Tools
Bacteroides Fragilis
Introduction
Anaerobes are bacteria that do not require oxygen to live. Anaerobes usually fit into two groups based on their gram stain into gram-positive and gram-negative and into cocci and bacilli based on their morphology. Of these, notable pathogenic gram-negative bacillus-shaped strains are Prevotella, Fusobacterium, Bacteroides, and Porphyromonas. Bacteroides species are important clinical pathogens and are present in most anaerobic infections, with an associated mortality of approximately 19%.[1] Bacteroides fragilis is an obligate anaerobic gram-negative bacillus. The human colon has the greatest population of bacteria in the body (over ten organisms per gram of wet weight), and the largest part of these organisms are anaerobes; of these, approximately 25% are species of Bacteroides.[2] Bacteroides fragilis is part of the normal microbiota of the human colon. Disruption of the mucosal surface either by inflammation, trauma, or surgery and spread of Bacteroides fragilis to the bloodstream or surrounding tissues results in clinically significant infection.
Etiology
Register For Free And Read The Full Article
Search engine and full access to all medical articles- 10 free questions in your specialty
- Free CME/CE Activities
- Free daily question in your email
- Save favorite articles to your dashboard
- Emails offering discounts
Learn more about a Subscription to StatPearls Point-of-Care
Etiology
Bacteroides fragilis is a part of the colonic microbiota, and Bacteroides thetaiotaomicron is more abundant than B. fragilis in the microbiota but has been less frequently identified as a pathogen. Humans acquire Bacteroides fragilis likely at birth. In the early months of life, the bacterial flora changes considerably, and by the age of one year, the intestinal microbiota converts toward an adult microbiota profile.[3]
Bacteroides fragilis infection is one of the common organisms involved in intrabdominal infection. Disruption of tissue barriers and the spread of intestinal flora into adjacent tissue causes polymicrobial infection. That is why Bacteroides fragilis is seldom the solitary organism of infection and usually part of other anaerobic organisms and Enterobacteriaceae.
Epidemiology
Bacteroides fragilis are part of the normal human colon flora. In a longitudinal analysis of the stool specimens collected from 15 healthy adults, B. fragilis was cultured from 87% of the cohort.[4] Bacteroides fragilis plays an intricate role in the human colon and has a beneficial relationship with the host. Still, if there is a breach in the integrity of the mucosal lining either by surgery or trauma, it can cause significant morbidity.[1]
A review of surgical site infections in Japan showed that in 12.8%of cases, Bacteroides species were isolated.[5] An epidemiological review of anaerobic infection from Greece showed that patients with an infection due to B. fragilis were more frequent in patients with recent surgery. Total mortality was 10.9% and was associated with bacteremia or malignancy.[6]
Between January 1, 1969, and December 31, 2012, 20 episodes of Bacteroides periprosthetic joint infections were observed in 17 patients at the Mayo Clinic in Rochester, MN.[7]
Pathophysiology
Bacteroides fragilis is usually a commensal organism that, when the mucosal barrier becomes disrupted, results in abscess formation and bacteremia. Bacteroides species have involvement in the prolongation of the intrinsic pathway of clotting in human blood.[8] Both B. fragilis and B. thetaiotaomicron cause the release of significant levels of bradykinin in human plasma, a mechanism that will provide the bacteria with an opportunity to spread by inhibition of clot formation.[8]
Bacteroides fragilis virulence is mostly by toxin production. Enterotoxigenic Bacteroides fragilis (ETBF) strains are strains of B. fragilis that secrete an enterotoxin termed the B. fragilis toxin (BFT) and may have a role in inflammatory diarrhea and flare-ups of inflammatory bowel disease.[9][10]
Outer-membrane vesicles (OMVs) are vesicles that bud out of the outer membrane of bacteria and are commonly produced by gram-negative bacteria and may play a role in trafficking bacterial biochemicals.[11] Elhenawy et al. .demonstrated the preferential packing of acidic glycosidases and proteases into Bacteroide's outer membrane vesicles and proposed that OMVs contribute to the establishment and balance of the gut microbiota.[12]
Histopathology
In an experimental study evaluating mixed anaerobic infection, including Bacteroides and Fusobacterium species, acute inflammatory processes were noted in tissue samples occurring within hours postinfection. By 48 hours after infection, both acute and chronic inflammatory cells infiltrate the liver parenchyma. In 2 to 6 weeks after inoculation, Large intrahepatic abscesses were present.[13]
