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PubMed1982

In vitro stimulation of Bacteroides fragilis growth by Escherichia coli.

The interaction between Bacteroides fragilis and Escherichia coli was investigated by following their growth kinetics in an in vitro mixed culture system. In Bacto-peptone or in a semisynthetic medium (SSM-M) Bacteroides fragilis could initiate growth only when a small number of viable Escherichia coli initially coexisted for a short period of time. Both Bacto-peptone and SSM-M previously spent by Escherichia coli also allowed Bacteroides fragilis growth to occur but the supplementation of heat killed Escherichia coli cells or viable cell homogenates to fresh media failed to stimulate Bacteroides fragilis growth. The in vitro stimulation of Bacteroides fragilis growth by Escherichia coli observed in this study may be best explained by the combination of (a) removal of oxygen and other toxic substances and (b) de novo production of Bacteroides fragilis growth stimulating factor(s) by coexistent Escherichia coli.

Abdomen↗
PubMedDate not supplied

Comparative in vitro activity of cefoxitin, cefotaxime alone, and in combination with desacetylcefotaxime against the Bacteroides species.

The agar dilution method was used to determine the inhibitory activity of cefotaxime (CTX) alone, desacetylcefotaxime (dCTX) alone, CTX plus dCTX, and cefoxitin against 74 clinical isolates of the Bacteroides species recovered from diabetic patients with foot ulcers. The study concluded that the addition of dCTX to CTX increased the inhibitory activity from 45% to 73% for all strains tested and from 50% to 81% among the 32 strains of Bacteroides fragilis. This synergistic interaction against B. fragilis resulted in a four- to nine-fold reduction in the MIC of seven strains (64-128 micrograms/ml, resistant category MICs). While the lowest CTX MIC for B. fragilis was 2 micrograms/ml (four strains), the addition of dCTX also produced a remarkable reduction in susceptible range CTX MICs to 0.05-2 micrograms/ml in 16 strains (50%). The overall susceptibility to cefoxitin and CTX plus dCTX was as follows: 100% and 100% for Bacteroides vulgatus, 50% and 66% for Bacteroides thetaiotaomicron, 100% and 33% for Bacteroides ovatus, and 83% and 82% for Bacteroides species other than the B. fragilis group.

Bacteroides↗
PubMedDate not supplied

Gram-negative anaerobic bacilli: their role in infection and patterns of susceptibility to antimicrobial agents. I. Little-known Bacteroides species.

The role in infection and the patterns of susceptibility to antimicrobial agents of 17 infrequently reported species of Bacteroides were studied. The findings of this research are summarized, and the literature dealing with recovery of these species from both the normal flora and infections of humans is reviewed. During a six-year period, 22% of 679 specimens from infections due to anaerobic bacteria that were studied by the authors yielded one or more of these "other Bacteroides species" (OBS). The most commonly isolated OBS were Bacteroides ruminicola subspecies brevis (63 patients), Bacteroides ureolyticus (38), Bacteroides bivius (26), and Bacteroides disiens (17). Appreciable resistance of some isolates to the beta-lactam antibiotics, erythromycin, and the tetracyclines was noted, whereas all strains were inhibited by chloramphenicol and metronidazole and almost all were inhibited by clindamycin. The data indicate that OBS are present in infection much more often than has been reported previously. The resistance of certain strains to some commonly used antimicrobial agents may necessitate a reassessment of the initial, empiric therapy of infections due to anaerobic bacteria.

Abdomen↗
PubMed2006

Bacteroides finegoldii sp. nov., isolated from human faeces.

