An uncooked vegan diet shifts the profile of human fecal microflora: computerized analysis of direct stool sample gas-liquid chromatography profiles of bacterial cellular fatty acids

The health advantage of a vegan diet: exploring the gut microbiota connection

This review examines whether there is evidence that a strict vegan diet confers health advantages beyond that of a vegetarian diet or overall healthy eating. Few studies include vegan subjects as a distinct experimental group, yet when vegan diets are directly compared to vegetarian and omnivorous diets, a pattern of protective health benefits emerges. The relatively recent inclusion of vegan diets in studies of gut microbiota and health allows us the opportunity to assess whether the vegan gut microbiota is distinct, and whether the health advantages characteristic of a vegan diet may be partially explained by the associated microbiota profile. The relationship between diet and the intestinal microbial profile appears to follow a continuum, with vegans displaying a gut microbiota most distinct from that of omnivores, but not always significantly different from that of vegetarians. The vegan gut profile appears to be unique in several characteristics, including a reduced abundance of pathobionts and a greater abundance of protective species. Reduced levels of inflammation may be the key feature linking the vegan gut microbiota with protective health effects. However, it is still unclear whether a therapeutic vegan diet can be prescribed to alter the gut microflora for long-term health benefits.

Association of dietary type with fecal microbiota in vegetarians and omnivores in Slovenia

PURPOSE

The purpose of this study was to discover differences in the human fecal microbiota composition driven by long-term omnivore versus vegan/lacto-vegetarian dietary pattern. In addition, the possible association of demographic characteristics and dietary habits such as consumption of particular foods with the fecal microbiota was examined.

METHODS

This study was conducted on a Slovenian population comprising 31 vegetarian participants (11 lacto-vegetarians and 20 vegans) and 29 omnivore participants. Bacterial DNA was extracted from the frozen fecal samples by Maxwell 16 Tissue DNA Purification Kit (Promega). Relative quantification of selected bacterial groups was performed by real-time PCR. Differences in fecal microbiota composition were evaluated by PCR-DGGE fingerprinting of the V3 16S rRNA region. Participants' demographic characteristics, dietary habits and health status information were collected through a questionnaire.

RESULTS

Vegetarian diet was associated with higher ratio (% of group-specific DNA in relation to all bacterial DNA) of Bacteroides-Prevotella, Bacteroides thetaiotaomicron, Clostridium clostridioforme and Faecalibacterium prausnitzii, but with lower ratio (%) of Clostridium cluster XIVa. Real-time PCR also showed a higher concentration and ratio of Enterobacteriaceae (16S rDNA copies/g and %) in female participants (p < 0.05 and p < 0.01) and decrease in Bifidobacterium with age (p < 0.01). DGGE analysis of the 16S rRNA V3 region showed that relative quantity of DGGE bands from certain bacterial groups was lower (Bifidobacterium, Streptococus, Collinsella and Lachnospiraceae) or higher (Subdoligranulum) among vegetarians, indicating the association of dietary type with bacterial community composition. Sequencing of selected DGGE bands revealed the presence of common representatives of fecal microbiota: Bacteroides, Eubacterium, Faecalibacterium, Ruminococcaceae, Bifidobacterium and Lachnospiraceae. Up to 4 % of variance in microbial community analyzed by DGGE could be explained by the vegetarian type of diet.

CONCLUSIONS

Long-term vegetarian diet contributed to quantity and associated bacterial community shifts in fecal microbiota composition. Consumption of foods of animal origin (eggs, red meat, white meat, milk, yoghurt, other dairy products, fish and seafood) and vegetarian type of diet explained the largest share of variance in microbial community structure. Fecal microbiota composition was also associated with participants' age, gender and body mass.

