Treatment of chronic sinusitis in a horse with systemic and intra-sinus antimicrobials

Abstract

A 12-year-old Norwegian Fjord gelding was diagnosed with paranasal sinusitis as a post-operative complication of tooth repulsion surgery. The infection with inspissated purulent material persisted despite sinus trephination and lavage, and systemic antimicrobial therapy. Resolution occurred following infusion of a gelatin/penicillin mixture into the right rostral and caudal maxillary sinus.

Case description

A 12-year-old Norwegian Fjord gelding was presented to the Atlantic Veterinary College (AVC) in September 2015 for evaluation of post-surgical complications, including a 2-day history of unilateral right mucopurulent nasal discharge. In June 2015, the horse was presented to the AVC with a history of fractured maxillary cheek tooth 109 and associated periapical infection. The patient also had concurrent sinusitis; therefore, tooth repulsion under general anesthesia was performed, as it was the surgeon’s preference to explore and debride the affected sinus at the time of tooth removal. A maxillary sinus flap was created and part of the maxillary septum was removed. The tooth was repulsed, the maxillary sinus was debrided, and the alveolus was appropriately packed with methyl methacrylate (Technovit 6019; Heraeus Kulzer GmbH, Wehrheim, Germany). The patient recovered well from surgery. The patient was prescribed 10 d of trimethoprim-sulfamethoxazole (TMS) (Apo-Sulfatrim DS; Apotex, Toronto, Ontario), 25 mg/kg body weight (BW), PO, q12h, and the surgical site was flushed 3 times on consecutive days with 1.5 L of lactated Ringers solution. The patient was discharged 4 d after surgery with no evidence of sinusitis or post-surgical complications. The patient was rechecked 1 mo after surgery to have the packing material removed. At that time, the packing material appeared to be in place; however, it was not possible to remove it from the alveolus. There was no evidence of post-operative complications; therefore, the packing material was left in place.

Upon presentation to the AVC in September 2015, the patient was quiet, but alert and responsive. His temperature, pulse, and respiration were all within normal limits. A firm facial swelling that persistently indented upon application of digital pressure was evident in the region of the right rostral and caudal maxillary sinuses. The swelling was noted to be painful on palpation. Malodorous mucopurulent unilateral right nasal discharge was noted and serous ocular discharge was present in the right eye. All other physical examination findings were unremarkable. Based on the patient’s history and presenting clinical signs, the most likely differential diagnosis was paranasal sinusitis.

Further diagnostics included skull radiographs and a thorough oral examination. A fronto-maxillary radiographic projection revealed a soft-tissue opacity in the entire right rostral and caudal maxillary sinuses and moderate deviation of the nasal septum toward the left side. Latero-lateral views demonstrated fluid lines within the maxillary sinus. No fluid lines were noted in the concho-frontal sinus. The ventral conchal sinus could not be distinguished on the radiographs; therefore, its involvement at that time was unknown. Radiographic findings were consistent with the presumptive diagnosis of sinusitis. The patient was subsequently sedated in order to perform an oral examination. The ventral aspect of the packing material was evaluated and determined to be intact and appropriately positioned, and the remainder of the oral examination revealed no abnormal findings.

Trephination and sinoscopy were done to further evaluate the right rostral and caudal maxillary sinuses. A 1/2-inch (13 mm) Galt trephine was used to penetrate the bone of the right maxillary sinus at a location 4 cm rostral and 2 cm ventral to the medial canthus of the eye. Trephination revealed thickening of the maxillary bone and resulted in entry into the rostral maxillary sinus. Previous partial removal of the maxillary septum allowed for concurrent evaluation of the rostral and caudal maxillary sinuses. A flexible 9.8-mm video endoscope (EG-2990i Video Gastroscope; Pentax, Mississauga, Ontario) was introduced into the right rostral and caudal maxillary sinuses and revealed hyperemic respiratory epithelium and approximately 200 mL of purulent and inspissated purulent material (Figure 1). The caudal and rostral portions of the maxillary sinus were flushed transendoscopically with 1.5 L of sterile saline, which allowed for drainage of purulent exudate. A sample of the purulent material was collected for routine culture and sensitivity, and the sinus was flushed again with 1.5 L of sterile saline. The inspissated purulent material inhibited visualization and insertion of the endoscope through the conchomaxillary aperture, which consequently prevented evaluation of the ventral conchal sinus. The dorsal aspect of the methyl methacrylate alveolar packing material was visualized. It appeared to be intact, but complete healing with granulation tissue had not occurred. There was no evidence of feed material within the maxillary sinus. In the surgeon’s experience, the packing material can be left in place for extended periods of time without causing secondary sinusitis. Therefore, to prevent the creation of an oromaxillary fistula, the packing material was not removed. A 10-day course of TMS (Apotex), 25 mg/kg BW, PO, q12h, was initiated, as well as a 3-day course of phenylbutazone (Phenylbutazone Tablets; Dominion Veterinary Laboratories, Winnipeg, Manitoba), 2.2 mg/kg BW, PO, q12h.

