Discovery of a novel antibacterial protein CB6-C to target methicillin-resistant Staphylococcus aureus

Given a serious threat of multidrug-resistant bacterial pathogens to global healthcare, there is an urgent need to find effective antibacterial compounds to treat drug-resistant bacterial infections. In our previous studies, Bacillus velezensis CB6 with broad-spectrum antibacterial activity was obtained from the soil of Changbaishan, China. In this study, with methicillin-resistant Staphylococcus aureus as an indicator bacterium, an antibacterial protein was purified by ammonium sulfate precipitation, Sephadex G-75 column, QAE-Sephadex A 25 column and RP-HPLC, which demonstrated a molecular weight of 31.405 kDa by SDS-PAGE. LC–MS/MS analysis indicated that the compound was an antibacterial protein CB6-C, which had 88.5% identity with chitosanase (Csn) produced by Bacillus subtilis 168. An antibacterial protein CB6-C showed an effective antimicrobial activity against gram-positive bacteria (in particular, the MIC for MRSA was 16 μg/mL), low toxicity, thermostability, stability in different organic reagents and pH values, and an additive effect with conventionally used antibiotics. Mechanistic studies showed that an antibacterial protein CB6-C exerted anti-MRSA activity through destruction of lipoteichoic acid (LTA) on the cell wall. In addition, an antibacterial protein CB6-C was efficient in preventing MRSA infections in in vivo models. In conclusion, this protein CB6-C is a newly discovered antibacterial protein and has the potential to become an effective antibacterial agent due to its high therapeutic index, safety, nontoxicity and great stability.

Therapeutic Role of miR-30a in Lipoteichoic Acid-Induced Endometritis via Targeting the MyD88/Nox2/ROS Signaling

Staphylococcus aureus (S. aureus), a notorious pathogenic bacterium prevalent in the environment, causes a wide range of inflammatory diseases such as endometritis. Endometritis is an inflammatory disease in humans and mammals, which prolongs uterine involution and causes great economic losses. MiR-30a plays an importan trole in the process of inflammation; however, the regulatory role of miR-30a in endometritis is still unknown. Here, we first noticed that there was an increased level of miR-30a in uterine samples of cows with endometritis. And then, bovine endometrial epithelial (BEND) cells stimulated with the virulence factor lipoteichoic acid (LTA) from S. aureus were used as an in vitro endometritis model to explore the potential role of miR-30a in the pathogenesis of endometritis. Our data showed that the induction of the miR-30a expression is dependent on NF-κB activation, and its overexpression significantly decreased the levels of IL-1β and IL-6. Furthermore, we observed that the overexpression of miR-30a inhibited its translation by binding to 3 ′ − UTR of MyD88 mRNA, thus preventing the activation of Nox2 and NF-κB and ROS accumulation. Meanwhile, in vivo studies further revealed that upregulation of miR-30a using chemically synthesized agomirs alleviates the inflammatory conditions in an experimental mouse model of endometritis, as indicated by inhibition of ROS and NF-κB. Taken together, these findings highlight that miR-30a can attenuate LTA-elicited oxidative stress and inflammatory responses through the MyD88/Nox2/ROS/NF-κB pathway and may aid the future development of novel therapies for inflammatory diseases caused by S. aureus, including endometritis.

Bacterial culture and immunohistochemical detection of bacteria and endotoxin in cats with suppurative cholangitis-cholangiohepatitis syndrome