Bacterial composition of murine fecal microflora is indigenous and genetically guided

Abstract The gastrointestinal tract and the microbes colonizing it form a complex ecosystem that has various effects on the well-being of the host. In addition to acute infections, the composition of the gastrointestinal microbiota has been suspected to influence the etiopathogenesis of many chronic diseases, such as rheumatoid arthritis and inflammatory bowel diseases. It has been suggested that the bacterial colonization of the gastrointestinal tract is genetically determined. Using gas-liquid chromatography of bacterial cellular fatty acids we show in this study that modulation of the microbiota by a course of antibiotics is followed by regeneration of the murine intestinal flora depending on the genotype of the host. The mice used in our study were acclimatized to identical living conditions before treatment with ciprofloxacin and clindamycin for 1 week via drinking water. Within a few days of finishing the antibiotic course, the cellular fatty acid profiles of fecal samples resembled those of the pre-course community, showing a considerable indigenous recovery potential. Colonization of the gastrointestinal tract appeared to be genetically regulated since differences in communities between the mouse strains were observed. Our results are in harmony with earlier observations, indicating that the gut community is not established by chance and that it is influenced by host-derived factors.

Deconjugation and degradation of flavonol glycosides by pig cecal microbiota characterized by Fluorescence in situ hybridization (FISH)

As the bioavailability of flavonoids is influenced by intestinal metabolism, we have investigated the microbial deconjugation and degradation of several flavonols and flavonol glycosides using the pig cecum in vitro model system developed in our group. For this model system the microbiota was directly isolated from the cecal lumen of freshly slaughtered pigs. The characterization of the cecal microbiota by fluorescence in situ hybridization (FISH) with 16S rRNA-based oligonucleotide probes confirmed the suitability of the model system for studying intestinal metabolism by the human microbiota. We have investigated the microbial degradation of quercetin-3-O-beta-d-rutinoside 1, quercetin-3-O-beta-d-glucopyranoside 2, quercetin-4'-O-beta-d-glucopyranoside 3, quercetin-3-O-beta-d-galactopyranoside 4, quercetin-3- O-beta-d-rhamnopyranoside 5, quercetin-3- O-[alpha-l-dirhamnopyranosyl-(1-->2)-(1-->6)-beta-d-glucopyranoside 6, kaempferol-3-O-[alpha-l-dirhamnopyranosyl-(1-->2)-(1-->6)-beta-d-glucopyranoside 7, apigenin 8, apigenin-8- C-glucoside (vitexin) 9, and feruloyl-O-beta-d-glucopyranoside 10 (100 microM), representing flavonoids with different aglycones, sugar moieties, and types of glycosidic bonds. The degradation rate was monitored using HPLC-DAD. The flavonol O-glycosides under study were almost completely metabolized by the intestinal microbiota within 20 min and 4 h depending on the sugar moiety and the type of glycosidic bond. The degradation rates of the quercetin monoglycosides showed a clear dependency on the hydroxyl pattern of the sugar moiety. The degradation of 2 with all hydroxyl groups of the glucose in the equatorial position was the fastest. The intestinal metabolism of di- and trisaccharides was much slower compared to the monoglycosides. The structure of the aglycone has not much influence on the intestinal metabolism; however, the type of glycosidic bond ( C- or O-glycoside) has substantial influence on the degradation rate. The liberated aglycones were completely metabolized within 8 h. Phenolic compounds such as 3,4-dihydroxyphenylacetic acid 12, 4-hydroxyphenylacetic acid 13, and phloroglucinol 18 were detected by GC-MS as main degradation products.

Dynamics of gut colonization and source of intestinal flora in healthy newborn infants

The aim of the study was to evaluate the dynamics of gut colonization and the main source of intestinal bacterial flora in infancy in a quantitative manner using computerized analysis of bacterial cellular fatty acid (CFA) profiles. Each stool was collected from 10 healthy newborn infants during their first 2-7 days of life and a follow-up sample at 6 months of age. Stool samples were collected from mothers and nurses for comparison. Gas-liquid chromatography of the 159 stool samples was used to produce bacterial cellular fatty acid (CFA) profiles by means of a previously developed computerized program. The CFA profiles for the infants fluctuated from hour to hour during the first days of life and resembled those for both the mothers and the nurses, doing so all the more in the case of the five infants examined 6 months after birth. Gut colonization fluctuated markedly from hour to hour in the perinatal period. The effect of the maternal flora on the initial gut colonization may be less than expected as the fecal flora of infants started to resemble both the fecal flora of the mother as well as that of the first nurse.

