Clinical significance of Bacteroides fragilis as a potential prognostic factor in colorectal cancer.

INTRODUCTION: Bacteroides fragilis (B. fragilis) is considered to act in an anti-inflammatory manner on the intestinal tract. On the contrary, enterotoxigenic B. fragilis (ETBF), a subtype of B. fragilis, produces an enterotoxin (BFT; B. fragilis toxin), leading to asymptomatic chronic infections and colonic tumor formation. However, the impact of B. fragilis and ETBF on the clinical outcome of colorectal cancer (CRC) remains unclear. We aim to assess whether their presence affects the outcome in patients with CRC after curative resection. METHODS: We obtained 197 pairs of matched formalin-fixed paraffin-embedded samples from cancerous and adjacent non-cancerous tissues of patients with pathological stage (pstage) II and III CRC after curative resection. The presence of B. fragilis and ETBF were estimated using real-time polymerase chain reaction, and recurrence-free survival (RFS) and overall survival (OS) of the patients were analyzed. RESULTS: 16S rRNA for B. fragilis and bft DNA were detected in 120 (60.9%) and 12 (6.1%) of the 197 patients, respectively. B. fragilis-positive patients had better RFS than B. fragilis-negative patients, although that was not statistically significant. In subgroup analysis, better outcomes on RFS were observed in the presence of B. fragilis in pstage II and left-sided CRC. The association of B. fragilis positivity on OS was accentuated in the depth of T4 subgroup. No significant differences were observed in RFS and OS between ETBF and non-toxigenic B. fragilis. CONCLUSIONS: Our findings suggest that the presence of B. fragilis is associated with better outcomes in patients with pstage II and III CRC after curative resection.

Intra-spinal abscess due to Bacteroides fragilis and Klebsiella pneumoniae co-infection in a child with spinal dysraphism.

Bacteroides fragilis (B. fragilis) is an uncommon cause of spinal abscess. We present a case of an 18-month-old child, with spinal dysraphism-Spina bifida occulta, who developed intra-spinal abscess infection with B. fragilis and Klebsiella pneumoniae. Magnetic resonance imaging (MRI) of the brain and spine showed multiple abscesses extending through the presacral fistula into the spinal cord. Patient was surgically treated along with administration of antimicrobial agents (ceftriaxone and metronidazole), resulting in an excellent clinical outcome.

Bacteroides fragilis vertebral osteomyelitis: A rare clinical entity.

Acute pyogenic vertebral osteomyelitis is mainly attributed to haematogenous spread of aerobic bacteria, while anaerobic osteomyelitis results from contiguous spread of polymicrobial infections through breaks in the gut mucosal barrier and involves the vertebral bodies in only about 2%-5%. Herein, we report two cases of vertebral osteomyelitis due to Bacteroides fragilis. It is noteworthy that cases of vertebral osteomyelitis due to Bacteroides fragilis have been attributed to the extension of intra-abdominal or pelvic floor infections. However, in the two cases described, there was no history of a previous medical intervention nor an intestinal or pelvic floor infection. Early recognition of the aetiological agent that causes vertebral osteomyelitis may lead to the timely treatment and therefore, may deter any neurosurgical/orthopaedic interventions.

A systemic review of the role of enterotoxic Bacteroides fragilis in colorectal cancer.

Enterotoxigenic Bacteroides fragilis (ETBF) has received significant attention for a possible association with, or causal role in, colorectal cancer (CRC). The goal of this review was to assess the status of the published evidence supporting (i) the association between ETBF and CRC and (ii) the causal role of ETBF in CRC. PubMed and Scopus searches were performed in August 2021 to identify human, animal, and cell studies pertaining to the role of ETBF in CRC. Inclusion criteria included the use of cell lines, mice, exposure to BFT or ETBF, and detection of bft. Review studies were excluded, and studies were limited to the English language. Quality of study design and risk of bias analysis was performed on the cell, animal, and human studies using ToxRTools, SYRCLE, and NOS, respectively. Ninety-five eligible studies were identified, this included 22 human studies, 24 animal studies, 43 cell studies, and 6 studies that included both cells and mice studies. We found that a large majority of studies supported an association or causal role of ETBF in CRC, as well as high levels of study bias was detected in the in vitro and in vivo studies. The high-level heterogeneity in study design and reporting made it difficult to synthesize these findings into a unified conclusion, suggesting that the need for future studies that include improved mechanistic models, longitudinal in vitro and in vivo evidence, and appropriate control of confounding factors will be required to confirm whether ETBF has a direct role in CRC etiopathogenesis.

