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At least 613 records · Page 34Linked to original sources
PubMed2002

Environmental factors influencing human viral pathogens and their potential indicator organisms in the blue mussel, Mytilus edulis: the first Scandinavian report.

This study was carried out in order to investigate human enteric virus contaminants in mussels from three sites on the west coast of Sweden, representing a gradient of anthropogenic influence. Mussels were sampled monthly during the period from February 2000 to July 2001 and analyzed for adeno-, entero-, Norwalk-like, and hepatitis A viruses as well as the potential viral indicator organisms somatic coliphages, F-specific RNA bacteriophages, bacteriophages infecting Bacteroides fragilis, and Escherichia coli. The influence of environmental factors such as water temperature, salinity, and land runoff on the occurrence of these microbes was also included in this study. Enteric viruses were found in 50 to 60% of the mussel samples, and there were no pronounced differences between the samples from the three sites. E. coli counts exceeded the limit for category A for shellfish sanitary safety in 40% of the samples from the sites situated in fjords. However, at the site in the outer archipelago, this limit was exceeded only once, in March 2001, when extremely high levels of atypical indole-negative strains of E. coli were registered at all three sites. The environmental factors influenced the occurrence of viruses and phages differently, and therefore, it was hard to find a coexistence between them. This study shows that, for risk assessment, separate modeling should be done for every specific area, with special emphasis on environmental factors such as temperature and land runoff. The present standard for human fecal contamination, E. coli, seems to be an acceptable indicator of only local sanitary contamination; it is not a reliable indicator of viral contaminants in mussels. To protect consumers and get verification of "clean" mussels, it seems necessary to analyze for viruses as well. The use of a molecular index of the human contamination of Swedish shellfish underscores the need for reference laboratories with high-technology facilities.

Animals↗
PubMed2003

Survival of bacterial indicator species and bacteriophages after thermal treatment of sludge and sewage.

The inactivation of naturally occurring bacterial indicators and bacteriophages by thermal treatment of a dewatered sludge and raw sewage was studied. The sludge was heated at 80 degrees C, and the sewage was heated at 60 degrees C. In both cases phages were significantly more resistant to thermal inactivation than bacterial indicators, with the exception of spores of sulfite-reducing clostridia. Somatic coliphages and phages infecting Bacteroides fragilis were significantly more resistant than F-specific RNA phages. Similar trends were observed in sludge and sewage. The effects of thermal treatment on various phages belonging to the three groups mentioned above and on various enteroviruses added to sewage were also studied. The results revealed that the variability in the resistance of phages agreed with the data obtained with the naturally occurring populations and that the phages that were studied were more resistant to heat treatment than the enteroviruses that were studied. The phages survived significantly better than Salmonella choleraesuis, and the extents of inactivation indicated that naturally occurring bacteriophages can be used to monitor the inactivation of Escherichia coli and Salmonella.

Bacteria↗
PubMed2003

Evaluation of potential indicators of viral contamination in shellfish and their applicability to diverse geographical areas.

The distribution of the concentration of potential indicators of fecal viral pollution in shellfish was analyzed under diverse conditions over 18 months in diverse geographical areas. These microorganisms have been evaluated in relation to contamination by human viral pathogens detected in parallel in the analyzed shellfish samples. Thus, significant shellfish-growing areas from diverse countries in the north and south of Europe (Greece, Spain, Sweden, and the United Kingdom) were defined and studied by analyzing different physicochemical parameters in the water and the levels of Escherichia coli, F-specific RNA bacteriophages, and phages infecting Bacteroides fragilis strain RYC2056 in the shellfish produced, before and after depuration treatments. A total of 475 shellfish samples were studied, and the results were statistically analyzed. According to statistical analysis, the presence of human viruses seems to be related to the presence of all potential indicators in the heavily contaminated areas, where E. coli would probably be suitable as a fecal indicator. The F-RNA phages, which are present in higher numbers in Northern Europe, seem to be significantly related to the presence of viral contamination in shellfish, with a very weak predictive value for hepatitis A virus, human adenovirus, and enterovirus and a stronger one for Norwalk-like virus. However, it is important to note that shellfish produced in A or clean B areas can sporadically contain human viruses even in the absence of E. coli or F-RNA phages. The data presented here will be useful in defining microbiological parameters for improving the sanitary control of shellfish consumed raw or barely cooked.

