Proposta de um fluxograma optimizado para a detecção de Cryptococcus sp. em amostras de líquido cefalorraquidiano no Laboratório de Microbiologia da Faculdade de Medicina

Abstract

Cryptococcus sp. is the main fungal agent causing meningitis in about 70% of cases in people living with HIV. In 2016, a prevalence of cryptococcal antigenemia of 19.4% was estimated in Mozambique in ART-naive adults with CD4 cells <200/mm3. The Microbiology Laboratory of the Faculty of Medicine (LM/FAMED) is one of the main laboratories providing diagnostic services for invasive fungal infection caused by Cryptococcus sp. in Maputo City, as it is believed that early diagnosis of the disease improves therapeutic management. However, the laboratory, after direct microscopic examination of cerebrospinal fluid impregnated with India ink, simultaneously applies two culture media, Sabouraud agar and canavanine-glycine-bromothymol blue agar, resulting in reagent waste and time consumption, considering that the two have different purposes and are interdependent. This study aimed to propose an optimized algorithm for the detection of Cryptococcus sp. in cerebrospinal fluid samples using microbiological result records from samples analyzed between January 2024 and August 2025, taking into account the accuracy of direct microscopic examination and culture techniques, considering the specific medium canavanine-glycine-bromothymol blue agar as a standard. The study took place in the Department of Microbiology of the Faculty of Medicine of Eduardo Mondlane University. Data analysis was performed using Microsoft Office Excel, where the accuracy assessment was based on diagnostic precision measures, namely sensitivity and specificity. The results were reported in tables.

In a total of 192 processed samples, there were variations in the detection of Cryptococcus sp. depending on the methodology applied. The positivity obtained through the standard culture method was 5.2% (10/192), while the direct examination with India ink showed a positivity of 13.5% (26/192). The accuracy assessment of the direct examination with India ink in relation to culture showed the following indices: sensitivity 30.0% and specificity 86.8%. Considering these results, the flowchart proposes maintaining direct examination with tinea versicolor as an initial approach, followed by culture on Sabouraud agar and confirmation on canavanine-glycine-bromothymol blue agar.