A Pilot Study for the Characterization of Bacillus spp. and Analysis of Possible B. thuringiensis/Strongyloides stercoralis Correlation

Abstract

Differentiating between Bacillus species is relevant in human medicine. Bacillus thuringiensis toxins might be effective against Strongyloides stercoralis, a nematode causing relevant human morbidity. Our first objective was to evaluate genomic and MALDI-TOF identification methods for B. thuringiensis. Our secondary objective was to evaluate a possible negative selection pressure of B. thuringiensis against S. stercoralis. PCR and Sanger were compared to MALDI-TOF on a collection of 44 B. cereus group strains. B. thuringiensis toxin genes were searched on 17 stool samples from S. stercoralis-infected and uninfected dogs. Metagenomic 16S rRNA was used for microbiome composition. The inter-rate agreement between PCR, Sanger, and MALDI-TOF was 0.631 k (p-value = 6.4 × 10−10). B. thuringiensis toxins were not found in dogs’ stool. Bacteroidota and Bacillota were the major phyla in the dogs’ microbiome (both represented >20% of the total bacterial community). Prevotella was underrepresented in all Strongyloides-positive dogs. However, the general composition of bacterial communities was not significantly linked with S. stercoralis infection. The genomic methods allowed accurate differentiation between B. thuringiensis and B. cereus. There was no association between B. thuringiensis and S. stercoralis infection, but further studies are needed to confirm this finding. We provide the first descriptive results about bacterial fecal composition in dogs with S. stercoralis infection.