Invasive phenotype and apoptosis induction of Plesiomonas shigelloides P-1 strain to Caco-2 cells

Circumventing aglycon transfer en route to the synthesis of pentasaccharide thioglycoside donor for the chain extension of Plesiomonas shigelloides strain 302-73 (serotype O1) repeating unit

Herein we report a chemical synthesis of a pentasaccharide thioglycoside repeating unit of Plesiomonas shigelloides Strain 302-73 (Serotype O1), as a chain extension unit. In our synthetic endeavor we encountered multiple aglycon transfer reactions during glycosylations. This problem was obviated by employing a PMP group as a transient protecting group.

Total Synthesis of the All-Rare Sugar-Containing Pentasaccharide Repeating Unit of the O-Polysaccharide of Plesiomonas shigelloides Strain 302-73 (Serotype O1)

First total synthesis of the conjugation-ready pentasaccharide repeating unit of Plesiomonas shigelloides strain 302-73 (serotype O1) is reported. The complex target pentasaccharide is composed of all-rare amino sugars such as orthogonally functionalized d-bacillosamine, l-fucosamine, and l-pneumosamine linked through four consecutive α-linkages. The poor nucleophilicity of axial 4-OH of l-fucosamine and stereoselective glycosylations are the key challenges in the total synthesis, which was completed via a longest linear sequence of 27 steps in 3% overall yield.

pH-sensitive dual drug loaded janus nanoparticles by oral delivery for multimodal analgesia

Background

Based on the concept of “multimodal analgesia”, a novel dual drug delivery system was designed to achieve synergistic analgesia between najanajaatra venom protein (αCT) and resveratrol (Res). In order to meet the joint loading of two drugs with different physicochemical properties without affecting each other, an oral Janus nanoparticle (JNP) with a unique cavity structure and synergistic drug delivery was constructed using an improved double emulsion solvent evaporation method, and combined with low-molecular-weight chitosan/sodium alginate and PLGA to achieve its pH-responsive.

Results

The synthesized αCT/Res-JNPs are homogeneous in shape, with a two-compartment structure, approximately 230 nm in size, and zeta potential of 23.6 mV. Drug release assayed in vitro show that JNP was stable in simulated gastric juice (pH = 1.2) but was released in phosphate buffer saline (pH = 7.4). After intragastric administration in rats, PK evaluation showed that αCT/Res-JNPs could significantly improve the oral bioavailability, and the simultaneous encapsulation of the two drugs had no significant interaction on PK parameters. An obvious synergistic analgesic effects of αCT/Res-JNPs was confirmed in a spinal cord injury and acute pain model. Confocal laser scanning microscopy and single-pass intestinal perfusion model provided strong evidence that αCT/Res-JNPs could pass through intestinal epithelial cells, and the endocytosis pathway was mainly involved in the mediation and pinocytosis of reticulin. The concentrations of αCT and Res from αCT/Res-JNP in lymphatic transport were only about 8.72% and 6.08% of their blood concentrations at 1 h, respectively, which indicated that lymphatic transport in the form of JNP has limited advantages in improving the oral bioavailability of Res and αCT. Cellular uptake efficiency at 4 h was about 10–15% in Caco-2 cell lines for αCT/Res-JNP, but was reduced to 7% in Caco-2/HT29-MTX co-culture models due to the hindrance by the mucus layers. Approximately 12–17% of αCT/Res-JNP were transported across Caco-2/HT29-MTX/Raji monolayers. The cumulative absorption of JNP in three cell models was higher than that of free drug.

Conclusions

This study investigated the contribution of Janus nanoparticles in oral absorption, and provide a new perspective for oral administration and analgesic treatment of dual drug delivery system containing peptide drugs.

Graphic Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00974-6.

