Paediatrician and Caregiver Awareness of Cryptosporidiosis and Giardiasis in Children: US Survey Responses

There appears to be no published information concerning the awareness and knowledge about diarrhoea caused by Cryptosporidium spp. or Giardia lamblia among US paediatricians and caregivers of young children. Two concurrent, separate surveys were conducted among paediatricians and caregivers (~1000 respondents in each survey) of children ages 1-12 years concerning their knowledge, perceptions and attitudes in the diagnosis and treatment of parasitic diarrhoea. Awareness of parasite-induced diarrhoea was low for specific aspects among both paediatricians and caregivers. Educational efforts to improve awareness on the appropriate clinical presentation, management and treatment of cryptosporidiosis and giardiasis in children with persistent diarrhoea should be undertaken.

Famotidine for infant gastro-oesophageal reflux: a multi-centre, randomized, placebo-controlled, withdrawal trial

BACKGROUND

Gastro-oesophageal reflux afflicts up to 7% of all infants. Histamine-2 receptor antagonists are the most commonly prescribed medications for this disorder, but few controlled studies support this practice.

AIM

To evaluate the safety and efficacy of famotidine for infant gastro-oesophageal reflux disease.

METHODS

Thirty-five infants, 1.3-10.5 months of age, entered an 8-week, multi-centre, randomized, placebo-controlled, two-phase trial: first 4 weeks, observer-blind comparison of famotidine 0.5 mg/kg and famotidine 1.0 mg/kg; second 4 weeks, double-blind withdrawal comparison (safety and efficacy) of each dose with placebo.

RESULTS

No serious adverse events were reported. Eleven patients had 16 non-serious, possibly drug-related adverse experiences: 6 patients with agitation or irritability (manifested as head-rubbing in two), 3 patients with somnolence, 2 patients with anorexia, 2 with headache, 1 patient with vomiting, 1 patient with hiccups, and 1 patient with candidiasis. Of the 35 infants, 27 completed Part I. There were significant score improvements for famotidine 0.5 mg/kg in regurgitation frequency (P = 0.04), and for famotidine 1.0 mg/kg in crying time (P = 0.027) and regurgitation frequency (P = 0.004) and volume (P = 0.01). Eight infants completed Part II on double-blind treatment, which was insufficient for meaningful comparisons.

CONCLUSIONS

Histamine-2 receptor antagonists may cause agitation and headache in infants. A possibly efficacious famotidine dose for infants is 0.5 mg/kg (frequency adjusted for age). As 1.0 mg/kg may be more efficacious in some, the dosage may require individualization based on response. Further sizeable placebo-controlled evaluations of histamine-2 receptor antagonists in infants with gastro-oesophageal reflux disease are warranted.

Protective anti-Helicobacter immunity is induced with aluminum hydroxide or complete Freund's adjuvant by systemic immunization

To determine whether systemic immunization against Helicobacter pylori could be achieved with an adjuvant approved for human use, the efficacy of vaccination with Helicobacter antigen in combination with aluminum hydroxide (AlOH) was evaluated in a murine model of Helicobacter infection. Immunization with antigen and AlOH induced interleukin-5-secreting, antigen-specific T cells, and immunization with antigen and complete Freund's adjuvant induced interferon-gamma-secreting, antigen-specific T cells, as determined by ELISPOT assay. Both immune responses conferred protection after challenge with either H. pylori or H. felis, as confirmed by the complete absence of any bacteria, as assessed by both histology and culture of gastric biopsy samples. Protection was antibody independent, as demonstrated with antibody-deficient muMT mice (immunoglobulin-gene knockout mice), and CD4(+) spleen T cells from immunized mice were sufficient to transfer protective immunity to otherwise immunodeficient rag1(-/-) recipients. These results suggest an alternative and potentially more expeditious strategy for development of a human-use H. pylori vaccine.

Techniques for the evaluation of dyspepsia in children

Dyspepsia can describe a subset of children with episodic or persistent abdominal symptoms--often related to feeding--that are thought to be caused by disorders of the proximal part of the digestive tract. Symptoms, such as vomiting, early satiety, postprandial epigastric abdominal pain, heartburn, abdominal fullness, poor weight gain, and/or anorexia, have been incorporated into the definition of dyspepsia. Unfortunately, presenting signs and symptoms in children with dyspepsia are nonspecific and can occur as a result of many diseases, such as parasitic infections, esophagitis, eosinophilic gastroenteritis, Helicobacter pylori infection, Crohn's disease, biliary tract or hepatic disease, pancreatitis, and lactose intolerance. This lack of specificity makes the evaluation of dyspepsia more difficult. Here, we describe an approach for the evaluation of dyspepsia that correlates in part with the child's presenting symptoms.

gamma-Glutamyltransferase is a Helicobacter pylori virulence factor but is not essential for colonization

The contribution of glutamyl transpeptidase (GGT) (gamma-glutamyltransferase [EC 2. 3. 2. 2]) to Helicobacter pylori virulence was investigated in piglets and mice using GGT-deficient isogenic strains. All animals became colonized. However, the bacterial load was significantly lower for mutant bacteria than for parent strains. These results suggest that GGT activity provides an advantage to H. pylori in colonization.

