Comparison of fecal microflora of elderly persons in rural and urban areas of Japan

The Fecal microflora of 15 healthy elderly persons with a median age of 84 years in a rural area whose inhabitants tend to be long-lived (Yuzurihara-area, Uenohara, Yamanashi Prefecture) was compared with the microflora of individuals with a median age of 68 years in an urban area (Tokyo). The diet of the elderly persons in the Yuzurihara area is characterized by a high intake of dietary fiber. Total numbers of anaerobic bacteria were significantly smaller in the elderly persons in the Yuzurihara area than those in the Tokyo area. A significantly large number of bifidobacteria, but not of lecithinase-negative clostridia, was observed in the elderly persons in the Yuzurihara area. Large numbers and high incidences of bacilli and lecithinase-positive clostridia (mainly Clostridium perfringens) were found in the elderly persons in the Tokyo area. Twenty-five genera and over 81 species were isolated from the elderly persons in the Yuzurihara area, and 25 genera and over 92 species were isolated from the elderly persons in the Tokyo area. Furthermore, significantly larger numbers of Bifidobacterium adolescentis and Fusobacterium mortiferum strains were found in the Yuzurihara group, but significant reductions in the Bacteroides buccae-oris group, B. thetaiotaomicron, Bacteroides spp., C. coccoides, C. paraputrificum, and Clostridium spp. were observed in the same group. A significantly higher isolation rate of Bacillus subtilis was observed in the elderly persons in the Tokyo area. The difference in the fecal microflora between elderly persons in Yuzurihara and those in the Tokyo area might be due to a difference in the intake of dietary fiber.     

Effect of rice fiber on human fecal microflora

The effects of brown rice, containing fourfold as much dietary fiber as polished rice, on the human fecal microflora were determined. Significantly increased numbers of Bifidobacterium adolescentis and Enterococcus faecalis were observed during the brown rice intake, whereas the total counts and the numbers of bacteroides, Eubacterium aerofaciens, and Escherichia coli during the intake were lower than those before and after the intake. Lower numbers of clostridia and low incidences of Clostridium paraputrificum and C. perfringens were observed during the brown rice intake.     

Comparison of the fecal microflora in rural Japanese and urban Canadians

The fecal microflora of nine rural healthy Japanese and eight urban healthy Canadians was examined. The two populations ate typical Japanese and western diets, respectively. The numbers of eubacteria (P less than 0.01), bifidobacteria (P less than 0.05), bacilli (P less than 0.01), lactobacilli and veillonellae and the frequency of occurrence of bifidobacteria were higher in the Japanese than in the Canadians. Higher numbers of bacteroides and lecithinase-negative clostridia were found in the Canadians. Twenty-three genera and over 75 species or biovars were isolated from the feces of Japanese and 18 genera and over 66 species or biovars from the Canadians. The numbers of Bacteroides vulgatus (P less than 0.05), Clostridium coccides (P less than 0.001), and C. tertium (P less than 0.05) and the incidence of B. uniformis (P less than 0.01), C. innocuum (P less than 0.05), and Bacillus spp. (P less than 0.01) were significantly lower in the Japanese than in the Canadians. In contrast, the numbers of Eubacterium aerofaciens (P less than 0.001), and the incidence of Bifidobacterium adolescentis biovar b (P less than 0.01) and Bacillus subtilis (P less than 0.01) were significantly higher in the Japanese than in the Canadians. These findings suggest that significant reductions in anaerobic gram-positive bacilli and increased numbers of bacteroides and clostridia in the feces were induced by the intake of a western diet.     

The effect of sucrose or starch-based diet on short-chain fatty acids and faecal microflora in rats

An investigation was carried out to determine whether variations of dietary carbohydrates could modify the colonic flora in rats. Sprague-Dawley rats were fed with two equicaloric diets based on the AIN-76 diet (American Institute of Nutrition 1977) but differing from that diet in content of carbohydrates, i.e. high sucrose (64%) of high corn starch (64%). Feeding was continued for 9 months ad libitum and no variation in weight gain was recorded among the different diets. A prevalence of aerobes, and a significant reduction in the ratio anaerobes/aerobes in the faeces of rats on the high starch diet compared with the high sucrose diet, was observed. The anaerobe genera identified included Actinomyces, Bacteroides, Bifidobacterium, Clostridium, Eubacterium, Lactobacillus and Propionibacterium. Bacteroides was the most prevalent genus in both dietary groups (51.2 and 29.5% in the faeces of rats fed the sucrose and starch diets, respectively). In contrast, clostridia were prevalent in the starch-fed group (23.8%) and less so in the sucrose diet (11.5%), as propionibacteria were prevalent in faeces of rats fed the starch diet (15.5%), and low in the sucrose diet (3.9%). The remaining genera were scarce in faeces from rats on either diet. Total short-chain fatty acids (SCFA) were significantly higher in the faeces of animals fed the starch diet compared with those fed the sucrose diet. The relative concentrations of acetic, propionic and butyric acids were not significantly different between the two dietary groups. In conclusion, high starch diet can markedly modify the composition of faecal flora and alter considerably the faecal concentration of SCFAs, compound which might have a health-promoting effect.     

