Pathogenic characteristics of an aggregated diarrhea event caused by Plesiomonas shigelloides from stream.

This study aimed to investigate the cause of a foodborne disease outbreak in Huzhou on August 14, 2023. Multiple enteropathogens were detected using FilmArray, and the pathogen was subsequently isolated and cultured from anal swabs of the cases and stream water. The isolated strains were identified using VITEK MS, and antimicrobial susceptibility test, pulsed field gel electrophoresis (PFGE) molecular typing, and whole genome sequencing (WGS) were performed on the isolates of Plesiomonas shigelloides. Gene annotation and sequence alignment were used to analyze the virulence genes and drug resistance genes of the strains. A phylogenetic tree was constructed based on single nucleotide polymorphism (SNP), and homology analysis was conducted to trace the origin of P. shigelloides. A total of 7 strains of P.shigelloides were isolated, with 3 from stream water and 4 from anal swabs. All 7 strains exhibited the same PFGE pattern and showed resistance to amikacin, trimethoprim-sulfamethoxazole, chloramphenicol, tetracycline, cefazolin, streptomycin, and florfenicol. The isolated strains carried the same resistance genes and virulence factors. In the sequences of the isolated strains from this outbreak, 11 mutation sites were detected. The phylogenetic tree based on SNP sites showed that these strains were homologous. This foodborne disease outbreak caused by P.shigelloides was the first reported in Huzhou. WGS can be used as a complementary method to PFGE for epidemiological investigations of disease outbreaks.

Pleisiomonas shigelloides bacteremia after catfish injury.

This case of Pleisimonas shigelloides bacteremia resulting after a catfish barb injury highlights an unusual presentation of a common condition that requires alternative therapy for successful treatment. An otherwise healthy male in his early 40s presented to the emergency department with sepsis and rapidly spreading cellulitis shortly after a catfish injury at a freshwater lake. His broad-spectrum antibiotics were narrowed to ciprofloxacin when P. shigelloides grew from his blood culture. The case presents a unique mode of bacteremia, as usually P. shigelloides bacteremia develops in immunocompromised hosts after bowel wall translocation. The venomous nature of catfish barbs also contributed to the severity and rapidity of his presentation secondary to the local tissue effects of envenomation. With proper antibiotics and supportive care, he made a full recovery.

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.

Transcriptome Analysis Reveals the Effect of PdhR in Plesiomonas shigelloides.

The pyruvate dehydrogenase complex regulator (PdhR) was originally identified as a repressor of the pdhR-aceEF-lpd operon, which encodes the pyruvate dehydrogenase complex (PDHc) and PdhR itself. According to previous reports, PdhR plays a regulatory role in the physiological and metabolic pathways of bacteria. At present, the function of PdhR in Plesiomonas shigelloides is still poorly understood. In this study, RNA sequencing (RNA-Seq) of the wild-type strain and the ΔpdhR mutant strains was performed for comparison to identify the PdhR-controlled pathways, revealing that PdhR regulates ~7.38% of the P. shigelloides transcriptome. We found that the deletion of pdhR resulted in the downregulation of practically all polar and lateral flagella genes in P. shigelloides; meanwhile, motility assay and transmission electron microscopy (TEM) confirmed that the ΔpdhR mutant was non-motile and lacked flagella. Moreover, the results of RNA-seq and quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) showed that PdhR positively regulated the expression of the T3SS cluster, and the ΔpdhR mutant significantly reduced the ability of P. shigelloides to infect Caco-2 cells compared with the WT. Consistent with previous research, pyruvate-sensing PdhR directly binds to its promoter and inhibits pdhR-aceEF-lpd operon expression. In addition, we identified two additional downstream genes, metR and nuoA, that are directly negatively regulated by PdhR. Furthermore, we also demonstrated that ArcA was identified as being located upstream of pdhR and lpdA and directly negatively regulating their expression. Overall, we revealed the function and regulatory pathway of PdhR, which will allow for a more in-depth investigation into P. shigelloides pathogenicity as well as the complex regulatory network.