Genotypic, clinical, and demographic characteristics of children infected with Helicobacter pylori

Helicobacter pylori isolates vary between geographic regions. Certain H. pylori genotypes may be associated with disease outcome. Thirty-eight children underwent diagnostic upper endoscopy at four medical centers and were retrospectively analyzed to determine if H. pylori virulence genes were associated with endoscopic disease severity, histologic parameters, and host demographics. The H. pylori virulence genotype was analyzed by a reverse hybridization line probe assay and type-specific PCR. Endoscopic ulcers or erosions were found in 17 (45%) patients, with 13 (34%) of these patients having antral nodularity. Histological gastritis, of varying severity, was present in all children. Four patients harbored more than one H. pylori strain: one subject had both cagA(+) and cagA-negative strains, while three patients harbored either two different cagA-negative strains (two children) or two cagA(+) strains (one child). There were 28 (74%) cagA(+) isolates; 19 were associated with the vacA s1b genotype, 7 were associated with the vacA s1a genotype, 1 was associated with the vacA s1c genotype, and 1 was associated with the s2 genotype. Of 14 cagA-negative isolates, 6 were vacA s2 genotype, 4 were vacA s1b, 3 were vacA s1a, and 1 was vacA s1c. Nine of ten (90%) Hispanics had similar H. pylori strains (vacA s1b,m1), and all Asian-Canadian children were infected by strains with vacA s1c genotype. No correlation between H. pylori strain and endoscopic or histopathologic abnormalities was found. This study provides a baseline framework of North American children and their H. pylori strains, serving as a powerful epidemiological tool for prospective investigations to better understand the transmission and evolution of diverse disease outcomes.

Helicobacter pylori infection in children: update

Despite its worldwide distribution, the pathogenesis of Helicobacter pylori associated gastroduodenal disease remains poorly understood. What is clear is that H. pylori infection rarely resolves spontaneously and that the chronic gastritis that accompanies infection is typically maintained for the duration of infection. Ultimately, if untreated, this chronic inflammation predisposes a subset of individuals to develop gastric or duodenal ulcers and even gastric cancer. Chronic long-lasting H. pylori infection, particularly when acquired early in childhood, can predispose an individual to a significantly increased risk of developing gastric cancer. These studies were so compelling that the World Health Organization has recently classified H. pylori as a type 1 human carcinogen. Since the discovery of H. pylori less than 20 years ago, this infection has continued to generate considerable interest in the medical and scientific community. As we enter the new millenium, there are now a number of effective treatments for children in whom H. pylori-associated peptic ulcer disease is diagnosed. Although there is now overwhelming evidence to confirm that H. pylori plays an etiologic role in the development of peptic ulcer disease, only a small number of these children develop H. pylori disease. In this review, we highlight some of the recently published pediatric studies addressing the role H. pylori plays in the development of gastroduodenal disease in children.

Immunology of Helicobacter pylori and prospects for vaccine

Since the initial discovery of H. pylori by Marshall and Warren 17 years ago, much progress has been made in treating this infection. However, as we enter the millennium, H. pylori infection continues to be one of the most common infections of mankind. In addition, eradication of H. pylori still requires multiple antimicrobial agents. A better understanding of the host immune response to H. pylori infection should allow investigators to develop immunotherapies to prevent the acquisition of infection and eradicate existing chronic H. pylori infection.

Normalizing results of 13C-urea breath testing for CO2 production rates in children

BACKGROUND

The 13C-urea breath test detects the presence of Helicobacter pylori from an enrichment of breath 13CO2, which, in turn, is critically dependent on the amount of dilution by endogenous CO2 production. The production of CO2 differs according to age (adults > children), sex (male > female) weight, and height. The cutoff value of 2.4 delta%(delta over baseline, DOB) for the 13C-urea breath test, defined in adults, does not take into account actual CO2 production. Therefore, this cutoff value (2.4 delta%) may or may not be appropriate for children. The purpose of this study was to determine a cutoff value that would provide accurate results in pediatric patients, independent of their differences in anthropometric parameters.

METHODS

Estimates of CO2 production were combined with DOB values to calculate the host-dependent urea hydrolysis rate.

RESULTS

Calculated as urea hydrolysis rate, the cutoff range for adults was 10.4 to 10.9 microg/min. Individual ranges were concentric (men, 9.6-10.9 microg/min; women, 8.5-12.2 microg/min). Results in studies of 312 children show that a urea hydrolysis rate of more than 10 m microg/min may also be appropriate to predict H. pylori infection.

