Cecal Flora Research Articles

Comparison by chemotaxonomy of the cecal and fecal flora in irritable bowel syndrome (IBS) and asymptomatic controls

Comparison by chemotaxonomy of the cecal and fecal flora in irritable bowel syndrome (IBS) and asymptomatic controls

Effect of oral genistein and isoflavone-free diet on cecal flora and bacterial translocation in antibiotic-treated mice.

There are several reports indicating that the isoflavone genistein may augment the integrity of the intestinal epithelial barrier as well inhibit bacterial internalization by cultured enterocytes. We speculated that oral genistein might enhance the integrity of the intestinal epithelial barrier as monitored by the extraintestinal dissemination of intestinal bacteria. Mice were treated with oral antibiotics to induce cecal bacterial overgrowth accompanied by bacterial translocation of antibiotic-resistant enterobacteria, especially Escherichia coli. These mice were divided into separate groups that included chow-fed mice orally inoculated either with saline, vehicle, or genistein, and mice fed isoflavone-free diet and orally inoculated with either saline, vehicle, or genistein. Intestinal bacterial overgrowth was monitored by quantitative culture of excised ceca and bacterial translocation was monitored by quantitative culture of draining mesenteric lymph nodes. Mice fed the isoflavone-free diet had decreased populations of cecal bacteria compared with chow-fed mice, and bacterial translocation was reduced in chow-fed mice compared with mice fed isoflavone-free diet. However, bacterial translocation was similar in mice given oral genistein compared with appropriate control mice. Oral genistein had no noticeable effect on bacterial translocation in this model. However, the isoflavone-free diet had an antibacterial effect on cecal flora, and the isoflavone-free diet was associated with decreased numbers of cecal bacteria and decreased incidence of bacterial translocation.

Effect of INT1 Gene on Candida albicans Murine Intestinal Colonization

Background. Increased intestinal colonization with Candida albicans is believed to be a major factor predisposing immunocompromised and postsurgical patients to systemic candidiasis, although the mechanisms facilitating C. albicans colonization remain unclear. Because previous studies have linked the C. albicans INT1 gene to filament formation, epithelial adherence, and mouse virulence, experiments were designed to evaluate the effect of INT1 on intestinal colonization.Materials and Methods. Mice were orally inoculated with either the parent strain (CAF2, INT/INT1), an int1 heterozygote (CAG1, INT1/int1), an int1 homozygote (CAG3, int1/int1), or a reintegrant (CAG5, int1/int1 + INT1), and sacrificed 3 and 7 days later for quantitative analysis of cecal C. albicans.Results. Following oral inoculation with 103C. albicans, only small numbers of each strain were recovered from the cecal flora of normal mice. However, in mice pretreated with oral antibiotics, cecal colonization of each strain was increased (P < 0.01). In addition, cecal colonization was reduced for all int1 mutant strains compared with the parent strain (P < 0.05). By light microscopy, all four C. albicans strains were easily observed in the ileal lumen as both budding yeast and filamentous forms, although only occasional yeast forms appeared adherent to the intestinal epithelium.Conclusions. C. albicans readily colonized and replicated in the ceca of antibiotic-treated mice. The presence of two functional copies of INT1 appeared to facilitate C. albicans cecal colonization, suggesting that intestinal colonization may be another virulence factor associated with INT1 and that the gene product may be an attractive target to control C. albicans intestinal colonization.

Inhibitory Effects of Competitive Exclusion and Fructooligosaccharide, Singly and in Combination, on Salmonella Colonization of Chicks