Experimental anaerobic maxillary sinusitis was induced in rabbits by inoculating Bacteroides fragilis in the nasal ostium. Moderate or severe inflammation appeared in all infected sinuses. The characteristic features were ciliary damage, desquamation, hyperplasia, and metaplasia of the epithelium.[14]
History and Physical
Predisposing factors for anaerobic infections include Bacteroides fragilis are recent surgery, trauma, and malignancy. Foul-smelling discharge and abscess formation are usually present on the clinical exam on anaerobic infections, including Bacteroides fragilis. Different clinical presentations depending on different tissues of involvement exist in the literature. Anaerobic bacteria, including Bacteroides fragilis, have been isolated from chronic pressure ulcers and diabetic foot ulcers. Enterotoxigenic Bacteroides fragilis may have involvement in inflammatory diarrhea. Bacteroides fragilis may also present in various clinical scenarios, such as necrotizing fasciitis and synergistic anaerobic infections. Bloodstream infection usually results from the spread of uncontrolled local infection into the bloodstream, or it could be a central line-associated bloodstream infection. In a review of anaerobic bacteremia, the Bacteroides fragilis group was the most common causative organism (41%), and the source was mostly intraabdominal infections.[15] The microbes involved in septic abortion are usually from the vaginal flora, but researchers also described septic abortion and bacteremia with distant abscess formation due to Bacteroides fragilis infection.[16] Anaerobic infection, including Bacteroides fragilis causing pyogenic arthritis of native joints, is a very infrequent presentation usually accompanied by bacteremia.[17][18] Bacteroides fragilis have also been an infrequent cause of periprosthetic joint infections. Necrotizing pancreatitis and anaerobic bacteremia are complications.[19] Anaerobic endocarditis is generally rare. Bacteroides fragilis endocarditis was present in a patient with Crohn disease.[20] Septic thrombophlebitis of the superior mesenteric vein has also occurred.[21]
Evaluation
The proper collection of specimens is critical to avoid contamination with the normal microbial flora. The key to appropriate processing is prompt transport to the laboratory for immediate handling. Needle aspiration and tissue biopsy are the best materials for anaerobic cultures. Exudates, swabs from burns, wounds, and skin abscesses are generally unacceptable for anaerobic cultures due to colonization by normal flora. (Mendoza, M.D. (Phil J Microbiol Infect Dis 1998; 27(2):71-73). Bacteroides fragilis are also diagnosable by PCR amplification.[22]
Treatment / Management
Bacteroides fragilis is resistant to penicillin due to the production of beta-lactamase. Cefoxitin, moxifloxacin, and clindamycin have low levels of susceptibility for Bacteroides fragilis, whereas Piperacillin/tazobactam, meropenem, and metronidazole have high susceptibility rates.[23] Metronidazole is the antibiotic of choice for the management of infections caused by anaerobes. The reported rate of metronidazole-resistant B. fragilis ranges from 0.5% to 7.8% across many surveys.[24] In anaerobes, acquired resistance to metronidazole may be due to a combination of various and complex mechanisms. Among them, nim genes, possibly located on mobile genetic elements, encode nitro-imidazole-reductases responsible for the drug inactivation.[25] The non-fragilis Bacteroides group (including B. intestinalis, B. nordii, B. pyogenes, B. stercoris, B. salyersiae, and B. cellulosilyticus) were found to be resistant to meropenem (14%) and cefotetan (71%).[26] An imipenem-resistant Bacteroides fragilis strain was found in Croatia.[27] Bacteroides fragilis infection is usually a part of polymicrobial infection that happens due to a breach of natural barriers either by surgery, inflammation, or trauma and result commonly in intrabdominal infections. Antimicrobial therapy of intraabdominal infections should include coverage for anaerobic infections along with Enterobacteriaceae. Coverage of Pseudomonas aeruginosa and Enterococcus faecalis is also a recommendation for hospital-associated intra-abdominal infections. (B3)
