成人腹泻轮状病毒的提纯及其高价免疫血清的制备

本文采用交叉免疫电泳技术,首先提纯了成人腹泻轮状病毒(Adult DiarrhoeaRotavirus简称:ADRV),并经电镜确认,用作免疫抗原,首次制备了高价兔与豚鼠抗ADRV血清和小鼠抗ADRV腹水,其特异性经交叉免疫电泳和对流免疫电泳鉴定,其效价经酶联免疫吸附试验(ELISA)检测均在1:2,000以上。     

Diversity of surface structures and virulence genetic markers among enteroaggregative Escherichia coli (EAEC) strains with and without the EAEC DNA probe sequence

The expression of surface structures and the presence of DNA sequences related to putative virulence factors were investigated in 22 enteroaggregative Escherichia coli strains (EAEC). Fimbria was the most frequent (72.7%) structure identified. Only strains hybridising with the EAEC DNA probe carried aggA, but one strain produced a similar but unrelated bundle-like structure. All probe-positive and 62.5% of the probe-negative strains carried the virulence genes tested; aspU and irp2 prevailed among the former strains. The EAEC probe-positive strains were more diverse, and some of these strains, which promoted cell detachment, also carried the hly and pap sequences, thus suggesting they might represent uropathogenic E. coli.     

Polymicrobial infections in children with diarrhoea in a rural area of Jordan

Polymicrobial infections associated with diarrhoea are common in developing countries. Stool specimens were collected from 220 patient children and 100 controls. Potential pathogenic agents isolated from 143 (65%) children were identified by molecular and standard microbiological methods. Co-infections with two or more agents were detected in 50 (35%) cases. Escherichia coli, Shigella dysenteriae, Giardia and Entamoeba histolytica were found to be predominant. The etiologic agents could not be determined in 77 (35%) cases. The most significant risk factors were the age, the education level of the mother and the use of non-chlorinated water. The high infection rate of diarrhoeal diseases is a strong indication that these pathogens circulate easily through the population.     

Influence of weaning and effect of post weaning dietary zinc and copper on electrophysiological response to glucose, theophylline and 5-HT in piglet small intestinal mucosa

This study aimed to examine how weaning and how dietary zinc and/or copper fed post weaning may affect the electrophysiological response to glucose and to chloride secretagogues in piglet small intestine in vitro. Study 1 included 54 piglets (six litters of nine piglets). One piglet from every litter was killed 1 day before weaning. The remaining 48 piglets were allocated at weaning (28 d) to four dietary zinc treatments and subsequently killed 1-2, 5-6 or 14-15 days after weaning. Study 2 included 48 piglets (six litters of eight piglets) allocated to four dietary treatments, consisting of high or low dietary zinc with or without high dietary copper. All piglets in study 2 were killed 5-7 days after weaning. The in vitro studies in Ussing chambers showed that weaning resulted in increased ileal glucose absorption as well as increased neuroendocrine-regulated (activated by 5-HT) and cAMP-dependent (activated by theophylline) chloride secretion. High zinc supplementation reduced the responses to 5-HT and theophylline. The study did not reveal any influence of copper on these parameters. It is concluded that the positive effect of zinc supplementation on diarrhoea in weaned piglets may be due to zinc reducing the intestinal mucosal susceptibility to secretagogues that activate chloride secretion.     

Cyst formation and faecal–oral transmission of Dientamoeba fragilis – the missing link in the life cycle of an emerging pathogen

Dientamoeba fragilis is a protozoan parasite emerging as a cause of diarrhoea and “irritable-bowel-like” gastrointestinal disease in humans with a propensity for establishing long-term, chronic infections in humans. Although Dientamoeba was discovered over a century ago its life cycle and mode of transmission is not known. No cyst stage has been described and no animal models are presently available for the study of this parasite. Here we describe the establishment of an animal model using laboratory rodents, the fulfilling of Koch’s postulates, and the discovery of a new cyst stage in the life cycle of D. fragilis. Our demonstration of long-term parasite carriage by rodents and prolonged shedding of cysts, together with elevated levels of calprotectin in the stool, confirms the capacity of this organism to cause disease and indicates dientamoebiasis should be considered in the differential diagnosis of gastrointestinal diseases such as Inflammatory Bowel Syndrome (IBS). Finally, we suggest that the cyst stage described here is the vehicle that mediates faecal–oral transmission of D. fragilis between hosts.     

Evaluation of some etiological factors predisposing to diarrhoea in lambs in “La Serena” (Southwest Spain)

This study compares some etiological factors involved in the naturally occurrence of lamb scours in 18 Merino sheep farms randomly selected in the area of “La Serena” (Southwest Spain).