The inhibitory effects of competitive exclusion (CE) and 0.1% concentration of fructooligosaccharide (FOS), singly and in combination, on Salmonella colonization of chicks were investigated. Moreover, quantitation of the major cecal flora (Bifidobacterium, Bacteroides, Lactobacillus, and Escherichia coli) was performed. One-day-old birds were divided into four groups: (i) control, (ii) CE, (iii) FOS, and (iv) CE plus FOS. Chicks received Salmonella Enteritidis at 7 days (experiment 1) or 21 days (experiment 2). Birds in each group were killed at 1 day, 7 days, and 14 days after inoculation of Salmonella Enteritidis for count of salmonella in cecal contents. In experiment 1, the mean number of Salmonella Enteritidis in the chicks inoculated with CE was significantly decreased compared with the other three groups at 1 day postinoculation. In experiment 2, the mean numbers of Salmonella Enteritidis in the chicks of the FOS group and the FOS plus CE group were significantly decreased compared with the control group at 1 day and 7 days postinoculation. On 7- and 21-day-old chicks, few changes on number of total bacteria, Bifidobacterium, Bacteroides, Lactobacillus, and E. coli were observed in the cecal contents of treated groups compared with the control group. Low-dose feeding of FOS in the diet of chicks with a CE treatment may result in reduced susceptibility to Salmonella colonization but may not lead to a shift in the intestinal gut microflora on 7- and 21-day-old chicks.

Establishment of specific pathogen-free rabbit colonies with limited-flora rabbits associated with conventional rabbit flora, and monitoring of their cecal flora.

In the present study we attempted to establish specific-pathogen-free (SPF) rabbit breeding colonies with two groups of limited-flora (LF) rabbits, both ex-germfree rabbits, and their offspring. Two groups of LF rabbits associated with cecal flora of conventional (CV) rabbits produced in a previous study [Exp. Animals, submitted], were transferred to individual barrier rooms and some of the LF rabbits were accommodated in isolators to maintain the basic flora for SPF rabbits. The composition of the cecal flora of LF rabbits was stable for a long period; bacteroides remained predominant and clostridia dominant. From the SPF rabbits, different types of bacteria, e.g., enterobacteriaceae and streptococci, which could not be isolated in the isolator were detected at a low population level at an early stage in the establishment of the SPF colonies, but the basic composition of the cecal flora was mainly bacteroidaceae and clostridia and did not change over a long period, and the floral composition became similar to that of CV rabbits. The fertility and weaning rates of the SPF rabbits were satisfactory for a SPF rabbit colony. In addition, these SPF colonies were free of more than one year rabbit-specific pathogens.

A mixture of organisms affects cholesterol metabolism together with rat cecal flora.

The effects of a mixture of organisms on cecal fermentation and cholesterol metabolism in sham-operated and cecectomized rats were investigated. Male F344 rats, allocated into four groups: cecectomized rats fed a mixture of organisms (CEMO), cecectomized rats fed rice bran (CERB), sham-operated rats fed a mixture of organisms (SHMO), and sham-operated rats fed rice bran (SHRB) for 4 weeks. The diets had 0.5% cholesterol and 0.125% sodium cholate added. There were no significant differences in the body weight gain and food intake among the groups. The cecal pH in the SHMO group was significantly lower than that in the other groups. The total cholesterol and (VLDL + IDL + LDL)-cholesterol concentrations in serum were significantly lower in the SHMO group than that in the SHRB group, and the triacylglycerol concentration in the sham-operated rats tended to decrease compared to the cecectomized rats. The fecal cholesterol excretion in the CERB group was higher than that in the other groups, and that in the SHMO group was significantly higher than in the SHRB group. The acetic acid, propionic acid, n-butyric acid, and total short-chain fatty acid concentrations in the cecum contents were significantly higher in the SHMO group than those in the other groups. Streptococcus, Bifidobacterium, and Lactobacillus in the SHMO group tended to be higher than the other groups and Bacteroidaceae in the CEMO and CERB groups were significantly higher than that in the SHMO group. The results demonstrate that the mixture of organisms was fermented with the cecal contents and that the metabolites such as short-chain fatty acid lowered the serum total cholesterol and liver cholesterol concentrations in the rats fed a cholesterol-containing diet.