Two strains, 199T and 176, of Gram-negative, anaerobic, rod-shaped, non-spore-forming bacteria were isolated during studies of microbiota in human faeces using polyamine-deficient medium. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the isolated strains belonged to the genus Bacteroides. The G+C content (42.4-43.0 mol%) and major fatty acid composition (anteiso-C15:0, 31.8-36.2 %) supported the affiliation of the two strains to the genus Bacteroides. 16S rRNA gene sequence similarities with their closest neighbours, Bacteroides thetaiotaomicron and Bacteroides ovatus, ranged from 94.6 to 96.5 %. DNA-DNA hybridization and phenotypic analysis showed that the two strains belonged to the same species (DNA-DNA relatedness of 89 %) and were distinct from their close relatives, B. thetaiotaomicron and B. ovatus (<23 % DNA-DNA relatedness). On the basis of these data, a novel species of the genus Bacteroides, Bacteroides finegoldii sp. nov., is proposed, comprising the designated type strain 199T (=JCM 13345T=DSM 17565T) and strain 176 (=JCM 13346).

Adult↗
PubMed1989

[Chemotherapy of bacteroides infection under clinical and experimental conditions].

Bacteroides were detected in pus and bioptates of the majority of 125 patients with purulent and purulent septic infections of various localization. In 90 per cent of the subjects the bacteroides were detected in association with aerobes, facultative and obligate anaerobic bacteria. The species of the bacteroides and concomitant microflora isolated from the cases with different diseases were defined by endogenic sources of the microbial contamination. Sensitivity of 112 bacteroide strains to antimicrobial agents was tested. Chloramphenicol, clindamycin, metronidazole, cefotaxime and heliomycin proved to be the most efficient. Efficacy of heliomycin was detected in hamsters with experimental bacteroide infection in the buccal sac. Thorough bacteriological examination is required for rational chemotherapy of bacteroide infections.

Animals↗
PubMed1979

[Bacteriological and clinical studies on metronidazole in Bacteroides fragilis infections (author's transl)].

The antimicrobial activity of 24 Bacteroides fragilis, 13 Bacteroides thetaiotaomicron and 5 Bacteroides vulgatus, all of which were recent clinical isolates, was determined by the agar dilution technique. These three species had similar susceptibility patterns, but the B. thetaiotaomicron strains were generally less susceptible than the B. fragilis strains. Clindamycin was very active against 81% of the Bacteroides strains at 3.1 mcg/ml of less while 21% of the Bacteroides strains had MICs of 100 mcg/ml or above. Metronidazole was active against all Bacteroides strains at 1.6 mcg/ml or less. The patients with decubitus ulcers and B. fragilis septicemia, who responded satisfactorily to the combination of metronidazole and tobramycin, were presented.

Aged↗
PubMed1982

Infection with Bacteroides fragilis: pathogenesis and immunoprophylaxis in an animal model.

Organisms of the genus Bacterioides represent the major group of obligate anaerobes involved in human infections. Bacteroides usually cause either bacteremia or localized abscesses. Of the numerous species of Bacteroides, Bacteroides fragilis is the single most frequent clinical isolate. B. fragilis and Bacteroides melaninogenicus have chemically incomplete lipopolysaccharides as compared with the lipopolysaccharides (endotoxins) of aerobic bacteria, and the lipopolysaccharides of Bacteroides lack of biologic potency characteristic of endotoxin. This inactivity may account for the very infrequent occurrence of disseminated intravascular coagulation or purpura that can accompany sepsis due to these organisms. Furthermore, strains of B. fragilis have an immunologically common capsular polysaccharide. In an animal model of intraabdominal sepsis, the encapsulated strains caused abscesses when given without other organisms. But abscess formation from unencapsulated strains of Bacteroides generally required the administration of a synergistic aerobe. The abscesses caused by encapsulated strains were shown to be directly attributable to the capsular polysaccharide, which is an important virulence factor of this organism. Antibody against the capsular antigen is protective against bacteremia due to B. fragilis, but T cell mediated immunity is protective against experimental intraabdominal abscesses.

Animals↗
PubMed2001

Analysis of a Bacteroides conjugative transposon using a novel "targeted capture" model system.