Factors influencing the composition of the intestinal microbiota in early infancy

OBJECTIVE

The aim of this study was to examine the contribution of a broad range of external influences to the gut microbiotic composition in early infancy.

METHODS

Fecal samples from 1032 infants at 1 month of age, who were recruited from the KOALA Birth Cohort Study in the Netherlands, were subjected to quantitative real-time polymerase chain reaction assays for the enumeration of bifidobacteria, Escherichia coli, Clostridium difficile, Bacteroides fragilis group, lactobacilli, and total bacterial counts. Information on potential determinants of the gut microbiotic composition was collected with repeated questionnaires. The associations between these factors and the selected gut bacteria were analyzed with univariate and multivariate analyses.

RESULTS

Infants born through cesarean section had lower numbers of bifidobacteria and Bacteroides, whereas they were more often colonized with C difficile, compared with vaginally born infants. Exclusively formula-fed infants were more often colonized with E coli, C difficile, Bacteroides, and lactobacilli, compared with breastfed infants. Hospitalization and prematurity were associated with higher prevalence and counts of C difficile. Antibiotic use by the infant was associated with decreased numbers of bifidobacteria and Bacteroides. Infants with older siblings had slightly higher numbers of bifidobacteria, compared with infants without siblings.

CONCLUSIONS

The most important determinants of the gut microbiotic composition in infants were the mode of delivery, type of infant feeding, gestational age, infant hospitalization, and antibiotic use by the infant. Term infants who were born vaginally at home and were breastfed exclusively seemed to have the most "beneficial" gut microbiota (highest numbers of bifidobacteria and lowest numbers of C difficile and E coli).

Mediterranean diet or extended fasting's influence on changing the intestinal microflora, immunoglobulin A secretion and clinical outcome in patients with rheumatoid arthritis and fibromyalgia: an observational study

BACKGROUND

Alterations in the intestinal bacterial flora are believed to be contributing factors to many chronic inflammatory and degenerative diseases including rheumatic diseases. While microbiological fecal culture analysis is now increasingly used, little is known about the relationship of changes in intestinal flora, dietary patterns and clinical outcome in specific diseases. To clarify the role of microbiological culture analysis we aimed to evaluate whether in patients with rheumatoid arthritis (RA) or fibromyalgia (FM) a Mediterranean diet or an 8-day fasting period are associated with changes in fecal flora and whether changes in fecal flora are associated with clinical outcome.

METHODS

During a two-months-period 51 consecutive patients from an Integrative Medicine hospital department with an established diagnosis of RA (n = 16) or FM (n = 35) were included in the study. According to predefined clinical criteria and the subjects' choice the patients received a mostly vegetarian Mediterranean diet (n = 21; mean age 50.9 +/-13.3 y) or participated in an intermittent modified 8-day fasting therapy (n = 30; mean age 53.7 +/- 9.4 y). Quantitative aerob and anaerob bacterial flora, stool pH and concentrations of secretory immunoglobulin A (sIgA) were analysed from stool samples at the beginning, at the end of the 2-week hospital stay and at a 3-months follow-up. Clinical outcome was assessed with the DAS 28 for RA patients and with a disease severity rating scale in FM patients.

RESULTS

We found no significant changes in the fecal bacterial counts following the two dietary interventions within and between groups, nor were significant differences found in the analysis of sIgA and stool ph. Clinical improvement at the end of the hospital stay tended to be greater in fasting vs. non-fasting patients with RA (p = 0.09). Clinical outcome was not related to alterations in the intestinal flora.