Neuroendocrine–Bacterial Interactions in a Neurotoxin-Induced Model of Trauma

Background: The destruction of noradrenergic nerve cell innervation and resultant release of norepinephrine into the systemic circulation accompany severe tissue trauma. To examine whether destruction of noradrenergic neurons may directly influence the growth of indigenous bacteriain vivo,the selective noradrenergic neurotoxic agent 6-hydroxydopamine (6-OHDA) was employed in a murine model of trauma-induced norepinephrine release. Materials and methods: Following 6-OHDA administration, the cecums of 6- to 8-week-old male CF-1 mice were excised and examined for total bacterial counts and identification of bacterial species present in both the luminal space and intestinal wall. Lipopolysaccharide levels were also measured. Results: An increase of 3–5 logs in the total gram-negative population, most notablyEscherichia coli,compared to controls on a per gram equivalent basis was observed at 1 day post-6-OHDA. Neurotoxin-induced alterations in cecal flora were completely inhibited by the prior administration of the catecholamine uptake blocker desipramine hydrochloride, indicating the specificity of the effect being due to the released norepinephrine. Within 14 days following chemical sympathectomy, during which regeneration of noradrenergic neurons occurs, the cecal flora returned to the distribution observed in controls. Levels of lipopolysaccharide were not increased in either the luminal contents or cecal tissue at any of the time points. Conclusions: These results suggest that the destruction of noradrenergic neurons during trauma and consequent release of norepinephrine into the systemic circulation may influence thein vivogrowth of the indigenous bacterial population within the gastrointestinal system.

The anti-anaerobe activities of a new penem, ritipenem acoxil, and its effect on murine cecal flora

The anti-anaerobe activities of a new penem, ritipenem acoxil, and its effect on murine cecal flora

Bacterial Translocation and Endotoxemia in Obstructive Jaundice: The Protective Effect of Lactulose

This is an experimental study in rats, examining bacterial translocation and endotoxemia in obstructive jaundice, as well as the protective effect of lactulose, an endotoxin-binding agent. Four groups were used: I = control, II = sham, III = common bile duct ligation and IV = common bile duct ligation + lactulose. Aerobic cultures of mesenteric lymph nodes and liver were performed, and endotoxin was measured in the portal vein and aorta. The aerobic bacterial concentration in the cecum was determined and the terminal ileum was examined histologically. The study showed that there was increased bacterial translocation as well as systemic and portal endotoxemia in all jaundiced animals. Lactulose treatment does not influence the occurrence of bacterial translocation, but it significantly reduced endotoxemia. All jaundiced animals presented an insignificant increase in their aerobic cecal flora, independently of lactulose treatment. Histology showed significant changes in intestinal morphology, which may contribute to disruption of the intestinal mucosal barrier. Our results indicate that lactulose treatment (a) had no effect on bacterial translocation in jaundiced rats and (b) it may decrease endotoxemia, probably due to intraluminal binding of endotoxin. These findings may be of clinical significance for surgery in the presence of obstructive jaundice.

Effects of Dietary Supplementation with Lactosucrose (4G-β-D-Galactosylsucrose) on Cecal Flora, Cecal Metabolites, and Performance in Broiler Chickens

The effects of dietary lactosucrose on cecal flora, cecal metabolites, and performance were studied in eight 20-d-old and eight 62-d-old broiler chickens fed a basal diet (control) or a diet with .15% lactosucrose added On Day 20 of age, the frequency of occurrence of lecithinase-negative clostridia were decreased (P < .05) by lactosucrose consumption. On Day 62 of age, the numbers of bifidobacteria were increased (P < .05) by lactosucrose consumption, but the counts of lecithinase-positive clostridia, including Clostridium perfringens, bacteriodaceae, and staphylococci, total anaerobic bacteria, and the frequency of occurrence of pseudomonads were decreased (P < .05). No detectable change was observed in counts of other organisms throughout the experimental period. Cecal concentration of ammonia (P < .01), phenol (P < .05), and cresol (P < .05) were decreased on Day 62 of lactosucrose consumption. Acetic acid and butyric acid were increased (P < .01 and P < .05, respectively) on Day 62 of lactosucrose consumption. Environmental ammonia and odor of chicken ceca were greatly reduced by lactosucrose consumption.