OBJECTIVE To characterize the frequency and type of bacterial infection by culture- and immunohistochemical (IHC)-based methods and determine the impact of infection on clinical features and survival time in cats with suppurative cholangitis-cholangiohepatitis syndrome (S-CCHS). ANIMALS 168 client-owned cats with S-CCHS (cases). PROCEDURES Clinical features, bacterial culture results, culture-inoculate sources, and survival details were recorded. Cases were subcategorized by comorbidity (extrahepatic bile duct obstruction, cholelithiasis, cholecystitis, ductal plate malformation, biopsy-confirmed inflammatory bowel disease, and biopsy-confirmed pancreatitis) or treatment by cholecystectomy or cholecystoenterostomy. Culture results, bacterial isolates, Gram-stain characteristics, and IHC staining were compared among comorbidities. Lipoteichoic acid IHC staining detected gram-positive bacterial cell wall components, and toll-like receptor expression IHC reflected pathologic endotoxin (gram-negative bacteria) exposure. RESULTS Clinical features were similar among cases except for more frequent abdominal pain and lethargy in cats with positive culture results and pyrexia, abdominal pain, and hepatomegaly for cats with polymicrobial infections. Bacteria were cultured in 93 of 135 (69%) cats, with common isolates including Enterococcus spp and Escherichia coli. IHC staining was positive in 142 of 151 (94%) cats (lipoteichoic acid, 107/142 [75%]; toll-like receptor 4, 99/142 [70%]). With in-parallel interpretation of culture and IHC-based bacterial detection, 154 of 166 (93%) cats had bacterial infections (gram-positive, 118/154 [77%]; gram-negative, 111/154 [72%]; polymicrobial, 79/154 [51%]). Greater frequency of bacterial isolation occurred with combined tissue, bile, and crushed cholelith inoculates. Infection and gram-positive bacterial isolates were associated with significantly shorter long-term survival times. CLINICAL RELEVANCE S-CCHS was associated with bacterial infection, pathologic endotoxin exposure, and frequent polymicrobial infection in cats. Combined tissue inoculates improved culture detection of associated bacteria.

Gram-Positive Staphylococcus aureus LTA Promotes Distinct Memory-like Effects in Murine Bone Marrow Neutrophils

Neutrophils as innate immune cells primarily act as first responders in acute infection and directly maintain inflammatory responses. However, a growing body of evidence suggests that neutrophils also bear the potential to mediate chronic inflammation by exhibiting memory-like features. We recently showed that priming by serial doses of lipopolysaccharide (LPS) from gram-negative bacteria can trigger opposing memory-like responses (exaggerated inflammation, i.e. trained sensitivity or suppression of inflammation, i.e. tolerance) depending on the LPS-dose. We now asked whether this observation could also hold true for lipoteichoic acid (LTA) from gram-positive S. aureus. We found comparable effects of LTA on neutrophil priming as seen for LPS. Low-dose (1 ng/mL) LTA-priming promoted increased production of pro-inflammatory mediators (i.e., TNF-α, IL-6, ROS), whereas high-dose (10 µg/mL) results in contrary reactions supporting anti-inflammatory responses by increased IL-10 and declined pro-inflammatory capacity. In vitro neutrophil recruitment was similarly regulated by LTA -priming. Investigation of signalling patterns revealed TLR2/MyD88-mediated regulation of NFκB-p65 through intermediate PI3Ks/MAPK. Collectively, our data suggest a previously unknown capacity of neutrophils to be differentially primed by varying doses of LTA, endorsing memory-like features in neutrophils.

Heat-Killed Lactobacilli Preparations Promote Healing in the Experimental Cutaneous Wounds

Probiotics are defined as microorganisms with beneficial health effects when consumed by humans, being applied mainly to improve allergic or intestinal diseases. Due to the increasing resistance of pathogens to antibiotics, the abuse of antibiotics becomes inefficient in the skin and in systemic infections, and probiotics may also provide the protective effect for repairing the healing of infected cutaneous wounds. Here we selected two Lactobacillus strains, L. plantarum GMNL-6 and L. paracasei GMNL-653, in heat-killed format to examine the beneficial effect in skin wound repair through the selection by promoting collagen synthesis in Hs68 fibroblast cells. The coverage of gels containing heat-killed GMNL-6 or GMNL-653 on the mouse tail with experimental wounds displayed healing promoting effects with promoting of metalloproteinase-1 expression at the early phase and reduced excessive fibrosis accumulation and deposition in the later tail-skin recovery stage. More importantly, lipoteichoic acid, the major component of Lactobacillus cell wall, from GMNL-6/GMNL-653 could achieve the anti-fibrogenic benefit similar to the heat-killed bacteria cells in the TGF-β stimulated Hs68 fibroblast cell model. Our study offers a new therapeutic potential of the heat-killed format of Lactobacillus as an alternative approach to treating skin healing disorders.

