Surgical wound infection, tuboovarian abscess, and sepsis caused by Edwardsiella tarda: case reports and literature review

Case Report: Disseminated Edwardsiella tarda infection in an immunocompromised patient

Human infection caused by bacteria of the Edwardsiella genus is rare and most often presents with gastroenteritis that rarely requires antibiotics. Our case report describes a medically complex patient with chronic steroid use contributing to an immunocompromised state, who presented with fever and abdominal pain. The patient was later found to have Edwardsiella tarda (E. tarda) bacteremia and underwent paracentesis confirming E. tarda bacterial peritonitis requiring a prolonged antibiotic course. This case report aims to illustrate the presentation, diagnosis, and management of an uncommon infection that can have severe complications especially among immunocompromised patients.

Cloning, DNA sequence, and expression of flagellins from high and low virulence strains of Edwardsiella tarda and their macrophage-stimulating activities

Edwardsiella tarda is a causative pathogen of edwardsiellosis in fish. Our previous studies on high (NUF251) and low (NUF194) virulent strains of E. tarda demonstrated that NUF251 strain induced significantly higher levels of NO and TNF-α from fish and mouse macrophages than NUF194 strain. Subsequent studies suggested that a flagellin-like protein secreted from E. tarda might be a responsible factor for the macrophage-stimulating activities. To evaluate the activities of flagellins of E. tarda, in this study, the flagellin genes of NUF251 and NUF194 strains were isolated by PCR and cloned into pQE-30 and pCold I expression vectors, and then the recombinant flagellins of two strains were overexpressed in E. coli JM109 and pG-Tf/BL21, respectively. The molecular weight of the purified recombinant flagellins of NUF251 and NUF194 strains were estimated to be 45 kDa and 37 kDa, respectively on SDS-PAGE analysis. Referring the three-dimensional structure of Salmonella flagellin, which has been reported to have 4 domains (D0, D1, D2, and D3), high sequence homology between two flagellins of E. tarda was observed at conservative domain (D0 and D1) regions, whereas the sequences equivalent to D2 and D3 domains were different, and even equivalent to 57 amino acids were deleted in NUF194. Both recombinant flagellins induced NO production, mRNA expression level of inducible NO synthase (iNOS), and intercellular ROS production in mouse macrophage cell line RAW264.7 cells. Also, the secretion of TNF-α and its mRNA expression level were increased by treatment of both recombinant flagellins. These results indicate that the recombinant flagellins from different virulent E. tarda strains can stimulate macrophages with nearly equal levels as judged by the parameters tested, even though they are differences in the structure and molecular weight, suggesting that conservative D0 and D1 domains are sufficient structural elements for the recombinant flagellins to induce a certain level of macrophage-stimulation in vitro. Further studies are necessary focusing on the role of D2 and D3 domain regions of the recombinant flagellins as macrophage-stimulating agent as well as their influence on host immune system in vivo.

A Comparative Analysis of Edwardsiella tarda-Induced Transcriptome Profiles in RAW264.7 Cells Reveals New Insights into the Strategy of Bacterial Immune Evasion

Edwardsiella tarda is a Gram-negative bacterial pathogen with a broad host range, including fish, reptiles, and mammals. One prominent virulence feature of E. tarda is its ability to survive and replicate in host phagocytes, but the relevant molecular mechanism is largely unknown. In this study, we examined the transcriptome profiles of RAW264.7 cells, a murine macrophage cell line, infected with live E. tarda or stimulated with dead E. tarda for 4 h and 8 h. Eighteen libraries were constructed, and an average of 69 million clean reads per library were obtained, with ~81.63% of the reads being successfully mapped to the reference genome. In total, 208 and 232 differentially expressed genes (DEGs) were identified between live and dead E. tarda-treated cells at 4 h and 8 h post-infection, respectively. The DEGs were markedly enriched in the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways associated with immunity. Live E. tarda differed strikingly from dead E. tarda in the regulation of immune related genes. Compared with dead E. tarda-treated cells, live E. tarda-treated cells exhibited marked and significant suppression in the induction of a large amount of immune genes, including RIG-I-like receptors, cytokines, and interferon-related genes. Furthermore, some of the immune genes highly regulated by live E. tarda formed complicated interaction networks with each other. Together, the results of this study revealed a transcriptome profile specifically induced by the active virulence elements of live E. tarda during the infection process, thus adding new insights into the intracellular infection mechanism of E. tarda. This study also provided a valuable set of target genes for further study of the immune evasion strategy of E. tarda.