Effect of Eimeria tenella Infection on Resistance to Salmonella typhimurium Colonization in Broiler Chicks Inoculated with Anaerobic Cecal Flora and Fed Dietary Lactose

This study evaluated the effect of Eimeria tenella infection on Salmonella typhimurium colonization of broiler chicks following oral inoculation with anaerobic cecal flora either alone or with a treatment of 10% dietary lactose. The number of chicks colonized by S. typhimurium was significantly lower (P < 0.05) in groups inoculated with cecal flora with or without the dietary lactose treatment than in control groups. In addition, significantly fewer S. typhimurium organisms were isolated from the cecal contents of chicks inoculated with anaerobic cecal flora and treated with 10% dietary lactose than in the control chicks. Infection with E. tenella had no effect on the resistance of treated groups to S. typhimurium colonization of the ceca but did cause higher S. typhimurium colonization in the untreated control chicks. The results indicated that: A) anaerobic cecal flora given orally on the day of hatch to chicks with or without dietary lactose enhanced the resistance of the birds to Salmonella cecal colonization; and B) coccidial infection had no detrimental effect on this resistance to Salmonella colonization.

In vitro and in vivo activities of tazobactam/piperacillin against anaerobes and effects on murine cecal flora

<I>In vitro</I> and <I>in vivo</I> activities of tazobactam/piperacillin against anaerobes and effects on murine cecal flora

Effect of Mixed Cecal Microflora Maintained in Continuous Culture and of Dietary Lactose on Salmonella typhimurium Colonization in Broiler Chicks

Mixed cecal microflora obtained from a mature chicken were maintained in vitro in continuous-flow (CF) culture. The effect of the CF culture and dietary lactose on Salmonella typhimurium cecal colonization in broiler chicks was evaluated. When averaged across four replicates, chicks treated with the culture alone (1.75 log10 decrease) or with 5% dietary lactose alone (2.98 log10 decrease) were protected against S. typhimurium. Optimum protection against S. typhimurium was observed when birds were treated with the culture in combination with dietary lactose (4.27 log10 decrease). Dietary lactose resulted in reduced cecal pH. A large increase in cecal propionic acid was observed in the birds given the CF culture. A significant correlation (P < 0.001) was observed between the cecal concentration of undissociated propionic acid and protection against S. typhimurium colonization (r = -0.78). The results indicated that indigenous cecal flora that protect against Salmonella colonization can be maintained without loss of efficacy in CF culture.

Comparison of Probiotics Maintained by In Vivo Passage Through Laying Hens and Broilers

Cecal colonization by salmonellae may be greatly reduced by inoculating chickens with normal cecal microflora, a phenomenon known as competitive exclusion. Unfortunately, it has not been possible to reliably store active cecal microflora over long time periods, and it is difficult to obtain consistent experimental results with different batches of microflora. In order to overcome these problems, the present authors have maintained active cecal flora through a 2-yr period by in vivo passage through both broiler chicks and layers that were fed a diet containing 5% lactose. Competitive exclusion cultures maintained in laying hens worked as well as cultures from broilers. Cecal microflora from either source excluded both nonlactose-fermenting and lactose-fermenting Salmonella strains. Colonization by both types of Salmonella was reduced even when the competitive exclusion organisms were given as late as 3 days after oral challenge inoculation with Salmonella typhimurium.

Effect of Anaerobic Cecal Microflora and Dietary Lactose on Salmonella Colonization in Bobwhite Quail (Colinus virginianus)

The effect of oral inoculation with anaerobic cultures of cecal microflora from adult broiler chickens and dietary lactose on Salmonella typhimurium cecal colonization was evaluated in bobwhite quail chicks. One-day-old chicks were divided into four groups and provided 1) no anaerobic cultures, no lactose (control); 2) anaerobic cultures; 3) 2.5% lactose (wt/vol) in drinking water; or 4) anaerobic cultures and lactose. All groups were challenged orally with 104S. typhimurium at 2 days of age. Salmonella growth in the cecal contents was significantly decreased (P < .05) at 15 days of age in each of the three treatment groups as compared with controls. Protection against Salmonella colonization was highest in the treatment group provided anaerobic cultures only. The results indicated that cecal flora from adult chickens enhances Salmonella colonization resistance in quail chicks.

