Fusobacterium bloodstream infections: A literature review and hospital-based case series

Fusobacterium nucleatum: An Overview of Evidence, Demi-Decadal Trends, and Its Role in Adverse Pregnancy Outcomes and Various Gynecological Diseases, including Cancers

Gynecological and obstetric infectious diseases are crucial to women's health. There is growing evidence that links the presence of Fusobacterium nucleatum (F. nucleatum), an anaerobic oral commensal and potential periodontal pathogen, to the development and progression of various human diseases, including cancers. While the role of this opportunistic oral pathogen has been extensively studied in colorectal cancer in recent years, research on its epidemiological evidence and mechanistic link to gynecological diseases (GDs) is still ongoing. Thus, the present review, which is the first of its kind, aims to undertake a comprehensive and critical reappraisal of F. nucleatum, including the genetics and mechanistic role in promoting adverse pregnancy outcomes (APOs) and various GDs, including cancers. Additionally, this review discusses new conceptual advances that link the immunomodulatory role of F. nucleatum to the development and progression of breast, ovarian, endometrial, and cervical carcinomas through the activation of various direct and indirect signaling pathways. However, further studies are needed to explore and elucidate the highly dynamic process of host-F. nucleatum interactions and discover new pathways, which will pave the way for the development of better preventive and therapeutic strategies against this pathobiont.

Case report: Metagenomics next-generation sequencing in the diagnosis of septic shock due to Fusobacterium necrophorum in a 6-year-old child

Fusobacterium necrophorum (F. necrophorum) infection is rare in pediatrics. In addition, the detection time of F. necrophorum by blood culture is long, and the positive rate is low. Infection with F. necrophorum bacilli usually follows rapid disease progression, resulting in high mortality. In previous reports of F. necrophorum-related cases, the most dangerous moment of the disease occurred after the appearance of Lemierre's syndrome. We report an atypical case of a 6-year-old female patient who developed septic shock within 24 h of admission due to F. necrophorum infection in the absence of Lemierre's syndrome. F. necrophorum was identified in a blood sample by metagenomics next-generation sequencing (mNGS) but not by standard blood culture. The patient was finally cured and discharged after receiving timely and effective targeted anti-infection treatment. In the present case study, it was observed that the heightened virulence and invasiveness of F. necrophorum contribute significantly to its role as a primary pathogen in pediatric septic shock. This can precipitate hemodynamic instability and multiple organ failure, even in the absence of Lemierre's syndrome. The use of mNGS can deeply and rapidly identify infectious pathogens, guide the use of targeted antibiotics, and greatly improve the survival rate of patients.

Fusobacterium ulcerans. From tropical ulcers to gut commensal and bacterial translocation?

The genusFusobacterium contains currently 13 species presenting as non-spore-forming, obligate anaerobic, gram-negative fusiform rods. Fusobacterium ulcerans was discovered in 1988 causing tropical ulcers. We present the case of a patient with diverticulitis complicated with bacteremia. Both aerobic bottles were positive at 20 and 24 h, while one anaerobic bottle was positive at 36 h. Escherichia coli and Fusobacterium ulcerans were identified from subcultures by MALDI-TOF MS with a score of 2.02 and 2.35, respectively. The 16S rRNA gene was sequenced in order to confirm the identification of F. ulcerans with a 100% homology to the reference strain. The patient was treated with 4 g/0,5 g of IV piperacillin/tazobactam and later with 1 g/0,2 g of amoxicillin/clavulanic during 7 days with good clinical evolution.

A Case of Fulminant Fusobacterium necrophorum Bacteremia Secondary to Non-severe COVID-19

The Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is more infectious than the previous variants but less severe; more patients are being followed up without hospitalization. Identification of patients with severe disease symptoms as early as possible and prompt initiation of treatment are crucial. A case of a 19-year-old man with mild COVID-19 is described in this report. He died of a secondary infection with Fusobacterium necrophorum bacteremia and a progressive hemorrhagic disorder. The diagnosis was made based on the clinical course and needle necropsy results. In non-severe COVID-19 patients, rapid deterioration of the disease symptoms requiring emergency treatment should lead to suspicion of additional fatal infections with similar clinical symptoms.