A Case of Pelvic Abscess Caused by Edwardsiella tarda followed by Laparoscopic Resection of a Hematoma Derived from Caesarean Section

Edwardsiella tarda (E. tarda) infections are rare and can be fatal. We report a case of an E. tarda abscess which developed in the hematoma originally derived from a caesarean section. A 24-year-old gravida 1 woman was admitted to our hospital with a complaint of abdominal pain. Approximately one month before her admission, pelvic hematoma had developed derived from caesarean section. Followed by the failure of conservative management, she underwent laparoscopic surgery to remove the hematoma 6 days before her admission. On computed tomography examination, we found that the abscess with a diameter of 9 cm was located in the right pelvic space. We punctured the abscess and identified E. tarda in the abscess. We continued administering antibiotics, but her symptoms, including fever and abdominal pain, became worse, and the abscess enlarged. We performed laparotomy drainage and ileocecal resection on the 10th posthospitalization day. After drainage surgery, the patient's condition improved gradually, and the patient was discharged uneventfully. There are no reports in patients of E. tarda infection during the perinatal period. E. tarda infection can be a life-threatening illness even in immunocompetent patients. In the case of E. tarda infection, intensive care and surgical procedures should be considered.

Edwardsiella tarda Bacteremia with Psoas and Epidural Abscess as a Food-borne Infection: A Case Report and Literature Review

Edwardsiella tarda is commonly isolated from aquatic environments and a variety of animals. We present the first case of E. tarda bacteremia with psoas and epidural abscess. The patient was a 65-year-old woman with recurrent gastric cancer who had frequently consumed raw fish and grilled eel. She was successfully treated with antimicrobials and surgery. We also review reports published in English regarding E. tarda bacteremia in Japan and the experience at our hospital. On the basis of this review, we conclude that the major underlying disease leading to E. tarda bacteremia is malignancy and that the gastrointestinal tract is the most commonly affected organ. The overall mortality rate due to E. tarda bacteremia in our review was 38.1% (8/21). Although E. tarda bacteremia is rare, clinicians should be aware of this fatal food-borne infection.

Transcriptome profiling provides gene resources for understanding gill immune responses in Japanese flounder (Paralichthys olivaceus) challenged with Edwardsiella tarda

Marine organisms are commonly under threats from various pathogens. Edwardsiella tarda is one of the fish pathogens that seriously infect cultured and wild fish species. Bacteremia caused by E. tarda can be a fatal disease in humans. Fish gill is a mucosa-associated lymphoid tissue that directly contacted with sea water. Generating gill transcriptomic resources that challenged by E. tarda is crucial for understanding the molecular mechanisms underlying gill immune responses. In this study, we performed transcriptome profiling of gene expression in Japanese flounder gills (Paralichthys olivaceus) challenged by E. tarda with different stress duration. An average of 40 million clean reads per library were obtained, of which approximately 83.2% were successfully mapped to the reference genome. 456 and 1037 differential expressed genes (DEGs) were identified at 8 h and 48 h post-injection, respectively. Gene annotation analysis and protein-protein interaction networks were conducted to obtain the key interaction relationships of immune-related DEGs during pathogens infection. 24 hub genes with multiple protein-protein interaction relationships or involved in multiple KEGG signaling pathways were discovered and validated by qRT-PCR. These hub genes mainly participated in Leukocyte transendothelial migration signaling pathway, B cell receptor signaling pathway, Wnt signaling pathway and Apoptosis signaling pathway. This study represents the first gill transcriptomic analysis based on protein-protein interaction networks in fish and provides valuable gene resources for understanding the fish gill immunity, which can pave the way to understand the molecular mechanisms of immune responses with E. tarda infection.

Transcriptome profiling based on protein-protein interaction networks provides a core set of genes for understanding blood immune response mechanisms against Edwardsiella tarda infection in Japanese flounder (Paralichthys olivaceus)

Marine organisms are commonly under threat from various pathogens. Edwardsiella tarda is one of the fish pathogens that can infect both cultured and wild fish species. E. tarda can also infect other vertebrates, including amphibians, reptiles, and mammals. Bacteremia caused by E. tarda can be a fatal disease in humans. Blood acts as a pipeline for the fish immune system. Generating blood transcriptomic resources from fish challenged by E. tarda is crucial for understanding molecular mechanisms underlying blood immune response process. In this study, we performed transcriptome-wide gene expression profiling of Japanese flounder (Paralichthys olivaceus) challenged by 8 and 48 h E. tarda stress. An average of 37 million clean reads per library was obtained, and approximately 85.6% of these reads were successfully mapped to the reference genome. In addition, 808 and 1265 differential expression genes (DEGs) were found at 8 and 48 h post-injection, respectively. Gene Ontology (GO) functional enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were conducted to search immune-related DEGs. A protein-protein interaction network was constructed to obtain the interaction relationship of immune genes during pathogens stress. Based on KEGG and protein association networks analysis, 30 hub genes were discovered and validated by quantitative RT-PCR. This study represents the first transcriptome analysis based on protein-protein interaction networks in fish and provides us with valuable gene resources for the research of fish blood immunity, which can significantly assist us to further understand the molecular mechanisms of humans and other vertebrates against E. tarda.

