Enteroaggregative Escherichia coli as a possible cause of diarrhea in an HIV-infected patient.
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AIDS-Related Opportunistic Infections↗
Biomedical subjects
C A Wanke
Publications and source records attributed to C A Wanke.
HIV-1 Tat modulates invasion by a bacterial enteric pathogen into a human intestinal cell line.
OBJECTIVE: To explore the possibility that an HIV-1 gene product may modulate entry of an invasive enteric pathogen into a terminally differentiated human intestinal cell line. HIV-1 Tat was selected for investigation because of its unique ability to cross cell membranes. METHODS: After transient transfection of HT29-C1 cells with plasmids containing HIV-1 long terminal repeat (LTR)-lacZ plus a Tat expression cassette, or with a pSR-lacZ control plasmid, bacterial invasion assays were performed on both groups of cells utilizing a clinical Salmonella isolate. Assays were performed concurrently on a control group of non-transfected cells. A second series of experiments compared bacterial invasion into cells transfected with the Tat expression vector alone versus cells transfected with either an isogenic expression vector that did not make Tat, or with pSR-lacZ. Finally, the ability of exogenous Tat protein to transactivate an HIV-1 LTR-chloramphenicol acetyltransferase (CAT) plasmid which had been transfected into HT29-C1 cells and to modulate Salmonella invasion was also assessed. RESULTS: HT29-C1 cells transfected with a Tat expression vector, either alone or in combination with another plasmid, were significantly less susceptible to bacterial invasion than cells that either did not undergo transfection, were transfected with an otherwise isogenic expression vector without Tat, or transfected with an unrelated plasmid. Duplicate experiments also demonstrated that exogenous purified Tat protein transactivated an HIV-1 LTR-CAT plasmid which had been transfected into HT29-C1 cells and inhibited Salmonella invasion compared with unexposed cells. CONCLUSION: HIV-1 Tat inhibits Salmonella invasion of a human enterocyte cell line whether the protein is expressed intracellularly or provided exogenously.
Animals↗
Characterization of an invasive phenotype associated with enteroaggregative Escherichia coli.
Enteroaggregative Escherichia coli (EAggEc) strains are associated with persistent diarrhea in children in the developing world and exhibit a classic aggregative phenotype. We have demonstrated that EAggEc strains isolated from children with persistent diarrhea in Brazil, Bangladesh, and Pakistan also have the potential to be internalized by HeLa cells in the gentamicin protection assay. We have confirmed this phenomenon with transmission electron micrographs of bacteria engulfed by HeLa cells. We examined the mechanisms by which this process occurs. Staurosporine inhibited internalization of EAggEc strain 162 by 50% at a concentration of 0.1 microM. Genistein inhibited internalization of this same organism by 50% at a concentration of 50 microM. Cytochalasin D inhibited internalization by 50% at a concentration of 1 microgram/ml. Staurosporine, genistein, and cytochalasin D inhibited the internalization of EAggEc strain 162 by HeLa cells in a dose-dependent manner. These data suggest that active cell processes such as signal transduction by protein kinase and/or tyrosine kinase may be involved in the internalization of EAggEc strain 162 by HeLa cells and that actin filaments and cytoskeletal structure may be important for this process.
Alkaloids↗
Enteropathogenic and enteroaggregative strains of Escherichia coli: clinical features of infection, epidemiology, and pathogenesis.
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Adult↗
Clinical features of microsporidiosis in patients with AIDS.
Microsporidia are protozoan parasites responsible for significant gastrointestinal disease in patients infected with human immunodeficiency virus. We report the clinical features of 20 patients with chronic diarrhea for whom microsporidian spores were identified by modified trichrome staining of stool smears and confirmed by biopsy and/or electron microscopy of stool. Of the 18 microsporidian protozoa identified to the species level, 14 (78%) were Enterocytozoon bieneusi and four (22%) were Septata intestinalis. The mean CD4 count in these patients was 35 +/- 29 cells/mm3. Parameters of absorption, specifically absorption of fat and D-xylose, and levels of zinc were strikingly abnormal in patients who were tested. Treatment with albendazole led to clinical responses in six of 10 patients, and dietary manipulation resulted in clinical improvement in eight of nine patients. We recommended that patients with chronic, intermittent diarrhea and CD4 counts of < 100 cells/mm3 be further evaluated for microsporidia by modified trichrome staining of stool and light and electron microscopy of small bowel biopsy specimens. Antiprotozoal therapies are currently experimental, but some patients who have been treated with these therapies have dramatic responses. We also recommend that special attention be paid to the measurement of parameters of absorption with appropriate modification of diet.