Identification of enterotoxigenic Bacteroides fragilis in patients with diarrhea: A study targeting 16S rRNA, gyrB and nanH genes.

OBJECTIVES: We aimed to identify the enterotoxigenic Bacteroides fragilis (ETBF) and bft subtypes among patients with diarrhea. In addition, we assessed whether DNA gyrase subunit B (gyrB) and neuraminidase (nanH) genes are useful determinants for identification of B. fragilis compared to 16S rRNA sequencing as a reference method. METHODS: The 530 fecal specimens were cultured on BBE agar. The colonies which supposed to be a member of B. fragilis group were subjected to 16S rRNA gene sequencing and PCR assays targeting the Bacteroides fragilis group (BFG), gyrB and nanH. The B. fragilis toxin (bft) gene and its subtype was detected by PCR. The specificity of PCR assays was calculated considering the 16S rRNA gene sequencing as the reference method. RESULTS: A total of 111 Gram-negative anaerobic coccobacilli were isolated from 530 fecal specimens using BBE agar. Of the 111 isolates, 100 (90.09%) were assumed to be a member of Bacteroides fragilis group as they yielded an amplicon through PCR using the group-specific primers (Bfra-F/g-Bfra-R). However, only 28 isolates out of 100 were definitively identified as species of Bacteroides using16S rRNA gene sequencing; of which 15 isolates were B. fragilis and the remaining 13 isolates were identified as B. thetaiotaomicron (n = 6), Parabacteroides distasonis (n = 3), B. vulgatus (Phocaeicola vulgatus) (n = 1), B. ovatus (n = 1), B. congonensis (n = 1) and B. nordii (n = 1). Among the 15 isolates of B. fragilis, 4 were found to be ETBF. Compared to the reference method, the specificity and accuracy of the PCR targeting gyrB gene (64.7% and 65%) was higher than of nanH (36.4% and 46%, respectively. CONCLUSIONS: This study demonstrated that more than one-fourth of B. fragilis isolates harbored bft gene and less than 1% of patients with diarrhea harbored ETBF. The slight agreement between the PCR assays -already used for identification of B. fragilis which targeting gyrB or nanH - and 16S rRNA gene sequencing as the reference method was noted.

Fusobacterium nucleatum and Bacteroides fragilis detection in colorectal tumours: Optimal target site and correlation with total bacterial load.

BACKGROUND: Mucosal infiltration by certain bacterial species may contribute to the development and progression of colorectal cancer (CRC). There is considerable variation in reported detection rates in human CRC samples and the extent to which bacterial infiltration varies across regions of the primary tumour is unknown. This study aimed to determine if there is an optimal site for bacterial detection within CRC tumours. METHODS: Presence of target bacterial species was assessed by quantitative real-time PCR (qPCR) in 42 human CRC tumours. Abundance in primary tumour regions, normal epithelium and at metastatic sites was investigated in an expanded cohort of 51 patients. Species presence/absence was confirmed by diversity profiling in five patients. Correlation with total bacterial load and clinicopathological features was assessed. RESULTS: Fusobacterium nucleatum and Bacteroides fragilis were detected in tumours from 43% and 24% of patients, respectively (17% positive for both species). The optimal detection site was the tumour luminal surface (TLS). Patients testing positive at the TLS frequently tested negative at other sites, including central tumour and invasive margin. F. nucleatum was detected at a higher frequency in tumour versus normal epithelium (p < 0.01) and was associated with more advanced disease (p = 0.01). Detection of both species correlated with total bacterial load. However, corroboration of qPCR results via diversity profiling suggests detection of these species may indicate a specific microbial signature. CONCLUSIONS: This study supports a role for F. nucleatum in CRC development. Presence of F. nucleatum and B. fragilis varies across primary tumour regions, with the TLS representing the optimal site for bacterial detection.

A Case of Native Joint Septic Arthritis Caused by Bacteroides fragilis.