CONCLUSION

Calculating 13C-urea breath test values as urea hydrolysis rate removes the effect of individual anthropometric differences on test outcome and provides a single cutoff value for pediatric patients of all ages.

Local and systemic antibody responses in humans with Helicobacter pylori infection

Immunization can prevent or cure an otherwise chronic helicobacter infection in several animal models despite the chronic nature of natural helicobacter infections. Differences in the antigenic specificity of the antibodies may contribute to the protection observed in these experimental animals. The goal of the present study was to compare the local and systemic antibody responses of humans with chronic Helicobacter pylori infection with those of an individual with spontaneous resolution of infection to find an immunological correlate of protection. Spontaneous resolution of infection was accompanied by a change in immunoblot profiles. Whereas a broad range of H pylori antigens was recognized in chronically infected patients (including the patient who ultimately cleared the infection spontaneously), resolution of infection in the absence of therapeutic agents resulted in the recognition of only several immunodominant antigens. The most dominant antigen was approximately 66 kDa in molecular mass. Immunoblot analysis demonstrated that these antibodies were specific for the structural subunits of the urease enzyme. These studies suggest that the success of antihelicobacter immunization may be due to the ability of vaccination to induce an immune response against antigens that are normally not immunodominant during the course of infection.

Host response and vaccine development to Helicobacter pylori infection

Studies in both humans and animals demonstrate that H. pylori is capable of illiciting an innate response that in part is regulated by the genetic makeup of the host. These innate responses includes stimulating immune effector mechanisms at the cellular and biochemical level resulting in the influx of neutrophils into the lamina propria and have even been shown to modify gastric acid secretion. The availability of good animal models of chronic Helicobacter infection has also allowed investigators to begin to examine how the adaptive host immune response prevents and/or exacerbates Helicobacter-induced gastroduodenal disease. The experimental H. felis/mouse model has been utilized by a number of laboratories to investigate mechanisms of host defense against chronic Helicobacter infection. This model and the more recently developed H. pylori rodent model has not only allowed investigators to confirm the feasibility of immunotherapy to prevent and/or cure Helicobacter infection but also to begin to examine how the host immune response prevents and/or exacerbates Helicobacter-induced gastroduodenal disease. Based on these studies a hypothesis is emerging that suggests that protection and/or cure from Helicobacter infection is mediated primarily by an upregulated cellular immune response which may act via an antibody independent mechanism. Paradoxically, following natural infection with H. pylori, a component of the cellular immune response also promotes chronic gastric inflammation without clearance of the organism. The recent development of reliable and reproducible H. pylori/rodent models of disease and the availability of numerous inbred strains, transgenic and knockout animals, will allow investigators to continue to explore the role the host cellular and humoral immune response plays in promoting or preventing this infection.

Qualitative and quantitative analysis of the local and systemic antibody response in mice and humans with Helicobacter immunity and infection

Immunization can prevent or cure an otherwise chronic gastric Helicobacter infection in several different animal models. The goal of the present study was to compare the titers and specificities of local and systemic antibody responses generated by Helicobacter infection and immunization. Protective immunization results in levels of specific gastric antibody significantly lower than induced by infection. However, antibodies from protectively immunized mice preferentially recognize immunodominant proteins of 10-22 and 30 kDa. Immunoblot analysis of infected mice and humans demonstrated that the serum IgA, but not serum IgG, binding profiles yield an accurate profile of the antigenic specificity of the host's gastric IgA. Therefore, serum IgA may be useful in evaluating the immunodominant antigens at the gastric mucosa of infected persons and possibly in determining the immunogenicity of orally applied Helicobacter vaccines.

Antibody-independent protective mucosal immunity to gastric helicobacter infection in mice

Helicobacter pylori infection of the gastric mucosa can result in gastritis and peptic ulcer disease. Although vaccination can induce protective immunity in animal models of Helicobacter infection, the mechanism(s) of protective immunity has not been fully elucidated. This study was designed to determine whether humoral immune responses are required for protective Helicobacter immunity. IgA-deficient or immunoglobulin-deficient mice were orally immunized against Helicobacter felis and then challenged with live H. felis. Both groups were protected at levels comparable to that of wild-type mice. Additionally, inflammation was equivalent in extent and character between wild-type and antibody-deficient mice. Therefore antibody-independent mechanisms of immunity can protect mice against gastric Helicobacter infection.

