Free-living animals as carriers of Salmonella.API/MALDI-TOF correlation of isolated bacteria

Abstract

Traditionally, the usual methods of bacterial identification in clinical laboratories have been based on classical biochemical identification tests. Technological advances have allowed the development of new identification methods that have led to progress in the current methodology of microbial identification. Due to the above, in this study we set out to determine Salmonella carriers in free-living animals and to study the reliability of the API system identification by comparing the results with those obtained by applying the Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) technique. Material and Methods: In this study, 44 faecal samples from free-living animals (blackbird, ferret, puffin, North African hedgehog, gull, owl, pigeon and lizard) were analysed. To check whether they were carriers of Salmonella spp. the ISO 6579-1:2017 standard was applied. Subsequently, the isolated bacteria were identified using API commercial galleries and the results were compared with those obtained by MALDITOF MS. The correlation between both identification methods was classified as correlation in genus, correlation in species and/or no correlation. Results: The presence of Salmonella spp. in faeces of the free-living animals studied (blackbird, ferret, puffin, North African hedgehog, gull and owl) could not be evidenced, however, they did carry bacteria that could imply a health risk. Of these, the most isolated bacterium was Proteus mirabilis (18/44) which corresponded to 40.91% of the total bacteria isolated. When comparing the results obtained using the API/MALDI-TOF systems, we obtained a correlation for genus of 92.045%, and for species 87.5%. The absence of correlation was observed in 7.945% of the bacteria identified, specifically in Leclercia adecarboxylata, Photobacterium damselae and Citrobacter freundii. We observed that some bacteria isolated from the study animals could represent a One Health risk. The identification of bacterial isolates using bioMérieux API commercial galleries showed excellent correlation with those obtained by MALDI-TOF MS.