The currently used commercial DNA-extraction methods give different results of clostridial and actinobacterial populations derived from human fecal samples

Recently several human health-related microbiota studies have had partly contradictory results. As some differences may be explained by methodologies applied, we evaluated how different storage conditions and commonly used DNA-extraction kits affect bacterial composition, diversity, and numbers of human fecal microbiota. According to our results, the DNA-extraction did not affect the diversity, composition, or quantity of Bacteroides spp., whereas after a week's storage at -20?°C, the numbers of Bacteroides spp. were 1.6-2.5 log units lower (P?相似文献   

The intestinal microflora of infants: composition of fecal flora in breast-fed and bottle-fed infants

The fecal flora of 35 breast-fed and 35 bottle-fed babies was determined. Bifidobacteria were the predominant fecal bacteria in both groups. Conversely, the counts of most of the other bacteria, such as bacteroides, eubacteria, peptococci, veillonella, clostridia, enterobacteria, streptococci, and bacilli in the bottle-fed group were significantly higher than those in the breast-fed group. The frequencies of occurrence of lecithinase positive clostridia, clostridia-others, pseudomonas and bacilli in the bottle-fed group were significantly higher than those in the breast-fed group. Twenty-one genera and 103 species or biovars of microorganisms were isolated from the feces of the breast-fed group and 20 genera and 97 species or biovars from the bottle-fed group. The organism that showed the highest number and the highest frequency of occurrence in both groups was Bifidobacterium breve. Bifidobacterium infantis, which was formerly the most prevalent Bifidobacterium species in baby feces, was never isolated in this study. Further, the counts and incidences of Clostridium paraputrificum, C. perfringens, and Bacillus subtilis, the counts of C. clostridiiforme, Bacteroides vulgatus, Veillonella parvula, Lactobacillus acidophilus, Escherichia coli, Streptococcus bovis, S. faecalis, and S. faecium and the incidences of C. difficile, C. tertium, and Pseudomonas aeruginosa in the bottle-fed infants were significantly higher than those in the breast-fed infants.     

实时荧光定量PCR法研究溃疡性结肠炎患者肠道双歧杆菌属、柔嫩梭菌属及拟杆菌属量的变化

目的应用荧光定量PCR技术对人粪便内双歧杆菌属、柔嫩梭菌属及拟杆菌属进行定量检测,揭示肠道相关菌群改变在溃疡性结肠炎（ulcerative colitis,UC）发病中的作用及意义。方法分别设计双歧杆菌属、柔嫩梭菌属及拟杆菌属的特异性引物。收集溃UC患者粪便标本60份及正常对照标本60份,提取细菌基因组DNA,应用实时荧光定量PCR反应测定细菌的数量。结果UC患者组双歧杆菌属及柔嫩梭菌属的数量较正常对照组明显减少（P〈0．05）,而拟杆菌属的数量较正常对照组明显增多（P〈0．05）,差异有统计学意义。结论UC患者粪便中双歧杆菌属及柔嫩梭菌属的数量较正常对照明显减少,而拟杆菌属的数量较正常对照明显增多,提示肠道菌群与UC的发生、发展有一定的关系。     

Effects of Age and Region on Fecal Microflora in Elderly Subjects Living in Bama,Guangxi, China

Intestinal microflora analysis was performed on 52 healthy elderly subjects of different ages and in different regions in Bama County, Guangxi, China. The participants were assigned to three groups depending on their age and location: longevous (group M; mean age = 98 years; n = 21); rural younger elderly (group S; mean age = 70 years; n = 18); and urban elderly (group C; mean age = 82 years; n = 13). Ten groups of bacteria were quantified using real-time PCR. Age-related differences were observed in the number of Clostridium coccoides–Eubacterium rectale—there were more in longevous participants. Region affected the numbers of Bacteroides—Prevotella and Clostridium perfringens subgroup, and longevous participants had significantly more of the two bacterial groups than urban elderly participants. Region-related effects were also observed for the relative abundance of E. coli, and rural elderly participants had a lower proportion. Both age and regional effects were observed in the amount of total bacteria, and longevous participants had higher numbers than urban elderly participants. A significantly higher proportion of lactobacilli was observed in rural younger elderly participants than urban elderly participants, but independent age or regional effects did not contribute to this difference. This study suggests that age and region can affect the intestinal microflora of elderly people.     