Large conjugative transposons (CTn's) are widespread among Bacteroides spp. and they are responsible for the high rates of Bacteroides tetracycline resistance, which is mediated by the tetQ gene. These elements are self-transmissible and conjugation can be induced up to 1000-fold by the addition of tetracycline to cultures prior to mating. In addition to self-transfer, the Bacteroides CTn's, such as CTn341, are able to mobilize unlinked genetic elements such as plasmids and mobilizable transposons in a tetracycline-inducible manner. To study the molecular properties of these unique elements, a vector was designed to capture CTn's for analysis in heterologous hosts. This plasmid, pFD670, consisted of the low-copy vector pWSK29, the RK2 oriT, an ermF gene, and a tetQ gene fragment containing the N-terminus and promoter. The vector was transferred into Bacteroides recipients containing CTn341 where it integrated into the tetQ gene by homologous recombination. This integrated construct then was transferred back into an Escherichia coli host where it replicated as a plasmid, pFD699, about 56 kb in size. Further analysis showed that pFD699 could be transferred into Bacteroides hosts where it displayed the same tetracycline-inducible properties as the native CTn341. The captured element appeared to utilize a circular intermediate in both transfer and transposition, and integration into the chromosome seemed to be random. Hybridization studies with a range of Bacteroides CTn's encoding tetracycline resistance revealed a great deal of homology between most of the CTn's but there was much variation seen in the restriction patterns of these elements, suggesting great diversity among this group.

Bacteroides↗
PubMed1997

Development of a bifunctional xylosidase/arabinosidase gene as a reporter gene for the gram-negative anaerobes Bacteroides and Porphyromonas, and Escherichia coli.

Members of the genera Bacteroides and Porphyromonas are common inhabitants of the human intestinal and oral microflora, and certain species are capable of causing disease states in humans. Genetic studies of these organisms are important for determining factors involved in the development of such diseases. A reporter gene for transcriptional fusions may prove useful for studies of gene regulation in these organisms. Bacteroides ovatus is a normal inhabitant of the human intestinal tract and is one of the few Bacteroides species capable of degrading xylan, a major component of fiber in the diet. A gene encoding for a bifunctional xylosidase/arabinosidase (XA) enzyme was previously cloned in our laboratory from B. ovatus V975 as part of a xylan-inducible operon. The XA gene was isolated by polymerase chain reaction and subcloned into the E. coli plasmid pBluescript II KS+. The XA gene is under transcriptional regulation in E. coli by the lac promoter, and both activities can be induced with isopropylthio-beta-galactoside (IPTG). The XA gene was subcloned into E. coli/Bacteroides shuttle vectors and introduced by conjugation into different Bacteroides species and Porphyromonas gingivalis. The results of transcriptional fusions in Bacteroides species and E. coli were evaluated. The characteristics of the XA reporter system are the low background or total lack of arabinosidase and xylosidase activities in most Bacteroides species, P. gingivalis, and E. coli, and the ease of enzymatic assays. In addition, bacterial colonies can be screened directly on agar plates by fluorescence with methylumbelliferyl derivatives as substrates for either enzymatic activity.

Artificial Gene Fusion↗
PubMed1988

Construction of shuttle cloning vectors for Bacteroides fragilis and use in assaying foreign tetracycline resistance gene expression.

Shuttle vectors capable of replication in both Escherichia coli and Bacteroides fragilis have been developed. Conjugal transfer of these plasmids from E. coli to B. fragilis is facilitated by inclusion of the origin of transfer of the IncP plasmid RK2. The vectors pDK1 and pDK2 provide unique sites for cloning selectable markers in Bacteroides. pOA10 is a cosmid vector containing the replication region of pCP1 necessary for maintenance in Bacteroides. pDK3, pDK4.1, and pDK4.2 contain the Bacteroides clindamycin resistance gene allowing selection and maintenance in B. fragilis of plasmids containing inserted DNA fragments. pDK3 was used to test the expression in B. fragilis of five foreign tetracycline resistance (TcR) genes. The tetA, -B, and -C markers from facultative gram-negative bacteria, as well as a TcR determinant from Clostridium perfringens, did not express TcR in B. fragilis. The tetM gene, originally described in streptococci, encoded a small but reproducible increase of TcR in Bacteroides. These studies demonstrate the utility of shuttle vectors for introducing cloned genes into Bacteroides and underscore the differences in gene expression in these anaerobes.

Bacteroides fragilis↗
PubMed1990

Plasmid transformation of Bacteroides spp. by electroporation.