Lactobacillus plantarum Lipoteichoic Acids Possess Strain-Specific Regulatory Effects on the Biofilm Formation of Dental Pathogenic Bacteria

Bacterial biofilm residing in the oral cavity is closely related to the initiation and persistence of various dental diseases. Previously, we reported the anti-biofilm activity of Lactobacillus plantarum lipoteichoic acid (Lp.LTA) on a representative dental cariogenic pathogen, Streptococcus mutans. Since LTA structure varies in a bacterial strain-specific manner, LTAs from various L. plantarum strains may have differential anti-biofilm activity due to their distinct molecular structures. In the present study, we isolated Lp.LTAs from four different strains of L. plantarum (LRCC 5193, 5194, 5195, and 5310) and compared their anti-biofilm effects on the dental pathogens, including S. mutans, Enterococcus faecalis, and Streptococcus gordonii. All Lp.LTAs similarly inhibited E. faecalis biofilm formation in a dose-dependent manner. However, their effects on S. gordonii and S. mutans biofilm formation were different: LRCC 5310 Lp.LTA most effectively suppressed the biofilm formation of all strains of dental pathogens, while Lp.LTAs from LRCC 5193 and 5194 hardly inhibited or even enhanced the biofilm formation. Furthermore, LRCC 5310 Lp.LTA dramatically reduced the biofilm formation of the dental pathogens on the human dentin slice infection model. Collectively, these results suggest that Lp.LTAs have strain-specific regulatory effects on biofilm formation of dental pathogens and LRCC 5310 Lp.LTA can be used as an effective anti-biofilm agent for the prevention of dental infectious diseases.

Purification, Characterisation and Synthesis of Glycerolipids Extracted from L. plantarum and B. longum subsp. infantis

<p>Glycolipids from the cell wall of Gram-positive bacteria have been the topic of my PhD. It is well known that many bacterial glycolipids (e.g. LPS, TDMs and PIMs) have profound immunological effects, and therefore the characterisation, biological testing and synthesis of gram-positive bacterial glycolipids is of interest. The first part of this thesis includes a description of the extraction and characterisation of glycolipids from gut bacteria including Bifidobacterium and Lactobacillus genus and the second part focussed on the chemical synthesis of Streptococcus sp. DSM 8747 glycolipids and lipoteichoic acid analogues (LTA). Members of the genus Lactobacillus are common in the gut microbiota and are often used as probiotics. As lactobacilli are known to have benefits to human health, compounds on its surface are of high interest. To date, the structures of the glycolipids from L. plantarum have not been conclusively assigned. Thus, for the first time, the full characterisation of the four principal glycolipids of the L. plantarum cell wall was reported using sugar, linkage and FAME analysis, as well as ESI-MS/MS and 1D- and 2D-NMR spectroscopy. The major glycolipids were identified as: α-D-Glcp-diglyceride, α-D-Galp-(1→2)-α-D-Glcp-diglyceride, β-D-Glcp-(1→6)-α-D-Galp-(1→2)-6-O-acyl-α-D-Glcp-diglyceride and β-D-Glcp-(1→6)-α-D-Galp-(1→2)-α-D-Glcp-diglyceride. These glycolipids showed weak activation of murine bone marrow macrophages in an initial biological screen. After having identified the structures of the glycolipids from L. plantarum, the glycolipids from Bifidobacterium, a dominant member of the gut microbiota in infants, were extracted. Bifidobacteria are considered to be important in the development of a healthy immune system and they are believed to exhibit anticancerous properties, alleviate the symptoms of irritable bowel syndrome, and are thought to reduce atopic disease. Despite this, the chemical nature of immunomodulatory compounds on the surface of bifidobacteria has not been well documented. Thus, glycolipids were extracted from B. longum subsp. infantis, fractionated chromatographically and analyzed using NMR spectroscopy, constituent sugar and linkage analysis, and fatty acid analysis. These analyzes revealed a novel glycolipid, containing an unprecedented mixed acetal moiety and a galactofuranose moiety as a head group. However, like L. plantarum glycolipids, bifidobacterial glycolipids were shown only to induce little macrophage activity when tested. Having successfully characterised a novel glycolipid present in bifidobacteria, analogues of this glycolipid as well as poly(glycerophosphate) lipotechoic acids analogues (LTAs) were then synthesised. Much debate still remains about the role of LTAs during Gram-positive bacterial infection. This is partly due to differences in the biological activities of extracted versus synthesised LTAs and highlights the need for structurally defined non-contaminated LTAs when investigating the effect of these glycolipids on the innate immune response. An efficient synthesis of the core lipoteichoic acid (LTA) anchor of the Streptococcus species DSM 8747, and derivatives thereof, was achieved. These Streptococcus glycolipids contain a galactofuranose moiety and thus have similarities to the novel glycolipid that was found in bifidobacteria. The syntheses, which commence with readily available D-galactose, are short (7-9 steps), convergent, and high-yielding (33-37% overall yield). In total 11 different targets were synthesised. The biological activity of these compounds was also investigated, with several analogues (particularly the sn-1,2-di-acylglycerol LTA anchors) found to induce macrophage activation.</p>