Biodiversity of human faecal bacteria isolated from phytic acid enriched chemostat fermenters

BACKGROUND: Myo-inositol hexaphosphate (IP6) or phytic acid is found mostly in cereals and legumes and is thought to possess anti-carcinogenic properties. AIM: To isolate and identify faecal bacteria capable of phytic acid metabolism and to assess the effectiveness of prebiotics (dietary oligosaccharides, metabolised by selective colonic bacteria) in preserving the integrity of phytic acid. METHODS: Faecal samples from three volunteers were used in continuous culture experiments under varying conditions of pH, substrate concentration and dilution rates, seventy three different isolates cultured at steady state were then screened for phytic acid metabolism and identified through partial sequencing of their 16S rRNA genes (16S ribosomal ribonucleic acid). Utilisation of phytic acid was also assessed in a continuous culture system enriched with prebiotic fructooligosaccharides (FOS). RESULTS: Bacteroides spp., Clostridium spp. and facultatively anaerobic bacteria generally appeared to maintain viable counts in the presence of phytic acid. Bifidobacterium spp. and Lactobacillus spp. appeared less able to maintain viable counts in the presence of phytic acid. These results were confirmed by an increase in viable counts of Bacteroides spp., Clostridium spp. and a decrease in viable counts of Bifidobacterium spp. and Lactobacillus spp. once phytic acid was introduced to a FOS enriched continuous culture. CONCLUSIONS: The phytate metabolising biodiversity from the human large intestine does not appear to encompass major bacterial genera associated with beneficial or benign health effects (e.g. Lactobacillus spp. and Bifidobacterium spp).     

Profiling of composition and metabolic activities of the colonic microflora of growing pigs fed diets supplemented with prebiotic oligosaccharides

It is evident that quantitative information on different microbial groups and their contribution in terms of activity in the gastrointestinal (GI) tract of humans and animals is required in order to formulate functional diets targeting improved gut function and host health. In this work, quantitative information on levels and spatial distributions of Bacteroides spp, Eubacterium spp, Clostridium spp, Escherichia coli, Bifidobacterium spp and Lactobacillus/Enterococcus spp. along the porcine large intestine was investigated using 16S rRNA targeted probes and fluorescent in situ hybridisation (FISH). Caecum, ascending colon (AC) and rectum luminal digesta from three groups of individually housed growing pigs fed either a corn-soybean basal diet (CON diet) or a prebiotic diet containing 10 g/kg oligofructose (FOS diet) or trans-galactooligosaccharides (TOS diet) at the expense of cornstarch were analysed. DAPI staining was used to enumerate total number of cells in the samples. Populations of total cells, Bacteroides, Eubacterium, Clostridium and Bifidobacterium declined significantly (P < 0.05) from caecum to rectum, and were not affected by dietary treatments. Populations of Lactobacillus/Enterococcus and E. coli did not differ throughout the large intestine. The relative percent (%) contribution of each bacterial group to the total cell count did not differ between caecum and rectum, with the exception of Eubacterium that was higher in the AC digesta. FISH analysis showed that the sum of all bacterial groups made up a small percentage of the total cells, which was 12.4%, 21.8% and 10.3% in caecum, AC and rectum, respectively. This supports the view that in swine, the diversity of GI microflora might be higher compared to other species. In terms of microflora metabolic activity, the substantially higher numerical trends seen in FOS and TOS treatments regarding total volatile fatty acid, acetate concentrations and glycolytic activities, it could be postulated that FOS and TOS promoted saccharolytic activities in the porcine colon.     