Severe cellulitis and bacteremia caused by Plesiomonas shigelloides following a traumatic freshwater injury

Plesiomonas shigelloides is a gram-negative bacillus that most commonly causes self-limited diarrhea in humans. Extraintestinal manifestations of P. shigelloides, including skin and soft tissue infections, are extremely uncommon. We present a case of severe cellulitis and bacteremia in an 80-year-old female caused by Plesiomonas shigelloides following a traumatic freshwater injury in Michigan, USA

Pathogenomics of Virulence Traits of Plesiomonas shigelloides That Were Deemed Inconclusive by Traditional Experimental Approaches

One of the major challenges of modern medicine includes the failure of conventional protocols to characterize the pathogenicity of emerging pathogens. This is particularly apparent in the case of Plesiomonas shigelloides. Although a number of infections have been linked to this microorganism, experimental evidence of its virulence factors (VFs), obtained by traditional approaches, is somewhat inconclusive. Hence, it remains unclear whether P. shigelloides is a true or opportunistic one. In the current study, four publicly available whole-genome sequences of P. shigelloides (GN7, NCTC10360, 302-73, and LS1) were profiled using bioinformatics platforms to determine the putative candidate VFs to characterize the bacterial pathogenicity. Overall, 134 unique open reading frames (ORFs) were identified that were homologous or orthologous to virulence genes identified in other pathogens. Of these, 52.24% (70/134) were jointly shared by the strains. The numbers of strain-specific virulence traits were 4 in LS1; 7 in NCTC10360; 10 in 302-73; and 15 in GN7. The pathogenicity islands (PAIs) common to all the strains accounted for 24.07% ORFs. The numbers of PAIs exclusive to each strain were 8 in 302-73; 11 in NCTC10360; 14 in GN7; and 18 in LS1. A PAI encoding Vibrio cholerae ToxR-activated gene d protein was specific to 302-73, GN7, and NCTC10360 strains. Out of 33 antibiotic multi-resistance genes identified, 16 (48.48%) genes were intrinsic to all strains. Further, 17 (22.08%) of 77 antibiotic resistance islands were found in all the strains. Out of 23 identified distinct insertion sequences, 13 were only harbored by strain LS1. The number of intact prophages identified in the strains was 1 in GN7; 2 in 302-73; and 2 in NCTC10360. Further, 1 CRISPR element was identified in LS1; 2 in NCTC10360; and 8 in 302-73. Fifteen (78.95%) of 19 secretion systems and secretion effector variants were identified in all the strains. In conclusion, certain P. shigelloides strains might possess VFs associated with gastroenteritis and extraintestinal infections. However, the role of host factors in the onset of infections should not be undermined.

Plesiomonas shigelloides exports a lethal cytotoxic-enterotoxin (LCE) by membrane vesicles

Plesiomonas shigelloides isolated from water in Brazil was previously described as a hemorrhagic heat-labile cytotoxic-enterotoxin producer. We purified this toxin from culture supernatants using ion metallic affinity chromatography (IMAC) followed by molecular exclusion chromatography. The pure toxin presented molecular mass of 50 kDa and isoelectric point (pI) around 6.9 by 2D electrophoresis. When injected intravenously, the purified cytotoxic-enterotoxin induced also severe spasms followed by sudden death of mice. Hence, we entitled it as lethal cytotoxic-enterotoxin (LCE). The presence of membrane vesicles (MVs) on cell surfaces of P. shigelloides was observed by scan electron microscopy (SEM). From these MVs the LCE toxin was extracted and confirmed by biological and serological assays. These data suggest that P. shigelloides also exports this cytotoxic-enterotoxin by membrane vesicles, a different mechanism of delivering extra cellular virulence factors, so far not described in this bacterium.