Animals↗
PubMed1981

Model of intraabdominal abscess in mice.

Intraperitoneal inoculation of sterile mouse feces into mice produced intraabdominal abscesses. The addition of Bacteroides fragilis increased the incidence and the number of abscesses.

Abdomen↗
PubMed1988

Use of lymphokines in treatment of experimental intra-abdominal abscess caused by Bacteroides fragilis.

The role of cell-free soluble factors (lymphokines) derived from mitogen-activated splenic cells of mice previously immunized against Bacteroides fragilis was evaluated in the treatment of B. fragilis intra-abdominal abscess (IAA). Neither clindamycin nor lymphokines alone were effective against an established B. fragilis IAA, but the combination of clindamycin and lymphokines decreased the abscess size and bacterial counts in the majority of animals. This suggests that the synergy of lymphokines with clindamycin effects cure of IAA caused by B. fragilis and that lymphokines might have an application as adjuncts to conventional antimicrobial therapy in this setting.

Abdomen↗
PubMed1996

Bacteroides fragilis toxin rapidly intoxicates human intestinal epithelial cells (HT29/C1) in vitro.

Enterotoxigenic Bacteroides fragilis strains associated with childhood diarrhea produce a 20-kDa protein toxin (BFT). Purified BFT causes striking morphologic changes in subconfluent human colonic epithelial cells (HT29/C1). In a 3-h HT29/C1 cell assay, the estimated half-maximal effective concentration of BFT was 12.5 pM, and morphologic effects were detectable as early as 30 min and nearly complete by 1.5 h. Concentrations as low as 0.5 pM could also cause intoxication, but morphologic changes were detectable only when the assay was extended to 18 h. The onset of this intoxication was concentration dependent and rapid, occurring within minutes (<7 min at 0.25 nM, <2 min at 2.5 nM). Notably, the onset of intoxication at 37 degrees C became irreversible to washing within 2 min after exposure to BFT. Morphologic changes were completely inhibited by treatment of HT29/C1 cells with BFT at 4 degrees C but could be demonstrated by subsequent warming to temperatures of 15 degrees C or higher after washing. The time required for the association of BFT with HT29/C1 cells at 4 degrees C was inversely correlated with concentration. Inhibitors of endosomal and Golgi trafficking (NH4Cl and brefeldin A) prevented the intoxication of HT29/C1 cells by Clostridium difficile toxin A and cholera toxin, respectively, but not by BFT. Agents altering microtubule structure did not affect the cellular activity of BFT. These data indicate that a purified toxin from B. fragilis strains associated with diarrhea rapidly and irreversibly intoxicates human intestinal epithelial cells (HT29/C1) in a concentration- and temperature-dependent manner and that the process of intoxication may not involve internalization mechanisms utilizing microtubules or sensitive to pH or brefeldin A.

Bacterial Toxins↗
PubMed1999

Identification of a third metalloprotease toxin gene in extraintestinal isolates of Bacteroides fragilis.

To further understand the epidemiology of enterotoxigenic Bacteroides fragilis (ETBF), 89 extraintestinal B. fragilis strains from Seoul, Korea, were examined for secretion of B. fragilis toxin (BFT) by the HT29/C1 biologic assay and for the B. fragilis toxin gene (bft) by colony blot hybridization and PCR. Complete agreement between the three techniques was found. Overall, 34 B. fragilis strains (38%) were identified as ETBF. Eleven of the 34 ETBF strains (32%) expressed a new isoform of BFT (Korea-BFT). This new isoform is more related to BFT-2 than to BFT-1. Like BFT-1 and BFT-2, Korea-BFT cleaves E-cadherin, the zonula adherens protein.

