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PubMed1998

Enteropathogenic and enterohaemorrhagic Escherichia coli: more subversive elements.

Enteropathogenic (EPEC) and enterohaemorrhagic Escherichia coli (EHEC) constitute a significant risk to human health worldwide. Both pathogens colonize the intestinal mucosa and, by subverting intestinal epithelial cell function, produce a characteristic histopathological feature known as the 'attaching and effacing' (A/E) lesion. Although EPEC was the first E. coli to be associated with human disease in the 1940s and 1950s, it was not until the late 1980s and early 1990s that the mechanisms and bacterial gene products used to induce this complex brush border membrane lesion and diarrhoeal disease started to be unravelled. During the past few months, there has been a burst of new data that have revolutionized some basic concepts of the molecular basis of bacterial pathogenesis in general and EPEC pathogenesis in particular. Major breakthroughs and developments in the genetic basis of A/E lesion formation, signal transduction, protein translocation, host cell receptors and intestinal colonization are highlighted in this review.

Animals↗
PubMed1999

Immunomodulatory effects of Lactobacillus plantarum colonizing the intestine of gnotobiotic rats.

We have studied the effect of the probiotic strain Lactobacillus plantarum 299v on the immune functions of gnotobiotic rats. One group of germ-free rats was colonized with the type 1-fimbriated Escherichia coli O6:K13:H1 and another group with the same E. coli strain together with L. plantarum 299v. One and 5 weeks after colonization, bacterial numbers were determined in the contents of the small intestine, caecum and mesenteric lymph nodes. Small intestinal sections were examined for CD8+, CD4+, CD25+ (IL-2R alpha-chain), IgA+ and MHC class II+ cells and mitogen-induced spleen cell proliferation was determined. Immunoglobulin levels and E. coli-specific antibodies were measured in serum. Rats given L. plantarum in addition to E. coli showed lower counts of E. coli in the small intestine and caecum 1 week after colonization compared with the group colonized with E. coli alone, but similar levels after 5 weeks. Rats colonized with L. plantarum + E. coli had significantly higher total serum IgA levels and marginally higher IgM and IgA antibody levels against E. coli than those colonized with E. coli alone. They also showed a significantly increased density of CD25+ cells in the lamina propria and displayed a decreased proliferative spleen cell response after stimulation with concanavalin A or E. coli 1 week after colonization. The results indicate that L. plantarum colonization competes with E. coli for intestinal colonization and can influence intestinal and systemic immunity.

Animals↗
PubMedDate not supplied

CT manifestations of lipomas of the small intestine and colon.

Seven cases of lipoma of the intestine demonstrated by computed tomography (CT) are reported. There were three men and four women who ranged in age from 47 to 78 years. The lipomas were in the small intestine in four patients, and in the colon in three. CT documented the characteristic low attenuation (fat density) of these masses in all patients. It is concluded that intestinal lipomas are important indications for CT evaluations.

Aged↗
PubMed1989

Intestinal decontamination for control of nosocomial multiresistant gram-negative bacilli. Study of an outbreak in an intensive care unit.

STUDY OBJECTIVE: To study the efficacy of intestinal decontamination by oral nonabsorbable antibiotic agents to control a nosocomial outbreak of intestinal colonization and infection with multiresistant Enterobacteriaceae, and to examine its effects on endemic nosocomial infection rates. DESIGN: A 10-week prospective incidence study (group 1), and then an 8-week randomized, open trial of intestinal decontamination (groups 2 and 3). SETTING: A medical intensive care unit of a tertiary care university hospital. PATIENTS: Consecutive patients with unit stay of over 2 days and a severity score at admission of more than 2; 124 patients were included in group 1, 50 in group 2 (control), and 36 in group 3 (intestinal decontamination). INTERVENTIONS: Neomycin, polymyxin E, and nalidixic acid were given to group 3 patients throughout their stay in the unit. MEASUREMENTS AND MAIN RESULTS: Intestinal colonization with multiresistant strains occurred in 19.6% of patients in group 1, at a mean of 16 days after admission, and preceded detection in clinical samples by a mean of 11 days. During the decontamination trial, intestinal colonization rates decreased to 10% (group 2), and 3% (group 3) (P = 0.12 and P less than 0.01, compared with group 1, respectively). Corresponding infection rates were 9% (group 1), 3% (group 2), and 0 (group 3). No new cases were detected in the following 4 months. The intestinal colonization rate with gram-positive cocci was higher in group 3 than group 2 (P less than 0.001). The overall rate of nosocomial infections was at 28% (group 1), 33% (group 2), and 32% (group 3). CONCLUSIONS: Intestinal decontamination can help to control an outbreak of intestinal colonization and infection with multiresistant gram-negative bacilli in the intensive care unit, but should not be recommended for routine prevention of endemic nosocomial infections.