AIDS-Related Opportunistic Infections↗
Physiological effects of HIV infection on human intestinal epithelial cells: an in vitro model for HIV enteropathy.
OBJECTIVES: To determine the role of direct infection of intestinal cells with HIV-1 in the pathogenesis of HIV-related enteropathy. METHODS: We infected HT-29-18-C1 intestinal cells with the IIIB strain of HIV and examined the physiologic effects of enterocyte function. Dipeptidase-IV, aminopeptidase-N, gamma glutamic transferase, and alkaline phosphatase were measured in HIV-infected and control cultures. The cellular second messengers intracellular calcium and cyclic adenosine monophosphate were also measured in infected and control cultures. RESULTS: A persistent infection was established for > 95 days with peak supernatant reverse transcriptase and HIV p24 antigen levels of 5.17 log10 c.p.m./ml and 45 ng/ml, respectively. Brush-border enzyme activity (nmol of product/min/mg protein) tended to be lower in infected cell cultures compared with controls early in infection (P < 0.02). Baseline second messenger concentrations were similar but infected cultures responded to stimulation with a calcium ionophore with an exaggerated increase in intracellular calcium (P = 0.03). CONCLUSIONS: These results suggest that absorptive and secretory function of enterocytes may be altered by direct HIV infection and that additional physiologic experiments with this in vitro model may lead to a better understanding of the clinical syndrome of HIV enteropathy.
Alkaline Phosphatase↗
Diagnostic strategies in HIV-infected patients with diarrhea.
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AIDS-Related Opportunistic Infections↗
Cytomegalovirus vasculitis. Case reports and review of the literature.
Cytomegalovirus (CMV) infection is a substantial cause of morbidity and mortality among immunocompromised patients. It may present with a mild, self-limited syndrome, retinitis, colitis, or invasive disease with pneumonitis, hepatitis, and bone marrow suppression. We review another, less common manifestation of CMV disease: CMV-associated vasculitis. CMV may productively infect vascular endothelial cells (25), causing a local vasculitis (3, 14, 19) and ischemia. Alternatively, the host immune response to cells expressing viral antigen may be the stimulus for vasculitis (12, 53). Since there are no pathognomonic appearances to mucosal or cutaneous lesions, biopsy of accessible sites is critical for diagnosis and expeditious initiation of appropriate antiviral therapy. The CMV-associated vasculitides represent a broad spectrum of diseases, with GI vasculitis in nontransplant recipients having the best prognosis. Cutaneous vasculitis associated with CMV seems to be a more fulminant disease, with the majority of cases having a fatal outcome. These differences likely reflect the degree of viral burden and the state of immune competence. Additionally, since the virus itself is immunosuppressive, host defenses may be further compromised by the infection. Although a large collective experience assessing the impact of ganciclovir and foscarnet is not currently available, both the prompt initiation of antiviral treatment and a concurrent reduction in any immunosuppressive regimen, including steroids, should be undertaken since these therapeutic strategies have clearly improved outcome for other CMV syndromes (22, 34, 55). As the number of recipients rises and the HIV pandemic spreads we are likely to see an increase in the number of cases of vasculitis associated with CMV infection.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Protothecosis complicating prolonged endotracheal intubation: case report and literature review.
Prototheca species are ubiquitous, aerobic, unicellular algae closely related to the green algae Chlorella. Their involvement in human disease--in both immunocompetent and immunocompromised patients--has been reported with increasing frequency. The wide array of presentations has included cutaneous, subcutaneous, mucosal, bursal, catheter-related, and (in rare instances) systemic disease. We report a case of protothecosis complicating prolonged endotracheal intubation presenting as a nasopharyngeal ulceration with a soft-tissue mass, and we review the presentation, treatment, and outcome of the 59 previously reported cases of protothecosis. Optimal therapy for protothecosis includes excision (where possible) followed by systemic administration of amphotericin B; the sole exception is in the case of olecranon bursitis, where excision alone appears curative. The role of the newer imidazoles is yet to be determined.
Adult↗
Epidemiology of persistent diarrhea and etiologic agents in Mirzapur, Bangladesh.
To determine the epidemiology and etiologic agents of persistent diarrhea we carried out an intensive diarrhea surveillance on children less than six years old in rural Bangladesh. From March 1987 to February 1989 we examined 363 children through diarrhea recall interviews and analyzed stool samples of all diarrhea cases for potential pathogens. Results showed that children had an average of two episodes per year and the incidence rate of diarrheal episodes defined as acute (< 14 d) and persistent (> or = 14 d) varied similarly with age. The peak incidence (episodes/child/year) of acute diarrhea (2.8) and persistent diarrhea (0.8) occurred in the 6-11 months age group. The data showed that an episode tended to be prolonged if the stool was loose/mucoid or bloody at onset. Aggregative adherent Escherichia coli was found significantly more often at onset in persistent than in acute episodes, whereas Shigella, Aeromonas, Giardia and toxigenic E. coli were isolated with less frequency in persistent than acute episodes. This suggests that other factors might be more important in the development of persistent diarrhea than specific pathogens.
