Human pythiosis is an emerging, life-threatening infectious disease, caused by the oomycete Pythium insidiosum. Thailand is an area where human pythiosis is endemic and the genetic blood disorder thalassemia is a predisposing factor. Patients with pythiosis present with arterial occlusions of the lower extremities, corneal ulcers, or chronic cutaneous infections. Diagnosis relies on time-consuming, relatively insensitive tests such as culture identification and immunodiffusion assay. Most patients undergo surgical removal of infected organs, and many die from the infection. Delayed diagnosis results in a poor prognosis. Here, we describe a hemagglutination (HA) test for rapid diagnosis of human pythiosis. Sheep red blood cells were coated with P. insidiosum protein extract and used in duplicated detection assays using serum samples from 33 patients with vascular (n ؍ 27), cutaneous (n ؍ 2), or ocular (n ؍ 4) pythiosis and serum samples from 289 control patients with other infectious diseases (n ؍ 77), with highly positive antinuclear antibody (n ؍ 5), with thalassemia (n ؍ 21), or with no known disorder (i.e., healthy blood donors) (n ؍ 186). Based on receiver-operating characteristic analysis, a serum titer of 1:160 was selected as the cutoff point for the HA test. Serum samples that generated HA at the cutoff titer were read as positive, while samples that did not were read as negative. Positive results were obtained with the serum samples of all patients with vascular and cutaneous pythiosis and with two serum samples from the control group. Negative results were obtained with serum samples from all ocular pythiosis patients and the 287 remaining serum samples from the control group. Sensitivity and specificity of the HA were 88% and 99%, respectively. In conclusion, the HA test for detection of anti-Pythium antibodies is a simple, rapid, and reliable test for serodiagnosis of vascular and cutaneous pythiosis.
A detection system for Legionella spp. based on the polymerase chain reaction (PCR) was used to assess the diagnostic value of PCR for the surveillance of contamination of man-made water systems by legionellas. A previously-published primer system was chosen to amplify a fragment of the 5S-ribosomal gene of Legionella spp. A total of 78 water samples from various sources were examined by PCR and culture on MWY Legionella selective agar. Fifty-seven of 78 water samples were positive by both test systems (73%), nine were positive by PCR only (11.5%), another nine were positive by culture but negative by PCR (11.5%), and three were negative by both techniques (3.8%). The PCR was inhibited when large amounts of rust were present in the samples. Culture failed to detect legionellas in samples that contained large numbers of other bacteria capable of overgrowing the legionellas. These results show that PCR is a rapid and sensitive technique for the detection of legionella contamination in water samples and that PCR and culture complement each other in monitoring of environmental water samples.
An immunodiffusion test was developed for diagnosing subcutaneous and systemic pythiosis in humans. When culture filtrate antigen (CFA) from P. insidiosum was reacted against patient and rabbit antisera, 1-5 precipitin bands occurred both in patient and rabbit antisera, and a line of identity also occurred between patient and rabbit sera. When control P. insidiosum CFA was reacted with 30 apparently normal persons, 20 Thalassemia patients, 2 candidosis and 5 aspergillosis patients, no precipitin bands were found. P. insidiosum CFA also tested with rabbit antibodies to B. dermatitidis, C. immitis, H. capsulatum, P. brasiliensis, C. albicans, M. furfur and A. fumigatus revealed no cross reactions. This test is practical, sensitive and specific.
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