Protein A/G-based immunochromatographic test for serodiagnosis of pythiosis in human and animal subjects from Asia and Americas

Abstract

Pythiosis is a life-threatening infectious disease of both humans and animals living in Asia, Americas, Africa, and parts of Australia and New Zealand. The etiologic pathogen is the fungus-like organism Pythium insidiosum The disease has high mortality and morbidity rates. Use of antifungal drugs are ineffective against P. insidiosum, leaving radical surgery the main treatment option. Prompt treatment leads to better prognosis of affected individuals, and could be achieved by early and accurate diagnosis. Since pythiosis has been increasingly reported worldwide, there is a need for a rapid, user-friendly, and efficient test that facilitates the diagnosis of the disease. This study aims to develop an immunochromatographic test (ICT), using the bacterial protein A/G, to detect anti-P. insidiosum IgGs in humans and animals, and compare its diagnostic performance with the established ELISA. Eighty-five serum samples from 28 patients, 24 dogs, 12 horses, 12 rabbits, and 9 cattle with pythiosis, and 143 serum samples from 80 human and 63 animal subjects in a healthy condition, with thalassemia, or with other fungal infections, were recruited for assay evaluation. Detection specificities of ELISA and ICT were 100.0%. While the detection sensitivity of ELISA was 98.8%, that of ICT was 90.6%. Most pythiosis sera, that were falsely read negative by ICT, were weakly positive by ELISA. In conclusion, a protein A/G-based ICT is a rapid, user-friendly, and efficient assay for serodiagnosis of pythiosis in humans and animals. Compared to ELISA, ICT has an equivalent detection specificity and a slightly lower detection sensitivity.

An initial survey of 150 horses from Thailand for anti-Pythium insidiosum antibodies

“…The ELISA + cutoff point was determined to be the mean EV of all tested serum samples plus 3 SDs, as previously described by other investigators [12,20,25].…”

“…All ELISA-positive sera, together with an equivalent number of randomly-selected ELISA-negative samples, were tested for the presence of anti-P. insidiosum antibodies by ICT [12] and Western blot analysis [20]. The positive and negative control sera were tested in parallel.…”

“…Direct contact with P. insidiosum can initiate the deadly condition called pythiosis [1,2,[8][9][10]. Laboratory tests are required to make a de nitive diagnosis of pythiosis [1,[10][11][12]. Early and proper treatment may substantially improve the clinical outcomes for pythiosis patients [1,2,10].…”

“…The relative paucity of reports of animal pythiosis in Thailand may result from under-recognition and under-diagnosis of the disease. To acquire evidence on the exposure of animals to the pathogen, we surveyed serum anti-P. insidiosum antibodies in 150 horses distributed across Thailand, using 3 established serological tests: a protein A/G-based enzyme-linked immunosorbent assay (ELISA); a protein A/G-based immunochromatographic test (ICT); and Western blot analysis [11,12,20]. This study is a rst step leading to a better understanding of the epidemiology of animal pythiosis in Thailand.…”

Protein A/G-based enzyme-linked immunosorbent assay for detection of anti-Pythium insidiosum antibodies in human and animal subjects

“…insidiosum antibody in humans and other animals. The assay relied on the use of protein A/G, which is a molecule that can bind the immunoglobulins from various animal species [16].…”