Newer drugs: eravacycline, a novel fluorocycline antibiotic, has been evaluated against complicated mixed aerobic/anaerobic intra-abdominal infections. eravacycline had good anaerobic in vitro activity with MICs of 4μg/ml or less against all Bacteroides and Parabacteroides strains tested, except for two B. ovatus strains that had MICs of 8 mcg/ml and one strain that had a MIC of 16 mcg/ml. Eravacycline was four-to-eight fold more active than tigecycline.[28] Another novel antibiotic, tazobactam/ceftolozane: The efficacy and safety of tazobactam/ceftolozane in combination with metronidazole, has been assessed and showed a good response for Bacteroides fragilis 95.2% (20/21) in Japanese patients with complicated intraabdominal infections.[29]
Differential Diagnosis
The clinical significance of identifying Bacteroides fragilis in cultures varies considerably based on the type of specimen collected. For example, if Bacteroides fragilis were identified in a swab from a diabetic foot ulcer or a decubitus ulcer, it would not have any clinical implications as the ulcers are usually colonized with a high bacterial load of mixed aerobic and anaerobic growth. On the other hand, if B. fragilis were identified in an aspirate from an intraabdominal fluid collection, then it signifies intrabdominal infection that should have management with targeted antimicrobial therapy along with source control of the infection. Bacteroides fragilis infections should merit consideration in patients with recent surgical intervention (especially abdominal surgery), trauma, and malignancy.
Pertinent Studies and Ongoing Trials
In an experimental study, B. fragilis exerted protective effects on a Clostridoides difficile infection mouse model through the modulation of gut microbiota and alleviating barrier destruction.[30]
Another study identified that Bacteroides fragilis species have a protective effect against antibiotic-associated diarrhea in rats by altering intestinal defenses and identified the vital role of B. fragilis strain ZY-312 in changing the colonic bacterial community.[31]
Diet could influence the determination of gut microbiota composition and the immune response.[32] Palmitic acid(dietary saturated fatty acid) had a stimulatory effect on the growth of B. fragilis and B. thetaiotaomicron.[33]
Prognosis
In a retrospective analysis by Cheng C.W. et al., the overall crude mortality rate of Bacteroides fragilis bacteremia is 30.7%, and malignancy was the most common comorbidity.[34] There have been suggestions that specific bacterial flora of the colon may play a role in the development of colorectal cancer. The risk of colorectal cancer increased in patients with bacteremia from B. fragilis or Streptococcus gallolyticus in a retrospective analysis in Hong Kong. These bacteria might enter the bloodstream from intestinal dysbiosis and perturbed barrier function.[35] However, a recent review from Denmark showed that overall, neither Fusobacterium nucleatum nor B. fragilis demonstrated a specific association with tumors of colorectal cancer patients. Still, both bacteria had a low presence in adenomas.[36]
Complications
Bacteroides species are found in most anaerobic infections, causing significant morbidity with an associated mortality of more than 19%.[1] Sepsis has occurred secondary to Bacteroides fragilis tubo-ovarian abscess requiring hysterectomy and bilateral salpingo-oophorectomy.[37]
Deterrence and Patient Education
Bacteroides fragilis is a bacteria that is a common component of the human colon bacteria. It has involvement in causing disease in humans under certain conditions. The human colon is lined by a mucosal barrier that protects body tissues from being invaded by the bacteria that inhabits the intestinal cavity. When the mucosal barrier is disrupted by trauma, surgery, or tumor, the bacteria invade the surrounding tissues through the disrupted barrier and start an infectious process. The human body's immune systems begin to combat the infection by an inflammatory process aiming to eradicate the infection. The inflammatory reactions of the body would manifest locally as abscess formation and systemically as fever, chills, and if the infection is severe, it may result in sepsis. The management of Bacteroides fragilis infection is usually by source control either by incision and drainage of the pus or aspiration along with antibiotics targeted toward the causative organism.
Pearls and Other Issues
- Bacteroides species are part of the human colon microbiota.
- Bacteroides fragilis is the most common cause of anaerobic infections in humans.
- Infection due to Bacteroides fragilis is usually polymicrobial and results from a disruption in tissue barriers.
- Source control and targeted antimicrobial therapy are the two keys to control Bacteroides fragilis infection.
- The role of Bacteroides fragilis in the development of colorectal cancer has been controversial among several studies.