BACKGROUND Bacteroides fragilis (B. fragilis) is an uncommon cause of native joint septic arthritis (NJSA). It is an anaerobic gram-negative rod that is normally found in the oral cavity, gastrointestinal tract, genitourinary system, and skin, and thus is rarely isolated from the musculoskeletal system. Risk factors for B. fragilis NJSA include inflammatory arthritis, malignancy, sickle cell disease, and ischemic heart disease. CASE REPORT We discuss a case of a 65-year-old man with coronary artery disease, heart failure, chronic kidney disease, and gout, who presented with 5 days of right knee pain, redness, swelling, and warmth. His history included a corticosteroid injection in the affected knee 2 months prior to presentation. The patient was febrile with a palpable right knee joint effusion on exam. Labs were significant for leukocytosis and elevated inflammatory markers. Synovial fluid was aspirated, which was diagnostic for septic arthritis, with cultures growing B. fragilis. Blood cultures were negative, so the infection was attributed to the prior joint injection. The patient was subsequently taken to the operating room for irrigation and debridement. He was started on metronidazole, but he unfortunately left against medical advice before treatment was complete and was lost to follow-up thereafter. CONCLUSIONS B. fragilis NJSA most often occurs in the setting of bacteremia or contiguous spread from a concomitant infection. Management involves antibiotics such as metronidazole and surgical drainage. Due to the paucity of data on an infection such as in the present case, the optimal duration of metronidazole is not well-established.

High frequency of enterotoxigenic Bacteroides fragilis and Enterococcus faecalis in the paraffin-embedded tissues of Iranian colorectal cancer patients.

BACKGROUND: The association between specific bacteria and colorectal cancer (CRC) has been proposed. Only a few studies have, however, investigated this relationship directly in colorectal tissue with conflicting results. So, we aimed to quantitate Streptococcus gallolyticus, Fusobacterium spp, Enterococcus faecalis and enterotoxigenic Bacteroides fragilis (ETBF) in formalin-fixed and paraffin-embedded (FFPE) colorectal tissue samples of Iranian CRC patients and healthy controls. METHODS: A total of 80 FFPE colorectal tissue samples of CRC patients (n = 40) and healthy controls (n = 40) were investigated for the presence and copy number of above bacterial species using quantitative PCR. Relative quantification was determined using ΔΔCT method and expressed as relative fold difference compared to reference gene. RESULTS: Relative abundance and copy number of E. faecalis and ETBF were significantly higher in CRC samples compared to control group. E. faecalis was more prevalent than ETBF in tumor samples. Frequency of ETBF and E. faecalis in late stages (III/IV) of cancer was significantly higher than early stages (I/II). We did not detect a significant difference in abundance of S. gallolyticus and Fusobacterium spp between two groups. CONCLUSION: Our study revealed the higher concentration of E. faecalis and ETBF in FFPE samples of CRC patients than controls. However, additional investigations on fecal and fresh colorectal cancer tissue samples are required to substantiate this correlation.

Rapid detection and surveillance of cfiA-positive Bacteroides fragilis using matrix-assisted laser desorption ionization time-of-flight mass spectrometry.

OBJECTIVES: To perform surveillance of cfiA-positive Bacteroides fragilis using new subtyping software module, MALDI Biotyper Subtyping Module (MBT Subtyping Module), on MALDI-TOF MS system, and to evaluate the detection ability of the module. METHODS: cfiA-positive strains were presumed using the module against B. fragilis isolated between 2006 and 2019. The cfiA gene was confirmed using PCR. In cfiA-positive B. fragilis, the insertion sequence (IS) elements were examined and the MBT STAR-BL assay was performed to examine meropenem hydrolysis activity. RESULTS: Of the 396 B. fragilis strains included, the MBT Subtyping Module detected 33 presumptive cfiA-positive strains (8.3%), of which 32 harbored the cfiA gene. The sensitivity and specificity of the MBT Subtyping Module for detecting cfiA-positive B. fragilis were 100.0% and 99.7%, respectively. Of the 32 strains harboring the cfiA gene, seven strains possessed IS elements, which were thought to induce high cfiA expression. Meropenem hydrolysis was detected in all seven strains that were positive for both cfiA and IS elements, and they exhibited resistance to meropenem and imipenem. The overall non-susceptibility rates to meropenem and imipenem were 84.8% and 36.4%, respectively, in the 33 presumptive cfiA-positive strains. CONCLUSION: The MBT Subtyping Module can detect cfiA-positive B. fragilis rapidly and accurately, supporting its use for surveillance of cfiA-positive B. fragilis in clinical settings.