Adult↗
PubMed1996

Salmonella typhimurium acrB-like gene: identification and role in resistance to biliary salts and detergents and in murine infection.

Salmonella serotype typhimurium transpositional mutants altered in resistance to biliary salts and detergents were isolated previously. We have characterized further the LX1054 mutant strain, the most sensitive of them. The chromosomal DNA segment flanking transposon insertion was cloned and sequenced. The highest level of identity was found for the acrB (formerly acrE) gene of Escherichia coli, a gene encoding a drug efflux pump of the Acr family. LX1054 exhibited a reduced capacity to colonize the intestinal tract. After passages in mice, the mutant strain lost the sensitive phenotype. In vitro, a resumption of growth appeared after 17 h of culture in medium with cholate or other tested biological or chemical detergents. Then, the acquired resistant phenotype seemed stable. The data suggested a role of S. typhimurium acrB-like gene in resistance to biliary salts and detergents and in mice intestinal colonization. However, the local and transient sensitivity observed in vivo, and the in vitro adaptations suggest that several detergent-resistance mechanisms operate in S. typhimurium.

Amino Acid Sequence↗
PubMed2003

Application of a novel multi-screening signature-tagged mutagenesis assay for identification of Klebsiella pneumoniae genes essential in colonization and infection.

Klebsiella pneumoniae is a common cause of urinary tract infections (UTIs) and pneumonia, especially in immunocompromised individuals. Epidemiological studies have revealed that K. pneumoniae infections are frequently preceded by gastrointestinal colonization and the gastrointestinal tract is believed to be the most important reservoir for transmission of the bacteria. To identify genes involved in the ability of K. pneumoniae to colonize the intestine and infect the urinary tract, a novel multi-screening signature-tagged mutagenesis (MS-STM) assay was implemented. In the MS-STM assay, PCR-amplified tags present in the inoculum as well as recovered pools from each infection model are simultaneously subjected to hybridization using each specific tag as a probe. Therefore, screenings of a mutant library in more than one infection model is significantly eased compared to the traditional signature-tagged mutagenesis methodology. From a total of 1,440 K. pneumoniae transposon mutants screened, 13 mutants were identified as attenuated in intestinal colonization as well as the UTI model. In addition, six mutants attenuated only in the UTI model were identified. Transposon insertion sites in attenuated mutants were, among others, in genes encoding well-known K. pneumoniae virulence factors such as lipopolysaccharide and capsule, as well as in genes of unknown function.

Animals↗
PubMed2003

Genetically engineered enteropathogenic Escherichia coli strain elicits a specific immune response and protects against a virulent challenge.

Enteropathogenic Escherichia coli (EPEC), a major cause of severe disease with diarrhea in infants, is also involved in weaned rabbit colibacillosis. EPEC O103 is frequent in rabbit-fattening units of Western Europe. It causes high mortality and growth retardation, leading to substantial economic losses. We report here the construction by allelic exchange of an EPEC O103 strain mutated in espB and tir, two essential virulence genes. Upon live oral administration to weaned rabbits, the E22DeltaTir/EspB mutant strain efficiently colonized the intestinal tract without any adverse consequences. The rabbits were challenged with the highly pathogenic parental strain E22. The mutant provided complete protection to rabbits and total resistance to intestinal colonization by E22. In addition, E22DeltaTir/EspB strain induced a specific humoral response against the bacterial adhesin AF/R2. These Abs prevent bacterial attachment to epithelial cells in vitro. These results open the way for the development of an efficient vaccine strategy against rabbit EPEC infections.

Adhesins, Escherichia coli↗
PubMed2005

Characterization of type 2 quorum sensing in Klebsiella pneumoniae and relationship with biofilm formation.

Quorum sensing is a process by which bacteria communicate by using secreted chemical signaling molecules called autoinducers. Many bacterial species modulate the expression of a wide variety of physiological functions in response to changes in population density by this mechanism. In this study, the opportunistic pathogen Klebsiella pneumoniae was observed to secrete type 2 signaling molecules. A homologue of luxS, the gene required for AI-2 synthesis in Vibrio harveyi, was isolated from the K. pneumoniae genome. A V. harveyi bioassay showed the luxS functionality in K. pneumoniae and its ability to complement the luxS-negative phenotype of Escherichia coli DH5alpha. Autoinducer activity was detected in the supernatant, and maximum expression of specific messengers detected by quantitative reverse transcription-PCR analysis occurred during the late exponential phase. The highest levels of AI-2 were observed in minimal medium supplemented with glycerol. To determine the potential role of luxS in colonization processes, a K. pneumoniae luxS isogenic mutant was constructed and tested for its capacity to form biofilms in vitro on an abiotic surface and to colonize the intestinal tract in a murine model. No difference was observed in the level of intestinal colonization between the wild-type strain and the luxS mutant. Microscopic analysis of biofilm structures revealed that the luxS mutant was able to form a mature biofilm but with reduced capacities in the development of microcolonies, mostly in the early steps of biofilm formation. These data suggest that a LuxS-dependent signal plays a role in the early stages of biofilm formation by K. pneumoniae.