Case report: vertical transmission of Plesiomonas shigelloides. Is it time to strengthen information on safety concerns for raw seafood dietary exposure in pregnancy?

The consumption of raw seafood, generally considered to be a healthy food, has greatly increased worldwide. Pathogens of fish can cause foodborne illnesses in humans, especially following the consumption of raw seafood from contaminated water.Foodborne illness in pregnant women is seldom the cause of neonatal infection, but, as in the reported cases, it has been associated with a high degree of morbidity and mortality.We present the case of a newborn with septicemia and meningitis caused by Plesiomonas shigelloides acquired via the transplacental route. There was a maternal history of ingestion of raw seafood 1 week prior to delivery. A few similar cases are described in the existing literature, which reports 7 neonatal deaths.Therefore, the primary objective of this paper is to highlight the fact that the popularity of raw seafood such as sushi, sashimi, and oysters, requires an improvement in dietary advice regarding unsafe choices in pregnancy in order to avoid preventable foodborne diseases, sometimes fatal for the newborn.

The ROK kinase N-acetylglucosamine kinase uses a sequential random enzyme mechanism with successive conformational changes upon each substrate binding.

N-acetyl-d-glucosamine (GlcNAc) is a major component of bacterial cell walls. Many organisms recycle GlcNAc from the cell wall or metabolize environmental GlcNAc. The first step in GlcNAc metabolism is phosphorylation to GlcNAc-6-phosphate. In bacteria, the ROK family kinase N-acetylglucosamine kinase (NagK) performs this activity. Although ROK kinases have been studied extensively, no ternary complex showing the two substrates has yet been observed. Here, we solved the structure of NagK from the human pathogen Plesiomonas shigelloides in complex with GlcNAc and the ATP analog AMP-PNP. Surprisingly, PsNagK showed distinct conformational changes associated with the binding of each substrate. Consistent with this, the enzyme showed a sequential random enzyme mechanism. This indicates that the enzyme acts as a coordinated unit responding to each interaction. Our molecular dynamics modeling of catalytic ion binding confirmed the location of the essential catalytic metal. Additionally, site-directed mutagenesis confirmed the catalytic base and that the metal-coordinating residue is essential. Together, this study provides the most comprehensive insight into the activity of a ROK kinase.

Using machine learning models to predict the effects of seasonal fluxes on Plesiomonas shigelloides population density.

Seasonal variations (SVs) affect the population density (PD), fate, and fitness of pathogens in environmental water resources and the public health impacts. Therefore, this study is aimed at applying machine learning intelligence (MLI) to predict the impacts of SVs on P. shigelloides population density (PDP) in the aquatic milieu. Physicochemical events (PEs) and PDP from three rivers acquired via standard microbiological and instrumental techniques across seasons were fitted to MLI algorithms (linear regression (LR), multiple linear regression (MR), random forest (RF), gradient boosted machine (GBM), neural network (NN), K-nearest neighbour (KNN), boosted regression tree (BRT), extreme gradient boosting (XGB) regression, support vector regression (SVR), decision tree regression (DTR), M5 pruned regression (M5P), artificial neural network (ANN) regression (with one 10-node hidden layer (ANN10), two 6- and 4-node hidden layers (ANN64), and two 5- and 5-node hidden layers (ANN55)), and elastic net regression (ENR)) to assess the implications of the SVs of PEs on aquatic PDP. The results showed that SVs significantly influenced PDP and PEs in the water (p < 0.0001), exhibiting a site-specific pattern. While MLI algorithms predicted PDP with differing absolute flux magnitudes for the contributing variables, DTR predicted the highest PDP value of 1.707 log unit, followed by XGB (1.637 log unit), but XGB (mean-squared-error (MSE) = 0.0025; root-mean-squared-error (RMSE) = 0.0501; R2 =0.998; medium absolute deviation (MAD) = 0.0275) outperformed other models in terms of regression metrics. Temperature and total suspended solids (TSS) ranked first and second as significant factors in predicting PDP in 53.3% (8/15) and 40% (6/15), respectively, of the models, based on the RMSE loss after permutations. Additionally, season ranked third among the 7 models, and turbidity (TBS) ranked fourth at 26.7% (4/15), as the primary significant factor for predicting PDP in the aquatic milieu. The results of this investigation demonstrated that MLI predictive modelling techniques can promisingly be exploited to complement the repetitive laboratory-based monitoring of PDP and other pathogens, especially in low-resource settings, in response to seasonal fluxes and can provide insights into the potential public health risks of emerging pathogens and TSS pollution (e.g., nanoparticles and micro- and nanoplastics) in the aquatic milieu. The model outputs provide low-cost and effective early warning information to assist watershed managers and fish farmers in making appropriate decisions about water resource protection, aquaculture management, and sustainable public health protection.