CONCLUSION

Neither Mediterranean diet nor fasting treatments affect the microbiologically assessed intestinal flora and sIgA levels in patients with RA and FM. The impact of dietary interventions on the human intestinal flora and the role of the fecal flora in rheumatic diseases have to be clarified with newer molecular analysis techniques. The potential benefit of fasting treatment in RA and FM should be further tested in randomised trials.

Comparison between cultured small-intestinal and fecal microbiotas in beagle dogs

The microbiota of the small intestine is poorly known because of difficulties in sampling. In this study, we examined whether the organisms cultured from the jejunum and feces resemble each other. Small-intestinal fluid samples were collected from 22 beagle dogs with a permanent jejunal fistula in parallel with fecal samples. In addition, corresponding samples from seven of the dogs were collected during a 4-week period (days 4, 10, 14, and 28) to examine the stability of the microbiota. In the jejunal samples, aerobic/facultative and anaerobic bacteria were equally represented, whereas anaerobes dominated in the fecal samples. Despite lower numbers of bacteria in the jejunum (range, 10(2) to 10(6) CFU/g) than in feces (range, 10(8) to 10(11) CFU/g), some microbial groups were more prevalent in the small intestine: staphylococci, 64% versus 36%; nonfermentative gram-negative rods, 27% versus 9%; and yeasts, 27% versus 5%, respectively. In contrast, part of the fecal dominant microbiota (bile-resistant Bacteroides spp., Clostridium hiranonis-like organisms, and lactobacilli) was practically absent in the jejunum. Many species were seldom isolated simultaneously from both sample types, regardless of their overall prevalence. In conclusion, the small intestine contains a few bacterial species at a time with vastly fluctuating counts, opposite to the results obtained for the colon, where the major bacterial groups remain relatively constant over time. Qualitative and quantitative differences between the corresponding jejunal and fecal samples indicate the inability of fecal samples to represent the microbiotas present in the upper gut.

Influence of major histocompatibility complex on bacterial composition of fecal flora

Very little is known about how the host genome influences the composition of the gastrointestinal flora, largely due to the great number and diversity of bacteria present in the flora and the difficulties of using traditional methods of bacterial isolation and identification. We have approached the problem by studying bacterium-derived cellular fatty acids in the stool samples of six mouse strains congenic for the major histocompatibility complex (MHC). The results obtained indicate that the composition of the fecal flora is genetically regulated. In addition to undefined gene loci, MHC alone has a pronounced effect, since mice with different MHC in the same background have significantly different fecal floras. Demonstration of the genetic influence on the gastrointestinal flora opens a new approach to studying the pathogenesis of bacterially induced diseases.

Age and disease related changes in intestinal bacterial populations assessed by cell culture, 16S rRNA abundance, and community cellular fatty acid profiles

BACKGROUND

The normal intestinal microflora plays an important role in host metabolism and provides a natural defence mechanism against invading pathogens. Although the microbiota in adults has been extensively studied, little is known of the changes that occur in the microflora with aging. These may have important consequences in elderly people, many of whom are receiving antibiotic therapy and who are most susceptible to intestinal dysbiosis.

AIMS

To characterise the major groups of faecal bacteria in subjects of different ages using a combination of cultural, molecular, and chemotaxonomic approaches.

METHODS

Comparative microbiological studies were made on four different subject groups: children (16 months to seven years, n=10), adults (21-34 years, n=7), healthy elderly subjects (67-88 years, n=5), and geriatric patients (68-73 years, n=4) diagnosed with Clostridium difficile diarrhoea. Selected faecal bacteria were investigated using viable counting procedures, 16S ribosomal RNA (rRNA) abundance measurements, and the occurrence of specific signature fatty acids in whole community fatty acid methyl ester profiles.