Amino Acid Sequence↗
PubMed2005

Bacteroides fragilis-derived lipopolysaccharide produces cell activation and lethal toxicity via toll-like receptor 4.

Bacteroides fragilis, which is part of the normal intestinal flora, is a frequent cause of serious disease, especially in diabetic and surgical patients. In these conditions, B. fragilis lipopolysaccharide (LPS) is likely to play a major pathophysiologic role. B. fragilis LPS is structurally different from classical enterobacterial LPS, whose biological activities are mediated by Toll-like receptor 4 (TLR4) activation. The ability of B. fragilis LPS to activate TLR4 and TLR2 was investigated here, since evidence on this issue is scarce and controversial. Each of four different protein-free B. fragilis LPS preparations could induce interleukin-8 responses in cells cotransfected with TLR4/CD14/MD2 but not TLR4/CD14 alone. Two of the preparations also induced cytokine production in cells cotransfected with TLR2/CD14 or in peritoneal macrophages from TLR4 mutant C3H/HeJ mice. Both of these activities, however, were lost after repurification with a modified phenol reextraction procedure. Importantly, all preparations could induce endotoxic shock in TLR2-deficient mice, but not in TLR4 mutant C3H/HeJ mice. Consistent with these findings, anti-TLR4 and anti-CD14, but not anti-TLR2, antibodies could inhibit B. fragilis LPS-induced cytokine production in human monocytes. Collectively, these results indicate that B. fragilis LPS signals via a TLR4/CD14/MD2-dependent pathway, and it is unable to activate TLR2. Moreover, our data document the occurrence of TLR2-activating contaminants even in highly purified B. fragilis LPS preparations. This may explain earlier contradictory findings on the ability of B. fragilis LPS to activate cells in the absence of functional TLR4. These data may be useful to devise strategies to prevent the pathophysiologic changes observed during B. fragilis sepsis and to better understand structure-activity relationships of LPS.

Adult↗
PubMed2006

Characterization of the primary starch utilization operon in the obligate anaerobe Bacteroides fragilis: Regulation by carbon source and oxygen.

The opportunistic pathogen Bacteroides fragilis is a commensal organism in the large intestine, where it utilizes both dietary and host-derived polysaccharides as a source of carbon and energy. In this study, a four-gene operon required for starch utilization was identified. The operon also was found to be oxygen responsive and thus was designated osu for oxygen-induced starch utilization. The first three genes in the operon were predicted to encode outer membrane proteins involved in starch binding, and a fourth gene, osuD, encoded an amylase involved in starch hydrolysis. Insertional mutation of the osuA gene (Omega osuA) resulted in the inability to utilize starch or glycogen and an insertional mutation into the osuD gene (Omega osuD) was severely impaired for growth on starch media. Transcriptional studies indicated that maltose, maltooligosaccharides, and starch were inducers of osu expression and that maltose was the strongest inducer. A transcriptional activator of osuABCD, OsuR, was identified and found to mediate maltose induction. The Omega osuA and Omega osuD mutants were able to grow on maltose but not starch, whereas a mutation in osuR abolished growth on both substrates, indicating that additional genes under the control of OsuR are needed for maltose utilization. The osuABCD operon also was induced by exposure to oxygen and was shown to be part of the oxidative stress response important for aerotolerance of B. fragilis. Transcriptional analyses showed that osuA was induced 20-fold by oxygen, but OsuR was not required for this activation. Analysis of osu mutants suggested that expression of the operon was important for survival during oxygen exposure but not to hydrogen peroxide stress.

Amylases↗
PubMed1999

Molecular evolution of the pathogenicity island of enterotoxigenic Bacteroides fragilis strains.