Pathogenicity of Plesiomonas shigelloides causing mass mortalities of largemouth bass (Micropterus salmoides) and its induced host immune response.

The outbreak of mass mortality of M. salmoides occurred in an aquaculture farm in Jiangsu province of China, showing signs of skin ulceration and haemorrhages. The bacteria were isolated from diseased largemouth bass, and identified as Plesiomonas shigelloides based on morphological, physiological and biochemical features, as well as 16S rRNA gene sequence analysis. The pathogenicity of P. shigelloides was determined by challenge experiments, and the median lethal dosage (LD50) of the isolate NJS1 for M. salmoides was calculated as 1.6 × 105 CFU/mL at 7 d post-infection. Histopathological analysis revealed that extensive necrosis, vacuolization and inflammation were presented in the kidney, liver and gill of the diseased fish. Detection of virulence-related genes showed that P. shigelloides NJS1 was positive for astA, astB, astD, astE, actP and 6 ahpA. Additionally, the host defensive response of M. salmoides infected by P. shigelloides was analyzed by quantitive real-time PCR (qRT-PCR), and the results showed that the expression levels of Cas3, Hep1, HIF, IgM, IL15 and TGF were significantly up-regulated in head kidney, liver and spleen in different hours post-infection, which revealed varying expression profiles and clear transcriptional activation of immune related genes. The results suggested that P. shigelloides was an etiological element in the mass mortalities of M. salmoides and this study provided deeper insights for the pathogenesis and host defensive system in P. shigelloides invasion.

RpoN is required for the motility and contributes to the killing ability of Plesiomonas shigelloides.

BACKGROUND: RpoN, also known as σ54, first reported in Escherichia coli, is a subunit of RNA polymerase that strictly controls the expression of different genes by identifying specific promoter elements. RpoN has an important regulatory function in carbon and nitrogen metabolism and participates in the regulation of flagellar synthesis, bacterial motility and virulence. However, little is known about the effect of RpoN in Plesiomonas shigelloides. RESULTS: To identify pathways controlled by RpoN, RNA sequencing (RNA-Seq) of the WT and the rpoN deletion strain was carried out for comparison. The RNA-seq results showed that RpoN regulates ~ 13.2% of the P. shigelloides transcriptome, involves amino acid transport and metabolism, glycerophospholipid metabolism, pantothenate and CoA biosynthesis, ribosome biosynthesis, flagellar assembly and bacterial secretion system. Furthermore, we verified the results of RNA-seq using quantitative real-time reverse transcription PCR, which indicated that the absence of rpoN caused downregulation of more than half of the polar and lateral flagella genes in P. shigelloides, and the ΔrpoN mutant was also non-motile and lacked flagella. In the present study, the ability of the ΔrpoN mutant to kill E. coli MG1655 was reduced by 54.6% compared with that of the WT, which was consistent with results in RNA-seq, which showed that the type II secretion system (T2SS-2) genes and the type VI secretion system (T6SS) genes were repressed. By contrast, the expression of type III secretion system genes was largely unchanged in the ΔrpoN mutant transcriptome and the ability of the ΔrpoN mutant to infect Caco-2 cells was also not significantly different compared with the WT. CONCLUSIONS: We showed that RpoN is required for the motility and contributes to the killing ability of P. shigelloides and positively regulates the T6SS and T2SS-2 genes.