Transformation of Bacteroides spp. with a variety of plasmid DNAs was accomplished using electroporation. The standard transformation assay system used to deduce the optimal electroporation parameters employed a 50-to 100-fold concentrated cell suspension of mid-logarithmic phase Bacteroides fragilis strain 638 and the 5.4-kb clindamycin resistance (Ccr) vector, pBI191. A variety of electroporation buffers were used successfully in transformation experiments but of these, 1 mM MgCl2 in 10% glycerol was superior. The incorporation of MgCl2 was essential for optimum viability prior to electroporation and for optimum transformation. Transformants were routinely obtained using 5-ms pulses over a range of field strengths from 5 to 12.5 kV/cm, with a maximum of greater than 10(6) micrograms-1 DNA at 12.5 kV/cm. The number of transformants increased linearly with respect to DNA concentration over the range 0.01-2 micrograms tested. Recovery of transformants required an expression period of up to 2.5 h following exposure to the electric field. This period, however, was dependent on the antibiotic resistance marker used for selection of transformants, with a significantly shorter incubation required when chloramphenicol rather than clindamycin was used in the selective medium. The effect of the DNA source on transformation was tested using the shuttle vector pFD288. Plasmid DNA isolated from Bacteroides uniformis, Bacteroides ovatus, or Bacteroides thetaiotaomicron transformed B. fragilis 638 at frequencies 7.5- to 12.5-fold less than those observed for controls with homologous DNA. Further reductions were seen with Escherichia coli purified pFD288, which transformed at 1000-fold lower frequencies. Finally, using homologous pFD288 or pBI191 isolated from strain 638, several strains of B. fragilis, B. uniformis, and B. ovatus were transformed successfully without modification of the standard assay system. Two strains each of B. thetaiotaomicron and Bacteroides ruminicola were not transformed using the methods described here.

Bacteroides↗
PubMed2000

Bacteroides, Prevotella, and Porphyromonas species: a review of antibiotic resistance and therapeutic options.

Recent basic and clinical research efforts have shed more light on the taxonomy, microbiology, epidemiology, antimicrobial susceptibility and treatment of Bacteroides, Prevotella, and Porphyromonas species. Of all anaerobic bacteria, Bacteroides is the most frequently isolated pathogen from clinical specimens, including blood. Bacteroides, Prevotella and/or Porphyromonas species have been isolated from clinical specimens in cases of infection from almost all anatomic sites. Several multicentre surveys have documented an alarming gradual increase of resistance rates of Bacteroides, Prevotella and Porphyromonas species worldwide. Antimicrobial agents active against >99% of clinical isolates of Bacteroides are metronidazole, chloramphenicol and carbapenems. Agents active against 95-99% of Bacteroides fragilis isolates are the beta-lactam/beta-lactamase inhibitor combinations. B. fragilis group species other than B. fragilis are more likely to be resistant to beta-lactam/beta-lactamase inhibitor combinations than B. fragilis.

Anti-Bacterial Agents↗
PubMed2006

Effect of nursing methods and faeces consumption on the development of the bacteroides, lactobacillus and coliform flora in the caecum of the newborn rabbits.

The effect of nursing method and ingestion of maternal faeces on the development of the bacteroides, lactobacillus and coliform flora of the caecum in the first 10 days of life were examined in freely nursed pups having access to maternal faeces (Group FF), pups nursed once a day and having access (Group CF), or having no access (Group CN) to maternal faeces. Colonisation of the caecum by Bacteroides commenced already on day 3 after birth. On day 2 the bacteroides counts were below 100, while on day 4 they were already between 100 and 10,000. In Group CN, the Bacteroides counts were lower (by 14 to 40%) throughout the 10-day period studied than in the groups having access to maternal faeces. Differences between groups were significant only on days 4 and 6. The average number of maternal faecal pellets left behind the doe in Group CN was 3-4 (between 0.5 and 6.4 per doe). In Groups FF and CF the pellets became smaller, crumbled and finally disappeared from the nest box, they were consumed by the pups and could be found in their gastric content. The lactobacillus counts decreased in all three groups with age, from 6.0 to 3.5 log10 CFU.g-1 (FF), 4.6 to 2.8 log10 CFU.g-1 (CF) and 5.1 to 3.1 log10 CFU.g-1 (CN), respectively. The coliform counts were higher in the first 4 days in FF (5.6 log10 CFU.g-1) than in CF (< 2 log10 CFU.g-1) and CN (2-3.6 log10 CFU.g-1) animals. Bacteroides could be cultured from the surface of the vulvar labia (max. 1000 colony count) and the vagina (max. 190 colony count), so young rabbits could become "infected" by them already in the doe's vagina. Thus prevention of ingestion of maternal faeces only slightly influenced the development of the bacteroides flora, the faeces left behind by the doe did not play an exclusive role in their colonisation.