Fermentation of [14 C]Lactose in Broiler Chicks by Cecal Anaerobes

Volatile fatty acids and lactic acid were products of [14 C]lactose metabolism in 10-day-old broiler chicks. The [14 C]lactose and unlabeled lactose were given to chicks in combination with cultures of cecal anaerobes (direct fed microbials) from adult broiler chickens. Aliquots of these cecal anaerobes had been used previously to reduce Salmonella typhimurium colonization in broiler chicks. In the current study, chicks were treated with anaerobes and anaerobes plus lactose on the day of hatch. Chicks given lactose plus anaerobes also received unlabeled lactose in the drinking water. Chicks in all treatment groups received [14 C]lactose on Day 10 posthatch. After 5 h, most of the radiolabel was detected in the foregut and intestine. Significantly lower concentrations of [14 C]lactic acid were detected in the serum and foregut of chicks given anaerobes and anaerobes plus lactose than in the similar samples from control chicks. Additionally, significantly less [14 C]lactic acid was detected in the feces of chicks treated with anaerobes plus lactose than in feces from control chicks and chicks receiving only anaerobes. Significant differences in the total content of volatile fatty acids and lactic acid were detected in the serum, liver, intestine, and ceca of chicks treated with anaerobes or anaerobes plus lactose. These data indicate that cecal flora utilize lactose to produce volatile fatty acids and lactic acid.

Influence of Infant Diets on the Ecology of the Intestinal Tract of Human Flora‐Associated Mice

SummaryThe effect of diet on intestinal ecology was studied in germ‐free mice that were inoculated orogastrically with predominant intestinal flora components isolated from the feces of breast‐fed human infants. The flora components colonized the intestines of mice and persisted at fixed population levels. Groups of flora‐ associated mice were fed either human milk, bovine milk, whey‐dominant formula, or formula modifications exclusively for 2 weeks, and then examined for changes in small intestinal and cecal flora composition, cecal pH, and resistance to intestinal colonization with Salmonella typhimurium. Dietary variations influenced the composition of the flora to a moderate degree but the differences were generally not statistically significant. However, the addition of bovine lactoferrin to the whey‐dominant formula resulted in significantly greater counts of Bifidobacterium, Bacteroides, Enterococcus and total aerobes in the small intestine when compared with mice fed unsup‐plemented formula. Bifidobacterium was present in large numbers in both the ceca and small intestines of mice fed the lactoferrin‐supplemented formula. Despite similarities in intestinal flora patterns among mice fed the various diets, human milk consumption resulted in a lower pH of cecal contents and a greater resistance to colonization by Salmonella typhimurium after orogastric challenge than the consumption of the other diets.

Influence of infant diets on the ecology of the intestinal tract of human flora-associated mice.

The effect of diet on intestinal ecology was studied in germ-free mice that were inoculated orogastrically with predominant intestinal flora components isolated from the feces of breast-fed human infants. The flora components colonized the intestines of mice and persisted at fixed population levels. Groups of flora- associated mice were fed either human milk, bovine milk, whey-dominant formula, or formula modifications exclusively for 2 weeks, and then examined for changes in small intestinal and cecal flora composition, cecal pH, and resistance to intestinal colonization with Salmonella typhimurium. Dietary variations influenced the composition of the flora to a moderate degree but the differences were generally not statistically significant. However, the addition of bovine lactoferrin to the whey-dominant formula resulted in significantly greater counts of Bifidobacterium, Bacteroides, Enterococcus and total aerobes in the small intestine when compared with mice fed unsupplemented formula. Bifidobacterium was present in large numbers in both the ceca and small intestines of mice fed the lactoferrin-supplemented formula. Despite similarities in intestinal flora patterns among mice fed the various diets, human milk consumption resulted in a lower pH of cecal contents and a greater resistance to colonization by Salmonella typhimurium after orogastric challenge than the consumption of the other diets.