Pathogenicity of Plesiomonas shigelloides and Citrobacter freundii isolated from the endangered Chinese sturgeon (Acipenser sinensis).

Chinese sturgeon (Acipenser sinensis) is an indigenous species of China and is listed as a critically endangered species. Recently, second filial generations of Chinese sturgeon in the Yangtze River Fisheries Research Institute suffered from a severe disease. In this study, two kinds of pathogenic bacteria were isolated from diseased sturgeon and identified as Plesiomonas shigelloides and Citrobacter freundii, based on 16S rDNA gene sequence alignment analysis. Antimicrobial susceptibility testing showed that P. shigelloides was resistant to ampicillin, penicillin, midecamycin, oxacillin, and clindamycin; and sensitive to tocefatriaxone, piperacillin, cefoperazone, cefazolin, and ciprofloxacin. C. freundii was resistant to ampicillin, penicillin, midecamycin, oxacillin, and clindamycin; and sensitive to chloramphenicol, cefuroxime, norfloxacin, ciprofloxacin, and ceftazidime. The median lethal dose (LD50) values of P. shigelloides and C. freundii were 4.50 × 103 colony forming units (CFU)/g and 3.20 × 103 CFU/g, respectively. Clinical symptoms of challenged sturgeons were the same as those of naturally infected sturgeons. Histopathological examination disclosed severe damage in the viscera of P. shigelloides and C. freundii-infected sturgeons. This is the first report suggesting that P. shigelloides infection is associated with mortality of Chinese sturgeon. The results of this study revealed the pathogenesis and severe pathogenicity of P. shigelloides and C. freundii in cultured Chinese sturgeon, and offer insights into the prevention and treatment of bacterial infection caused by P. shigelloides and C. freundii in cultured sturgeons.

Clinical and microbiological features of intratumor abscess with bloodstream infection caused by Plesiomonas shigelloides, Citrobacter freundii, Streptococcus mitis/oralis, Clostridium perfringens, and Candida albicans in a patient with cholangiocarcinoma: A case report.

Plesiomonas shigelloides is a gram-negative facultative anaerobic bacillus, usually found in soil and freshwater, which causes self-limited diarrhea, although reports of bacteremia are rare. Here, we report the first case of an intratumoral abscess with mixed bacteremia caused by P. shigelloides, Citrobacter freundii, Streptococcus mitis/oralis, Clostridium perfringens, and Candida albicans in a patient with recurrent postoperative cholangiocarcinoma. A 77-year-old man with hilar cholangiocarcinoma and hypertension was admitted to our hospital with fever and abdominal pain. He had visited Vietnam for 3 years, 20 years ago. Abdominal computed tomography showed air within the recurrent tumor at the left liver lobectomy resection margin site, which was diagnosed as an intratumor abscess perforating the intestinal tract. P. shigelloides, C. freundii, S. mitis/oralis, C. perfringens, and C. albicans were isolated in blood culture. P. shigelloides was identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and 16S ribosomal RNA (16S rRNA) sequencing. Piperacillin-tazobactam was administered for almost a week, ampicillin-sulbactam and levofloxacin for almost 3 weeks, and antifungal agents for almost 2 weeks, and the patient was discharged thereafter. Although bloodstream infections caused by P. shigelloides in patients with cancer are extremely rare, long-term colonization and the potential for future intra-abdominal infections were implicated.

Isolation, Identification, and Investigation of Pathogenic Bacteria From Common Carp (Cyprinus carpio) Naturally Infected With Plesiomonas shigelloides.