Enhancing Healthcare Team Outcomes
The management of Bacteroides fragilis infection requires collaboration among healthcare professionals. It usually starts with the clinical suspicion of anaerobic infection in the setting of underlying trauma, recent surgical intervention, or malignancy. The proper specimen collection usually improves the diagnosis of Bacteroides fragilis infection. Anaerobic cultures obtained from sterile sites have the highest diagnostic yield. For example, cerebrospinal fluid cultures, blood cultures, and pleural fluid cultures growing Bacteroides fragilis are clinically significant and warrant treatment for meningitis, bloodstream infection, and empyema.
On the other hand, wound cultures wound swabs, or stool cultures will have very low diagnostic yield and may represent colonization that would not require any treatment. Anaerobic cultures must be collected in the appropriate containers and transported immediately to the microbiology laboratory. The handling of anaerobic infections in the microbiology lab is costly and requires expertise and proper equipment. The clinical interpretation of Bacteroides fragilis cultures usually requires the skill of Infectious disease physicians and pharmacists to help decide the clinical significance and to direct the targeted antimicrobial therapy. Bacteroides infections are typically severe infections and part of a polymicrobial invasion. The management strategy has two major goals: targeted antimicrobial therapy and adequate source control, and that usually involves coordination between the treating healthcare provider and surgical and interventional radiologist consultations. The interprofessional team, including physicians, nurses, lab technicians, and pharmacists, can improve outcomes. Pharmacists review medication selection, dosage, and drug-drug interactions and inform the prescriber of any concerns. Nurses are often involved in specimen collection and administration of antibiotics, as well as patient counsel, follow-up for compliance, and reporting their findings to the clinical staff. Pathologists and lab technicians must ensure proper specimen processing. All these examples of interprofessional collaboration and communication will contribute to better patient outcomes. [Level 5]
References
Wexler HM. Bacteroides: the good, the bad, and the nitty-gritty. Clinical microbiology reviews. 2007 Oct:20(4):593-621 [PubMed PMID: 17934076]
Salyers AA. Bacteroides of the human lower intestinal tract. Annual review of microbiology. 1984:38():293-313 [PubMed PMID: 6388494]
Endo A, Pӓrtty A, Kalliomӓki M, Isolauri E, Salminen S. Long-term monitoring of the human intestinal microbiota from the 2nd week to 13 years of age. Anaerobe. 2014 Aug:28():149-56. doi: 10.1016/j.anaerobe.2014.06.006. Epub 2014 Jun 13 [PubMed PMID: 24933584]
Level 1 (high-level) evidenceZitomersky NL, Coyne MJ, Comstock LE. Longitudinal analysis of the prevalence, maintenance, and IgA response to species of the order Bacteroidales in the human gut. Infection and immunity. 2011 May:79(5):2012-20. doi: 10.1128/IAI.01348-10. Epub 2011 Mar 14 [PubMed PMID: 21402766]