Polymyxin B reduces cecal flora, TNF production and hepatic steatosis during total parenteral nutrition in the rat

Hepatic complications are common in patients receiving total parental nutrition (TPN) and who have no underlying liver disease. In the present study we examined the hypothesis that endotoxin (LPS) or possibly TNF derived from the overgrowth of intestinal gram-negative bacteria is responsible for TPN-associated hepatic steatosis, and that bowel decontamination and specific anti-LPS activity of polymyxin B will reduce fatty infiltration of the liver during TPN. Forty-five male Sabra rats underwent jugular vein cannulation, were placed in metabolic cages, and were randomized into five groups. Group I was continuously infused with normal saline and allowed food ad lib, while group II–V were continuously infused with a TPN formula containing 4.25% amino acids and 25% dextrose for a total of 36 calories and 3.0 g protein per 100 g body weight/day. In addition, groups III–IV were also treated by oral polymyxin B while Groups IV and V received a combination of neomycin, metronidazole, and vancomycin (NMV). Thus, Group III received polymyxin B, Group IV received both polymyxin B and NMV, while Group V received NMV only. On Days 7–8 of the study, all animals were sacrificed and spontaneous production of TNF by peritoneal macrophages, bacterial translocation to mesenteric lymph nodes, culture of the cecum, and fat, triglyceride, and cholesterol contents of the liver were determined. All groups infused with TPN exhibited higher levels of total fat, triglycerides, and cholesterol compared to the free feeding control group ( P < 0.001). Both groups receiving oral polymyxin exhibited a significant reduction in total liver fat ( P < 0.02) and triglyceride ( P < 0.001) levels compared to rats receiving TPN or TPN + NMV. The amount of gram-negative bacteria in the cecum of TPN-treated rats (Group II) was significantly higher than found in the free feeding rats (Group I). All antibiotic-treated groups had significantly lower gram-negative CFU than both the TPN and control groups due to bowel decontamination either by polymyxin B, NMV, or both. Simultaneously, spontaneous production of TNF by peritoneal macrophages of TPN-treated rats was significantly higher compared to control rats ( P < 0.005) or those who received TPN with antimicrobial therapy ( P < 0.03-0.005). In the present study both groups receiving polymyxin B exhibited reduced bacterial counts, reduced TNF production by peritoneal macrophages, representing the splanchnic reticuloendothelial system, and lower total fat and triglyceride levels in the livers of TPN rats. As the detrimental effects of LPS and the production of TNF in response to lipopolysaccaride were shown to be blocked by polymyxin B, this could well explain the protection afforded by polymyxin B against lipopolysaccharide-induced hepatic toxicity and steatosis, in addition to its very effective antibacterial activity in the gut, as demonstrated by the reduced gram-negative bacterial counts in the cecum of polymyxin B-treated rats.

Effect of Anaerobic Cecal Microflora and Dietary Lactose on Colonization Resistance of Layer Chicks to Invasive Salmonella enteritidis

The effect of oral inoculation with anaerobic cultures of cecal microflora and providing lactose in the feed on colonization resistance to invasive Salmonella enteritidis was evaluated in newly hatched leghorn chicks. Salmonella colonization of the ceca, tissue invasion and organ colonization, horizontal transmission, and seroconversion were significantly decreased (P less than 0.01) in chicks inoculated with cecal flora. The addition of lactose to the feed, in the absence of cecal microflora, failed to provide protection. Dietary lactose enhanced colonization resistance in chicks that were inoculated with anaerobic cultures of cecal flora. The results indicated that establishment of normal cecal flora in layer chicks together with the addition of lactose to the diet markedly increases resistance to cecal colonization and organ invasion, and decreases horizontal transmission of S. enteritidis.