Recombinant cholera toxin B subunit is not an effective mucosal adjuvant for oral immunization of mice against Helicobacter felis

Cholera toxin is a potent oral mucosal adjuvant for enteric immunization. Several studies suggest that commercial cholera toxin B subunit (cCTB; purified from holotoxin) may be an effective non-toxic alternative for oral immunization. The present study was performed, using an infectious disease model, to determine if the oral mucosal adjuvanticity of CTB is dependent on contaminating holotoxin. Mice were orally immunized with Helicobacter felis sonicate and either cholera holotoxin, cCTB or recombinant cholera toxin B subunit (rCTB). Serum immunoglobulin G (IgG) and intestinal immunoglobulin A (IgA) antibody responses were determined and the mice were challenged with live H. felis to determine the degree of protective immunity induced. All orally immunized mice responded with serum IgG antibody titres regardless of the adjuvant used. However, only mice immunized with either holotoxin or the cCTB responded with an intestinal mucosal IgA response. Consistent with the production of mucosal antibodies, mice immunized with either holotoxin or cCTB as adjuvants were protected from challenge while mice receiving H. felis sonicate and rCTB all became infected. cCTB induced the accumulation of cAMP in mouse thymocytes at a level equal to 0.1% of that induced by holotoxin, whereas rCTB was devoid of any activity. These results indicate that CTB possesses no intrinsic mucosal adjuvant activity when administered orally. Therefore, when used as an oral adjuvant, CTB should also include small, non-toxic doses of cholera toxin.

Review article: Immunological determinants that may affect the Helicobacter pylori cancer risk

A large body of literature supports a role for Helicobacter pylori as an environmental factor which contributes to the development of gastric cancer through an intermediate stage of atrophic gastritis. The mechanism(s) by which H. pylori-associated chronic inflammation progresses to more serious diseases such as peptic ulcer and gastric cancer in certain individuals is not clear. Variations in the phenotype or genotype of the infecting H. pylori strain can play a role in the severity of disease. However, individuals infected with the 'more virulent' strains of H. pylori often never develop serious disease. Our experiments in inbred strains of mice provide evidence that host genetics also play a significant role in H. pylori-related gastritis. We have demonstrated that gastritis is dominated by a TH1 adaptive immune response, the degree of which directly correlates with the severity of disease. Treatment of mice with IL-12 or anti-IFN-gamma antibodies can increase or decrease, respectively the severity of gastritis in infected mice and adoptive transfer of TH1 cell lines significantly exacerbates disease. Thus, the tendency of an individual to respond to infection with specific immune mechanisms can dramatically affect the severity of disease and possibly put an individual at increased risk of progressing to disorders such as gastric cancer.

Murine CD4 T-cell response to Helicobacter infection: TH1 cells enhance gastritis and TH2 cells reduce bacterial load

BACKGROUND & AIMS

Previous findings suggest that TH1 cellular immune responses contribute to Helicobacter-associated gastritis. To further investigate this issue, interleukin 4 gene targeted mice were infected with Helicobacter felis, and a series of adoptive transfer experiments was performed to evaluate the role of both TH1 and TH2 cells.

METHODS

Antigen-specific spleen cells from immunized/challenged or nonimmunized/infected mice or CD4+ T-cell lines were transferred adoptively into naive recipients before live bacterial challenge.

RESULTS

Transfer of cells from both groups of donors as well as TH1 or TH2 cell lines exacerbated gastric inflammation in the recipients. No effect on bacterial load was observed in recipients of bulk spleen cells from infected mice or recipients of TH1 cell lines. In contrast, when either a TH2 cell line or bulk cells from immunized challenged mice were transferred adoptively, recipients showed a dramatic reduction in bacterial load. Increased numbers of bacteria were also noted in interleukin 4-deficient mice.

CONCLUSIONS

These data suggest a differential contribution of TH1 and TH2 cell-mediated immune responses in Helicobacter infection: one associated with the pathogenesis of disease (TH1 phenotype) and the other associated with protection from or control of infection (TH2 phenotype).

What is the role for vaccination in Helicobacter pylori?

Helicobacter pylori has been implicated in the etiology of peptic ulcer disease, chronic gastritis, gastric carcinoma, and gastric mucosa-associated lymphoid tissue lymphoma. Although significant progress has been made in treating this infection with combinations of either antimicrobial agents or antimicrobial agents plus proton pump inhibitors, these antimicrobial-based treatments continue to be suboptimal. Over the past few years it has become increasingly recognized that direct mucosal immunization can induce protection from infection at mucosal surfaces. Therefore, prevention of H. pylori infection by oral immunization is an alternative approach for the control of H. pylori disease. Using the Helicobacter felis mouse model or H. pylori mouse model, both prophylactic and therapeutic oral immunizations have been shown to be effective against H. pylori. In addition, several H. pylori proteins have been identified as potential candidate vaccines, and a phase 1 clinical trial has been completed that demonstrates the safety and tolerability of urease as a vaccine antigen. Such antigens in combination with a safe mucosal adjuvant could be used in the form of an oral vaccine administered during childhood before exposure to H. pylori to prevent infection. In addition, therapeutic immunization alone or as an adjunct to antimicrobial therapy may be capable of achieving a cure rate approaching 100%.