Animals↗
PubMed2003

Emergence of fluoroquinolone resistance among Bacteroides species.

BACKGROUND: Several newer generation fluoroquinolones have demonstrated good in vitro activity against Bacteroides species; particularly when first introduced. However, resistance of Bacteroides to quinolones appears to be increasing. MATERIALS AND METHODS: From 1994 to 2001, consecutive non-duplicated Bacteroides isolates from clinical specimens in 12 US hospitals were sent to the Tufts anaerobe laboratory for identification and susceptibility testing. NCCLS recommended methodology for testing was employed. Breakpoints of 8 mg/l for trovafloxacin and 4 mg/l for moxifloxacin were used to examine susceptibility trends. RESULTS: In total, 4434 isolates were analysed. The geometric mean MIC increased significantly for clinafloxacin, trovafloxacin and moxifloxacin. Resistance to trovafloxacin (breakpoint of 8 mg/l) and moxifloxacin (breakpoint of 4 mg/l) increased from 8% to 25% and from 30% to 43%, respectively. Increased resistance was observed for all Bacteroides species, for all sites of isolation, and in 11 of 12 participating hospitals. Bacteroides vulgatus and isolates from decubitus ulcers were associated with increased resistance. During 2001, trovafloxacin and moxifloxacin resistance among blood isolates was 27% and 52%, respectively. The association between increased resistance and year of isolation remained significant after adjustment for hospital, species and site of isolation. CONCLUSIONS: Fluoroquinolone resistance among Bacteroides isolated in the US has markedly increased during the years 1994 to 2001. High rates of resistance among blood isolates are of particular concern.

Academic Medical Centers↗
PubMed2000

Bacteroides acidifaciens sp. nov., isolated from the caecum of mice.

During studies of the bacterial flora in the intestines of mice, we isolated characteristic strains which lowered the pH of peptone-yeast broth containing Fildes' digest. Based on 16S rRNA sequence comparison, these isolates were considered to belong to the Bacteroides cluster in the bacteroides subgroup of the Cytophaga-Flavobacterium-Bacteroides phylum, and were divided into two groups. Their phenotypic characteristics, i.e. growth in 20% bile, aesculin hydrolysis, and glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) activity, were the same as those of the 'Bacteroides fragilis group'. The low level of DNA-DNA hybridization with type strains in the Bacteroides cluster confirmed the novel species status of these isolates. It is proposed that these isolates be named Bacteroides acidifaciens, the type strain of which is A40T (= JCM 10556T).

Animals↗
PubMed1989

Further studies on the degradation of immunoglobulins by black-pigmented Bacteroides.

The ability of several species of black-pigmented Bacteroides to degrade immunoglobulins A and G was confirmed in this study. The cleavage products from IgG strongly stimulated the growth of bacteria degrading IgG. Growth of Bacteroides gingivalis on limiting media supplemented with IgG paralleled growth on complete medium. The degradation of IgG and IgA by black-pigmented Bacteroides appeared to occur in 2 stages. The molecules were broken into large fragments which were subsequently degraded into small peptides not visible on SDS-PAGE. B. gingivalis degraded IgG to peptides with Mrs of 33,000 and 11,000 whereas Bacteroides asaccharolyticus, Bacteroides intermedius and Bacteroides loescheii formed only the 33,000 Mr peptide. Electrophoresis in polyacrylamide gels containing covalently linked IgG, IgA and bovine serum albumin revealed that B. gingivalis elaborated 8 electrophoretically distinct proteolytic activities. The proteases protected the cell from reaction with anti-B. gingivalis antibody and were capable of hydrolyzing antibody bound to the bacterial cell surface.

