Paromomycin: no more effective than placebo for treatment of cryptosporidiosis in patients with advanced human immunodeficiency virus infection. AIDS Clinical Trial Group

Infection with Cryptosporidium hominis and reinfection with Cryptosporidium parvum in a transplanted ileum

A transplanted ileum was found to be infected with Cryptosporidium hominis 6 days after transplantation. Although the infection resolved, the ileum was later found to be infected with Cryptosporidium parvum. The presence of the parasite was not always correlated with diarrhea. No other gastrointestinal symptom was ever detected. Treatment with azithromycin and paromomycin apparently failed.

Indinavir reduces Cryptosporidium parvum infection in both in vitro and in vivo models

The use of highly active antiretroviral therapy in persons with acquired immunodeficiency syndrome has reduced the prevalence of infection with Cryptosporidium parvum and the length and severity of its clinical course. This effect has in most cases been attributed to the recovery of the host immunity; however, some works suggest that human immunodeficiency virus protease inhibitors, indinavir in particular, which is one of the human immunodeficiency virus protease inhibitors used in highly active antiretroviral therapy, may be capable of controlling Microsporidia and Cryptosporidium infections, which are refractory to other treatments. The objective of the present study was to investigate the effect of human immunodeficiency virus protease inhibitors on C. parvum infections. Since preliminary experiments using ritonavir, saquinavir, and indinavir showed a drastic reduction of C. parvum infection both in vivo (neonatal Balb/c mice) and in vitro (human ileocecal adenocarcinoma tumour cell line) models, indinavir alone was tested in successive experiments. In vitro, the treatment of the sporulated oocysts with different concentrations of indinavir reduced the percentage of human ileocecal adenocarcinoma tumour cell line infected cells in a dose-dependent manner. For established infection, the treatment with 50 microM of indinavir decreased the percentage of infected cells in a time-dependent manner. In vivo, mice treated with indinavir at the same time they were infected with the oocysts showed a 93% reduction in the number of oocysts present in the entire intestinal contents and a 91% reduction in the number of intracellular parasites in the ileum. For established infection, indinavir treatment reduced the number of oocysts in the entire intestinal content by about 50% and the number of intracellular parasites in the ileum by about 70%. These data show that indinavir directly interferes with the cycle of C. parvum, resulting in a marked reduction in oocyst shedding and in the number of intracellular parasites. Protease inhibitors could be considered as good candidates for the treatment of cyptosporidiosis in immunosuppressed persons.

Cryptosporidium and host resistance: historical perspective and some novel approaches

Cryptosporidium parvum is recognized as a major cause of diarrheal disease in neonatal bovine calves. In addition, this protozoan parasite has emerged as an important cause of disease in both immunocompromised and immunocompetent humans. Despite years of research, no consistently effective means of prevention or treatment are readily available for cryptosporidiosis in any species. Infection through ingestion of contaminated water has been widely documented; C. parvum was reported to be responsible for the largest waterborne outbreak of infectious disease in US history. In addition to its role as a primary disease agent, C. parvum has potential to initiate or exacerbate other gastrointestinal disorders, such as inflammatory bowel disease. Thus, control of C. parvum infection in both animals and humans remains an important objective. Research in our laboratory has focused on understanding mechanisms of resistance to C. parvum. We have demonstrated that acquisition of intestinal flora increases resistance to C. parvum. Substances present in the intestinal mucosa of adult animals can transfer resistance when fed to susceptible infants. Both expression of intestinal enzymes and rate of proliferation of epithelial cells may be altered following C. parvum infection. These and other changes may have profound effects on host resistance to C. parvum.