Various bacterial diseases have caused great economic losses to the high-density and intensive aquaculture industry; however, the pathogenic mechanism underlying the large-scale challenged to caused by many bacteria remain unclear, making the prevention and treatment of these diseases difficult. In the present study, we isolated a bacterial strain from Cyprinus carpio having a typical bacterial disease and named it Cc2021. Through subsequent morphological observations, a regression challenge, biochemical identification, and 16S rRNA gene sequence analysis, we determined Cc2021 to be Plesiomonas shigelloides. Subsequently, we comprehensively investigated the pathogenicity of P. shigelloides in C. carpio through a regression challenge and assessed the underlying the pathogenic mechanism. Mortality results revealed that P. shigelloides is highly pathogenic and infects various tissues throughout the body, resulting in edema of the liver, spleen, and body and head kidneys. Histopathological analysis revealed obvious inflammation, bleeding, and necrosis in the intestine, spleen, and head kidney. The body's immune tissues actively produce complement C3, superoxide dismutase, and lysozyme after a challenge to resist bacterial invasion. With regard to the underlying pathogenesis of P. shigelloides, comparative transcriptome analysis revealed 876 upregulated genes and 828 downregulated genes in the intestine of C. carpio after the challenge. Analysis of differentially expressed unigenes revealed the involvement of major immune pathways, particularly the TNF signaling pathway, interleukin (IL)-17 signaling pathway, and Toll-like receptor signaling pathway. The present study provides new valuable information on the immune system and defense mechanisms of P. shigelloides.

Bacterial and parasite co-infection in Mexican golden trout (Oncorhynchus chrysogaster) by Aeromonas bestiarum, Aeromonas sobria, Plesiomonas shigelloides and Ichthyobodo necator.

BACKGROUND: Bacterial infections are responsible of high economic losses in aquaculture. Mexican golden trout (Oncorhynchus chrysogaster) is a threatened native trout species that has been introduced in aquaculture both for species conservation and breeding for production and for which no studies of bacterial infections have been reported. CASE PRESENTATION: Fish from juvenile stages of Mexican golden trout showed an infectious outbreak in a farm in co-culture with rainbow trout (Oncorhynchus mykiss), showing external puntiform red lesions around the mouth and caudal pedunculus resembling furuncles by Aeromonas spp. and causing an accumulated mortality of 91%. Isolation and molecular identification of bacteria from lesions and internal organs showed the presence of Aeromonas bestiarum, Aeromonas sobria, Plesiomonas shigelloides and Ichthyobodo necator isolated from a single individual. All bacterial isolates were resistant to amoxicillin-clavulanic acid and cefazoline. P. shigelloides was resistant to third generation ß-lactamics. CONCLUSIONS: This is the first report of coinfection by Aeromonas bestiarum, Aeromonas sobria, Plesiomonas shigelloides and Ichthyobodo necator in an individual of Mexican golden trout in co-culture with rainbow trout. Resistance to ß-lactams suggests the acquisition of genetic determinants from water contamination by human- or livestock-associated activities.

Virulence Profiles among Gastrointestinal and Extraintestinal Clinical Isolates of Plesiomonas shigelloides.

The genus Plesiomonas, represented by a single species, Plesiomonas shigelloides, is a gram-negative bacillus associated with gastrointestinal and extraintestinal diseases in humans. In this study, 44 clinical isolates (gastrointestinal, n = 41; extraintestinal, n = 3) were genetically confirmed to be P. shigelloides using the hug gene. All 20 virulence genes were detected in the gastrointestinal isolates, ranging from 7.7% to 100%; however, only 12 genes were detected in the extra-gastrointestinal isolates, ranging from 33.3% to 100%. The phlA gene was significantly associated with the gastrointestinal isolates (P = 0.0216). The results of this study suggest that phlA may play a role in gastrointestinal infections. However, pilF, tolC, and fur were detected in both gastrointestinal and extraintestinal clinical isolates, and further investigations are warranted to elucidate their role in the pathogenesis of P. shigelloides.

