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Identifying Gram positive rods from equine uterine samples

Ringley, Magdalen Mae
Mass spectrometry (MALDI-TOF) has become one of the most common tools for identifying bacteria in diagnostic laboratory specimens. However, identification of unknown organisms is only possible if the protein profile exists in the database. Although the database is extensive there are some organisms that continue to provide challenges in identification. Our laboratory has experienced a challenge in identifying Gram positive organisms, particularly from equine uterine samples. The goal of this study was to identify these bacteria, whose protein profiles were not well represented in the Bruker database. Forty-eight isolates from equine uterine samples submitted to the Wyoming State Veterinary Laboratory (WSVL) between June 2018 to September 2020 were maintained frozen. All were identified as Gram-positive rods, with low or no MALDI scores to profiles in the existing database. The isolates were sub-cultured, MSP profiles were created for our local MALDI database, and DNA extracted for whole genome sequencing. The MSP profiles for each isolate were used to create a dendrogram, and a minimum of one isolate from each branch was targeted for whole genome sequencing. We hypothesized that unidentified Gram-positive rods would be in the same genus of bacteria, however preliminary sequencing results indicate that there are at least three distinct genera. These include Cutibacterium, Corynebacterium, and Arcanobacterium. All are now associated with MSP profiles in our expanded database and will aid in more efficient identification of Gram-positive rods in future WSVL diagnostic samples.
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University of Wyoming Libraries
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gram positive bacteria,bioinformatics pipeline,Bacteria Identification,Bacteriology,MALDI mass spectrometry data,Cutibacterium spp,Arcanobacterium spp,Corynebacterium spp,Diagnostic Efficiency
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