Culture‐independent and dependent evaluation of the equine paranasal sinus microbiota in health and disease

Abstract

Summary Background Horses with bacterial sinusitis frequently undergo empirical treatment with antimicrobials, however, in some cases bacterial culture of the affected sinus is used to direct therapy. Data regarding which organisms are part of the commensal microbiota of the equine sinus are lacking making it difficult to interpret culture results and guide empiric antimicrobial selection. Objectives Our objectives were to describe the bacterial and fungal microbiota of the paranasal sinuses in clinically normal horses using culture‐dependent and independent approaches and to compare the bacterial culture and susceptibility patterns of normal horses with those from horses affected with primary and secondary sinusitis. Study design Experimental study and descriptive retrospective review of case records. Methods Sinus washes were collected from 23 healthy horses. Washes were submitted for routine culture and susceptibility testing and DNA was isolated for next generation sequencing of bacterial and fungal marker genes. For clinical cases of sinusitis, medical records from 2010 to 2017 were reviewed and horses diagnosed with primary and/or secondary sinusitis were included. Results The paranasal sinus cavity hosts multiple bacterial and fungal organisms. The bacterial microbiota of healthy horses consists largely of uncultivable, aerobic bacteria. While few anaerobes were isolated from normal horses, the majority of clinical cases resulted in growth of anaerobic organisms with no difference in the proportion of aerobic and anaerobic bacteria isolated from clinical cases. Main limitations Small sample size in both populations of horses and heterogeneity of the population prevent a more in‐depth analysis. Conclusions The microbiota of the paranasal sinuses of horses consists primarily of aerobic bacteria and fungal organisms, the majority of which are uncultivable via common clinical methods. Anaerobic bacteria are found in the majority of horses with clinical sinusitis. These findings suggest anaerobic bacteria are associated with sinusitis and their presence should be considered when treating horses with sinusitis.

The clinical and histopathologic effects of potentiated chlorhexidine in the upper respiratory tract of horses

“…), Aspergillus and Malassezia. 1 Many of these microorganisms coincide with those identified by conventional culture methods, including Streptococcus, Escherichia coli, Actinomyces spp., Pasteurella spp., Malassezia 2 and Aspergillus spp. 3 ; and it is accepted that commensal populations play an important role in the health of the upper respiratory tract of horses to prevent over-colonization and infection by pathogenic species.…”

“…), Actinobacteria (e.g., Mycobacterium and Corynebacterium spp. ), Aspergillus and Malassezia 1 . Many of these microorganisms coincide with those identified by conventional culture methods, including Streptococcus , Escherichia coli , Actinomyces spp., Pasteurella spp., Malassezia 2 and Aspergillus spp 3 …”

Maxillary Sinusitis by Staphylococcus aureus Infection in a Thoroughbred Gelding: Case Report

“…In Korea, S. zooepidemicus isolated from horses is sensitive to gentamicin and beta-lactam antibiotics such as penicillin, ampicillin, ceftiofur, oxacillin, and cefoxitin (6). In equine practice, primary sinusitis frequently resolves well with empirical antimicrobials (3,25). The local clinic used penicillin and gentamicin for the treatment of sinusitis in patients without antibiotic sensitivity testing.…”

“…Although sinusitis occurs infrequently, it is a clinically important disease because of difficulties in treatment and the chronic nature of the disease (18,24). Sinusitis occurs mainly in the paranasal sinuses of horses (3), and it is categorized as primary and secondary sinusitis upon its causes (9,18). Primary sinusitis is followed by an upper respiratory tract infection of the paranasal sinuses (9,18).…”

Nasopharyngeal bacterial and fungal microbiota in normal horses and horses with nasopharyngeal cicatrix syndrome

“…In people and in cattle, there is comprehensive understanding of the nasopharyngeal microbiota 8‐11 . The bacterial microbiota in equine nasal passages and sinuses is largely uncultivable, aerobic bacteria 12 . Therefore, next generation sequencing including 16srDNA and internal transcribed spacer (ITS) region offers better characterization of the nasopharyngeal bacterial and fungal microbiota as compared with traditional culture approaches 13,14 .…”