Test Performance and Potential Clinical Utility of the GenMark Dx ePlex Blood Culture Identification Gram-Negative Panel

The test performance and potential clinical utility of the ePlex blood culture identification Gram-negative (BCID-GN) panel was evaluated relative to matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry on bacterial isolates and conventional antimicrobial susceptibility testing. The majority (106/108, 98.1%) of GN bacteria identified by MALDI were on the BCID-GN panel, and valid tests (107/108, 99.1%) yielded results on average 26.7 h earlier. For all valid tests with on-panel organisms, the positive percent agreement was 102/105 (97.2%) with 3 false negatives and the negative percent agreement was 105/105. Chart review (n = 98) showed that in conjunction with Gram stain results, negative pan-Gram-positive (GP) markers provided the opportunity to discontinue GP antibiotic coverage in 63/98 (64.3%) cases on average 26.2 h earlier. Only 8/12 (66.7%) Enterobacterales isolates with resistance to third-generation cephalosporins harbored the CTX-M gene. In contrast, 8/8 CTX-M⁺ samples yielded a resistant isolate. Detection of 1 Stenotrophomonas maltophilia (18 h), 1 OXA23/48⁺ Acinetobacter baumannii (52.4 h), and 3 CTX-M⁺ Enterobacterales isolates on ineffective treatment (47.1 h) and 1 on suboptimal therapy (72.6 h) would have additionally enabled early antimicrobial optimization in 6/98 (6.1%) patients. IMPORTANCE The GenMark Dx ePlex rapid blood culture diagnostic system enables earlier time to identification of antimicrobial-resistant Gram-negative bacteria causing bloodstream infections. Its ability to rule out Gram-positive bacteria enabled early discontinuation of unnecessary antibiotics in 63/98 (64.3%) cases on average 26.2 h earlier. Detection of bacteria harboring the CTX-M gene as well as early identification of highly resistant bacteria such as Stenotrophomonas maltophilia and Acinetobacter baumannii enabled optimization of ineffective therapy in 6/98 (6.1%) patients. Its implementation in clinical microbiology laboratories optimizes therapy and improves patient care.

Fn-Dps, a novel virulence factor of Fusobacterium nucleatum, disrupts erythrocytes and promotes metastasis in colorectal cancer

Fusobacterium nucleatum (Fn) is a critical colorectal cancer (CRC)-associated bacterium. DNA hunger/stationary phase protective proteins (Dps) are bacterial ferritins that protect DNA from oxidative stress. However, little is known about the regulatory roles of Fn-Dps towards host cellular functions. Here, we identified Fn-Dps from the culture supernatant of Fn by mass spectrometry, and prepared the recombinant of Fn-Dps protein. We show a novel virulence protein of Fn, Fn-Dps, which lyses and disrupts erythrocytes by the competition for iron acquisition. Also, Fn-Dps facilitates intracellular survival of Fn in macrophages by upregulating the expression of the chemokine CCL2/CCL7. In addition, Fn-Dps can elicit a strong humoral immune response, and mucosal immunization with Fn-Dps conferred protection against Fn in the intestinal tract. Moreover, a high level of anti-Fn-Dps antibody was prevalent in populations, and elevated anti-Fn-Dps antibody levels were observed in CRC patients. Furthermore, Fn-Dps promotes the migration of CRC cells via the CCL2/CCL7-induced epithelial-mesenchymal transition (EMT) and promotes CRC metastasis in vivo.

