to induce inflammatory response and prevent fatal S. suis infection in mice. The rSLY(P353L) mutant, as compared with hemolytic rSLY, elicited lower levels of IL-6, KC and IL-10 at 3h and 5h post-treatment (p<0.05), indicating that hemolytic activity is associated with rSLY-mediated inflammation. Furthermore, passive immunization with anti-SLY(P353L) antisera protected mice from acute death after infection with S. suis SC84 (p<0.05). Effects were not due to protection against tissue damage, as S. suis SC84 caused no detectable histopathological lesions in mice within 24h. However, immunization with rSLY(P353L) caused significantly reduced levels of KC and IL-1ß at 6 and 9h post-challenge and IL-6 at 9h post-challenge (p<0.05). In conclusion, rSLY(P353L) may provide a potential vaccine for protection against S. suis-induced STSS due to its reduction in proinflammatory response early in S. suis infection.

High Refractive Index Inorganic-Organic Interpenetrating Polymer Network (IPN) Hydrogel Nanocomposite toward Artificial Cornea Implants.

The use of artificial cornea implants has received increasing attention for treating cornea-related diseases and vision errors due to the low side effects. To achieve long-term successful vision correction, stable and biocompatible materials of high refractive index (RI) need to be developed. Herein, we developed an interpenetrating polymer network (IPN) hydrogel containing well-dispersed ZnS nanoparticles (∼3 nm) covalently linked to the first polymer network, poly(2-hydroethyl methacrylate) (PHEMA). The second polymer network used was poly(acrylic acid) (PAA). The resultant ZnS/PHEMA/PAA IPN nanocomposite is clear and transparent at both dry and hydrated states with their RIs measured to be as high as 1.65 and 1.49, respectively. The equilibrium water content of the hydrogel nanocomposite reached 60.2% which is reasonably near to that of cornea. The material exerted minimal cytotoxicity toward primary epidermal keratinocyte cells. The high RI IPN hydrogel nanocomposite developed here might be an excellent candidate for artificial cornea implants.

Crystal structure of cytotoxin protein suilysin from Streptococcus suis.

Cholesterol-dependent cytolysins (CDC) are pore forming toxins. A prototype of the CDC family members is perfringolysin O (PFO), which directly binds to the cell membrane enriched in cholesterol, causing cell lysis. However, an exception of this general observation is intermedilysin (ILY) of Streptococcus intermedius, which requires human CD59 as a receptor in addition to cholesterol for its hemolytic activity. A possible explanation of this functional difference is the conformational variation between the C-terminal domains of the two toxins, particularly in the highly conserved undecapeptide termed tryptophan rich motif. Here, we present the crystal structure of suilysin, a CDC toxin from the infectious swine pathogen Streptococcus suis. Like PFO, suilysin does not require a host receptor for hemolytic activity; yet the crystal structure of suilysin exhibits a similar conformation in the tryptophan rich motif to ILY. This observation suggests that the current view of the structure-function relationship between CDC proteins and membrane association is far from complete.

Clinical, experimental, and genomic differences between intermediately pathogenic, highly pathogenic, and epidemic Streptococcus suis.

BACKGROUND: Streptococcus suis emerged to cause an unusual outbreak of streptococcal toxic-shock-like syndrome (STSLS) in 2005. The mechanisms involved are unknown. METHODS: Clinical, laboratory, and epidemiologic data on patients infected with culture-confirmed S. suis were analyzed. The strain involved in the outbreak, "epidemic" strain ST7, was compared with both a classical highly pathogenic strain, ST1, and an intermediately pathogenic strain, ST25, to determine both its capacity to induce cytokines in experimentally infected mice and its genomic difference. RESULTS: Of 38 patients infected with culture-confirmed S. suis, 14 presented with STSLS. During the early phase of the disease, serum levels of interleukin (IL)-1beta, IL-6, IL-8, IL-12p70, interferon-gamma, and tumor necrosis factor-alpha were more elevated in patients with STSLS than in those with meningitis only. Serum levels of proinflammatory cytokines were significantly higher in mice infected with ST7 than in those infected with either ST1 or ST25. Genomic comparisons with ST25 showed that ST1 had acquired 132 genomic islands, including 5 pathogenicity islands, and that ST7, the epidemic strain, had acquired an additional 5 genomic islands. CONCLUSION: Intermediately pathogenic strain ST25 has evolved to become highly pathogenic strain ST1, which, in turn, has more recently evolved to become epidemic strain ST7. ST7 has the ability to stimulate the production of massive amounts of proinflammatory cytokines, leading to STSLS.

[Development of a protocol on pulsed field gel electrophoresis analysis for Streptococcus suis].

OBJECTIVE: To develop a PFGE protocol for Streptococcus suis. METHODS: We developed and optimized a PFGE protocol for S. suis, in terms of plug preparation, choice of restriction endonucleases and optimized electrophoresis parameters. By analyzing the genome sequences of S. suis P1/7 with Mapdraw of DNAStar, we found three restriction enzymes, Swa I, Sma I and Apa I, were more suitable than others. RESULTS: Analysis of 100 isolates of S. suis including 34 of 35 serotypes identified, 59, 53 and 43 patterns were obtained from Swa I, Sma I and Apa I restriction, respectively. The enzyme Swa I had the greatest power for discrimination ability. CONCLUSION: By optimization of the protocol at various conditions, a rapid, reproducible, economic and practical PFGE method for S. suis was developed.

Streptococcus suis sequence type 7 outbreak, Sichuan, China.

An outbreak of Streptococcus suis serotype 2 emerged in the summer of 2005 in Sichuan Province, and sporadic infections occurred in 4 additional provinces of China. In total, 99 S. suis strains were isolated and analyzed in this study: 88 isolates from human patients and 11 from diseased pigs. We defined 98 of 99 isolates as pulse type I by using pulsed-field gel electrophoresis analysis of SmaI-digested chromosomal DNA. Furthermore, multilocus sequence typing classified 97 of 98 members of the pulse type I in the same sequence type (ST), ST-7. Isolates of ST-7 were more toxic to peripheral blood mononuclear cells than ST-1 strains. S. suis ST-7, the causative agent, was a single-locus variant of ST-1 with increased virulence. These findings strongly suggest that ST-7 is an emerging, highly virulent S. suis clone that caused the largest S. suis outbreak ever described.