Surveillance and laboratory collaboration in response to an outbreak of Vibrio parahaemolyticus, Plesiomonas shigelloides, and Aeromonas hydrophila in Sekondi-Takoradi, Ghana: a case series.

BACKGROUND: The detection of epidemic-prone pathogens is important in strengthening global health security. Effective public health laboratories are critical for reliable, accurate, and timely testing results in outbreak situations. Ghana received funding as one of the high-risk non-Ebola affected countries to build and strengthen public health infrastructure to meet International Health Regulation core capacities. A key objective was to build laboratory capacities to detect epidemic-prone diseases. CASE PRESENTATION: In June 2018, a local hospital received eight patients who presented with acute diarrhea. A sample referral system for Ghana has not been established, but the Sekondi Zonal Public Health Laboratory staff and mentors collaborated with Disease Surveillance Officers (DSOs) to collect, package, and transport stool specimens from the outbreak hospital to the Public Health Laboratory for laboratory testing. The patients included seven females and one male, of Fante ethnicity from the Fijai township of Sekondi-Takoradi Municipality. The median age of the patients was 20 years (interquartile range: 20-29 years). Vibrio parahaemolyticus was identified within 48 hours from four patients, Plesiomonas shigelloides from one patient, and Aeromonas hydrophila from another patient. There was no bacteria growth from the samples from the two other patients. All patients were successfully treated and discharged. CONCLUSION: This is the first time these isolates have been identified at the Sekondi Zonal Public Health Laboratory, demonstrating how rapid response, specimen transportation, laboratory resourcing, and public health coordination are important in building capacity towards achieving health security. This capacity building was part of the United States Centers for Disease Control and Prevention engagement of international and local partners to support public health laboratories with supplies, diagnostic equipment, reagents, and logistics.

Plesiomonas shigelloides, an Atypical Enterobacterales with a Vibrio-Related Secondary Chromosome.

About 10% of bacteria have a multichromosome genome with a primary replicon of bacterial origin, called the chromosome, and other replicons of plasmid origin, the chromids. Studies on multichromosome bacteria revealed potential points of coordination between the replication/segregation of chromids and the progression of the cell cycle. For example, replication of the chromid of Vibrionales (called Chr2) is initiated upon duplication of a sequence carried by the primary chromosome (called Chr1), in such a way that replication of both replicons is completed synchronously. Also, Chr2 uses the Chr1 as a scaffold for its partition in the daughter cells. How many of the features detected so far are required for the proper integration of a secondary chromosome in the cell cycle? How many more features remain to be discovered? We hypothesized that critical features for the integration of the replication/segregation of a given chromid within the cell cycle program would be conserved independently of the species in which the chromid has settled. Hence, we searched for a chromid related to that found in Vibrionales outside of this order. We identified one in Plesiomonas shigelloides, an aquatic and pathogenic enterobacterium that diverged early within the clade of Enterobacterales. Our results suggest that the chromids present in P. shigelloides and Vibrionales derive from a common ancestor. We initiated in silico genomic and proteomic comparative analyses of P. shigelloides, Vibrionales, and Enterobacterales that enabled us to establish a list of features likely involved in the maintenance of the chromid within the host cell cycle.

Plesiomonas: A Review on Food Safety, Fish-Borne Diseases, and Tilapia.