Quantitative analysis of the intestinal bacterial community in one- to three-week-old commercially reared broiler chickens fed conventional or antibiotic-free vegetable-based diets

AIMS: To explore the effect of drug-free poultry production on the intestinal microflora of broiler chickens, the bacterial community of this environment was quantitatively profiled in both conventionally reared birds and birds reared without antibiotic growth promotants (AGPs) on a vegetable-based diet. METHODS AND RESULTS: Quantitative, real-time PCR with group-specific 16S rDNA primer sets was used to enumerate the abundance of the following chicken gastrointestinal (GI) tract phylogenetic groups: the Clostridium leptum-Faecalibacterium prausnitzii subgroup (Clostridium genus cluster IV), the Clostridium coccoides - Eubacterium rectale subgroup (Clostridium cluster XIVa and XIVb), the Bacteroides group (including Prevotella and Porphyromonas), Bifidobacterium spp., the Enterobacteriaceae, the Lactobacillus group (including the genera Leuconostoc, Pediococcus, Aerococcus and Weissella), the Clostridium perfringens subgroup (Clostridium cluster I), Enterococcus spp., Veillonella spp., Atopobium spp., Campylobacter spp. and the domain Bacteria. A species-specific 5'-nuclease (Taqman) assay was also employed to specifically assess Cl. perfringens abundance. Ten birds were sampled from each of two commercial chicken houses, one in which feed was supplemented with AGPs and exogenous animal protein, and the other vegetable-based and drug-free, at 7, 14 and 21 days of age. The ileal community was dominated by two large populations, the lactobacilli and the Enterobacteriaceae, with those taxa much more numerous in drug-free vegetable-based diet fed birds than those conventionally reared at the 7- and 14-day time periods. The progressive changes in microflora in both the conventional and drug-free caeca were similar to each other, with the Enterobacteriaceae sequences dominating at day 7, but being replaced by obligate anaerobe signature sequences by day 14. Of note was the finding that all the day 14 and day 21 replicate caecal samples from the drug-free house were positive for Campylobacter spp. averaging >10(8) 16S rDNA gene copies per gram wet weight. CONCLUSIONS: Quantitative, real-time PCR indicates that the effects of drug-free rearing on the chicken GI tract microbial community are most pronounced in the ileal region, but AGPs may be important in controlling Campylobacter colonization of the caecum. SIGNIFICANCE AND IMPACT OF THE STUDY: A quantitative taxonomic understanding of the shifting microbial ecology of the broiler chicken gut microbiota is important in the light of AGP withdrawal. AGP withdrawal has occurred in response to concerns over the transfer of antimicrobial-resistant bacteria to humans via the food production chain.     

A Human Volunteer Study on the Prebiotic Effects of HP-Inulin—Faecal Bacteria Enumerated Using Fluorescent In Situ Hybridisation (FISH)

An in vivo study was carried to determine the effect of HP-inulin, a high-molecular-weight fraction of chicory-derived inulin, on the human gut microflora composition. Ten healthy volunteers were allowed a free-living diet whereby they also ingested 8 g/d of maltodextrin for 14 days and this was followed by 8 g/d HP-inulin for 14 days. Nine of the ten volunteers completed the trial. The trial was conducted in a double blind manner and faeces were collected periodically such that predominant groups of gut bacteria i.e. total bacterial populations, Bacteroides spp., Bifidobacterium spp., Clostridium perfringens/histolyticum sub-group and lactobacilli/enterococci could be enumerated. To overcome difficulties with culture-based techniques, the bacteria were enumerated using fluorescent in situ hybridisation (FISH). A small but statistically significant increase in bifidobacteria was observed when data from the volunteers were pooled. Similarly, a statistically significant increase was observed in clostridial numbers, although the magnitude of change in this bacterial group was about ten times less than that seen with bifidobacteria. HP-inulin intake had little or no effect on numbers of total bacteria,Bacteroides spp., or lactobacilli and enterococci present in the gut microflora of the volunteers. This study has confirmed the prebiotic nature of HP-inulin. However, in this trial the effects were most marked in those volunteers with low starting levels of bifidobacteria—indicating that there may be a relationship between prebiotic effect and initial bifidobacterial numbers.     

3-(6-Chloronicotinyl)-2-nitromethylene-thiazolidine as a New Class of Insecticide Acting against Lepidoptera Species

The growth responses of a variety of human intestinal bacteria to partially hydrolyzed guar gum (PHGG) were investigated in vitro and in vivo. In an in vitro experiment, PHGG moderately enhanced growth of some bacterial strains including Bacteroides ovatus, Clostridium coccoides, C. butyricum, and Peptostreptococcus productus.