Takesue Y, Kusachi S, Mikamo H, Sato J, Watanabe A, Kiyota H, Iwata S, Kaku M, Hanaki H, Sumiyama Y, Kitagawa Y, Mizuguchi T, Ambo Y, Konosu M, Ishibashi K, Matsuda A, Hase K, Harihara Y, Okabayashi K, Seki S, Hara T, Matsui K, Matsuo Y, Kobayashi M, Kubo S, Uchiyama K, Shimizu J, Kawabata R, Ohge H, Akagi S, Oka M, Wakatsuki T, Suzuki K, Okamoto K, Yanagihara K. Antimicrobial susceptibility of pathogens isolated from surgical site infections in Japan: Comparison of data from nationwide surveillance studies conducted in 2010 and 2014-2015. Journal of infection and chemotherapy : official journal of the Japan Society of Chemotherapy. 2017 Jun:23(6):339-348. doi: 10.1016/j.jiac.2017.03.010. Epub 2017 Apr 5 [PubMed PMID: 28391954]
Papaparaskevas J, Katsandri A, Pantazatou A, Stefanou I, Avlamis A, Legakis NJ, Tsakris A. Epidemiological characteristics of infections caused by Bacteroides, Prevotella and Fusobacterium species: a prospective observational study. Anaerobe. 2011 Jun:17(3):113-7. doi: 10.1016/j.anaerobe.2011.05.013. Epub 2011 Jun 2 [PubMed PMID: 21664284]
Level 2 (mid-level) evidenceShah N, Osmon D, Tande AJ, Steckelberg J, Sierra R, Walker R, Berbari EF. Clinical and Microbiological Characteristics of Bacteroides Prosthetic Joint Infections. Journal of bone and joint infection. 2017:2(3):122-126. doi: 10.7150/jbji.17129. Epub 2017 Mar 19 [PubMed PMID: 28540148]
Murphy EC, Mörgelin M, Cooney JC, Frick IM. Interaction of Bacteroides fragilis and Bacteroides thetaiotaomicron with the kallikrein-kinin system. Microbiology (Reading, England). 2011 Jul:157(Pt 7):2094-2105. doi: 10.1099/mic.0.046862-0. Epub 2011 Apr 28 [PubMed PMID: 21527472]
Sears CL. Enterotoxigenic Bacteroides fragilis: a rogue among symbiotes. Clinical microbiology reviews. 2009 Apr:22(2):349-69, Table of Contents. doi: 10.1128/CMR.00053-08. Epub [PubMed PMID: 19366918]
Level 3 (low-level) evidenceBasset C, Holton J, Bazeos A, Vaira D, Bloom S. Are Helicobacter species and enterotoxigenic Bacteroides fragilis involved in inflammatory bowel disease? Digestive diseases and sciences. 2004 Sep:49(9):1425-32 [PubMed PMID: 15481314]
Level 2 (mid-level) evidenceSchwechheimer C, Kuehn MJ. Outer-membrane vesicles from Gram-negative bacteria: biogenesis and functions. Nature reviews. Microbiology. 2015 Oct:13(10):605-19. doi: 10.1038/nrmicro3525. Epub [PubMed PMID: 26373371]
Elhenawy W, Debelyy MO, Feldman MF. Preferential packing of acidic glycosidases and proteases into Bacteroides outer membrane vesicles. mBio. 2014 Mar 11:5(2):e00909-14. doi: 10.1128/mBio.00909-14. Epub 2014 Mar 11 [PubMed PMID: 24618254]
McCallum RE, Rohrer MD, Urbaschek R, Urbaschek B. Histopathology of mixed anaerobic intraabdominal infection in mice. Klinische Wochenschrift. 1982 Jul 15:60(14):702-4 [PubMed PMID: 6126612]
Level 3 (low-level) evidenceWestrin KM, Norlander T, Stierna P, Carlsöö B, Nord CE. Experimental maxillary sinusitis induced by Bacteroides fragilis. A bacteriological and histological study in rabbits. Acta oto-laryngologica. 1992:112(1):107-14 [PubMed PMID: 1374207]
Level 3 (low-level) evidenceTan TY, Ng LS, Kwang LL, Rao S, Eng LC. Clinical characteristics and antimicrobial susceptibilities of anaerobic bacteremia in an acute care hospital. Anaerobe. 2017 Feb:43():69-74. doi: 10.1016/j.anaerobe.2016.11.009. Epub 2016 Nov 25 [PubMed PMID: 27890724]
Yamanaka Y, Shimabukuro A. Septic abortion presenting as a right lower trapezius abscess secondary to Bacteroides fragilis bacteraemia. BMJ case reports. 2017 Aug 21:2017():. pii: bcr-2016-219135. doi: 10.1136/bcr-2016-219135. Epub 2017 Aug 21 [PubMed PMID: 28827296]