Bacterial Proteins↗
PubMed1987

Enkephalin convertase in the gastrointestinal tract an associated organs characterized and localized with [3H]guanidinoethylmercaptosuccinic acid.

Enkephalin convertase (carboxypeptidase EH; EC 3.4.17.10), a carboxypeptidase B-like enzyme which processes hormone and neuropeptide precursors, has been characterized in the gastrointestinal tract, submandibular gland, and pancreas using a binding assay with [3H]guanidinoethylmercaptosuccinic acid. Binding to homogenates of the membrane and soluble fractions of stomach, small intestine, colon, and submandibular gland is saturable, with Kd values of about 2 nM. Partial purification of the membrane fractions reveals a Co+2-stimulated carboxypeptidase B activity which is not detectable in crude homogenates. In vitro autoradiography with [3H]guanidinoethylmercaptosuccinic acid localizes enkephalin convertase to the epithelial cells of the stomach, colon, and intestine, the islet cells of the pancreas, and the acinar cells of the submandibular gland. This localization contrasts to the distribution of enkephalins and other neuropeptides in the gastrointestinal tract and associated organs, suggesting that enkephalin convertase may serve functions other than neuropeptide and prohormone processing.

Animals↗
PubMed1999

Dietary polyamines are essential luminal growth factors for small intestinal and colonic mucosal growth and development.

BACKGROUND: Polyamines are essential for cell growth. Dietary and probably gut bacterial derived polyamines contribute significantly to the polyamine body pool. AIMS: To evaluate the influence of dietary, luminal polyamines on growth and development of different gastrointestinal organs in normally growing rats. METHODS: Male suckling Wistar rats were randomly allocated to four treatment groups: polyamine deficient diet (PDD); PDD plus antibiotics (neomycin 2 g/kg and metronidazole 34 mg/kg); PDD plus polyamine supplementation at normal concentrations; or normal standard laboratory chow. After a six month feeding period 7-10 animals/group were sacrificed. RESULTS: No differences in body weight gain, food consumption, or general behaviour could be observed between the four groups of animals. Feeding of PDD alone or PDD plus antibiotics resulted in a highly significant decrease in organ weight, protein content, and DNA content in small intestinal and colonic mucosa whereas no alterations were found in the liver. CONCLUSIONS: Long term feeding of polyamine deficient diets resulted in a significant hypoplasia of small intestinal and colonic mucosa. Dietary, luminal polyamines are important local factors for growth and the development of small intestinal and colonic mucosa.

Animal Nutritional Physiological Phenomena↗
PubMed1986

[Diagnosis of inflammatory and tumorous changes of the large intestine using colonic sonography].

By water instillation into the large intestine, sonographic visualization of the whole length of the colon from the recto-sigmoid to the caecum can be achieved. Detailed evaluation of the lumen, the wall and the surrounding connective tissue may be carried out. Diagnostic sonography of the colon in 41 patients with pathological changes confirmed by colonoscopy showed that colonic polyps and carcinomas can be detected by this method. In Crohn's disease, typical changes can be seen, which allow the degree of inflammatory infiltration to be assessed. Thus, sonography of the colon is a diagnostic procedure which gives discriminating evidence in diseases of the large intestine.

Adult↗
PubMed1989

[Motility of the large intestine].

Colonic motility has a number of tasks to fulfill: mixing, storage and slow transportation of intestinal contents, and rapid evacuation of feces. All this requires complex motor patterns. Phases of contraction alternate with phases of motor inactivity. Contractile activity is controlled by the myoelectric activity. Spikes and oscillations are superimposed on the electrical control activity. Short spike bursts are associated with contractions of short duration and serve for mixing; long spike bursts and oscillations are accompanied by tonic contractions of long duration, and are mainly propulsive. Giant migrating contractions occur sporadically and result in the emptying of large sections of the colon. Disturbances of colonic motility are of pathogenetic significance in a number of diseases. This has diagnostic and therapeutic consequences.

Colon↗