Purification, Characterisation and Synthesis of Glycerolipids Extracted from L. plantarum and B. longum subsp. infantis

<p>Glycolipids from the cell wall of Gram-positive bacteria have been the topic of my PhD. It is well known that many bacterial glycolipids (e.g. LPS, TDMs and PIMs) have profound immunological effects, and therefore the characterisation, biological testing and synthesis of gram-positive bacterial glycolipids is of interest. The first part of this thesis includes a description of the extraction and characterisation of glycolipids from gut bacteria including Bifidobacterium and Lactobacillus genus and the second part focussed on the chemical synthesis of Streptococcus sp. DSM 8747 glycolipids and lipoteichoic acid analogues (LTA). Members of the genus Lactobacillus are common in the gut microbiota and are often used as probiotics. As lactobacilli are known to have benefits to human health, compounds on its surface are of high interest. To date, the structures of the glycolipids from L. plantarum have not been conclusively assigned. Thus, for the first time, the full characterisation of the four principal glycolipids of the L. plantarum cell wall was reported using sugar, linkage and FAME analysis, as well as ESI-MS/MS and 1D- and 2D-NMR spectroscopy. The major glycolipids were identified as: α-D-Glcp-diglyceride, α-D-Galp-(1→2)-α-D-Glcp-diglyceride, β-D-Glcp-(1→6)-α-D-Galp-(1→2)-6-O-acyl-α-D-Glcp-diglyceride and β-D-Glcp-(1→6)-α-D-Galp-(1→2)-α-D-Glcp-diglyceride. These glycolipids showed weak activation of murine bone marrow macrophages in an initial biological screen. After having identified the structures of the glycolipids from L. plantarum, the glycolipids from Bifidobacterium, a dominant member of the gut microbiota in infants, were extracted. Bifidobacteria are considered to be important in the development of a healthy immune system and they are believed to exhibit anticancerous properties, alleviate the symptoms of irritable bowel syndrome, and are thought to reduce atopic disease. Despite this, the chemical nature of immunomodulatory compounds on the surface of bifidobacteria has not been well documented. Thus, glycolipids were extracted from B. longum subsp. infantis, fractionated chromatographically and analyzed using NMR spectroscopy, constituent sugar and linkage analysis, and fatty acid analysis. These analyzes revealed a novel glycolipid, containing an unprecedented mixed acetal moiety and a galactofuranose moiety as a head group. However, like L. plantarum glycolipids, bifidobacterial glycolipids were shown only to induce little macrophage activity when tested. Having successfully characterised a novel glycolipid present in bifidobacteria, analogues of this glycolipid as well as poly(glycerophosphate) lipotechoic acids analogues (LTAs) were then synthesised. Much debate still remains about the role of LTAs during Gram-positive bacterial infection. This is partly due to differences in the biological activities of extracted versus synthesised LTAs and highlights the need for structurally defined non-contaminated LTAs when investigating the effect of these glycolipids on the innate immune response. An efficient synthesis of the core lipoteichoic acid (LTA) anchor of the Streptococcus species DSM 8747, and derivatives thereof, was achieved. These Streptococcus glycolipids contain a galactofuranose moiety and thus have similarities to the novel glycolipid that was found in bifidobacteria. The syntheses, which commence with readily available D-galactose, are short (7-9 steps), convergent, and high-yielding (33-37% overall yield). In total 11 different targets were synthesised. The biological activity of these compounds was also investigated, with several analogues (particularly the sn-1,2-di-acylglycerol LTA anchors) found to induce macrophage activation.</p>