Level 3 (low-level) evidenceNolla JM, Murillo O, Narvaez J, Vaquero CG, Lora-Tamayo J, Pedrero S, Cabo J, Ariza J. Pyogenic arthritis of native joints due to Bacteroides fragilis: Case report and review of the literature. Medicine. 2016 Jun:95(25):e3962. doi: 10.1097/MD.0000000000003962. Epub [PubMed PMID: 27336895]
Level 3 (low-level) evidenceMartin T, Aziz H. Bacteroides fragilis: a case study of bacteremia and septic arthritis. Clinical laboratory science : journal of the American Society for Medical Technology. 2009 Summer:22(3):131-5 [PubMed PMID: 19827405]
Level 3 (low-level) evidenceHan ML, Lin HF, Liu KL, Lee TH, Liao WC. Anaerobic bacteraemia in a patient with necrotising pancreatitis. Transverse colon perforations at hepatic and splenic flexures. Gut. 2008 Nov:57(11):1530, 1553. doi: 10.1136/gut.2008.152827. Epub [PubMed PMID: 18941007]
Level 3 (low-level) evidenceSingh S, Goyal V, Padhi P, Aoun E. Bacteroides fragilis endocarditis in a patient with Crohn's disease. BMJ case reports. 2013 Apr 18:2013():. doi: 10.1136/bcr-2013-009248. Epub 2013 Apr 18 [PubMed PMID: 23605837]
Level 3 (low-level) evidenceHadano Y, Iwata H. Septic thrombophlebitis of the superior mesenteric vein with bacteraemia caused by Bacteroides fragilis and Streptococcus intermedius as a complication of diverculitis. BMJ case reports. 2013 Feb 5:2013():. doi: 10.1136/bcr-2013-008661. Epub 2013 Feb 5 [PubMed PMID: 23389727]
Level 3 (low-level) evidenceMiki T, Kuwahara T, Nakayama H, Okada N, Kataoka K, Arimochi H, Ohnishi Y. Simultaneous detection of Bacteroides fragilis group species by leuB-directed PCR. The journal of medical investigation : JMI. 2005 Feb:52(1-2):101-8 [PubMed PMID: 15751280]
Level 3 (low-level) evidenceTakesue Y, Kusachi S, Mikamo H, Sato J, Watanabe A, Kiyota H, Iwata S, Kaku M, Hanaki H, Sumiyama Y, Kitagawa Y, Nakajima K, Ueda T, Uchino M, Mizuguchi T, Ambo Y, Konosu M, Ishibashi K, Matsuda A, Hase K, Harihara Y, Okabayashi K, Seki S, Hara T, Matsui K, Matsuo Y, Kobayashi M, Kubo S, Uchiyama K, Shimizu J, Kawabata R, Ohge H, Akagi S, Oka M, Wakatsuki T, Suzuki K, Okamoto K, Yanagihara K. Antimicrobial susceptibility of common pathogens isolated from postoperative intra-abdominal infections in Japan. Journal of infection and chemotherapy : official journal of the Japan Society of Chemotherapy. 2018 May:24(5):330-340. doi: 10.1016/j.jiac.2018.02.011. Epub 2018 Mar 16 [PubMed PMID: 29555391]
Ghotaslou R, Bannazadeh Baghi H, Alizadeh N, Yekani M, Arbabi S, Memar MY. Mechanisms of Bacteroides fragilis resistance to metronidazole. Infection, genetics and evolution : journal of molecular epidemiology and evolutionary genetics in infectious diseases. 2018 Oct:64():156-163. doi: 10.1016/j.meegid.2018.06.020. Epub 2018 Jun 21 [PubMed PMID: 29936037]
Alauzet C, Lozniewski A, Marchandin H. Metronidazole resistance and nim genes in anaerobes: A review. Anaerobe. 2019 Feb:55():40-53. doi: 10.1016/j.anaerobe.2018.10.004. Epub 2018 Oct 11 [PubMed PMID: 30316817]
Byun JH, Kim M, Lee Y, Lee K, Chong Y. Antimicrobial Susceptibility Patterns of Anaerobic Bacterial Clinical Isolates From 2014 to 2016, Including Recently Named or Renamed Species. Annals of laboratory medicine. 2019 Mar:39(2):190-199. doi: 10.3343/alm.2019.39.2.190. Epub [PubMed PMID: 30430782]
Bogdan M, Perić L, Ördög K, Vuković D, Urbán E, Sóki J. The first characterized carbapenem-resistant Bacteroides fragilis strain from Croatia and the case study for it. Acta microbiologica et immunologica Hungarica. 2018 Aug 1:65(3):317-323. doi: 10.1556/030.65.2018.024. Epub 2018 Apr 13 [PubMed PMID: 29651861]