Figure 1.

Endoscopic view of the right maxillary sinus, which revealed inspissated purulent material and inflamed mucosa.

The subsequent day sinoscopy revealed that a significant amount of purulent and inspissated material persisted within the maxillary sinus and little improvement had occurred from the previous day. Transendoscopic sinus lavage was performed with approximately 6 L of sterile saline. A fluid rate of 300 mL/min through the 2.8 mm insertion tube of the endoscope was used to increase the pressure of the lavage solution in an attempt to disrupt the inspissated material. However, the increased pressure of the lavage solution directed at areas of inspissated material did not result in disruption of the exudate. The procedure was repeated the following day and once again, minimal improvement was noted as a significant amount of purulent and inspissated material was still present.

Culture results revealed moderate growth of Trueperella pyogenes. This bacterium has a slow rate of growth; therefore, susceptibility testing was not performed as the results would not have been valid. Anaerobic culture was not performed, but it was assumed that anaerobic bacteria were present within the sinus due to the presence of T. pyogenes. A 50-mL gelatin/penicillin solution, for use in guttural pouch empyema, was then prepared as reported by Verheyen et al (1) and infused into the patient’s right rostral and caudal maxillary sinuses (1). The solution was prepared by combining 2 g of gelatin (household grade) with 40 mL of sterile water. The solution was heated in the microwave for approximately 20 s to dissolve the gelatin. The solution was cooled to 45°C to 50°C. A sodium penicillin solution was prepared by adding 10 mL of sterile water to 10 000 000 units of sodium benzyl penicillin G (Penicillin G; Pharmaceutical Partners of Canada, Richmond Hill, Ontario) and mixed with the cooled gelatin. The solution was dispensed into 2 syringes and placed in the refrigerator at 4°C overnight to set. Sinus lavage was performed before instillation of the gelatin/penicillin mixture into the right rostral and caudal maxillary sinuses. Sinoscopy and sinus lavage was performed 2 days following the infusion and revealed a dramatic improvement. The mucosa appeared to be less inflamed and the purulent discharge was markedly reduced compared to the previous sinoscopy (Figure 2). Another gelatin/penicillin mixture was instilled into the right rostral and caudal maxillary sinuses and 2 days later sinoscopy revealed significant improvement in that the mucosa appeared normal and there was no purulent exudate present. A final sinus lavage and infusion of the gelatin/penicillin mixture into the right maxillary sinus was done and the patient was discharged. At 6 mo after infusion of the gelatin/penicillin mixture, the patient continued to do well at home with no evidence of recurrent sinusitis.

Figure 2.

Endoscopic view of the right maxillary sinus following the first instillation of the gelatin/penicillin mixture.

Discussion

The case described in this report emphasizes complications and challenges that can be encountered during the treatment of secondary sinusitis due to tooth repulsion surgery. Therapy, which typically involves sinus lavage and appropriate antimicrobial therapy, is not always effective at eliminating the infection; therefore, additional therapy may be warranted in complicated cases. This case report describes the addition of a gelatin/penicillin mixture into the maxillary sinus as an unprecedented adjunct therapy for cases of chronic sinusitis.

Equine sinonasal disease occurs infrequently; however, it is a clinically significant disease due to difficulties in treatment and the chronic nature of the disease (2). Sinusitis is the most common disease that affects the paranasal sinuses, and it is classified as either primary or secondary and acute or chronic (2). Primary sinusitis usually results from a previous upper respiratory tract infection, whereas secondary sinusitis occurs as a consequence of another disease process (3,4). Causes of secondary sinusitis include dental disease, facial trauma, maxillary cysts, ethmoid hematomas, sinonasal neoplasia, and post-operative complication of tooth repulsion surgery (3,4).