First case of an invasive Bacteroides dorei infection detected in a patient with a mycotic aortic aneurysm-raising a rebellion of major indigenous bacteria in humans: a case report and review.

BACKGROUND: Bacteroides dorei is an anaerobic gram-negative bacterium first described in 2006. Because of the high similarity in mass spectra between B. dorei and Bacteroides vulgatus, discriminating between these species is arduous in clinical practice. In recent decades, 16S rRNA gene sequencing has been a complementary method for distinguishing taxonomically close bacteria, including B. dorei and B. vulgatus, at the genus and species levels. Consequently, B. dorei has been shown to contribute to some diseases, including type 1 autoimmune diabetes mellitus and atherosclerotic diseases. However, there are no reports on invasive infectious diseases caused by B. dorei. This report describes the first case of direct invasion and colonisation of human tissue by B. dorei, thus providing a warning regarding the previously proposed application of B. dorei as a live biotherapeutic for atherosclerotic diseases. CASE PRESENTATION: A 78-year-old Japanese man complained of intermittent chest/back pain and was diagnosed with a mycotic thoracic aortic aneurysm by enhanced computed tomography on admission. Despite strict blood pressure control and empirical antibiotic therapy, the patient's condition worsened. To prevent aneurysmal rupture and eliminate infectious foci, the patient underwent surgical treatment. The resected specimen was subjected to tissue culture and 16S rRNA gene sequencing analysis to identify pathogenic bacteria. A few days after the surgery, culture and sequencing results revealed that the pathogen was B. dorei/B. vulgatus and B. dorei, respectively. The patient was successfully treated with appropriate antibacterial therapy and after improvement, was transferred to another hospital for rehabilitation on postoperative day 34. There was no recurrence of infection or aneurysm after the patient transfer. CONCLUSIONS: This report describes the first case of invasive infectious disease caused by B. dorei, casting a shadow over its utilisation as a probiotic for atherosclerotic diseases.

What we actually know about the pathogenicity of Bacteroides pyogenes.

The aim of the study was to evaluate the pathogenic potential of Bacteroides pyogenes, rarely identified in clinical laboratories anaerobic bacteria. To increase the knowledge about this poorly understood anaerobic microorganism, the study also includes cases of infections described so far in the literature. Only the use of 16S rRNA sequencing and mass spectrometry technique allowed the identification of B. pyogenes from clinical specimens. We reported 13 severe human infections caused by B. pyogenes. Bacteria were cultured from the wound after biting by animals, chronic infections within the oral cavity, from patients with histologically or radiological proven osteomyelitis, surgical site infection, and from urine sample collected after a urological procedure. Most (9/13) of the patients required hospitalization. Almost 70% of them needed urgent admission via the emergency room. Two inpatients due to a life-threatening condition were admitted to the intensive care unit. Almost 50% of isolates were resistant to penicillin. All resistant to penicillin strains were isolated from skin and mucous membrane infections.

Yaws, Haemophilus ducreyi, and Other Bacterial Causes of Cutaneous Ulcer Disease in the South Pacific Islands.

Cutaneous ulcers in the tropics are a painful and debilitating condition that anchors people into poverty. In rural regions of the South Pacific, infectious cutaneous ulcers are caused mainly by bacteria, including Treponema pallidum pertenue (yaws), Haemophilus ducreyi, and polymicrobial ulcers. For this group of infections the term cutaneous ulcer disease (CUD) is proposed. Some infections can cause malformations on the bone that have a permanent impact on lives in endemic communities. Better characterization of CUD may help design diagnostic tools and more effective antimicrobial therapies. This review updates the knowledge of CUD and discusses optimized terminology and syndromic management.

Spontaneous Bacteroides fragilis spondylodiscitis in an elderly lady.

A 76-year-old woman presented following two episodes of unexplained falls at home. Blood cultures were positive for Bacteroides fragilis and following investigations she was diagnosed with L4/L5 spondylodiscitis confirmed on spine MRI. She was initially treated with intravenous metronidazole and flucloxacillin prior to switching to ceftriaxone with good results. No primary cause of B. fragilis bacteraemia was found in this case. B. fragilis is a rare cause of spondylodiscitis.