Effects of PHGG intake (7 g/volunteer, 3 times per day, for 14 days) on fecal microflora, bacterial metabolites, and pH were investigated using nine healthy human volunteers. The count of Bifidobacterium spp. and the percentage of these species in the total count increased significantly during the PHGG intake periods. Among the acid-forming bacteria, Lactobacillus spp. also increased. The fecal pH and fecal bacterial metabolites such as β-glucuronidase activity, putrefactive products, and ammonia content were significantly decreased by PHGG intake. Two weeks after the end of PHGG intake, the bacterial counts and their biological manifestations appeared to return to the former state.     

断奶仔猪肠道菌群的研究

研究断奶仔猪在不同生理状况下的肠道菌群,结果表明：健康仔猪肠道内容物中,从十二指肠到结肠,所测定的８种细胞数量都随肠段后移而逐渐增加,４３日龄仔猪肠道内容物中以乳杆菌、肠球菌和梭菌占绝对优势,双歧杆菌次之;与健康仔猪相比,下痢仔猪肠道中肠球菌、梭菌和乳杆菌等优势菌群的数量明显低于对照组;饲喂了含肠球菌的活菌制剂的仔猪肠道中双歧杆菌和类杆菌的数量比对照组明显增加,但肠球菌数量却无显著改变。     

Impact of Bifidobacterium longum on human fecal microflora.

The effects of Bifidobacterium longum feedings for five weeks on the fecal microflora, water contents, pH values, ammonia concentration, and beta-glucuronidase activity were investigated in five healthy human volunteers. Although numbers of major bacterial groups of the fecal microflora were not changed by the bifidobacteria feedings, a remarkably decreasing number of lecithinase-negative clostridia was observed. The percentage of lecithinase-negative clostridia and bacteroides to the total bacterial numbers isolated were decreased during the feedings and numbers of C. paraputrificum and C. innocuum were reduced. A significant reduction of fecal pH values for the last week of the feeding was observed. Ammonia concentration and beta-glucuronidase activity in the feces during the feedings were significantly lower than those before or after the feedings. The oral supplement of B. longum may be introduced to improve the fecal properties such as fecal ammonia concentration and beta-glucuronidase activity, but not the composition of fecal flora.     

Evidence for natural horizontal transfer of tetQ between bacteria that normally colonize humans and bacteria that normally colonize livestock.

Though numerous studies have shown that gene transfer occurs between distantly related bacterial genera under laboratory conditions, the frequency and breadth of horizontal transfer events in nature remain unknown. Previous evidence for natural intergeneric transfers came from studies of genes in human pathogens, bacteria that colonize the same host. We present evidence that natural transfer of a tetracycline resistance gene, tetQ, has occurred between bacterial genera that normally colonize different hosts. A DNA sequence comparative approach was taken to examine the extent of horizontal tetQ dissemination between species of Bacteroides, the predominant genus of the human colonic microflora, and between species of Bacteroides and of the distantly related genus Prevotella, a predominant genus of the microflora of the rumens and intestinal tracts of farm animals. Virtually identical tetQ sequences were found in a number of isolate pairs differing in taxonomy and geographic origin, indicating that extensive natural gene transmission has occurred. Among the exchange events indicated by the evidence was the very recent transfer of an allele of tetQ usually found in Prevotella spp. to a Bacteroides fragilis strain.     

Protein degradation by human intestinal bacteria

Analysis of human gut contents showed that substantial quantities of soluble protein, ammonia and branched chain volatile fatty acids occurred throughout the large intestine [0.1-24.4 g (kg contents)-1, 7.7-66.0 mmol (kg contents)-1 and 1.5-11.1 mmol (kg contents)-1 respectively]. The presence of these metabolites suggested that substantial proteolysis was occurring. In vitro studies showed that casein and bovine serum albumin were partly degraded in slurries of human faeces over a 96 h incubation period, to produce TCA-soluble peptides, ammonia and volatile fatty acids. Proteolytic activity detected in the stools of five individuals ranged from 3.5 to 19.8 mg azocasein hydrolysed h-1 (g faecal material)-1. Washed cell and washed particulate faecal fractions accounted for 24-67% of total activity. The predominant proteolytic bacteria in the faecal samples examined were identified as Bacteroides spp. [1.0 X 10(11)-1.3 X 10(12) (g dry wt faeces)-1] and Propionibacterium spp. [1.2 X 10(8)-1.0 X 10(10) (g dry wt faeces)-1]. Other proteolytic bacteria which occurred in lesser numbers were identified as belonging to the genera Streptococcus, Clostridium, Bacillus and Staphylococcus. These results demonstrate that the gut microflora could potentially play a major role in proteolysis in the human colon.     