Animals↗
Oral ingestion of egg yolk immunoglobulin from hens immunized with an enterotoxigenic Escherichia coli strain prevents diarrhea in rabbits challenged with the same strain.
White Leghorn hens were immunized with enterotoxigenic Escherichia coli B16-4 with heat-labile enterotoxin and colonization factor antigen I in Freund's adjuvant. Specific antibodies were detected by an enzyme-linked immunosorbent assay in the serum after 8 days and in eggs after 10 days, with levels reaching peaks at 15 and 20 days after the first immunization, respectively. The protective effects of the egg yolk antibodies were tested in the rabbit reversible ileal tie model of diarrhea. Five control rabbits developed severe diarrhea within 72 h after inoculation with enterotoxigenic E. coli B16-4. Oral ingestion of egg yolks from immunized hens for 4 days prior to inoculation protected five rabbits from diarrhea after challenge with the same strain of E. coli. The rabbits showed no adverse effects from the ingestion of the egg yolks. Four rabbits fed control eggs were also afforded some protection in that three rabbits developed mild diarrhea and one rabbit remained entirely well. In vitro experiments showed that immunoglobulin from egg yolks interfered with the binding of E. coli to purified small bowel mucins; immunoglobulin from immunized hens reduced binding more than immunoglobulin from nonimmunized hens. These findings indicate that eggs from hens immunized with appropriate antigens have potential as a useful source of passive immunity.
Administration, Oral↗
Potential role of adherence traits of Escherichia coli in persistent diarrhea in an urban Brazilian slum.
We examined stools from 40 children with persistent diarrhea (duration, 14 days or more), from 50 children with acute diarrhea and from 38 control children to determine infectious etiologies for persistent diarrhea in Goncalves Dias, an urban favela (slum) in Fortaleza, Ceara, Brazil. Children with persistent diarrhea and children with acute diarrhea had similar rates of isolation of routine viral, bacterial and parasitic enteric pathogens. Routine pathogens were identified in at least 20% of cultures done more than 14 days into the diarrheal illness. We examined Escherichia coli isolated from these stools for adherence potential. Enteroaggregative E. coli were isolated significantly more often from children with persistent diarrhea than from control children or children with acute diarrhea (P less than 0.05). E. coli with hemagglutination patterns suggestive of adherence pili were also isolated more often from children with persistent diarrhea than from children with acute diarrhea (38% vs. 18%; P less than 0.05). Enterotoxigenic E. coli were isolated in combination with rotavirus more often from children with persistent diarrhea than from children with acute diarrhea. E. coli which were hydrophobic or exhibited hemagglutination were also seen more often in association with Giardia in children with persistent diarrhea. These findings suggest that the etiology of persistent diarrhea in children is complex and that the aggregative E. coli are associated with prolonged diarrheal illness. Although routine diarrheal pathogens may be present for more than 14 days, combinations of pathogens, including E. coli with adherence potential, may also contribute to prolonged diarrheal disease.
Animals↗
A prospective study of persistent diarrhea among children in an urban Brazilian slum. Patterns of occurrence and etiologic agents.
Persistent diarrhea is a major health problem among children in developing areas of the world. Since few community-based studies have addressed the epidemiology or etiology of this condition, we undertook prospective diarrheal surveillance among a cohort of 175 children less than 5 years of age over a 28-month period in an urban slum in northeastern Brazil. Very high diarrhea illness burdens were found. The children in this cohort had an average of 11 episodes per year and spent 82 days per year with diarrhea. A total of 65% of children had at least one episode of persistent diarrhea (greater than or equal to 14 days duration). These episodes accounted for 50% of all days of diarrhea and 11% of all episodes. The occurrence of at least one episode of persistent diarrhea identified all children who spent at least 15% percent of days with diarrhea. Among children with and without diarrhea, rotavirus was the agent isolated most frequently, followed by Giardia lamblia and enterotoxigenic coliforms. The agents isolated from children with acute and persistent diarrhea were similar, which suggests that other factors must be operative in the development of persistent diarrhea.
Brazil↗
Characterization of binding of Escherichia coli strains which are enteropathogens to small-bowel mucin.
