Effects of Pretreating Serum Samples on the Performance of a Latex Agglutination Test for Serodiagnosis of Paracoccidioidomycosis

Abstract

b Paracoccidioidomycosis (PCM) is a fungal disease caused by Paracoccidioides brasiliensis, and Brazil is one of the principal countries where it is endemic. Diagnosis is based on the observation of budding P. brasiliensis yeast in clinical specimens from patients; however, the sensitivity of the visualization of fungi is low, indicating that serological tests are used for early diagnosis. The double-immunodiffusion test (ID) is the "gold standard" test for serology in PCM, although the execution of this test requires the availability of laboratorial infrastructure. We report the improved performance of a latex agglutination test (LAT) by pretreating 30 serum samples from PCM patients and 71 controls (histoplasmosis and aspergillosis patients, patients with bacterial infections, and normal human sera) with a dilution buffer incubated at 37°C for 30 min. The sensitivity and specificity of the LAT test in the nonpretreated samples were 73% and 79%, respectively. However, when samples were pretreated, the sensitivity and specificity of the test increased to 90%. In this study, we did not observe cross-reactivity with histoplasmosis patient sera, but some reactions to sera from patients with aspergillosis and bacterial infections were noted. Normal human sera were not reactive in our tests. These results indicate the need for the elimination of heterologous reactions so that we can adequately use this method for screening cases of PCM.

Serum antibody levels correlate with oral fungal cell numbers and influence the patients' response to chronic paracoccidioidomycosis

“…In the present study, DID was performed using the exoantigen from Pb 339 according to Camargo et al . ; we detected a predominance of low and moderate antibody levels, while no high level was found, which was consonant with previous findings …”

“…Negative serologic results cannot be used to rule out the disease. About 2–10% of chronic PCM patients show negative titres, and there are two hypotheses that could explain it: firstly, the immune system of the patient is suppressed and does not count with enough antibodies to precipitate in a DID test . In fact, there is a marked reduction in the detection of anti‐ Pb antibodies in the sera of PCM patients co‐infected with human immunodeficiency virus .…”

“…Nonetheless, variable serologic scores from chronic PCM patients may happen and are still not well understood; for instance, some Pb ‐infected patients may present negative antibody titres at diagnosis, what is surely an intriguing fact. Moreover, distinct serum antibody levels may be found among patients infected with different Pb strains .…”

Rapid Waterborne Pathogen Detection with Mobile Electronics

“…After the filtration process, 99.5% of liquid is removed from the original water sample, yielding a 200-fold enrichment in sample concentration and accelerated immunochemistry reaction rate. Traditionally, immunoagglutination is only used in a qualitative test; however, together with the narrow beam technique, immunoagglutination offers a simple, generally applicable, and non-hazardous method for fast and bacterium-specific quantitative detection [ 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 ]. More importantly, the agglutination reaction is a one-step reaction method mediated by specific reactions between antibodies immobilized on microbeads and antigens in the sample, requiring no further washing steps prior to detection.…”