Sequencing-based network analysis provides a core set of gene resource for understanding kidney immune response against Edwardsiella tarda infection in Japanese flounder

Marine organisms are under a frequent threat from various pathogens. Edwardsiella tarda is one of the major fish pathogens infecting both cultured and wild fish species. It can also infect a variety of other vertebrates, including amphibians, reptiles, and mammals, and bacteremia caused by E. tarda can be fatal in humans. The kidney is the largest lymphoid organ in fish, and generating kidney transcriptomic information under different stresses is crucial for understanding molecular mechanisms underlying the immune responses in the kidneys. In this study, we performed transcriptome-wide gene expression profiling of the Japanese flounder (Paralichthys olivaceus) challenged by 8 and 48 h of E. tarda infection. An average of 40 million clean reads per library was obtained, and approximately 81.6% of these reads were successfully mapped to the reference genome. In addition, 1319 and 4439 differentially expressed genes (DEGs) were found at 8 and 48 h post-injection, respectively. Gene Ontology (GO) functional enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed to search immune-related DEGs. A protein-protein interaction network was constructed to ascertain the relationship between interacting immune genes during pathogen-induced stress. Based on the KEGG and protein association networks analysis, 24 hub genes were discovered and validated by qRT-PCR. To our knowledge, this study is the first to represent the kidney transcriptome analysis based on protein-protein interaction networks in fish. Our results provide valuable gene resources for further research on kidney immune response in fish, which can significantly improve our understanding of the molecular mechanisms underlying the immune response to E. tarda in humans and other vertebrates.

Unusual presentations of Comamonas kerstersii infection

The association of Comamonas kerstersii with peritonitis resulting from the presence of perforated appendix has previously been described by our research team. In the present study, we describe the isolation of this microorganism from two forms of unusual presentations of C. kerstersii infection not previously described in the literature: localized intra-abdominal infection (psoas abscess) and pelvic peritonitis.

Diversity and function of the Antarctic krill microorganisms from Euphausia superba

The diversity and ecological function of microorganisms associated with Euphausia superba, still remain unknown. This study identified 75 microbial isolates from E. superba, that is 42 fungi and 33 bacteria including eight actinobacteria. And all the isolates showed NaF tolerance in conformity with the nature of the fluoride krill. The maximum concentration was 10%, 3% and 0.5% NaF for actinobacteria, bacteria and fungi, respectively. The results demonstrated that 82.4% bacteria, 81.3% actinobacteria and 12.3% fungi produced antibacterial metabolites against pathogenic bacteria without NaF; the MIC value reached to 3.9 μg/mL. In addition, more than 60% fungi produced cytotoxic metabolites against A549, MCF-7 or K562 cell lines. The presence of NaF led to a reduction in the producing antimicrobial compounds, but stimulated the production of cytotoxic compounds. Furthermore, seven cytotoxic compounds were identified from the metabolites of Penicillium citrinum OUCMDZ4136 under 0.5% NaF, with the IC₅₀ values of 3.6-13.1 μM for MCF-7, 2.2-19.8 μM for A549 and 5.4-15.4 μM for K562, respectively. These results indicated that the krill microbes exert their chemical defense by producing cytotoxic compounds to the mammalians and antibacterial compounds to inhibiting the pathogenic bacteria.

Edwardsiella tarda bacteremia with metastatic gastric cancer

Edwardsiella tarda (E. tarda) is a rare human pathogen; however, the overall mortality of bacteremia is reported to be up to 50%. Here, we describe a case of cholangitis with E. tarda bacteremia who had a pancreatoduodenectomy for a locally advanced gastric cancer. He was successfully treated using a cefmetazole, a second generation cephalosporin for 14 days. To the best of our knowledge, this is the first case report about E. tarda bacteremia after biliary reconstruction.

Edwardsiella tarda bacteremia. A rare but fatal water- and foodborne infection: Review of the literature and clinical cases from a single centre

BACKGROUND

Edwardsiella tarda bacteremia (ETB) can be a fatal disease in humans.

OBJECTIVES

To determine the significant risk factors associated with death caused by ETB, and to examine the geographical, seasonal, environmental and dietary factors of the disease.

METHODS

A retrospective, observational, case control study was performed. The PubMed MEDLINE and Japanese Medical Abstract Society (www.jamas.or.jp) databases were searched for ETB case reports and meeting abstracts. In additon, retrospective chart reviews of patients with ETB at the Tokyo Women's Medical University Hospital (Tokyo, Japan) were conducted to evaluate the risk factors associated with death using multivariate analyses.