Colonization of Fusobacterium nucleatum is an independent predictor of poor prognosis in gastric cancer patients with venous thromboembolism: a retrospective cohort study

BACKGROUND

Fusobacterium nucleatum (F. nucleatum) often colonizes cancerous gastric tissues and is characterized by the promotion of platelet aggregation and the development of visceral thrombosis. Venous thromboembolism (VTE) leads to a significant increase in the mortality of gastric cancer (GC) patients. However, the relationship between the colonization of F. nucleatum and the prognosis of GC patients is still unknown.

AIM

The aim of this study was to explore whether the colonization of F. nucleatum is related to the prognosis of GC patients complicated with VTE and to explore other potential risk factors.

METHODS

From 2017-2021, the data of 304 patients with new VTEs during the treatment of GC at the Affiliated Cancer Hospital of Zhengzhou University were collected. Fluorescence in situ hybridization of F. nucleatum was performed on pathological sections of cancer tissues from the patients. Survival analysis methods, including the Kaplan‒Meier method and Cox proportional hazard model, were performed.

RESULTS

F. nucleatum colonization was significantly associated with splanchnic vein thrombosis, higher platelet-lymphocyte ratio (PLR), and lower absolute lymphocyte count. In the multivariable Cox model, F. nucleatum colonization was found to be an independent risk factor for the prognosis of GC, with an adjusted HR of 1.77 (95% CI, 1.17 to 2.69 [P = 0.007]). In addition, patients with high PLR (HR: 2.65, P = 0.004) or VTE occurring during four cycles of chemotherapy (HR: 2.32, P = 0.012) exhibited shorter survival. Conversely, those experiencing VTE later (HR per month from diagnosis of GC: 0.95, P = 0.006) or using IVC filters (HR: 0.27, P = 0.011) had longer survival.

CONCLUSION

Colonization of F. nucleatum in GC tissues was associated with lower absolute lymphocyte count and higher PLR in GC patients with VTE. F. nucleatum colonization also appeared to be associated with the development of VTE in specific sites, in particular the splanchnic vein. Colonization of F. nucleatum may potentially represent an independent predictor of poor prognosis in GC patients. Additional research is necessary to validate these findings.

A case report of severe Fusobacterium nucleatum sepsis secondary to nephrectomy

Background

Fusobacterium nucleatum (F. nucleatum) is a resident anaerobic bacterium, which in rare cases may invade blood from the head and neck or the digestive tract to cause bacteremia and induce venous thrombosis. F. nucleatum is closely related to abdominal tumors, but it has not been reported in relation to renal tumors. We report herein a possible case.

Case presentation

This patient had kidney cancer with thrombosis in the right renal vein but had no sign of infection. After radical nephrectomy, thrombi formed in his left renal vein, and when removed, severe sepsis occurred. He did not respond to treatment with antibiotics and died, but the blood culture done confirmed that he had F. nucleatum bacteremia.

Conclusion

F. nucleatum may also be associated with kidney cancer, and could cause post-operative renal vein thrombosis, and sepsis or septic shock after thrombectomy.

A discrepant presentation of bacteremia in the emergency department linked to a Fusobacterium nucleatum infection: a case report

BACKGROUND

Fusobacterium nucleatum is an anaerobic bacterium mainly responsible for acute or chronic infection of the ear, nose, and throat, potentially bacteremic with a risk of extraoral metastatic infection. Bacteremia occurs mainly in the elderly or in immunodeficient individuals, with high mortality. F. nucleatum is not the first cause of tonsillar infection in emergency departments, which are more often the consequence of a viral or streptococcal infection, but it is a risk factor for severe bacterial infection, especially in a viral pandemic context.