RESULTS

The principal microbiological difference between adults and children was the occurrence of higher numbers of enterobacteria in the latter group, as determined by viable counts (p<0.05) and 16S rRNA (p<0.01) measurements. Moreover, a greater proportion of children's faecal rRNA was hybridised by the three probes (bifidobacteria, enterobacteria, bacteroides-porphyromonas-prevotella) used in the study, indicating a less developed gut microbiota. Species diversity was also markedly lower in the Clostridium difficile associated diarrhoea group, which was characterised by high numbers of facultative anaerobes and low levels of bifidobacteria and bacteroides. Although it was a considerably less sensitive diagnostic tool, cellular fatty acid analysis correlated with viable bacterial counts and 16S rRNA measurements in a number of bacteria, including bacteroides.

CONCLUSIONS

Polyphasic analysis of faecal bacteria showed that significant structural changes occur in the microbiota with aging, and this was especially evident with respect to putatively protective bifidobacteria. Reductions in these organisms in the large bowel may be related to increased disease risk in elderly people.

Evaluation of 16s rRNA and cellular fatty acid profiles as markers of human intestinal bacterial growth in the chemostat

Chemostats were used to study the effects of carbon and nitrogen limitation and specific growth rate on 16S rRNA synthesis and cellular fatty acid (CFA) profiles in four human intestinal bacteria (Bacteroides thetaiotaomicron, Bifidobacterium adolescentis, Clostridium bifermentans and Cl. difficile). Cellular fatty acid synthesis varied with dilution rate and nutrient availability in different species, but these cellular constituents were relatively stable phenotypic characteristics in Bact. thetaiotaomicron, where branched chain and hydroxy CFA were good taxonomic markers. Conversely, CFA in the Gram-positive bacteria varied markedly with changes in growth environment. For example, in chemostats, cyclopropane CFA were only synthesized in Cl. bifermentans and Cl. difficile under N-limited conditions. Similarly, Dimethyl acetal (DMA) fatty acids in Bif. adolescentis were primarily produced during N-limited growth, and this was inversely related to dilution rate. At low growth rates, 16S rRNA concentrations (microg rRNA per ml culture) correlated with viable bacterial counts, but were more closely related to specific growth rate when expressed as a function of cell mass (microg rRNA per mg dry weight bacteria). However, this did not reveal differences in bacterial population size and rRNA concentration in C-limited cultures. Thus, at low dilution rates, C limitation strongly reduced rRNA synthesis in Cl. bifermentans, despite viable cell counts being similar to those in N-limited cultures. These results indicate that, while 16S rRNA is a useful indicator of microbial activity, cell growth rate does not necessarily relate to rRNA concentration under all nutritional conditions. Consequently, bowel habit and diet will affect both CFA and rRNA content in bacteria isolated from intestinal samples, and this should be taken into consideration when interpreting such data measurements.

Stability of cyclopropane and conjugated linoleic acids during fatty acid quantification in lactic acid bacteria

Seven methods commonly used for fatty acid analysis of microorganisms and foods were compared to establish the best for the analysis of lyophilized lactic acid bacteria. One of these methods involves fat extraction followed by methylation of fatty acids, while the other methods use a direct methylation of the samples, under different operating conditions (e.g., reaction temperature and time, reagents, and pH). Fatty acid methyl esters were identified by gas chromatography-mass spectrometry and quantified by on-column capillary gas chromatography. Two reliable methods for the analysis of fatty acids in bacteria were selected and further improved. They guarantee high recovery of classes of fragile fatty acids, such as cyclopropane and conjugated acids, and a high degree of methylation for all types of fatty acid esters. These two direct methylation methods have already been successfully applied to the analysis of fatty acids in foods. They represent a rapid and highly reliable alternative to classical time- and solvent-consuming methods and they give the fatty acid profile and the amount of each fatty acid. Using these methods, conjugated linoleic acids were identified and quantified in lactic acid bacteria.