Before an enteropathogen binds to the small bowel, it must interact with the small-bowel mucus (SBM) layer. To determine whether this interaction involves specific binding of diarrheagenic Escherichia coli, we used a quantitative assay with labeled, purified rabbit SBM. Binding of SBM from an adult rabbit was significantly greater to strain 162, an agglutinating E. coli strain, than it was to RDEC-1, a rabbit pathogen, and was significantly greater to strain 2348/PMAR, an enteropathogenic E. coli strain, than it was to strains 1392+ and 1392-, which are enterotoxigenic E. coli strains with and without colonizing fimbriae, respectively. Binding of strains RDEC-1, 2348/PMAR, and 162-4 was significantly greater to SBM than to bovine serum albumin. Binding of all strains increased in a linear fashion with increasing amounts of SBM and was reproducible (r = 0.85). Binding was significantly greater at pH 5.7 than at pH 7.4 or 8.0 for all five strains. Temperature did not alter the binding of any strain. Strains 162-4 and RDEC-1 bound significantly more to proximal SBM than to rabbit distal SBM, while strains 1392+ and 1392- bound significantly more to distal SBM. Oxidation of sugars from SBM significantly decreased the binding of all strains. Each pathogenic E. coli strain bound distinctively to SBM; the SBM sugars appeared to mediate this binding for all E. coli strains. Binding was also dependent on mucin characteristics, as binding varied by region of the gut (increased for proximal SBM for strains 162-4 and RDEC-1 and for distal SBM for strains 1392+ and 1392-). The developmental age of the gut significantly affected binding only of the rabbit pathogen RDEC-1.
Age Factors↗
Net fluid secretion and impaired villous function induced by colonization of the small intestine by nontoxigenic colonizing Escherichia coli.
The role of colonizing bacteria in the small bowel in causing diarrhea remains unclear. We examined whether colonizing, nontoxigenic Escherichia coli could alter small bowel function by determining net water and electrolyte fluxes and sucrase activity in colonized and noncolonized ileal segments by using the reversible-ileal-tie adult rabbit model. Colonization of the ileum with nontoxigenic E. coli for greater than or equal to 72 h at greater than or equal to 10(4)/cm2 was associated with significant functional derangements, as follows: (i) overt liquid diarrhea in 50% of animals colonized at greater than 10(4)/cm2; (ii) reversal of normal net ileal absorption to net secretion of water, sodium, and chloride; and (iii) significant decrease in mucosal sucrase activity. We conclude that small bowel colonization by colonizing, nontoxigenic E. coli impairs water and electrolyte absorption and sucrase activity in the absence of recognized enterotoxin, cytotoxin, invasion, or effacement traits.
Animals↗
Infectious diarrhoea in tropical and subtropical regions.
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Bacterial Infections↗
Production of a unique cytotoxin by Campylobacter jejuni.
Campylobacter jejuni is an important diarrheal pathogen worldwide; the mechanisms by which it causes disease remain unclear. Because of its association with inflammatory diarrhea, we postulated that C. jejuni might produce a cytotoxin similar to that produced by Shigella sp., enterohemorrhagic Escherichia coli O157, or Clostridium difficile. Filtrates of 12 polymyxin-treated isolates of C. jejuni were placed on HeLa cells (sensitive to Shiga toxin cytotoxicity) and Chinese hamster ovary (CHO) cells. Of 12 isolates of C. jejuni tested, 5 killed 50% of the cells at greater than or equal to 1:4 dilutions of filtered suspensions of 10(9) bacteria per ml; killing was similar in HeLa and CHO cells (the CHO cells being insensitive to Shiga cytotoxin). One isolate produced a titer of 1:32 to 1:128. The relative potency in HeLa cells was comparable to that of E. coli strains that produce intermediate amounts of Shiga-like toxin. The other seven strains showed no cytotoxic effect, nor did the control diluents, polymyxin B, or supernatants of C. jejuni not treated with polymyxin B. Sonication also released active cytotoxin, but slightly less well than did polymyxin. The cytotoxic effect was dose dependent. Concentration of the C. jejuni in suspension by 10-fold before treatment with polymyxin B resulted in a 10-fold increase in the 50% cytotoxic dose. The cytotoxin effect was not neutralized by Shiga toxin immune serum against either Shiga-like toxin I or II or by anti-Clostridium difficile antiserum. The C jejuni cytotoxin was partially labile to trypsin (0.25%) and to heating to greater than or equal to 60 degrees C. Cytotoxicity was retained in Scientific Products dialysis tubing D1615-1 (Mr cutoff, 12,000 to 14,000). Some isolates of C. jejuni release a substance lethal to HeLa or CHO cells in vitro that is distinct from Shiga-like or Clostridium difficile toxin. This cytotoxin may contribute to the colonic mucosal invasive process that characterizes C. jejuni enteritis.
Animals↗