Fish and fish products are considered a fundamental part of the human diet due to their high nutritional value. Food-borne diseases are considered a major public health challenge worldwide due to their incidence, associated mortality, and negative economic repercussions. Food safety is the guarantee that foods will not cause harm to the health of those who consume them, and it is a fundamental property of food quality. Food safety can be at risk of being lost at any stage of the food chain if the food is contaminated by pathogenic microorganisms. Many diverse bacteria are present in the environment and as part of the microbiota of food that can be transmitted to humans during the handling and consumption of food. Plesiomonas shigelloides has been mainly associated with outbreaks of gastrointestinal diseases due to the consumption of fish. This bacterium inhabits the environment and aquatic animals and is associated with the microbiota of fish such as tilapia, a fish of importance in fishing, aquaculture, commercialization, and consumption worldwide. The purpose of this document is to provide, through a bibliographic review of databases (Scopus, Web of Science, and Google Scholar, among others), a general informative perspective on food-borne diseases and, in particular, the consumption of fish and tilapia. Diseases derived from contamination by Plesiomonas shigelloides are included, and control and prevention actions and sanitary regulations for fishery products established in several countries around the world are discussed to promote the safety of foods of aquatic origin intended for human consumption and to protect public health.

The effect of ArcA on the growth, motility, biofilm formation, and virulence of Plesiomonas shigelloides.

BACKGROUND: The anoxic redox control binary system plays an important role in the response to oxygen as a signal in the environment. In particular, phosphorylated ArcA, as a global transcription factor, binds to the promoter regions of its target genes to regulate the expression of aerobic and anaerobic metabolism genes. However, the function of ArcA in Plesiomonas shigelloides is unknown. RESULTS: In the present study, P. shigelloides was used as the research object. The differences in growth, motility, biofilm formation, and virulence between the WT strain and the ΔarcA isogenic deletion mutant strain were compared. The data showed that the absence of arcA not only caused growth retardation of P. shigelloides in the log phase, but also greatly reduced the glucose utilization in M9 medium before the stationary phase. The motility of the ΔarcA mutant strain was either greatly reduced when grown in swim agar, or basically lost when grown in swarm agar. The electrophoretic mobility shift assay results showed that ArcA bound to the promoter regions of the flaK, rpoN, and cheV genes, indicating that ArcA directly regulates the expression of these three motility-related genes in P. shigelloides. Meanwhile, the ability of the ΔarcA strain to infect Caco-2 cells was reduced by 40%; on the contrary, its biofilm formation was enhanced. Furthermore, the complementation of the WT arcA gene from pBAD33-arcA+ was constructed and all of the above features of the pBAD33-arcA+ complemented strain were restored to the WT level. CONCLUSIONS: We showed the effect of ArcA on the growth, motility, biofilm formation, and virulence of Plesiomonas shigelloides, and demonstrated that ArcA functions as a positive regulator controls the motility of P. shigelloides by directly regulating the expression of flaK, rpoN and cheV genes.

Screening of a Plesiomonas shigelloides phage and study of the activity of its lysis system.

Plesiomonas shigelloides is an important fish pathogen that causes significant losses in aquaculture. Phage therapy is a new approach to overcome the problem of multidrug-resistant bacteria. Herein, a virulent phage of P. shigelloides was isolated from the intestines of grass carp. This phage belongs to the Siphoviridae family and was designated PSP01. The optimal multiplicity of infection of PSP01 was 1 with a latent period of 30 min and a lytic period of 140 min. Good activity was observed over a wide range of temperatures (-20 °C-50 °C), pH values (3-12), and NaCl concentrations (0.1-3.5%). The phage PSP01 lysis cassette is composed of 3 genes, HolPSP, LysPSP-1 and LysPSP-2. Expression of HolPSP or LysPSP-2 in Escherichia coli resulted in bacterial lysis, and a synergistic effect was observed when the HolPSP and LysPSP-1 proteins were co-expressed. In-frame deletion uncovered an important role of the transmembrane domain (TMD) in HolPSP and the signal peptide (SP) in LysPSP-2 for bacterial lysis function. The protective effects of phage PSP01 were investigated by intraperitoneal injection into grass carp infected with P. shigelloides, showing a 33.3% increase in the survival rate of the infected grass carp. Pathological analysis of the spleens from the infected grass carp revealed alleviation of the pathological symptoms. In conclusion, isolation and bacterial lysis investigations of phage PSP01 provide a new tool for the control of fish pathogens and possesses potential for aquaculture applications.

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.