Parasitic infections of the gastrointestinal tract

Intestinal parasites continue to be a significant health problem in both developed and developing countries. In developed countries, protozoans are more commonly the cause of gastrointestinal infections than are helminths. Some protozoan parasites have stages in which, in addition to being resistant to chemicals used for water treatment, they are small enough to pass through commonly used filtration processes. The relatively large size of helminth eggs increases the likelihood of their removal during water filtration. The direct impact of protozoan parasites on both human and animal health is considerable, and there is some evidence that infection may contribute to the development of various forms of intestinal dysregulation as well as disseminated infection, especially in AIDS patients. Protozoans of special interest, due to either their frequency of isolation or their role as emerging pathogens, include Giardia duodenalis, Cryptosporidium parvum, Cyclospora cayetanensis, and the microsporidians, Enterocytozoon bieneusi and Encephalitozoon intestinalis.

Effect of nitazoxanide on morbidity and mortality in Zambian children with cryptosporidiosis: a randomised controlled trial

BACKGROUND

Cryptosporidiosis in children in developing countries causes persistent diarrhoea and malnutrition and is associated with increased mortality, but there is no effective treatment. We aimed to assess the effect of nitazoxanide-a new broad-spectrum antiparasitic drug-on morbidity and mortality in Zambian children with diarrhoea due to Cryptosporidium parvum.

METHODS

Children with cryptosporidial diarrhoea who were admitted to the University Teaching Hospital, Lusaka, Zambia, between November, 2000, and July, 2001, and whose parents consented to their having an HIV test were randomly assigned nitazoxanide (100 mg twice daily orally for 3 days) or placebo. The primary endpoint was clinical response on day 7 after the start of treatment. Secondary endpoints included parasitological response by day 10 and mortality at day 8. Analysis was by intention to treat, with exclusion of patients subsequently found to be negative for C parvum or co-infected at baseline. The trial was stratified by HIV serology.

FINDINGS

50 HIV-seropositive and 50 HIV-seronegative children were recruited for the study, four of whom were subsequently excluded. In HIV-seronegative children, diarrhoea resolved in 14 (56%) of 25 receiving nitazoxanide and 5 (23%) of 22 receiving placebo (difference 33%, 95% CI 7-59; p=0.037). C parvum was eradicated from stool in 13 (52%) of 25 receiving nitazoxanide and three (14%) of 22 receiving placebo (38%, 95% CI 14-63; p=0.007). Four children (18%) of 22 in the placebo group had died by day 8, compared with none of 25 in the nitazoxanide group (-18%, -34 to 2; p=0.041). HIV-seropositive children did not benefit from nitazoxanide. Nitazoxanide was not significantly associated with adverse events in either stratum.

INTERPRETATION

A 3-day course of nitazoxanide significantly improved the resolution of diarrhoea, parasitological eradication, and mortality in HIV-seronegative, but not HIV-seropositive, children.

Cryptosporidiosis: biology, pathogenesis and disease

Ninety-five years after discovery and after more than two decades of intense investigations, cryptosporidiosis, in many ways, remains enigmatic. Cryptosporidium infects all four classes of vertebrates and most likely all mammalian species. The speciation of the genus continues to be a challenge to taxonomists, compounded by many factors, including current technical difficulties and the apparent lack of host specificity by most, but not all, isolates and species.

Some aspects of protozoan infections in immunocompromised patients- a review

Protozoa are among the most important pathogens that can cause infections in immunocompromised hosts. These microorganisms particularly infect individuals with impaired cellular immunity, such as those with hematological neoplasias, renal or heart transplant patients, patients using high doses of corticosteroids, and patients with acquired immunodeficiency syndrome. The protozoa that most frequently cause disease in immunocompromised patients are Toxoplasma gondii, Trypanosoma cruzi, different Leishmania species, and Cryptosporidium parvum; the first two species cause severe acute meningoencephalitis and acute myocarditis, Leishmania sp. causes mucocutaneous or visceral disease, and Cryptosporidium can lead to chronic diarrhea with hepatobiliary involvement. Various serological, parasitological, histological and molecular methods for the diagnosis of these infections are currently available and early institution of specific therapy for each of these organisms is a basic measure to reduce the morbidity and mortality associated with these infections.