Characterization of the periodontal microflora by the fatty acid profile of the broth-grown microbial population

The applicability of fatty acid analysis to the characterization of periodontal microflora was investigated using gas-liquid chromatography (GLC) and the software of the Sherlock Microbial Identification System (MIS) from MIDI Inc. Sulcus fluid was collected with paper points and anaerobically cultured in broth at 35 degrees C for four days. The broth-grown microbial population was extracted and the fatty acid methyl esters (FAME) were separated by GLC. The investigation of 67 specimens from asymptomatic sulci and of 32 specimens from inflamed sulci showed that the patterns of FAME profiles, the clustering of FAME profiles by computerized 2-D plot procedure, and the determination of the peak area index (PAI) of the FAME profiles differentiate between normal and pathological sulcus flora. Comparison of the clinical sulcus rating and the FAME data indicated that a pathological FAME profile may precede manifest periodontitis, and the normalization of the FAME profile may precede healing. It is concluded that the FAME analysis of sulcus fluid is a diagnostic aid for periodontological surveillance, for the initiation of preventive treatment of periodontitis, and for controlling the antimicrobial efficiency of therapeutic measures.

Monitoring impact of a pesticide treatment on bacterial soil communities by metabolic and genetic fingerprinting in addition to conventional testing procedures

Herbogil (dinoterb), a reference herbicide, the mineral oil Oleo (paraffin oil used as an additive to herbicides), and Goltix (metamitron) were taken as model compounds for the study of impacts on microbial soil communities. After the treatment of soil samples, effects on metabolic sum parameters were determined by monitoring substrate-induced respiration (SIR) and dehydrogenase activity, as well as carbon and nitrogen mineralization. These conventional ecotoxicological testing procedures are used in pesticide registration. Inhibition of biomass-related activities and stimulation of nitrogen mineralization were the most significant effects caused by the application of Herbogil. Even though Goltix and Oleo were used at a higher dosage (10 times higher), the application of Goltix resulted in smaller effects and the additive Oleo was the least-active compound, with minor stimulation of test parameters at later observation times. The results served as a background for investigation of the power of "fingerprinting" methods in microbial ecology. Changes in catabolic activities induced by treatments were analyzed by using the 95 carbon sources provided by the BIOLOG system. Variations in the complex metabolic fingerprints demonstrated inhibition of many catabolic pathways after the application of Herbogil. Again, the effects of the other compounds were expressed at much lower levels and comprised stimulations as well as inhibitions. Testing for significance by a multivariate t test indicated that the sensitivity of this method was similar to the sensitivities of the conventional testing procedures. The variation of sensitive carbon sources, as determined by factor weights at different observation times, indicated the dynamics of the community shift induced by the Herbogil treatment in more detail. DNA extractions from soil resulted in a collection of molecules representing the genetic composition of total bacterial communities. Distinct and highly reproducible community patterns, or genetic fingerprints, resulting from application of the different herbicides were obtained by the sequence-specific separation of partial 16S rDNA amplification products in temperature gradient gel electrophoresis. Significant pattern variations were quantified. For detailed analysis, application-responsive bands from the Herbogil and Oleo treatments were sequenced and their tentative phylogenetic positions were identified. Data interpretation and the potentials and biases of the additional observation windows on microbial communities are discussed.

The effect of food restriction on the composition of intestinal microflora in rats

The effect of a food-restricted diet on the fecal microflora of rats was studied by determining total anaerobic bacteria, bacterial cellular fatty acids, and the predominant intestinal bacteria shown by polymerase chain reaction (PCR) primers specific for the 16S rRNA gene sequences of 12 bacterial species. Twenty-four female Fischer 344 rats, 57 days old were divided into two groups and maintained on an NIH-31 diet. One group was fed ad libitum while the other group received 60% of ad libitum food intake (40% food restriction supplemented with vitamins and minerals equal to the ad libitum animals). After 2, 10, and 20 weeks on this dietary regimen, groups of four animals were sacrificed and the intestinal contents analyzed for changes in the bacterial flora. The anaerobic population for two-week (short-term) food-restricted rats was 3.2 x 10(8) per gram, slightly less than the 9.1 x 10(8) per gram found in the ad libitum-fed rats. The anaerobic populations in 20-week food restricted and ad libitum fed rats were 1.9 x 10(9) and 2.7 x 10(9) per gram, respectively. The total anaerobic population did not change significantly in either group during the 20-week study. No statistically significant differences were observed in the bacterial cellular fatty acid profiles between the two groups as determined by gas-liquid chromatography. PCR analysis of the intestinal contents indicated no significant shifts in the predominant flora due to dietary changes. The results, using three different methods to detect changes in the rat intestinal microflora, suggest that long-term dietary restriction had little effect on the microflora of female Fischer 344 rats.