Enterotoxigenic Bacteroides fragilis (ETBF) strains, which produce a 20-kDa zinc metalloprotease toxin (BFT), have been associated with diarrheal disease in animals and young children. Studying a collection of ETBF and nontoxigenic B. fragilis (NTBF) strains, we found that bft and a second metalloprotease gene (mpII) are contained in an approximately 6-kb pathogenicity island (termed B. fragilis pathogenicity island or BfPAI) which is present exclusively in all 113 ETBF strains tested (pattern I). Of 191 NTBF strains, 100 (52%) lack both the BfPAI and at least a 12-kb region flanking BfPAI (pattern II), and 82 of 191 NTBF strains (43%) lack the BfPAI but contain the flanking region (pattern III). The nucleotide sequence flanking the left end of the BfPAI revealed a region with the same organization as the mobilization region of the 5-nitroimidazole resistance plasmid pIP417 and the clindamycin resistance plasmid pBFTM10, that is, two mobilization genes (bfmA and bfmB) organized in one operon and a putative origin of transfer (oriT) located in a small, compact region. The region flanking the right end of the BfPAI contains a gene (bfmC) whose predicted protein shares significant identity to the TraD mobilization proteins encoded by plasmids F and R100 from Escherichia coli. Nucleotide sequence analysis of one NTBF pattern III strain (strain I-1345) revealed that bfmB and bfmC are adjacent to each other and separated by a 16-bp GC-rich sequence. Comparison of this sequence with the appropriate sequence of ETBF strain 86-5443-2-2 showed that in this ETBF strain the 16-bp sequence is replaced by the BfPAI. This result defined the BfPAI as being 6,036 bp in length and its precise integration site as being between the bfmB and bfmC stop codons. The G+C content of the BfPAI (35%) and the flanking DNA (47 to 50%) differ greatly from that reported for the B. fragilis chromosome (42%), suggesting that the BfPAI and its flanking region are two distinct genetic elements originating from very different organisms. ETBF strains may have evolved by horizontal transfer of these two genetic elements into a pattern II NTBF strain.

Amino Acid Sequence↗
PubMed1979

Fluorescent antibody test kit for rapid detection and identification of members of the Bacteroides fragilis and Bacteroides melaninogenicus groups in clinical specimens.

The Fluoretec fluorescent antibody test kit (Pfizer Inc., New York, N.Y.), developed for the rapid detection of members of the Bacteroides fragilis and B. melaninogenicus groups, was evaluated by testing 58 stock cultures and 76 clinical specimens. The test reagents detected 100% of 40 B. fragilis and B. thetaiotaomicron stock culture strains, although only 22% of 18 B. vulgatus, B. distasonis, and B. ovatus strains showed positive fluorescence. The 76 clinical specimens were evaluated by examining fluorescent antibody-stained smears of 49 specimens of purulent material and smears of 27 blood cultures which were positive for gram-negative bacilli by Gram stain or subculture. The fluoretec reagent detected members of the B. fragilis group in 28 (97%) of the 29 specimens of purulent material and all (100%) of the 16 blood cultures in which these anaerobes were demonstrated by culture. Overall, the Fluoretec reagent detected members of B. fragilis group in 44 (98%) of the 45 clinical specimens which were shown by culture to contain these anaerobes. Two of the 76 clinical specimens gave positive fluorescence for members of the B. fragilis group but failed to yield these organisms by culture. Members of the B. melaninogenicus group were detected by culture in 15 specimens and in each case their presence was demonstrated by the Fluoretec reagent. No members of the B. melaninogenicus group were isolated from five clinical specimens that gave positive fluorescence with the B. melaninogenicus reagent.

Anaerobiosis↗
PubMed1981

Rapid detection and identification of Bacteroides fragilis and Bacteroides melaninogenicus by immunofluorescence.

Bacteroides fragilis group and Bacteroides melaninogenicus group fluorescent-antibody kits were evaluated with 188 clinical specimens and 116 fresh aerobic and anaerobic bacterial isolates. Fluorescent-antibody and culture results corresponded in 88% of clinical specimens of the B. fragilis group and 94% of clinical specimens of the B. melaninogenicus group. There was greater than or equal to 90% correlation for both kits with colony smears. Antigen sharing by Bacteroides bivius, Bacteroides disiens, and B. melaninogenicus was demonstrated.