Level 3 (low-level) evidenceGoldstein EJC, Citron DM, Tyrrell KL. In vitro activity of eravacycline and comparator antimicrobials against 143 recent strains of Bacteroides and Parabacteroides species. Anaerobe. 2018 Aug:52():122-124. doi: 10.1016/j.anaerobe.2018.06.016. Epub 2018 Jul 4 [PubMed PMID: 30018028]
Mikamo H, Monden K, Miyasaka Y, Horiuchi T, Fujimoto G, Fukuhara T, Yoshinari T, Rhee EG, Shizuya T. The efficacy and safety of tazobactam/ceftolozane in combination with metronidazole in Japanese patients with complicated intra-abdominal infections. Journal of infection and chemotherapy : official journal of the Japan Society of Chemotherapy. 2019 Feb:25(2):111-116. doi: 10.1016/j.jiac.2018.10.012. Epub 2018 Dec 6 [PubMed PMID: 30528561]
Deng H, Yang S, Zhang Y, Qian K, Zhang Z, Liu Y, Wang Y, Bai Y, Fan H, Zhao X, Zhi F. Bacteroides fragilis Prevents Clostridium difficile Infection in a Mouse Model by Restoring Gut Barrier and Microbiome Regulation. Frontiers in microbiology. 2018:9():2976. doi: 10.3389/fmicb.2018.02976. Epub 2018 Dec 21 [PubMed PMID: 30619112]
Level 2 (mid-level) evidenceZhang W, Zhu B, Xu J, Liu Y, Qiu E, Li Z, Li Z, He Y, Zhou H, Bai Y, Zhi F. Bacteroides fragilis Protects Against Antibiotic-Associated Diarrhea in Rats by Modulating Intestinal Defenses. Frontiers in immunology. 2018:9():1040. doi: 10.3389/fimmu.2018.01040. Epub 2018 May 9 [PubMed PMID: 29868005]
Level 2 (mid-level) evidenceMaslowski KM, Mackay CR. Diet, gut microbiota and immune responses. Nature immunology. 2011 Jan:12(1):5-9. doi: 10.1038/ni0111-5. Epub [PubMed PMID: 21169997]
Level 3 (low-level) evidenceMirjafari Tafti ZS, Moshiri A, Ettehad Marvasti F, Tarashi S, Sadati Khalili SF, Motahhary A, Fateh A, Vaziri F, Ahmadi Badi S, Siadat SD. The effect of saturated and unsaturated fatty acids on the production of outer membrane vesicles from Bacteroides fragilis and Bacteroides thetaiotaomicron. Gastroenterology and hepatology from bed to bench. 2019 Spring:12(2):155-162 [PubMed PMID: 31191841]
Cheng CW, Lin HS, Ye JJ, Yang CC, Chiang PC, Wu TS, Lee MH. Clinical significance of and outcomes for Bacteroides fragilis bacteremia. Journal of microbiology, immunology, and infection = Wei mian yu gan ran za zhi. 2009 Jun:42(3):243-50 [PubMed PMID: 19812858]
Level 2 (mid-level) evidenceKwong TNY, Wang X, Nakatsu G, Chow TC, Tipoe T, Dai RZW, Tsoi KKK, Wong MCS, Tse G, Chan MTV, Chan FKL, Ng SC, Wu JCY, Wu WKK, Yu J, Sung JJY, Wong SH. Association Between Bacteremia From Specific Microbes and Subsequent Diagnosis of Colorectal Cancer. Gastroenterology. 2018 Aug:155(2):383-390.e8. doi: 10.1053/j.gastro.2018.04.028. Epub 2018 May 3 [PubMed PMID: 29729257]
Bundgaard-Nielsen C, Baandrup UT, Nielsen LP, Sørensen S. The presence of bacteria varies between colorectal adenocarcinomas, precursor lesions and non-malignant tissue. BMC cancer. 2019 Apr 29:19(1):399. doi: 10.1186/s12885-019-5571-y. Epub 2019 Apr 29 [PubMed PMID: 31035942]
Feuerstein JL, O'Gorman J, Jakus J. Sepsis Secondary to Bacteroides Fragilis Tubo-Ovarian Abscess Requiring Hysterectomy and Bilateral Salpingo-Oophorectomy. BMJ case reports. 2018 Jan 26:2018():. pii: bcr-2017-222460. doi: 10.1136/bcr-2017-222460. Epub 2018 Jan 26 [PubMed PMID: 29374639]
Level 3 (low-level) evidence