CASE PRESENTATION

A 25-year-old European woman with no history presented to the emergency department with fever (38.9 °C), pharyngeal symptoms, intermittent headaches, and alteration of general condition. On examination, she presented odynophagia associated with moderate tonsillar hypertrophy, her neck was painful but flexible. A rapid diagnostic test for beta-hemolytic group streptococcus was negative. First biological analyses revealed an inflammatory syndrome with C-reactive protein of 76 mg/L. Procalcitonin was measured secondarily, and was 2.16 µg/L. Faced with discordant clinical and biological findings, a lumbar puncture was performed, which came back negative. At hour eight, hypotension was observed but corrected after filling with physiological serum. The patient was hospitalized for monitoring, based on a hypothesis of severe viral presentation. At hour 24, pyrexia confirmed this hypothesis. A spontaneous but transient improvement and no new hemodynamic event led to early discharge. At day three, she was rehospitalized for increased and continuous headaches, without hemodynamic severity. A broad-spectrum probabilistic antibiotic therapy of ceftriaxone and metronidazole was started due to first blood cultures positive for anaerobic Gram-negative bacilli, while waiting for identification of the pathogen. Three days later, F. nucleatum was identified. According to the microbiological results, antibiotic therapy was adapted with amoxicillin and clavulanic acid, and no further complications were observed during clinical or complementary examinations. The final diagnosis was a F. nucleatum oropharyngeal infection complicated by bacteremia, without metastatic spread.

CONCLUSION

The etiologies of tonsillar infection are not limited to benign viruses or bacteria. These should not be overlooked in emergency medicine, especially when the clinical presentation is discrepant. A combination of early bacterial investigations as blood culture and close clinical monitoring is the only safe way to detect bacteremia, especially in immunocompetent patients.

A rare case of rectal bleeding and Fusobacterium mortiferum sepsis due to solitary fibrous tumour originating from the mesentery

Solitary fibrous tumours (SFTs) are rare mesenchymal tumours that are mostly seen in the pleura. Lately, they have also been described in other locations. Recent discovery of the NAB2-STAT6 fusion gene which is specific for SFTs has led to an accurate diagnosis of SFTs. The occurrence of SFTs in the mesentery is very rarely reported in the literature. We report a case of a 63-year-old female who presented with abdominal pain, rectal bleeding and Fusobacterium bacteraemia, who was ultimately found to have a mesenteric SFT.

A Multicenter Clinical Study To Demonstrate the Diagnostic Accuracy of the GenMark Dx ePlex Blood Culture Identification Gram-Negative Panel

Bacteremia can progress to septic shock and death without appropriate medical intervention. Increasing evidence supports the role of molecular diagnostic panels in reducing the clinical impact of these infections through rapid identification of the infecting organism and associated antimicrobial resistance genes. We report the results of a multicenter clinical study assessing the performance of the GenMark Dx ePlex investigational-use-only blood culture identification Gram-negative panel (BCID-GN), a rapid diagnostic assay for detection of bloodstream pathogens in positive blood culture (PBC) bottles. Prospective, retrospective, and contrived samples were tested. Results from the BCID-GN were compared to standard-of-care bacterial identification methods. Antimicrobial resistance genes (ARGs) were identified using PCR and sequence analysis. The final BCID-GN analysis included 2,444 PBC samples, of which 926 were clinical samples with negative Gram stain results. Of these, 109 samples had false-negative and/or -positive results, resulting in an overall sample accuracy of 88.2% (817/926). After discordant resolution, overall sample accuracy increased to 92.9% (860/926). Pre- and postdiscordant resolution sample accuracy excludes 37 Gram-negative organisms representing 20 uncommon genera, 10 Gram-positive organisms, and 1 Candida species present in 5% of samples that are not targeted by the BCID-GN. The overall weighted positive percent agreement (PPA), which averages the individual PPAs from the 27 targets (Gram-negative and ARG), was 94.9%. The limit of detection ranged from 10⁴ to 10⁷ CFU/ml, except for one strain of Fusobacterium necrophorum at 10⁸ CFU/ml.

Extensive microbial diversity within the chicken gut microbiome revealed by metagenomics and culture

BACKGROUND

The chicken is the most abundant food animal in the world. However, despite its importance, the chicken gut microbiome remains largely undefined. Here, we exploit culture-independent and culture-dependent approaches to reveal extensive taxonomic diversity within this complex microbial community.