Intestinal microflora of autistic children

Autistic behavior is often accompanied by numerous disturbing symptoms on the part of gastrointestinal system, such as abdominal pain, constipation or diarrhea. These problems are often connected with deregulation of physiological microflora in intestine. The aim of this study was to determine differences in intestinal microflora of autistic and healthy children. Strains of Clostridium spp. and enterococci were isolated more frequently from stool samples of autistic children and rarely lactobacilli. Quantitative differences were observed maliny among staphylococci, Candida spp. and Clostridium perfringens. Monitoring and stabilization of intestinal microflora and knowledge about role of particular strains in etiology of autistic disorders can increase the chances for appropriate therapy.     

A comparative in vitro investigation into the effects of cooked meats on the human faecal microbiota

Protein fermentation is one of the important microbial activities in the human colon. Meat foods rich in protein provide substantial resource for this metabolic activity. However, little information exists on the relative impact of different meats on the composition and activities of the human gut microbiota. Similarly, little information is available on the confounding effects of cooking on these activities. In this study, beef, chicken and fish (salmon) were examined in vitro for their impact on the human faecal microbiota. The influence of cooking method was also investigated by using either frying or boiling. Upon fermentation over 48 h the Clostridium perfringens/histolyticum group increased significantly in number in the beef fermentations, either fried (p = 0.023) or boiled (p = 0.017). Cooking method appeared to influence Clostridium spp. growth, with higher numbers in fried meat compared to boiled meats after 5 h (p = 0.024) and 48 h (p = 0.003) fermentation. Significant differences between meat types were also seen for numbers of Bifidobacterium spp. at 48 h (p = 0.028), Bacteroides group at 24 h (p = 0.016) as well as Coriobacterium/Atopobium group at 10 h (p = 0.038). Most types of short chain fatty acids increased significantly in concentration over the experiment (p < 0.05). Significant differences between meat types were found in n-butyric acid production at 24, 30 and 48 h (p = 0.015, p = 0.024 and p = 0.035 respectively) and in i-valeric acid production at 10, 24, 30 and 48 h (p = 0.026, p = 0.002, p = 0.019 and p = 0.022 respectively). The concentration of i-valeric acid differed significantly between cooking methods at 24 h (p = 0.042). These findings suggest that both the type of meat and cooking process can influence fermentation profiles within the human gut microbiota. Interactions between ingested cooked meats and the gut microbiota may represent a novel corollary to mechanisms underlying the observed increased risk of intestinal and systemic diseases associated with high intake of certain meats/processed meats.     

The abattoir source of culturable psychrophilic Clostridium spp. causing 'blown pack' spoilage of vacuum-packed chilled venison

AIMS: To identify the abattoir source(s) of culturable psychrophilic clostridia causing 'blown pack' spoilage of vacuum-packed chilled meats. METHODS AND RESULTS: Psychrophilic and psychrotolerant clostridia were isolated from hides, faeces and tonsils of deer slaughter stock, and from a meat plant environment. The isolates were differentiated using restriction fragment length polymorphism analysis of the 16S rDNA gene (PCR-RFLP) and 16S-23S rDNA internal transcribed spacer (ITS) analysis. PCR-RFLP group I clostridia were found to have restriction patterns indistinguishable from the patterns of 'blown pack'-causing Clostridium gasigenes DB1A(T) and R26. Gas production in packs inoculated with vegetative cells of PCR-RFLP group I clostridia was first evident after 14 days at 2 degrees C. The prevalence of these clostridia was similar in hide and faecal samples from slaughter animals, but these micro-organisms were absent from tonsils and the meat plant environment. Banding patterns of PCR-RFLP group II clostridia showed some cross-similarity with patterns of the 'blown pack'-causing micro-organism Cl. estertheticum DSM 8809(T) and Cl. estertheticum-like meat strains. The majority of clostridia in PCR-RFLP group II were found in the faeces of slaughter animals. Isolates representing PCR-RFLP group II did not, however, produce gas in vacuum packs stored at 2 degrees C for 84 days. CONCLUSIONS: The data suggest that soil particles attached to hide or present in faeces are the most probable primary reservoir from which 'blown pack' clostridia are introduced onto carcasses. Therefore, dressing procedure hygiene remains paramount in order to control the spread of psychrophilic Clostridium spp. in a meat plant. SIGNIFICANCE AND IMPACT OF THE STUDY: The paper provides information critical for controlling 'blown pack' spoilage in meat processing plants. It reports on the use of molecular techniques for determination of abattoir sources of 'blown pack'-causing clostridia.