Review and analysis of the effects of olestra, a dietary fat substitute, on gastrointestinal function and symptoms

Olestra, a dietary fat substitute, was recently made available to consumers in savory snacks in three cities. Early reports of gastrointestinal complaints attributed to olestra attracted media coverage and fostered confusion among physicians and consumers about the nature of olestra and its effects on the digestive system. We reviewed all published studies of olestra's gastrointestinal effects and all relevant unpublished studies submitted to the Food and Drug Administration. Each study was analyzed by a group of expert gastroenterologists and epidemiologists. The symptoms reported with olestra ingestion are similar to those reported with ingestion of fiber and sorbitol, although the mechanisms involved in changing stool characteristics differ among these food additives. Olestra's effects on stool habit and characteristics are due to its presence in the stool. Large amounts are more likely to induce gastrointestinal symptoms than small amounts. There is no evidence that olestra induces pathological change in bowel function: there is no increased fluid or electrolyte nor is there altered gastrointestinal motility or microflora. Olestra and triglyceride ingestion resulted in a similar frequency of symptoms in normal adults and children and in people with chronic inflammatory bowel disease in remission. Olestra traverses the digestive tract intact to become a stool additive. Some subjects develop a change in bowel habit and stool characteristics due to the presence of more olestra in the stool. These changes resemble those associated with ingestion of sorbitol and fiber.

Therapeutic immunization against Helicobacter mustelae in naturally infected ferrets

BACKGROUND & AIMS

Helicobacter infection of the gastric antrum is responsible for a number of gastric disorders. Antibiotic therapy is lengthy and is not always effective. It has been shown previously that oral immunization against Helicobacter felis in mice can prevent colonization after challenge. The aim of this study was to investigate the efficacy of therapeutic immunization in eradicating an established Helicobacter infection and in reducing gastritis.

METHODS

Domestic ferrets, confirmed to be infected with Helicobacter mustelae by gastric endoscopy, were orally immunized with varying doses of purified Helicobacter pylori urease in combination with the mucosal adjuvant cholera toxin. Ferrets were assessed 1 week and 6 weeks after treatment for infection and pathology.

RESULTS

Therapeutic immunization eradicated Helicobacter colonization in 30% of all immunized ferrets, although there was no difference in efficacy between the varying doses of antigen tested. The difference was statistically significant when compared with animals administered cholera toxin alone or buffer (P = 0.04). The intensity of inflammation was also significantly reduced in immunized animals (P = 0.0003).

CONCLUSIONS

Oral immunization with purified H. pylori urease and cholera toxin can eradicate H. mustelae in a natural host pathogen model. Oral immunization of chronically infected animals markedly reduced gastric inflammation.

Characterization and therapy for experimental infection by Helicobacter mustelae in ferrets

BACKGROUND

Numerous clinical trials evaluating the efficacy of various antimicrobial compounds against Helicobacter pylori infection have been performed in humans. A convenient animal model for Helicobacter infection would facilitate the evaluation of novel therapies. These experiments were performed to evaluate the use of ferrets as a model of Helicobacter infection.

MATERIALS AND METHODS

Ferrets were infected experimentally with Helicobacter mustelae and subsequently treated with bismuth subsalicylate (BSS) triple therapy (BSS, metronidazole, and amoxicillin), or left untreated. The status of infection and serology was assessed during treatment and for 8 weeks posttreatment. Seven ferrets successfully treated with triple therapy were challenged with H. mustelae and monitored for infection for an additional 5 weeks.

RESULTS

Infection of ferrets by H. mustelae was accompanied by gastritis and a specific antibody response. Treatment of H. mustelae-infected ferrets with BSS suppressed bacterial growth in four of nine animals but did not eradicate infection. Triple therapy eradicated infection in all nine ferrets with a reduction in gastric inflammation. No relapse of infection occurred up to 8 weeks posttherapy. Challenge with H. mustelae of ferrets successfully treated with triple therapy resulted in a 100% rate of reinfection.

CONCLUSIONS

H. mustelae infection can be eliminated by triple therapy, but this does not result in protective immunity against reinfection by H. mustelae. This model, using a strain of Helicobacter indigenous to the host, may be useful for assessing therapeutic efficacy of novel therapies for the treatment of human infection by H. pylori.

Vaccine strategies for prevention of Helicobacter pylori infection

OBJECTIVE

To examine the level and duration of the humoral immune response to Helicobacter felis following oral immunization or infection.

DESIGN AND METHODS

Germ-free mice were orally immunized with sonicated H. felis plus cholera toxin five times over 6 weeks. One week after immunization was completed, immunized and control non-immunized mice received an oral challenge of live H. felis organisms. The animals were killed at 3-week intervals and serum, gastric washings, intestinal washings and gastric biopsies were obtained. H. felis infection was confirmed by a positive urease test or culture of the gastric biopsy. Serum gastric and intestinal antibody titers were determined by enzyme-linked immunosorbent assay.

