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Diagnosing Parasitic Infections
Published in Firza Alexander Gronthoud, Practical Clinical Microbiology and Infectious Diseases, 2020
Cystoisospora belli (formerly known as Isospora belli, Cyclospora cayetanensis and Cryptosporidium cause self-limiting watery diarrhoea in immunocompetent individuals which can last several weeks. Immunocompromised individuals are at risk of developing severe and prolonged infection with malabsorption and weight loss.
Pyrimethamine
Published in M. Lindsay Grayson, Sara E. Cosgrove, Suzanne M. Crowe, M. Lindsay Grayson, William Hope, James S. McCarthy, John Mills, Johan W. Mouton, David L. Paterson, Kucers’ The Use of Antibiotics, 2017
Bianca Graves, David Looke, M. Lindsay Grayson
The key clinical use of pyrimethamine has been in combination with sulfadoxine as an antimalarial, commonly referred to as Fansidar or abbreviated as S/P. However, the development of widespread resistance in Plasmodium falciparum has led to a decline in its use for treatment of falciparum malaria. It remains useful for intermittent preventive therapy for malaria in pregnancy (IPTp) and intermittent preventive therapy for malaria in infancy (IPTi). It also remains a key drug for treatment of toxoplasmosis, Pneumocystis jiroveci pneumonia, and diarrhea due to Cystoisospora belli, often in combination with non-sulfa compounds such as clindamycin (see Chapter 85, Clindamycin and lincomycin).
Viral infections
Published in Phillip D. Smith, Richard S. Blumberg, Thomas T. MacDonald, Principles of Mucosal Immunology, 2020
Sarah Elizabeth Blutt, Mary K. Estes, Satya Dandekar, Phillip D. Smith
Several principles govern the interaction between opportunistic pathogens and HIV-1 infection (Table 28.3). First, susceptibility to mucosal, as well as systemic, opportunistic infections is inversely related to the level of immunosuppression, and clearance of the infection usually occurs after restoration of immune function with antiretroviral therapy. For example, the presence of active cytomegalovirus infection is inversely proportional to the number of circulating CD4+ T cells, with mucosal cytomegalovirus-induced inflammation and ulceration usually occurring after the number of CD4+ T cells declines to less than 100 cells mm−3, indicating severe immunosuppression. Conversely, cytomegalovirus disease resolves with HAART-induced restoration of immune function. Second, replication of some opportunistic pathogens may enhance HIV-1 transcription and vice versa in dual-infected cells and in lymphoid tissue. For example, the bidirectional upregulation of Mycobacterium avium complex replication and HIV-1 transcription has been detected in dual-infected macrophages in lymph nodes. Bidirectional upregulation likely occurs in dual-infected immune cells in the mucosa. Third, the route of HIV-1 entry does not determine the site of mucosal infections. Thus, HIV-1 transmitted by the genital route can lead to opportunistic infections in the gastrointestinal mucosa and/or the genital mucosa. Fourth, the specific mucosal pathogen acquired reflects in part the pathogens endemic to a specific geographical area and the sexual practices of the HIV-1-infected host. For example, among HIV-1-infected people, Cystoisospora belli is more common in Africa and the Caribbean region than in the United States, and Histoplasma capsulatum is more common in the Mississippi and Ohio River valleys than other regions of the United States. Regarding the influence of sexual practices on mucosal infection, Chlamydia trachomatis proctitis, for example, occurs only in men who practice receptive anal intercourse.
Treatment of cryptosporidiosis: nitazoxanide yes, but we can do better
Published in Expert Review of Anti-infective Therapy, 2023
Maria A. Caravedo, A. Clinton White
The recommended treatments for all other apicomplexan parasites (including malaria, toxoplasmosis, Cyclospora, and Cystoisospora) involve combinations of antiparasitic drugs. In vitro studies have demonstrated synergistic effects of combination therapy for Cryptosporidium [48] There is only limited data on combination antiparasitic drugs in human cryptosporidiosis. Smith et al. prospectively studied the combination of Paromomycin and Azithromycin for cryptosporidiosis in AIDS patients with CD4 counts <100, finding a clinical improvement and a significant reduction in oocyte excretion at 12 weeks [49]. Observational studies suggest that the combination of nitazoxanide and azithromycin might be more effective than either drug alone in transplant recipients. Double, or triple coverage with a combination of the above medications in transplanted and AIDS have been suggested as alternative treatments in refractory cases [2,3] Most recently, Tomczak et al. reported a case of a renal transplant patient with chronic diarrhea that resolved with reduced immunosuppression and 3-drug combination therapy with nitazoxanide, azithromycin, and rifaximin [2] However, there is still no controlled trial data on combination therapy in cryptosporidiosis.
Structure-activity relationships of Toxoplasma gondii cytochrome bc 1 inhibitors
Published in Expert Opinion on Drug Discovery, 2022
P. Holland Alday, Aaron Nilsen, J. Stone Doggett
Cytochrome (cyt) bc1 has proven to be a tractable drug target for the majority of veterinary and human apicomplexan pathogens. In addition to T. gondii, cyt bc1 inhibitors have been found to be effective across orders of the phylum Apicomplexa: Haemosporida, Plasmodia spp.; the Piroplasmida, Babesia spp., and Theileria equii; and the Eucoccidiorida, Sarcocystis neurona, Eimeria spp., Neospora caninum, and Besnoitia besnoiti [5–10]. Cryptosporidium, the human gastrointestinal parasite, is a notable exception. It lacks a mitochondrion with genes for enzymes of oxidative phosphorylation, including cyt b and instead contains mitochondrion-related organelles [11]. On the other hand, the human gastrointestinal parasites Cyclospora cayetanensis and Cystoisospora belli encode cyt b in their mitochondrial genomes, although cyt bc1 inhibitors have not been thoroughly evaluated for these diseases.
The impact of water crises and climate changes on the transmission of protozoan parasites in Africa
Published in Pathogens and Global Health, 2018
Shahira A. Ahmed, Milena Guerrero Flórez, Panagiotis Karanis
Waterborne protozoa (WBP) are a group of parasites that cause diarrheal diseases. Diversity of WBP can be found in water. Cryptosporidium spp. and Giardia duodenalis (intestinalis) took the lead among other protozoan parasites to account the majority of waterborne outbreaks (524, 344 outbreaks respectively) [10–12]. Whereas Acanthamoeba spp., Balantidium coli, Blastocystis spp., Cyclospora cayetanensis, Cystoisospora belli, Microsporidium spp., Naegleria spp., Sarcocystis spp., and Toxoplasma gondii are less reported parasites [10–12].