XI International Meeting on Paracoccidioidomycosis

XI International Meeting on Paracoccidioidomycosis

Resume:50-1

Poster (Painel)

50-1	Effects of inactivation or pretreatment of serum samples in the performance of latex agglutination test for the serodiagnosis of paracoccidioidomycosis (PCM)
Authors:	Fabíola Silveira Gomes (UFPA - Universidade Federal do ParáIEC - Insituto Evandro Chagas) ; Maurimélia Mesquita da Costa (IEC - Insituto Evandro Chagas) ; Elaine Patrícia Tavares do Espírito Santo (UFPA - Universidade Federal do Pará) ; Silvia Helena Marques da Silva (IEC - Insituto Evandro Chagas)

Abstract

PCM is a chronic fungal disease caused by the dimorphic fungus Paracoccidioides brasiliensis. Definitive diagnosis is made through the visualization of the fungus on patients clinical samples or the culture of the pathogen, but serological tests are frequently used as a tool for early diagnosis where immunodiffusion is a routine serological test. A latex agglutination test (LA test) was recently evaluated for the detection of anti-P. brasiliensis antibodies, but it has produced cross-reaction with patients samples with aspergillosis (ASP), histoplasmosis (HP) and other non-fungal diseases (NFD). In this study, we evaluated the effect of the inactivation or the pretreatment of PCM samples with low or non-reactivity and cross-reaction in the LA test assay previously performed.Crude exoantigen of -P. brasiliensis was used to coat the latex particles, and the test was realized mixing 25 μL of latex suspension with 25 μL of sera sample inactivated or pretreated. Samples were inactivated by incubation at 56•C/30 min and pretreated by addition of dilution buffer (qualitative test) and incubated at 37•C/30 min.In the pilot test, positive control serum (pool of sera of PCM patients) non-treated, inactivated or pretreated showed pattern 3+, whose titers were 1:16 (non-treated) and 1:8 (inactivated). No reactions were observed with samples of human normal sera. The samples of the previous work tested here were from cases of PCM (a total of 21, where 13 showing a one plus {1+}, and 8 negative), HP (1 showing a 1+), ASP (3 showing of 1+ to 2+), and NFD (11 ranged of 1+ to 3+). After inactivation, 4 PCM samples were negative and 17 were positive ranging from 1+ to 4+ (titers up to 1:64). Among the non-PCM sera, cross-reactivity with HP has been eliminated, however, 2 samples of patients with ASP showed 2+; 6 cases of NFD were reactive ranging from 1+ to 2+. No reactions were observed above 1:4. When the samples were pretreated, 3 PCM samples were negative and 18 were positive ranging from 1+ to 4+. As for the non-PCM sera, reaction of the HP sample was also eliminated, while 2 samples showed ASP 1+; 4 cases of NFD were reactive ranging from 1+ to 2+.Although the number of samples is small, we can conclude that to increase the performance of LA test it is better to use the pretreatment, because the non-specific and false-negative reactions decrease considerably.

Keyword: Increased performance, Latex Agglutination test, Paracoccidioidomycosis

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