CONCLUSION

Infection and immunization against H. felis produces a specific humoral response. The humoral response in infection alone is significantly smaller than that of immunized animals until 6 weeks after infection. The humoral response following oral immunization persists for at least 18 weeks without further stimulation. The presence of an H. felis-specific antibody immune response before infection may be needed to protect animals from acute Helicobacter infection.

Urease-specific monoclonal antibodies prevent Helicobacter felis infection in mice

Experiments were performed to determine the antigenic specificity of a monoclonal antibody (immunoglobulin A [IgA] 71) previously demonstrated to neutralize the ability of Helicobacter felis to colonize mice. Immunoprecipitation of radiolabeled H. felis outer membrane proteins with IgA 71 revealed specificity for a 62-kDa protein. Another of our monoclonal antibodies, IgG 40, precipitated a protein of similar molecular weight. IgA 71 but not IgG 40 also precipitated purified recombinant H. pylori urease. The antigenic specificity of both antibodies was confirmed to be urease by the ability of each to select Escherichia coli clones expressing the H. felis urease genes. The two antibodies were shown to bind nonoverlapping epitopes in a competition enzyme-linked immunosorbent assay. Both IgA 71 and IgG 40 could effectively neutralize H. felis infectivity by incubating the bacteria with the antibodies prior to oral administration to naive mice. The mechanism of protection does not appear to be inhibition of urease activity, as IgA 71 does not inhibit the conversion of urea to ammonia by H. pylori urease in vitro. These results support a protective role for the secretory humoral immune response in Helicobacter immunity and provide further evidence that the urease enzyme can serve as a protective antigen.

Helicobacter-associated gastritis in SCID mice

Immunodeficient (SCID) and immunocompetent mice were infected with Helicobacter felis to address the role of autoimmunity in Helicobacter-associated gastritis. The extents of inflammation were equivalent in the two groups. The numbers of H. felis organisms were marginally increased in the SCID mice but did not achieve statistical significance. These results indicate that autoimmunity is not necessary to induce disease and that the presence of an adaptive immune system does not significantly affect H. felis colonization.

In vitro susceptibility of Helicobacter pylori to trospectomycin, pirlimycin (U-57930E), mirincamycin (U-24729A) and N-demethyl clindamycin (U-26767A)

The in vitro activity of trospectomycin, pirlimycin, mirincamycin and N-demethyl clindamycin was measured against 46 clinical isolates of Helicobacter pylori using an agar dilution technique. The MIC50 and MIC90 were 4 and 64 micrograms/ml for pirlimycin and N-demethyl clindamycin, and 32 and 128 micrograms/ml for mirincamycin, respectively. All 46 strains were sensitive to trospectomycin with an MIC50 of 8 micrograms/ml and an MIC90 of 16 micrograms/ml. Of seven strains with the highest trospectomycin MICs (8 or 16 micrograms/ml) 100% were found to be resistant to metronidazole. Among ten strains with low trospectomycin MICs (2 micrograms/ml or less) 100% were sensitive to metronidazole. Possible explantations for the apparent correlation between the MICs of the two drugs are discussed. Since all metronidazole resistant strains were sensitive to trospectomycin, this drug may be useful in treating infection with metronidazole resistant Helicobacter pylori.

Evaluation of QuickVue, a rapid enzyme immunoassay test for the detection of serum antibodies to Helicobacter pylori

QuickVue is an enzyme immunoassay test for qualitative detection of serum immunoglobulin-G antibodies to Helicobacter pylori. We evaluated its ability to predict infection by H. pylori in 100 adult and 49 pediatric patients referred for gastric endoscopy. A patient was defined as infected with H. pylori if either culture or histology was positive. Of the 100 adult patients, 64 had H. pylori infection and QuickVue correctly identified 59 of the 64. Of 36 H. pylori-negative patients, 20 were correctly identified as negative by the test. In this sample of patients, QuickVue had a sensitivity of 92% and a specificity of 56%. In the 49 pediatric patients, QuickVue correctly identified nine of 11 infected cases and 34 of 38 noninfected patients. In this group, the sensitivity was 82% and the specificity was 89%. Overall the test had a sensitivity of 91% and a specificity of 73%. The positive predictive value was 77% and the negative predictive value was 89%.

Diagnosis of Helicobacter pylori infection by means of a polymerase chain reaction assay for gastric juice aspirates

A polymerase chain reaction (PCR) assay for Helicobacter pylori was developed with use of primer sequences from the ureA structural gene coding for the small subunit of urease. The PCR amplification was 100% specific for H. pylori in tests with 40 stock isolates of this species and with 30 control organisms, including two species of urease-producing Helicobacter. Thirty-four dyspeptic patients were evaluated by culture and histologic assessment of antral biopsy samples as well as by PCR of gastric juice aspirates. In 26 of the 34 patients, infection with H. pylori was diagnosed by culture and histology. PCR correctly identified 25 of these 26 patients. All eight patients with negative cultures and histologic findings also had negative PCR results. In this group of patients, therefore, PCR had a sensitivity of 96% and a specificity of 100%. Thus PCR of gastric juice aspirates can be used to diagnose H. pylori infection. This information is important since gastric juice can be aspirated through a nasogastric tube without gastroduodenoscopy. In addition, since clinical samples can be collected at one institution and mailed to a laboratory at another without compromising the outcome of the test, diagnostic PCR is accessible even to those clinicians at whose institutions the technology required for the procedure is not available.