RESULTS

The literature search yielded 46 publications, comprising 72 cases from the English (n=30), French (n=1), Spanish (n=1) and Japanese (n=14) literature. Five cases at the Tokyo Women's Medical University Hospital were also included. Of the included 77 cases, the mean age was 61 years and 39% of patients were female; 77.2% of the cases occurred between June and November, and 45.5% were reported in Japan. Dietary factors (raw fish/meat exposure) were reported for 10.4% of patients and 12.9% reported environmental (ie, brackish water) exposure. The overall mortality rate was 44.6%; however, this rate increased to 61.1% for ETB patients with soft tissue infections. Liver cirrhosis was determined to be an independent risk factor associated with death (OR 12.0 [95% CI 2.46 to 58.6]; P=0.00213) using multivariate analyses.

DISCUSSION

To our knowledge, the present analysis was the first and largest multi-language review of ETB. Clinical characteristics of ETB resemble those of Aeromonas, typhoid fever and Vibrio vulnificus infections, in addition to sharing similar risk factors.

CONCLUSION

ETB should be categorized as a severe food- and waterborne infection, which results in high mortality for patients with liver cirrhosis.

Tubo-Ovarian Abscess Caused by Candida Albicans in an Obese Patient

BACKGROUND

Tubo-ovarian abscess (TOA) arises in most cases from pelvic infection. Appropriate treatment includes use of antimicrobials and, especially in patients with increased BMI, drainage of the contents.

CASE

A 44-year-old morbidly obese woman (BMI 72) had a persistent TOA despite receiving antibiotic treatment for four months. She had no history of diabetes, and denied being sexually active. Imaging demonstrated a pelvic abscess of 14.9 × 8.9 × 11.1 cm. Successful percutaneous drainage was performed yielding purulent material which grew Candida albicans. The patient recovered after drainage of the abscess and the addition of fluconazole to her antimicrobials. She had no apparent risk factor for acquiring such an opportunistic infection, other than her morbid obesity.

CONCLUSION

Because morbid obesity may confer a relative immunodeficiency, morbidly obese patients may develop unusual infections such as opportunistic fungal abscesses.

Structure of the O-polysaccharide of Edwardsiella tarda PCM 1150 containing an amide of D-glucuronic acid with L-alanine

Mild acid degradation of the lipopolysaccharide of Edwardsiella tarda PCM 1150 afforded an O-polysaccharide, which was isolated by GPC on Sephadex G-50 and studied by sugar and methylation analyses along with 1D and 2D 1H and 13C NMR spectroscopies, including experiments performed in a 9:1 H2O/D2O mixture to detect NH protons and their correlations with CH protons. The O-polysaccharide was found to contain an amide of d-glucuronic acid with l-alanine (d-GlcA6Ala) and the following structure of the branched hexasaccharide repeating unit was established: -->4)-β-D-GlepA6Ala-(1-->4)-α-L-Fucp-(1-->4)-α-D-Glcp-(1-->4)-α-D-Quip-(1-->3)-β-D-GlcpNAc-(1-->3<--1α-D-GalpNAc.

Edwardsiella comparative phylogenomics reveal the new intra/inter-species taxonomic relationships, virulence evolution and niche adaptation mechanisms

Edwardsiella bacteria are leading fish pathogens causing huge losses to aquaculture industries worldwide. E. tarda is a broad-host range pathogen that infects more than 20 species of fish and other animals including humans while E. ictaluri is host-adapted to channel catfish causing enteric septicemia of catfish (ESC). Thus, these two species consist of a useful comparative system for studying the intricacies of pathogen evolution. Here we present for the first time the phylogenomic comparisons of 8 genomes of E. tarda and E. ictaluri isolates. Genome-based phylogenetic analysis revealed that E. tarda could be separate into two kinds of genotypes (genotype I, EdwGI and genotype II, EdwGII) based on the sequence similarity. E. tarda strains of EdwGI were clustered together with the E. ictaluri lineage and showed low sequence conservation to E. tarda strains of EdwGII. Multilocus sequence analysis (MLSA) of 48 distinct Edwardsiella strains also supports the new taxonomic relationship of the lineages. We identified the type III and VI secretion systems (T3SS and T6SS) as well as iron scavenging related genes that fulfilled the criteria of a key evolutionary factor likely facilitating the virulence evolution and adaptation to a broad range of hosts in EdwGI E. tarda. The surface structure-related genes may underlie the adaptive evolution of E. ictaluri in the host specification processes. Virulence and competition assays of the null mutants of the representative genes experimentally confirmed their contributive roles in the evolution/niche adaptive processes. We also reconstructed the hypothetical evolutionary pathway to highlight the virulence evolution and niche adaptation mechanisms of Edwardsiella. This study may facilitate the development of diagnostics, vaccines, and therapeutics for this under-studied pathogen.