Evaluation of Matrix-Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF) Mass Spectrometry for Identification of Adult Schistosoma mansoni Worms and Eggs

Abstract

Schistosomiasis, a neglected tropical disease (NTD), affects humans and leads to con siderable clinical morbidity and severe long-term sequelae. Laboratory diagnostics for Schistosoma mansoni are mainly based on microscopic identification of eggs in stool, but sensitivity varies with infection intensity. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) is the gold standard for bacterial identification in high-income countries. Here, we first evaluate the capacity of MALDI-TOF MS and our existing ‘in-house helminths’ database for the identification of S. mansoni worms and eggs. A subset of adult worms and egg samples was used to generate MALDI reference spectra, which were added to the database and evaluated by blind-test identifi cation. Subsequently, egg-free human stool was spiked with purified S. mansoni eggs and analyzed by MALDI-TOF MS. Log score values (LSVs) were employed to assess the relia bility of identification. A total of 62/90 (68.9%, 95% confidence interval (CI): 58.3–78.2%) adult samples were correctly identified. After database expansion, 90/90 (100%, 95% CI: 96.0–100%) and 59/60 (98.3%, 95% CI: 91.1–100%) were correctly identified for adult worms and purified eggs, respectively. In contrast, the analysis of 35 human stool samples spiked with S. mansoni as eggs did not yield identifiable spectra. MALDI-TOF MS can be applied for the identification of isolated adult S. mansoni worms and eggs. Further investigations and optimization are necessary before potential application to clinical samples (e.g., for egg detection in stool).