Protection of germ-free mice from infection by Helicobacter felis after active oral or passive IgA immunization

Helicobacter pylori infection of human gastric epithelium has been associated with gastritis, ulcers and gastric cancers. In an H. felis, germ-free mouse model of infection, oral immunization with bacterial antigens plus cholera toxin resulted in elevated serum, gastric and intestinal anti-H. felis antibody titres and protection from acute infection. Mice given monoclonal IgA anti-H. felis antibody at the time of initial challenge were also protected from infection. These results demonstrate that oral vaccination may be a feasible approach for the prevention of H. pylori infection of humans.

Diagnosis of Helicobacter pylori infection in adult and pediatric patients by using Pyloriset, a rapid latex agglutination test

Pyloriset (Orion Diagnostica, Espoo, Finland) is a rapid antibody test using latex particles coated with acid-extracted antigen of Helicobacter pylori. We evaluated its ability to predict infection in 100 adult patients and 50 pediatric patients referred for gastric endoscopy. Sixty of 65 H. pylori-infected adults were correctly identified by the test. There were 12 false-positive and 5 false-negative reactions seen. Pyloriset had a sensitivity of 92% and a specificity of 66%. The positive predictive value was 83% and the negative predictive value 82%. In contrast, sensitivity dropped to 36% in the pediatric patients and the positive predictive value was only 40%. Pyloriset could become an important alternative to other more time-consuming diagnostic tests for H. pylori-infected adult patients but is inadequate for diagnosis of pediatric H. pylori infection.

Diagnosis of gastritis caused by Helicobacter pylori in children by means of an ELISA

In this study, the systemic immune response to bacterial cell sonicates of Helicobacter pylori was characterized in children with symptomatic gastroduodenal disease. Isotype-specific antibodies to H. pylori in samples of serum from 16 children with culture-proven disease caused by H. pylori and from 19 controls with negative cultures were measured by ELISA with bacterial cell lysates. The levels in serum of IgA antibody to cell sonicates of H. pylori were significantly higher in the patients with positive cultures than in the controls. Only 45% of patients were infected when the established optical density cutoff was used to discriminate between patients infected and not infected with H. pylori. Levels of IgM antibody in serum were not significantly higher in patients who were infected with H. pylori. On the basis of this survey and of previous work conducted in our laboratory, we conclude that at a serum dilution of 1:800, IgG but not IgA or IgM antibody to H. pylori is useful in the rapid screening of symptomatic children for the presence of H. pylori.

Oral immunization against Helicobacter pylori

Helicobacter pylori, which has been associated with gastritis and duodenal ulcers, commonly chronically infects adults. Eradication of this microorganism, which is difficult to achieve, results in normalization of gastritis and marked reduction in the relapse rate of duodenal ulcers. Since eradication is difficult to achieve, prevention of initial colonization of the gastrointestinal tract may be a viable alternative for abrogation of H. pylori-associated gastroduodenal disease. To test the feasibility of this approach, mice and ferrets were orally immunized with killed H. pylori. Immunization induced immunoglobulin A and G anti-H. pylori antibodies in both gastrointestinal secretions and sera of mice. These responses were enhanced when cholera toxin was included in the immunization protocol as a mucosal adjuvant. In ferrets, addition of cholera toxin resulted in significant enhancement of anti-H. pylori antibody levels in sera and intestines. Thus, oral immunization with killed H. pylori may be feasible approach to protect hosts from this infection and the accompanying gastroduodenal disease.

Relationship between gastric inflammatory response and symptoms in patients infected with Helicobacter pylori

The relationship between the histologic severity of gastritis and associated symptoms was examined in 19 adult patients infected with Helicobacter pylori. At the time of gastrointestinal endoscopy, symptoms of dyspepsia were assessed by means of a linear analog scale. Gastric inflammation was quantitated with histomorphometric techniques. Symptoms such as epigastric pain, burping/belching, and nausea correlated with the degree of inflammation. These positive correlations suggest that the severity of the histologic gastritis contributes to the severity of symptoms. Therefore, utilization of a linear analog scale to assess symptoms may be a useful technique in evaluating the outcome of therapeutic trials of patients with symptomatic H. pylori infection.