Bacteroides↗
PubMed2001

Multicenter survey of the changing in vitro antimicrobial susceptibilities of clinical isolates of Bacteroides fragilis group, Prevotella, Fusobacterium, Porphyromonas, and Peptostreptococcus species.

In vitro surveys of antimicrobial resistance among clinically important anaerobes are an important source of information that can be used for clinical decisions in the choice of empiric antimicrobial therapy. This study surveyed the susceptibilities of 556 clinical anaerobic isolates from four large medical centers using a broth microdilution method. Piperacillin-tazobactam was the only antimicrobial agent to which all the isolates were susceptible. Similarly, imipenem, meropenem, and metronidazole were highly active (resistance, <0.5%), whereas the lowest susceptibility rates were noted for penicillin G, ciprofloxacin, and clindamycin. For most antibiotics, blood isolates were less susceptible than isolates from intra-abdominal, obstetric-gynecologic, and other sources. All isolates of the Bacteroides fragilis group were susceptible to piperacillin-tazobactam and metronidazole, while resistance to imipenem and meropenem was low (<2%). For these same isolates, resistance rates (intermediate and resistant MICs) to ampicillin-sulbactam, cefoxitin, trovafloxacin, and clindamycin were 11, 8, 7, and 29%, respectively. Among the individual species of the B. fragilis group, the highest resistance rates were noted among the following organism-drug combinations: for clindamycin, Bacteroides distasonis and Bacteroides ovatus; for cefoxitin, Bacteroides thetaiotaomicron, B. distasonis, and Bacteroides uniformis; for ampicillin-sulbactam, B. distasonis, B. ovatus, and B. uniformis; and for trovafloxacin, Bacteroides vulgatus. For the carbapenens, imipenem resistance was noted among B. fragilis and meropenem resistance was seen among B. fragilis, B. vulgatus, and B. uniformis. With few exceptions all antimicrobial agents were highly active against isolates of Prevotella, Fusobacterium, Porphyromonas, and Peptostreptococcus. These data further establish and confirm that clinically important anaerobes can vary widely in their antimicrobial susceptibilities. Fortunately most antimicrobial agents were active against the test isolates. However, concern is warranted for what appears to be a significant increases in resistance to ampicillin-sulbactam and clindamycin.

Bacterial Infections↗
PubMed1981

Black-pigmented Bacteroides spp. in the human oral cavity.

Five healthy children under 6 years of age, five healthy adults, and 10 adult periodontitis patients were examined for the prevalence and distribution of black-pigmented Bacteroides in the oral cavity. A total of 13 samples was obtained from each individual, including four supragingival and four subgingival dental plaques, dental occlusal surface, buccal mucosa, dorsal tongue, tonsil, and whole saliva. Black-pigmented Bacteroides were recovered from nine adult periodontitis patients. Healthy adults harbored the organisms in low incidence and proportions, whereas the children exhibited no cultivable black-pigmented Bacteroides. The organisms were isolated in highest proportions from dental plaque, especially subgingival plaque, and from the tonsil area, indicating that these sites constitute the organisms' primary ecological niche in the oral cavity. The predominant isolate was Bacteroides melaninogenicus subsp. intermedius followed by Bacteroides gingivalis and B. melaninogenicus subsp. melaninogenicus. B. melaninogenicus subsp. levii constituted low proportions of supragingival microflora of one adult periodontitis patient. A positive correlation was demonstrated between the proportion of black-pigmented Bacteroides (mainly B. melaninogenicus subsp. intermedius) and both the severity of gingival inflammation and the periodontal pocket depth, suggesting that these organisms may contribute to the pathogenesis of certain forms of periodontal disease.

Adult↗