Research Article: Bacterial microbiome in the nose of healthy cats and in cats with nasal disease

Date Published: June 29, 2017

Publisher: Public Library of Science

Author(s): Elisabeth S. Dorn, Barbara Tress, Jan S. Suchodolski, Tariq Nisar, Prajesh Ravindran, Karin Weber, Katrin Hartmann, Bianka S. Schulz, Hauke Smidt.


Traditionally, changes in the microbial population of the nose have been assessed using conventional culture techniques. Sequencing of bacterial 16S rRNA genes demonstrated that the human nose is inhabited by a rich and diverse bacterial microbiome that cannot be detected using culture-based methods. The goal of this study was to describe the nasal microbiome of healthy cats, cats with nasal neoplasia, and cats with feline upper respiratory tract disease (FURTD).

DNA was extracted from nasal swabs of healthy cats (n = 28), cats with nasal neoplasia (n = 16), and cats with FURTD (n = 15), and 16S rRNA genes were sequenced. High species richness was observed in all samples. Rarefaction analysis revealed that healthy cats living indoors had greater species richness (observed species p = 0.042) and Shannon diversity (p = 0.003) compared with healthy cats living outdoors. Higher species richness (observed species p = 0.001) and Shannon diversity (p<0.001) were found in middle-aged cats in comparison to healthy cats in different age groups. Principal coordinate analysis revealed separate clustering based on similarities in bacterial molecular phylogenetic trees of 16S rRNA genes for indoor and outdoor cats. In all groups examined, the most abundant phyla identified were Proteobacteria, Firmicutes, and Bacteroidetes. At the genus level, 375 operational taxonomic units (OTUs) were identified. In healthy cats and cats with FURTD, Moraxella spp. was the most common genus, while it was unclassified Bradyrhizobiaceae in cats with nasal neoplasia. High individual variability was observed. This study demonstrates that the nose of cats is inhabited by much more variable and diverse microbial communities than previously shown. Future research in this field might help to develop new diagnostic tools to easily identify nasal microbial changes, relate them to certain disease processes, and help clinicians in the decision process of antibiotic selection for individual patients.

Partial Text

Microorganisms, including bacteria, fungi, and viruses, colonize the entire body. To understand their complex community structure, biology, and ecology, analyses of the microbial diversity of the body are important [1]. The microbiome is defined as the collection of microbes and their genomes, such as bacteria, archaea, viruses, and fungi, which can be either symbiotic, pathogenic, or commensal [2]. In humans, a subject’s microbiome is personalized but dynamic throughout the first year of life [3]. The microbiome is a metabolically active organ with the potential to influence both the physiology and phenotype of the host [4]. Most interactions between humans and their microorganisms are not disease-related [5], and instead most microorganisms live in a symbiotic relationship with their host [6]. It is known that the microbiome supports the stimulation, development, and modulation of the immune system [7]. Furthermore, it influences the structure of the mucosa and skin and prevents its host from being colonized by potentially pathogenic microorganisms [8]. However, an imbalance of the microbiome can result in damage to its host [9]. In the last decade, a number of studies have reported compositional alterations in the microbiome of the nose of healthy and diseased humans [10–28]. The development [29–31] and influence of environmental factors [32, 33] on the nasal microbiome during childhood and changes in the nasal microbiome during aging [34, 35] have also been the subject of different studies.

The present study demonstrates that the nasal microbiome in cats is much more diverse than previously reported using culture-based methods [55–58]. Sequence data revealed a high individual variability among the samples collected from cats. Although additional samples from more cats are needed to arrive at further conclusions, the results suggest that the composition of the bacterial community is influenced by age and different environmental factors. In humans, a subject’s microbiome is personalized but includes dynamic changes throughout the first year of life characterized by a greater bacterial density and decreased diversity at a young age [3]. Similarly, the present study detected differences in the nasal microbial composition of healthy cats at different ages. Because of the strong influence of age on the nasal microbial composition, this parameter was not useful to compare healthy cats with diseased cats belonging to other age groups. In this case, differences in the microbiome could not only result from the underlying disease process but would also be affected by age. This phenomenon had to be kept in mind when interpreting the nasal microbial composition of cats with FURTD in the present study because FURTD is frequently detected in kittens younger than one year of age. In contrast, cats suffering from nasal neoplasia tend to be older. Because healthy cats had to be free from clinical signs of disease, few healthy old cats were eligible to enter the study. In the present study, the age of the healthy cats, cats with neoplasia, and cats with FURTD were significantly different. Therefore, a statistical comparison of the microbiome of cats with different disease statuses status was not performed.

In conclusion, the present study revealed a large number of currently uncultivable bacteria, demonstrating that the nose of cats is inhabited by richer and more diverse microbial communities than has been previously described using culture-based methods. Furthermore, age and environmental factors seemed to influence the nasal microbial composition. Researchers are only just beginning to understand the complex interactions between the host and bacterial microbiota and the impact of disrupting this fragile homeostasis in disease states. The results of the present study represent a first step in the description of the nasal microbiome in healthy and diseased cats and the identification of intrinsic and extrinsic factors that influence the microbial composition. Future research in this field might help to develop new diagnostic tools to easily identify nasal microbial changes, relate them to certain disease processes, and help clinicians in the decision process of antibiotic selection for individual patients.