Plesiomonas shigelloides Revisited

After many years in the family Vibrionaceae, the genus Plesiomonas, represented by a single species, P. shigelloides, currently resides in the family Enterobacteriaceae, although its most appropriate phylogenetic position may yet to be determined. Common environmental reservoirs for plesiomonads include freshwater ecosystems and estuaries and inhabitants of these aquatic environs. Long suspected as being an etiologic agent of bacterial gastroenteritis, convincing evidence supporting this conclusion has accumulated over the past 2 decades in the form of a series of foodborne outbreaks solely or partially attributable to P. shigelloides. The prevalence of P. shigelloides enteritis varies considerably, with higher rates reported from Southeast Asia and Africa and lower numbers from North America and Europe. Reasons for these differences may include hygiene conditions, dietary habits, regional occupations, or other unknown factors. Other human illnesses caused by P. shigelloides include septicemia and central nervous system disease, eye infections, and a variety of miscellaneous ailments. For years, recognizable virulence factors potentially associated with P. shigelloides pathogenicity were lacking; however, several good candidates now have been reported, including a cytotoxic hemolysin, iron acquisition systems, and lipopolysaccharide. While P. shigelloides is easy to identify biochemically, it is often overlooked in stool samples due to its smaller colony size or relatively low prevalence in gastrointestinal samples. However, one FDA-approved PCR-based culture-independent diagnostic test system to detect multiple enteropathogens (FilmArray) includes P. shigelloides on its panel. Plesiomonads produce β-lactamases but are typically susceptible to many first-line antimicrobial agents, including quinolones and carbapenems.

Cell adherence-promoted activity of Plesiomonas shigelloides groEL

Previously, it has been demonstrated that the invasion of Caco-2 cells by Plesiomonas shigelloides induces apoptotic cell death. Therefore, the attachment to and colonization of eukaryotic intestinal host cells by P. shigelloides are important steps in causing pathogenicity. In this study, the participation of P. shigelloides GroEL in the attachment of P. shigelloides was examined. The groESL operon of P. shigelloides was isolated by PCR. The nucleotide sequence of the groESL operon of P. shigelloides revealed two ORFs of 294 nucleotides for groES and 1647 nucleotides for groEL. Cell fractionation and immunostaining experiments suggested that the GroEL of P. shigelloides was associated with the bacterial cell surface. The expression of the groEL gene was upregulated during the attachment and apoptosis-induction stages, and the expression of the protein was also induced during the attachment stage. Furthermore, GroEL efficiently promoted the attachment of P. shigelloides to Caco-2 cells, as measured by a FACSCalibur flow cytometer. These results demonstrated that GroEL has a positive influence on the attachment of P. shigelloides to Caco-2 cells.

Structure of the lipid A-inner core region and biological activity of Plesiomonas shigelloides O54 (strain CNCTC 113/92) lipopolysaccharide

Plesiomonas shigelloides is a Gram-negative rod associated with episodes of intestinal infections and outbreaks of diarrhea in humans. The extraintestinal infections caused by this bacterium, for example, endopthalmitis, meningitidis, bacteremia, and septicemia, usually have gastrointestinal origin and serious course. The lipopolysaccharide (LPS, endotoxin) as virulence factor is important in enteropathogenicity of this bacterium. LPSs of P. shigelloides and especially their lipid A part, that is, the immunomodulatory center of LPS, have not been extensively investigated. The structure of P. shigelloides O54 lipid A was determined by chemical analysis combined with MALDI-TOF mass spectrometry, and the intact Kdo-containing core region was investigated by NMR spectroscopy on deacylated LPS. Products from alkaline deacylation of LPS, containing 4-substituted uronic acids, are usually very complex and difficult to separate. Since Kdo residues, like sialic acids, form complexes with serotonin, we used immobilized serotonin for one-step isolation of oligosaccharide containing the intact Kdo region from the reaction mixture by affinity chromatography. The major form of lipid A was built of beta-d-GlcpN4PPEtn-(1-->6)-alpha-d-GlcpN1P disaccharide substituted with 14:0(3-OH), 12:0(3-OH), 14:0(3-O-14:0), and 12:0(3-O-12:0) acyl groups at N-2, O-3, N-2', and O-3', respectively. This is a novel structure among known lipid A molecules. Analysis of intact Kdo-lipid A region, lipid A and its linkage with the core oligosaccharide completes the structural investigation of P. shigelloides O54 LPS, resolving the entire molecule. Biological activities and observed discrepancy between in vitro and in vivo activity of P. shigelloides and Escherichia coli LPS are discussed.