A lack of influence of some variables (flock size, type of facilities, type of breeding, lambing percentage, isolation of Campylobacter jejuni, Rotavirus spp., Coronavirus spp. and Salmonella spp.) on lamb mortality rate was detected. The opposite was true for cleaning of the lambing areas, organization of lambing periods, accumulation of lambs in the pens, high content of fat, protein and lactose in milk and low serum gamma globulin and total protein in lambs and ewes. Cryptosporidium spp. and Escherichia coli isolation showed a trend to be linked to the presence of diarrhoea. A positive correlation was found between serum total protein in ewes and serum gamma globulin in lambs. Thus, the measure of serum total protein in ewes before lambing would be a valuable indicator of the risk of lamb scouring and it would be useful to establish an adequate programme to prevent this condition in the farms of this geographical area.     

Glycoprotein 60 diversity in C. hominis and C. parvum causing human cryptosporidiosis in NSW, Australia

Management and control of cryptosporidiosis in human requires knowledge of Cryptosporidium species contributing to human disease. Markers that are able to provide information below the species level have become important tools for source tracking. Using the hypervariable surface antigen, glycoprotein 60 (GP60), C. hominis (n = 37) and C. parvum (n = 32) isolates from cryptosporidiosis cases in New South Wales, Australia, were characterised. Extensive variation was observed within this locus and the isolates could be divided into 8 families and 24 different subtypes. The subtypes identified have global distributions and indicate that anthroponotic and zoonotic transmission routes contribute to sporadic human cryptosporidiosis in NSW.     

HEp-2 cell adherence and Vero cell cytotoxin production by EPEC strains isolated from children with diarrhoea in New Zealand

Abstract A total of 112 EPEC strains isolated from children with diarrhoea in New Zealand were examined for mannose-resistant HEp-2 cell adherence and production of exotoxins. Enterotoxin production was not detected in any of the strains examined. Verotoxin production was detected in 13 (11.6%) strains and of these 4 were also found to adhere to HEp-2 cells. HEp-2 cell adherence was displayed by a total of 29 (25.8%) strains of which 22 were diffusely adherent. Only 3 (2.7%) strains were shown to belong to the new virulence phenotype, entero-aggregative adherence, when examined in the adherence assay. We identified one strain with the novel characteristics of causing detachment of HEp-2 cells from glass coverslips and are further investigating this possible virulence mechanism. These results suggest that if EPEC strains are to be considered as a cause of diarrhoea, the search for new virulence factors must be extended.     

Characterization of non-membrane-damaging cytotoxin of non-toxigenic Vibrio cholerae O1 and its relevance to disease

The non-membrane-damaging cytotoxin which causes dramatic cell rounding of cultured HeLa cells was purified to homogeneity from a clinical strain (WO5) of non-toxigenic Vibrio cholerae O1 Inaba belonging to the El Tor biotype. The purified protein has a denatured molecular weight of 35 kDa and a native molecular weight of approximately 37 kDa indicating the monomeric nature of the protein. The 15 N-terminal amino acid sequence of non-membrane-damaging cytotoxin showed complete homology to the hemagglutinin protease previously purified and characterized from V. cholerae O1. Purified non-membrane-damaging cytotoxin from V. cholerae O1 was immunologically and biochemically identical to that previously purified from V. cholerae O26. Non-membrane-damaging cytotoxin was found to be enterotoxic in rabbit ileal loop assay inducing accumulation of non-hemorrhagic fluid at 100 μg and elicited a concentration dependent increase in short circuit current and tissue conductance of rabbit ileal mucosa mounted on Ussing chambers. A significant serum immunoglobulin G response against non-membrane-damaging cytotoxin was elicited by patients infected with V. cholerae O139 but not with V. cholerae O1. These properties make non-membrane-damaging cytotoxin a potential virulence factor of V. cholerae which should be taken into consideration while making live, attenuated recombinant vaccine strains against cholera.     

Impairment of Na+,K+-ATPase activity following enterotoxigenic Campylobacter jejuni infection: changes in Na+, Cl− and 3-O-methyl-D-glucose transport in vitro, in rat ileum

Abstract Unidirectional fluxes of Na⁺, Cl⁻ and 3-O-methyl-D-glucose (3-MG) were measured in vitro across Campylobacter jejuni live culture-infected and control rat ileal short-circuited tissues by the Using Chamber technique. Net secretion of Na⁺ and enhanced secretion of Cl⁻ ions was observed in the infected animals ( P < 0.001, n =6) as compared to the net absorption of Na⁺ and marginal secretion of Cl⁻ ions in the control animals. There was a significant decrease in the mucosal-to-serosal fluxes of 3-MG in C. jejuni -infected rat ileum. The specific Na⁺,K⁺-ATPase activity when measured biochemically in the membrane-rich fraction of enterocytes was found to be significantly lower (58%) in the infected group as compared to the control group ( P < 0.001). Our results therefore suggest that infection with an enterotoxigenic C. jejuni inhibits the Na⁺,K⁺-ATPase activity in rat enterocytes. The impairment of Na⁺,K⁺-ATPase activity thus appears to induce a secondary change in Na⁺,Cl⁻ and 3-MG transport in vitro in rat ileum.