RESULTS

We performed metagenomic sequencing of fifty chicken faecal samples from two breeds and analysed these, alongside all (n = 582) relevant publicly available chicken metagenomes, to cluster over 20 million non-redundant genes and to construct over 5,500 metagenome-assembled bacterial genomes. In addition, we recovered nearly 600 bacteriophage genomes. This represents the most comprehensive view of taxonomic diversity within the chicken gut microbiome to date, encompassing hundreds of novel candidate bacterial genera and species. To provide a stable, clear and memorable nomenclature for novel species, we devised a scalable combinatorial system for the creation of hundreds of well-formed Latin binomials. We cultured and genome-sequenced bacterial isolates from chicken faeces, documenting over forty novel species, together with three species from the genus Escherichia, including the newly named species Escherichia whittamii.

CONCLUSIONS

Our metagenomic and culture-based analyses provide new insights into the bacterial, archaeal and bacteriophage components of the chicken gut microbiome. The resulting datasets expand the known diversity of the chicken gut microbiome and provide a key resource for future high-resolution taxonomic and functional studies on the chicken gut microbiome.

Lactococcus lactis KA-FF 1-4 reduces vancomycin-resistant enterococci and impacts the human gut microbiome

Probiotic is an alternative method to treat intestinal infection disease caused by antibiotic-resistant bacteria. In this study, Lactococcus lactis KA-FF 1-4 demonstrated to have the potential to inhibit the growth of Vancomycin-resistant enterococci (VRE) by producing anti-microbial substance. In co-culture, L. lactis KA-FF 1-4 (10⁸ CFU/mL) inhibited the growth of VRE from 10³-10⁴ CFU/mL to zero after 6 h of exposure. However, in a gut model contained human gut microbiota, this anti-VRE activity of L. lactis KA-FF 1-4 was reduced to only 3.59-6.12%. The unexpected difference in efficacy between the experimental models could be explained by the fact that the growth of L. lactis KA-FF 1-4 was stable in the gut model. Leaving aside these limitations, we observed that adding L. lactis KA-FF 1-4 into the human gut model containing VRE was able to enhance microbial richness and diversity. Specifically, a higher abundance of beneficial microbes from the group of Bifidobacterium spp. and Bacteroides fragilis. L. lactis KA-FF 1-4 also enhanced the abundance of Parabacteroides, Lactococcus, and Fusobacterium and promoted the production of lactic acid in the gut model. However, these effects were not observed in the gut model without L. lactis KA-FF 1-4. Even though this study could not demonstrate a significant anti-VRE effect of the L. lactis KA-FF 1-4 in a gut model, our results still offer evidence that L. lactis KA-FF 1-4 could positively modulate the gut microbiota by promoting the growth of beneficial microbes and their metabolite. L. lactis KA-FF 1-4 has probiotic properties to fight against VRE infection, therefore further investigation in animal model is needed.

Relevance of anaerobic bacteremia in adult patients: A never-ending story?

Obligate anaerobic bacteria are considered important constituents of the microbiota of humans; in addition, they are also important etiological agents in some focal or invasive infections and bacteremia with a high level of mortality. Conflicting data have accumulated over the last decades regarding the extent in which these pathogens play an intrinsic role in bloodstream infections. Clinical characteristics of anaerobic bloodstream infections do not differ from bacteremia caused by other pathogens, but due to their longer generation time and rigorous growth requirements, it usually takes longer to establish the etiological diagnosis. The introduction of matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS) has represented a technological revolution in microbiological diagnostics, which has allowed for the fast, accurate and reliable identification of anaerobic bacteria at a low sample cost. The purpose of this review article is to summarize the currently available literature data on the prevalence of anaerobic bacteremia in adults for physicians and clinical microbiologists and to shed some light on the complexity of this topic nowadays.