Cryptosporidiosis and the challenges of chemotherapy

Cryptosporidium parvum is a protozoan parasite that infects the epithelial cells of the small intestine causing diarrheal illness in humans. Cryptosporidium has a worldwide distribution and is considered an emerging zoonosis. Despite intensive efforts to develop workable experimental models, and the evaluation of over 200 chemotherapeutic agents, adequate therapies to clear the host of these parasites are still lacking. The reasons for the lack of drug efficacy are probably manifold and may include the unusual location of the parasite in the host cell, distinct structural and biochemical composition, or its ability to either block import or rapidly efflux drug molecules. Understanding some of the basic mechanisms by which drugs are transported to the parasite and identifying unique targets is a first step in developing effective therapeutic agents.

[Prophylaxis with tercef of infection-related complications after cesarean section]

The purpose of this prospective and case controlled study is to determine the effectiveness and safety of antibiotic prophylaxis with Tercef (ceftriaxone) in women undergoing cesarean section and to compare the results with those of 24 hours regiment of Cefazolin and also with a group without prophylaxis. The study includes 122 cases of elective and emergency CS: 41 with a single intravenous dose of 1.0 g Tercef after clamping of the umbilical cord; 41 cases of antibiotic prophylaxis with Cefazolin three times 2.0 g for 24 hours and 40 low infectious risk CS without antibiotic prophylaxis. We take in account the existing before the CS risk factors for postoperative infectious complications as: hours of PROM; length of labor, number of vaginal examinations before CS, previous sections, duration of the operation, anemia, bacteriuria and diabetes. For post CS infection-related complications we take: febrile morbidity, endometritis, wound infections, infection of urinary tract. The results show infection complication in the three groups as follow: 14.6% for tercef, 17.1% for cefazolin and 20.0% for the group without antibiotic. There is not statistically significant difference. According our study in cases of CS with increased risk of post-operative infectious complications the antibiotic prophylaxis reduce the rate of infection-related complications even below that of CS with low infectious risk. The single dose of 1 g tercef i.v. is effective and suitable in comparison with 24 hours regiment of cefazolin.

Update on protozoan parasites of the intestine

The last year has seen new approaches to the diagnosis, treatment, and prevention of protozoal infections of the gastrointestinal tract. Some of the news is not good: new foodborne and swimming pool outbreaks of cyclosporiasis and cryptosporidiosis, respectively, occurred in North America; paromomycin was shown to be ineffective treatment for cryptosporidiosis; and these parasitic diseases continued to have a worldwide impact on human health. On the bright side, there were important advances in the understanding of the pathogenesis of cryptosporidiosis and the diagnosis of amebiasis and giardiasis, and some new leads on the treatment of cryptosporidiosis and refractory giardiasis. Finally, evidence was found of acquired mucosal immunity to amebiasis in Bangladeshi children, offering a guide for the development of an amebiasis vaccine. This review is not intended to be comprehensive, but contains a variety of articles that the authors hope will be of interest to the reader.

Cryptosporidiosis: an update

Cryptosporidiosis was recognised in human beings in 1976, and was prominent in the 1980s and 1990s as a cause of severe diarrhoeal illness in patients with AIDS. It is now additionally recognised as a major cause of waterborne diarrhoeal illness in developed regions, and as a pathogen with long-term effect on childhood growth and development in impoverished areas. This update focuses on recent changes in our understanding of the taxonomy of cryptosporidium, its epidemiology, effects, pathogenesis, diagnosis, and treatment.

Parasitic infections of the intestine

Intestinal protozoal infections cause significant disease not only in the tropics but also in immunocompromised hosts and returning travellers in the developed world. Precise diagnosis of protozoal intestinal infection by microscopy can be difficult. Enzyme immunoassays for antigen detection are being used for some protozoal infections with some limitations which will, it is hoped, be overcome by molecular techniques. Nucleic acid amplification techniques could help improve detection of microsporidial species, which are difficult to detect microscopically and allow differentiation between Entamoeba histolytica and Entamoeba dispar. Definitive treatment for Cryptosporidium parvum infection remains elusive but new drugs are being evaluated. Cessation of thiabendazole production should not affect therapy of intestinal nematode infections as potent alternative therapy is available.