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EC22-028: Characterizing the blood microbiota in healthy and febrile domestic cats via 16s rRNA sequencing

Kitson L, Becker AAMJ, Hartmann K, Bergmann M, Sepulveda-Garcia P, Canales N, Muller A. Characterizing the blood microbiota in healthy and febrile domestic cats via 16s rRNA sequencing. Sci Rep. 2024 May 8;14(1):10584. doi: 10.1038/s41598-024-61023-4. An EveryCat Funded Study- Final Publication


The microbiome has been a recent topic of intensive investigation in both human and veterinary medicine. The advent of readily available DNA-based technologies to rapidly quantify and qualify the populations of different types of bacteria in a location has lead to a greater understanding of bacterial dynamics and their relationship with the host’s health and disease. In cats, there has been extensive investigation of the gastrointestinal, respiratory, and skin microbiome, however little investigation into the normal blood microbiota has been performed.
This EveryCat funded study used 16S rRNA gene sequencing to analyze the bacterial communities present in feline blood, and compared them to bacterial diversity in other areas (ie GI and respiratory). It also compared the distribution of bacterial flora in cats with and without fevers.

The inclusion criteria for the healthy cats in the study were having no abnormalities on physical examination, no antibiotic therapy within 30 days prior to consultation, negative tests for FIV, FeLV, Hemotropic Mycoplasma spp., and Cytauxzoon felis, a normal complete blood count (CBC), and an age between 2 months and 15 years. A total of 300 samples were collected from cats, of which 285 had sufficient DNA concentration. Bacterial phyla were investigated and reported as a dominant presence, of Actinobacteria (39.33% Firmicutes (32.02%)and Proteobacteria (24.01%) and a lower relative abundance of Bacteroidetes (2.15%). These bacterial phylla make up the main groups of concern in most microbiota studies, and so may be compared to populations in other parts of the body.

Comparisons between the blood microbiota of healthy and febrile cats revealed a predominance of Actinobacteria, followed by Firmicutes and Proteobacteria, and a lower relative abundance of Bacteroidetes in both. While no differences at phylum level were observed between healthy and febrile cats, significant differences were found in families. The families Faecalibacterium and Kineothrix (Firmicutes), and Phyllobacterium had increased abundance in febrile samples. There was no difference in the alpha or beta diversity (measures of the variability within and between different groups of bacteria) of the blood microbiota by age or sex within the healthy group. Sex and age were not significant factors affecting the blood microbiota of febrile cats nor healthy ones. Overall, the findings suggest that age, health status and nature of disease are significant factors affecting blood microbiota diversity and composition in cats, but sex is not.

This study is a preliminary investigation into bacterial diversity and changes within the blood of cats. As with many microbiome studies, this research is yet to be translated into direct clinical relevance, and the determination of whether changes in microbiota are a cause or an effect of disease is as yet unknown. Nonetheless, this provides a framework by which further investigation into the blood microbiome may be performed.

See Also
Whittle, E., Leonard, M. O., Harrison, R., Gant, T. W. & Tonge, D. P. Multi-method characterization of the human circulating microbiome. Front. Microbiol. https://doi.org/10.3389/fmicb.2018.03266 (2019).

Vientós-Plotts, A. I. et al. Dynamic changes of the respiratory microbiota and its relationship to fecal and blood microbiota in healthy young cats. PLoS ONE. 12, e0173818 (2017).

Scarsella, E., Meineri, G., Sandri, M., Ganz, H. H. & Stefanon, B. Characterization of the blood microbiome and comparison with the fecal microbiome in healthy dogs and dogs with gastrointestinal disease. Vet. Sci. 10, 277 (2023).