Bacteroides in colonic mucosa-associated microbiota affects the development of minimal hepatic encephalopathy in patients with cirrhosis.

BACKGROUND/PURPOSE: Gut microbiota has been associated with liver cirrhosis and, possibly, hepatic encephalopathy. However, only a few studies have examined the link between mucosa-associated microbiota (MAM) and minimal hepatic encephalopathy (MHE). Our aim was to investigate this relationship. METHODS: Twenty-four patients with cirrhosis underwent colon biopsies at our institution, between January 2014 and April 2015. Patterns of microbial colonization were examined using 16S rRNA gene sequences. MHE was diagnosed using the Neuropsychological Test. RESULTS: Ten (41.7%) of the 24 patients were diagnosed as having MHE. There was no significant difference in the diversity of gut microbiota by sampling locations between those with and without MHE. However, the diversity of the gut microbiota and the proportion of the genus Bacteroides decreased as a function of declining liver function. We divided patients into those with the highest proportion of the genus Bacteroides (Bacteroides-dominant group; n = 9) and into a Bacteroides non-dominant group (n = 15). In the Bacteroides-dominant group, only 1 patient (11.1%) was diagnosed as having MHE, with the incidence rate of MHE being significantly lower in the Bacteroides-dominant group than in the non-dominant group (p = 0.019). The Child-Pugh score (p = 0.05) and use of proton-pump inhibitors (p = 0.015) were negatively correlated to the proportion of Bacteroides. Furthermore, the proportion of the family Clostridiaceae was significantly higher in the Bacteroides-dominant group than in the non-dominant group (p = 0.078). CONCLUSIONS: The decrease in microbial diversity and genus Bacteroides in MAM is a risk factor for MHE in patients with liver cirrhosis.

Bacteroides Spp. Blebitis, Keratitis, and Endophthalmitis Following Uncomplicated Trabeculectomy.

PURPOSE: To describe the first known case of Bacteroides spp. related blebitis, keratitis, and endophthalmitis following uncomplicated trabeculectomy. METHODS: This was a case report and literature review. CASE: A 63-year-old immunocompetent white male underwent uncomplicated trabeculectomy of his right eye. Two weeks later, a blebitis with adjacent keratitis was diagnosed, progressing over several days to endophthalmitis despite hourly topical fortified antibiotic therapy. Although gram stain and culture of the bleb surface, a conjunctival suture, the aqueous humor, and the vitreous were negative, topical real-time quantitative polymerase chain reaction testing disclosed the presence of Bacteroides spp. Following treatment with topical and intravitreal clindamycin and intravenous meropenem, all clinical evidence of infection resolved. Best spectacle-corrected visual acuity improved to 20/25 (0.8) subsequent to combined cataract extraction, intraocular lens implantation, and pars plana vitrectomy for persistent vitreous debris. CONCLUSIONS: Bacteroides may be a rare cause of postoperative blebitis, keratitis, and endophthalmitis. A favorable outcome may be attained, provided that an accurate diagnosis and effective treatment can be provided, which may be facilitated by real-time quantitative polymerase chain reaction in select cases.

Bloodstream infection caused by Bacteroides denticanum, a close relative of Bacteroides pyogenes, misidentified by MALDI TOF- mass spectrometry.

Bacteroides pyogenes can cause infections in humans. We describe a case of bloodstream infection caused by Bacteroides denticanum that probably originated from a dog bite. MALDI-TOF MS misidentified this new species as B. pyogenes. Subsequent analysis using the 16S rRNA sequencing approach identified the species as B. denticanum.

Diffusion-weighted imaging is helpful in the accurate non-invasive diagnosis of breast abscess: correlation with necrotic breast cancer.

Clinical differentiation of atypical breast abscesses from necrotic tumour in premenopausal women is challenging and may delay appropriate therapy. In this case report, we present a 36-year-old woman with signs, symptoms and conventional imaging features of malignancy who underwent breast MRI. On diffusion-weighted imaging (DWI), profoundly low apparent diffusion coefficient values were a distinguishing sign of breast abscess from necrotic breast cancer, and helped manage the patient conservatively. We present a companion case of necrotic breast tumour highlighting significant differences in DWI.