Bacteriological Techniques↗
PubMed1984

Splenic abscess caused by Shigella flexneri and Bacteroides fragilis.

We report a case of splenic abscess from which only Shigella flexneri (serotype 1a) and Bacteroides fragilis were isolated. The patient was a 59-year-old diabetic female who displayed minimal gastrointestinal symptoms. The S. flexneri isolate was resistant to chloramphenicol and tetracycline. The possible synergistic relationship between the two organisms is discussed.

Abscess↗
PubMed1985

Bacteroides fragilis meningitis.

A fatal case of pyogenic meningitis due to Bacteroides fragilis in a 6-year-old boy is reported. The need for processing cerebrospinal fluid of patients with underlying conditions such as chronic otitis media for recovery of both aerobes and anaerobes is discussed.

Bacteroides Infections↗
PubMed1986

DNA probes for identification of clinically important Bacteroides species.

Conventional procedures for identifying gram-negative anaerobes such as Bacteroides spp. are cumbersome and time-consuming. A simpler approach would be to use DNA probes to identify these organisms. Since many different species of gram-negative anaerobes are isolated from clinical specimens, the most useful DNA probes would be probes that identify a few clinically significant groups of anaerobes. To obtain such probes, we cloned HindIII-digested chromosomal DNA from various Bacteroides species and then screened these probes, labeled with 32P by nick translation, for hybridization to DNA from various species of Bacteroides, Fusobacterium, and other gram-negative bacteria. We identified three DNA probes (pBFII-4, pBFII-5, and pBFII-6) that hybridized specifically to DNA from Bacteroides fragilis, the species that accounts for about half of all isolates from clinical specimens containing anaerobes. We identified one DNA probe (pBE-3) that hybridized to all members of the B. fragilis group, a group of species that resemble B. fragilis with respect to fermentation pattern and antibiotic resistances. We also identified one probe (pBO-21) that hybridized to DNA from all Bacteroides sp. strains as well as to DNA from strains of Fusobacterium necrophorum and Fusobacterium nucleatum. pBO-21, but not pBE-3, cross-hybridized with a cloned Bacteroides sp. 16S rRNA gene. The limit of detection for these probes was 10(6) bacteria. The probes could detect B. fragilis in blood culture medium and in mixed cultures with other gram-negative bacteria. Attempts to use biotin-labeled DNA probes instead of 32P-labeled probes were not successful because the Bacteroides sp. extracts contained material that bound the streptoavidin-peroxidase detection reagent.

Animals↗
PubMed1987

Isolation of enterotoxigenic Bacteroides fragilis from humans with diarrhea.

Enterotoxigenic Bacteroides fragilis was isolated from stool specimens of 8 of 44 diarrheic individuals (ages, 4 months to 69 years). The individuals had watery diarrhea and intestinal cramping; and infants had hyperthermia, vomiting, and blood in the stools. No recognized enteric pathogens were detected in seven of the eight diarrheic individuals positive for enterotoxigenic B. fragilis. The bacterium produced an enterotoxin detectable in concentrated broth that supported bacterial growth. Fifteen adult rabbits with ligated ceca developed fatal enteric disease following intraileal injection with 5 x 10(9) CFU of enterotoxigenic B. fragilis. Conversely, eight control rabbits injected with nonenterotoxigenic B. fragilis remained clinically normal. As few as 5 x 10(3) CFU of enterotoxigenic B. fragilis caused fatal enteric disease in the rabbit model. Disease in rabbits was characterized by mucoid, often hemorrhagic, diarrhea. The bacterium colonized the caudal small intestine and the colon of the rabbits and caused moderate to severe necrotizing colitis. Enterotoxigenic B. fragilis is widespread in the intestinal tract of diarrheic humans and is enteropathogenic in adult rabbits with ligated ceca. Its possible role in the enteric disease complex merits further study.

Adult↗