Ribotyping of AdherentLactobacillusfrom Weaning Pigs: a Basis for Probiotic Selection Based on Diet and Gut Compartment

Dietary inoculates for weaned pigs often include lacobacilli, but the effects of age and diet on the ecology of adherent lactobacilli are not well known. Four experimental treatments included 16 newborn piglets: a pre-weaning treatment (PW) included four pigs that were sacrificed at 28 days of age; a sow treatment (Sow) had four pigs that remained with the sow (Sow) from 28 to 38 days of age and were sacrificed at 38 days of age; and two treatments in which four pigs each, were placed on a corn-soy diet with (CSL), or without (CS) 40% lactose. Adherent lactobacilli were isolated from the pars esophagus, ileum, and cecum, and characterised phenotypically. A 23S rDNA probe hydrized toEcoRI orPstI digested DNA, and a 74.8% cut-off individualize isolates into 36 clusters. The most predominant strains found in the Sow, CSL, and CS treatments were the same, but different strains predominated in the PW animals. The most predominant strains found in the pars esophagus and ileum were the same, but different strains predominated in the cecum.

Intestinal microflora of Estonian and Swedish infants

The intestinal microflora of 1-y-old healthy Estonian (n = 27) and Swedish infants (n = 29) was studied by quantitative culture of faecal samples. The major differences were high counts of lactobacilli and eubacteria in the former and increased numbers of clostridia in the latter babies. Bifidobacteria and anaerobic cocci prevailed equally in both groups, while eubacteria and enterococci were the major microorganisms in many Estonian infants and bacteroides and clostridia in many Swedish infants. The microflora of the Estonian infants was in many aspects similar to the flora prevailing in infants of western Europe in the 1960s. The results suggest a shift in the intestinal microflora among infants in western industrialized countries.

Use of gas-liquid chromatography for subgrouping coagulase-negative staphylococci during a nosocomial sepsis outbreak

Gas-liquid chromatographic (GLC) fatty acid profile correlation analysis was applied for the subgrouping of 169 coagulase-negative staphylococci collected during an outbreak of nosocomial sepsis in a hematologic unit. The fatty acid profile similarity index between six ciprofloxacin-resistant Staphylococcus epidermidis septicemia strains was as high as 98.39 +/- 0.68, indicating a high degree of resemblance. This finding corroborated the finding by conventional typing methods that the isolates shared the same strain characteristics and, therefore, could be derived from the same epidemiological origin. Further, the GLC fatty acid profiles were analyzed for coagulase-negative staphylococcal cutaneous isolates recovered from colonization cultures of the patients and personnel in that same unit. The similarity index between 88 ciprofloxacin-resistant Staphylococcus epidermidis skin isolates with similar plasmid profiles was as high as 95.47 +/- 3.78, whereas the correlation coefficient between 45 ciprofloxacin-susceptible Staphylococcus epidermidis skin isolates with different plasmid profiles was only 85.23 +/- 10.82. Cluster analysis grouped the ciprofloxacin-resistant Staphylococcus epidermidis isolates into one distinct cluster, while most of the ciprofloxacin-susceptible Staphylococcus epidermidis isolates were grouped into two separate clusters. When compared with the plasmid profiling, the GLC method congruously grouped 127 (87%) of the 146 Staphylococcus epidermidis isolates, thereby suggesting its potential value in subgrouping coagulase-negative staphylococci during nosocomial outbreaks.