Opsonic activity of specific human IgG against Helicobacter pylori

There is a strong association between chronic gastroduodenal disease in adults and children and the recovery of Helicobacter pylori (formerly Campylobacter pylori) from gastric biopsy specimens. However, data relevant to host defense mechanisms directed against this organism are scarce. The ability of H. pylori-specific antibody and complement to enhance the in vitro phagocytosis and killing of H. pylori by human peripheral blood polymorphonuclear leukocytes (PMNL) were studied. Sera with IgG antibody to H. pylori from five children with culture-proven H. pylori gastric disease markedly enhanced complement-dependent phagocytosis of H. pylori in an assay using flow cytometry to measure uptake of fluorescent-labeled bacteria by PMNL. Absorption of specific antibody from patient sera with an excess of H. pylori organisms completely abrogated this enhancement. IgG purified from plasma with high IgG antibody titers to H. pylori enhanced complement-dependent phagocytosis of H. pylori and increased the killing of this organism by PMNL in the presence of 5% human opsonic complement by one full log. IgG antibody to H. pylori appears to be highly functional in vitro in promoting complement-dependent phagocytosis and killing of H. pylori by PMNL.

Effects of topical anesthetic agents on Campylobacter pylori

The susceptibility of Campylobacter pylori was determined for the two topical anesthetic agents commonly used prior to gastroscopy. Campylobacter pylori proved to be extremely sensitive to the anti-infective activity of benzocaine, the active ingredient in most commonly used topical anesthetic agents, with minimum inhibitory concentrations of 0.14 mg/ml. However, lidocaine-containing agents did not interfere with the growth of this microorganism. Specifically, in patients with histologic evidence of C. pylori, the bacterium was recovered from significantly more patients anesthetized with lidocaine than with benzocaine. Thus, the use of benzocaine-containing topical anesthetic agents limits recovery of Campylobacter pylori from clinical specimens and might account for the low colonization rates reported in some recent publications.

Enlarged gastric folds in association with Campylobacter pylori gastritis

Enlarged gastric folds in pediatric patients are uncommon. Fifteen patients with upper gastrointestinal (GI) tract symptoms of chronic epigastric abdominal pain, vomiting, or hematemesis underwent radiologic upper GI barium studies and were found to have Campylobacter pylori gastritis at endoscopic biopsy. Seven patients (47%) with C pylori gastric disease had radiologic evidence of enlarged folds. There was no clinical or pathologic evidence of Ménétrier disease. Therefore, C pylori gastritis should be considered in the differential diagnosis of children with upper GI tract symptoms and radiologic evidence of enlarged folds.

Susceptibility of Campylobacter pylori to the newer cephalosporin antibiotics

The susceptibility of 23 strains (pediatric and adult) of Campylobacter pylori to eight cephalosporin antibiotics was determined. All strains were sensitive to cefoxitin, cefuroxime, ceftizoxime, latamoxef, and ceftriaxone. Ceftazidime and cefoperazone showed only moderate activity against C. pylori. C. pylori was resistant to cefsulodin.

Campylobacter pylori--associated gastritis and peptic ulcer disease in children

Specimens obtained at gastric biopsies performed for suspected acid peptic disease in patients 5 through 17 years of age were retrospectively reviewed for the presence of Campylobacter pylori (CP), a gram-negative bacillus associated with chronic gastritis and peptic ulcer disease in adults. Of 98 patients who underwent antral biopsy (the most reliably colonized site in the stomach), 40 had chronic gastritis histologically. Of those 40 patients, 22 (55%) had CP present on the gastric surface. None of the 58 patients without gastritis present in biopsy specimens had CP. The gastritis in children with CP was more severe than in those without the organism: 86% of those with moderate gastritis and 92% of those with severe gastritis had CP. Eight patients with duodenal ulcers and one patient with a gastric ulcer had CP on biopsy. Among those patients without CP, only one had a duodenal ulcer and eight had gastric ulcers. An additional nine patients found to have CP on gastric fundic biopsy were identified, for a total of 31 patients with CP identified by either antral (22) or fundic (nine) biopsy. Initial resolution of symptoms with standard acid-antagonist therapy was noted in the 25 of 31 CP(+) patients so treated, but a high relapse rate was noted within one to two years in the patients who also had gastritis and duodenal ulcer. These findings support a strong association between CP colonization of the stomach and the presence of chronic gastritis and duodenal ulcer disease in children.

Susceptibility of Campylobacter pylori isolated from pediatric and adult patients to seven new quinolone antibiotics and nalidixic acid

The susceptibility of 26 strains of Campylobacter pylori to 7 new quinolone antibiotics and nalidixic acid was determined. All strains were resistant to nalidixic acid. Difloxacin, A-56620, A-62254, and ciprofloxacin were equally effective against the test strains with MICs ranging from 0.06 to 2.0 micrograms/ml. Fleroxacin, amifloxacin, perfloxacin, and norfloxacin showed only moderate activity against C. pylori. The new quinolone agents, which are bactericidal, may prove useful in the eradication of C. pylori from the gastric mucosa.