Abstract
Disposal of organic plant wastes and by-products from the food or pharmaceutical industries usually involves high costs. In the present study, 42 samples derived from such by-products were screened in vitro against Cryptosporidium parvum, a protozoan parasite that may contaminate drinking water and cause diarrhoea. The novel bioassay was previously established in the microtitre plate format. Human ileocaecal adenocarcinoma (HCT-8) cell cultures were seeded with C. parvum oocysts and parasite development was monitored by an indirect fluorescent antibody technique (IFAT) and microscopic assessment for clusters of secondary infection (CSI). Minimum inhibitory concentrations (MICs) and potential detrimental effects on the host cells were determined. An ethanolic extract from olive (Olea europaea) pomace, after oil pressing and phenol recovery, reproducibly inhibited C. parvum development (MIC = 250–500 μg mL−1, IC50 = 361 (279–438) μg mL−1, IC90 = 467 (398–615) μg mL−1). Accordingly, tyrosol, hydroxytyrosol, trans-coniferyl alcohol and oleuropein were selected as reference test compounds, but their contributions to the observed activity of the olive pomace extract were insignificant. The established test system proved to be a fast and efficient assay for identifying anti-cryptosporidial activities in biological waste material and comparison with selected reference compounds.
Highlights
Cryptosporidium parvum is a protozoan parasite of worldwide distribution with significance for both human and animal health [33]
Human ileocaecal adenocarcinoma (HCT-8) cell cultures were seeded with C. parvum oocysts and parasite development was monitored by an indirect fluorescent antibody technique (IFAT) and microscopic assessment for clusters of secondary infection (CSI)
Inhibitory concentrations of olive pomace (OEE) were calculated without logarithmic transformation of data: IC50 = 361 (279–438) lg mLÀ1, IC90 = 467 (398–615) lg mLÀ1 (95% fiducial limits are indicated in brackets)
Summary
Cryptosporidium parvum is a protozoan parasite of worldwide distribution with significance for both human and animal health [33]. Cryptosporidiosis is characterised by transient diarrhoea and associated problems like malabsorption and dehydration, and can follow a severe course in immunocompromised patients and young animals. Cryptosporidia are naturally resistant to many drugs with known anti-protozoal activities. Despite a large-scale screening experiment indicating some activity for 40 out of 101 tested drugs [46], only a few were able to suppress parasite development completely at low concentrations in vitro. Availability of anti-cryptosporidial drugs for treatment of affected patients is still extremely limited. Azithromycin, paromomycin and nitazoxanide are mostly used, together with other strategies like highly active anti-retroviral therapy (HAART) [38]. Only a small number of drugs have been found to be effective against animal cryptosporidiosis [33]
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