Tracheal microbial populations in horses with moderate asthma

Abstract

Background There are limited data on potential dysbiosis of the airway microbiota in horses with asthma. Hypothesis/Objectives We hypothesized that the respiratory microbiota of horses with moderate asthma is altered. Our objectives were (a) to quantify tracheal bacterial populations using culture and qPCR, (2) to compare aerobic culture and qPCR, and (c) to correlate bacterial populations with bronchoalveolar lavage fluid (BALF) cytology. Animals Eighteen horses with moderate asthma from a hospital population and 10 controls. Methods Prospective case‐control study. Aerobic culture was performed on tracheal aspirates, and streptococci, Pasteurella multocida, Chlamydophila spp., Mycoplasma spp., as well as 16S (bacterial) and 18S (fungal) rRNA subunits were quantified by qPCR. Results Potential pathogens such as Streptococcus spp., Actinobacillus spp., and Pasteurellaceae were isolated from 8, 5, and 6 horses with asthma and 3, 0, and 2 controls, respectively. There was a positive correlation between Streptococcus spp. DNA and 16S rRNA gene (r ≥ 0.7, P ≤ 0.02 in both groups), but the overall bacterial load (16S) was lower in asthma (1.5 ± 1.3 versus 2.5 ± 0.8 × 104 copy/μL, P < 0.05). There was no association between microbial populations and clinical signs, tracheal mucus or BALF inflammation. Conclusions and Clinical Importance This study does not support that bacterial overgrowth is a common feature of chronic moderate asthma in horses. Lower bacterial load could suggest dysbiosis of the lower airways, either as a consequence of chronic inflammation or previous treatments, or as a perpetuating factor of inflammation.

Nicoletella semolina in the airways of healthy horses and horses with severe asthma

“…Approximately 68% of tracheal aspirates of horses yield growth in standard aerobic culture, whereas all samples are positive for 16S rRNA gene quantification. 24 Similar results are obtained when analyzing nasopharyngeal and sputum samples from humans with bronchial asthma 25 or with pneumonia. 26 The increased sensitivity of molecular methods compared to culture is further enhanced by the fact that Pasteurellaceae show limited survival outside their hosts.…”

The Role of Thoracic Ultrasonography and Airway Endoscopy in the Diagnosis of Equine Asthma and Exercise-Induced Pulmonary Hemorrhage

“…In fact, the prolonged colonization of the airways by these bacteria could be a consequence, rather than the cause, of the increased mucus accumulation in the trachea [38,41]. Moreover, the previously mentioned studies were mainly performed on young racehorses, while a recent investigation only including adult horses (over 8 years of age) observed no association between bacterial overgrowth and airway inflammation [42]. In our study, the MEA horses had more positive results to bacterial culture compared to the SEA horses.…”

Characterization of the seminal bacterial microbiome of healthy, fertile stallions using next-generation sequencing

“…This technique is more efficient for analysing microbial flora than culture-based methods, especially for hard-to-cultivate species (Zhang et al, 2016). That is why it has been used for characterizing gut microbiome (Su et al, 2020), lower respiratory tract (Manguin et al, 2020), conjunctive (LaFrentz et al, 2020. To the best of our knowledge, there is only one paper analysing the seminal microbiome in stallions with NGS technology (Al-Kass et al, 2020).…”

“…These discoveries have led to the use of probiotics as a prophylactic and sometimes therapeutic tool for some digestive conditions in the horse (Coverdale, 2016;Swyers et al 2008). These findings have opened the door to study the microbiome in new niches, such as lower respiratory tract (Manguin et al, 2020), conjunctive (LaFrentz et al, 2020) or female reproductive tract (Barba et al, 2020;Hou et al, 2013). However, little is known regarding the commensal flora of the male reproductive tract.…”