Decrease in anti-Proteus mirabilis but not anti-Escherichia coli antibody levels in rheumatoid arthritis patients treated with fasting and a one year vegetarian diet

OBJECTIVE

To measure Proteus mirabilis and Escherichia coli antibody levels in patients with rheumatoid arthritis (RA) during treatment by vegetarian diet.

METHODS

Sera were collected from 53 RA patients who took part in a controlled clinical trial of fasting and a one year vegetarian diet. P mirabilis and E coli antibody levels were measured by an indirect immunofluorescence technique and an enzyme immunoassay, respectively.

RESULTS

The patients on the vegetarian diet had a significant reduction in the mean anti-proteus titres at all time points during the study, compared with baseline values (all p < 0.05). No significant change in titre was observed in patients who followed an omnivorous diet. The decrease in anti-proteus titre was greater in the patients who responded well to the vegetarian diet compared with diet non-responders and omnivores. The total IgG concentration and levels of antibody against E coli, however, were almost unchanged in all patient groups during the trial. The decrease from baseline in proteus antibody levels correlated significantly (p < 0.001) with the decrease in a modified Stoke disease activity index.

CONCLUSION

The decrease in P mirabilis antibody levels in the diet responders and the correlation between the decrease in proteus antibody level and decrease in disease activity supports the suggestion of an aetiopathogenetic role for P mirabilis in RA.

Channel structures in aerobic biofilms of fixed-film reactors treating contaminated groundwater

Scanning electron microscopy, confocal scanning laser microscopy, and fatty acid methyl ester profiles were used to study the development, organization, and structure of aerobic multispecies biofilm communities in granular activated-carbon (GAC) fluidized-bed reactors treating petroleum-contaminated groundwaters. The sequential development of biofilm structure was studied in a laboratory reactor fed toluene-amended groundwater and colonized by the indigenous aquifer populations. During the early stages of colonization, microcolonies were observed primarily in crevices and other regions sheltered from hydraulic shear forces. Eventually, these microcolonies grew over the entire surface of the GAC. This growth led to the development of discrete discontinuous multilayer biofilm structures. Cell-free channel-like structures of variable sizes were observed to interconnect the surface film with the deep inner layers. These interconnections appeared to increase the biological surface area per unit volume ratio, which may facilitate transport of substrates into and waste products out of deep regions of the biofilm at rates greater than possible by diffusion alone. These architectural features were also observed in biofilms from four field-scale GAC reactors that were in commercial operation treating petroleum-contaminated groundwaters. These shared features suggest that formation of cell-free channel structures and their maintenance may be a general microbial strategy to deal with the problem of limiting diffusive transport in thick biofilms typical of fluidized-bed reactors.

Vegetarian diet for patients with rheumatoid arthritis--status: two years after introduction of the diet

We have previously reported that a significant improvement can be obtained in rheumatoid arthritis patients by fasting followed by an individually adjusted vegetarian diet for one year. The patients who changed their diet could be divided into diet responders and diet nonresponders. After the clinical trial the patients were free to change diet or medication and after approximately one year they were asked to attend a new clinical examination. We compared the change from baseline (i.e. at the time of study entry) to the time of the follow-up examination for diet responders, diet nonresponders and controls who ate an omnivorous diet. The following variables favoured diet responders: pain score, duration of morning stiffness, Stanford Health Assessment Questionnaire index, number of tender joints, Ritchie's articular index, number of swollen joints, ESR and platelet count [corrected]. The difference between the three groups were significant for all the clinical variables, except for grip strength. There was no significant difference between the groups with regard to laboratory or anthropometric variables. At the time of the follow-up examination all diet responders but only half of the diet nonresponders still followed a diet. Our findings indicate that a group of patients with rheumatoid arthritis benefit from dietary manipulations and that the improvement can be sustained through a two-year period.