Paranasal sinusitis, especially cases of secondary or chronic disease, can be difficult to treat, as it depends on the cause of the disease, as well as the bacteria involved (5). The most common bacterial isolates in cases of primary sinusitis are Streptococcus equi and Streptococcus zooepidemicus (5,6), whereas culture of secondary sinusitis samples generally yields a mixed bacterial population, including anaerobes (7,8). Treatment of primary sinusitis involves sinus lavage with copious volumes of sterile saline, to which a broad-spectrum antibiotic or antiseptic may be added (9). Systemic antibiotics are also commonly used in treatment of primary sinusitis, for which the choice of antibiotic is generally based on sample culture and sensitivity tests (5). However, while awaiting the culture and sensitivity results, treatment with penicillin, TMS, and/or metronidazole is recommended, as these are effective antimicrobials against the most common isolates in cases of sinusitis (3,10). Treatment of secondary sinusitis requires removal of the inciting cause, in addition to the therapies recommended for the treatment of primary sinusitis (5). In cases of chronic sinusitis, the response rate can be poor and additional therapy and surgical drainage are often required for successful treatment (5,11).

Secondary sinusitis caused by underlying dental disease typically involves tooth removal either by oral extraction, buccotomy, or repulsion (10). In this case, the patient had a fractured tooth 109, an associated periapical infection, and concurrent sinusitis; therefore, evaluation of the sinus in conjunction with tooth repulsion surgery via maxillary bone flap technique was the surgeon’s preferred treatment option. Serious complications of tooth repulsion surgery include chronic sinusitis, infection of a second tooth, bone sequestration, retained dental packing, and feed impaction (12). These complications have been noted to occur in up to 32% to 70% of cases following tooth repulsion surgery (11,13,14). Therefore, the fact that the horse in this report had paranasal sinusitis as a post-operative complication of tooth repulsion surgery was not unforeseen.

Since there was no evidence of an orosinusoidal fistula or another underlying disease on presentation, this horse was routinely treated for sinusitis, which as previously mentioned, typically relies on antimicrobial therapy and copious lavage of the affected sinus(es) (3,9). Aerobic culture results in this case showed moderate growth of Trueperella pyogenes, which to the authors’ knowledge, has not been reported as an isolate in equine sinusitis cases. However, T. pyogenes is ubiquitous, a commensal organism in the mucosa of the upper respiratory tract of animals, and an opportunistic bacterium that is often associated with pyogenic infections. Therefore, isolation of T. pyogenes in this case was not surprising (15,16). Since T. pyogenes is an opportunistic bacterium, it often contributes to disease as a secondary invader to another bacterial infection, which often includes anaerobic bacteria (15,16). Consequently, a mixed bacterial infection with an anaerobic component was assumed to be present in this case. The assumption of a multispecies infection was based on characteristics of sinusitis caused by a tooth root infection, which in this case, was most likely due to residual exudate from the horse’s previous periapical infection (3,7). Trueperella pyogenes is consistently susceptible to penicillin and has a high rate of resistance against TMS (15). Obligate anaerobic bacteria are also generally susceptible to penicillin; therefore, addition of penicillin to the treatment regimen was appropriate in this case (15). In addition, local delivery of the penicillin was considered to be the most appropriate route of administration, as it would allow for antimicrobial action at the site of infection.

Topical antimicrobial therapy in the management of chronic sinusitis in horses is much less common than systemic treatment; however, it may be warranted in cases that are non-responsive to conventional therapy (9). Topical use of antimicrobials in cases of sinusitis has been limited to the addition of antimicrobials to the lavage solution (9). This is beneficial in that it allows for antimicrobial action at the site of infection. However, since the lavage solution drains from the sinus immediately, local antimicrobial activity diminishes rapidly (9). Therefore, a technique to prolong local antimicrobial activity, such as the use of antibiotic impregnated biomaterial, would likely improve the effectiveness of local therapy (17). While antimicrobial resistance is a potential concern, the use of antibiotic impregnated biomaterial at the site of infection minimizes this risk, as it allows for prolonged drug concentrations above the minimum inhibitory concentration at the target site (17). In the case reported here, minimal improvement was noted following 3 consecutive days of transendoscopic sinus lavage and systemic antimicrobial therapy. The presence of inspissated purulent material was the primary suspected reason for treatment failure. However, ineffective antimicrobial therapy, chronic inflammation, and accumulation of purulent material in the ventral conchal sinus were also considered as possible reasons for treatment failure (6,11). Since the patient in this case was not responding to systemic antimicrobial therapy and sinus lavage, adjunctive local therapy involving antibiotic impregnated biomaterial was deemed appropriate.

In conjunction with sinus lavage and systemic TMS, the patient also received an intra-sinus antimicrobial infusion, which consisted of a gelatin/penicillin mixture. To the authors’ knowledge, a gelatin/penicillin mixture has never been locally administered into a sinus in the treatment of equine sinusitis; however, it has been used locally in the guttural pouch to successfully treat empyema (1,18). In cases of guttural pouch empyema caused by S. equi, the gelatin/penicillin mixture improved the treatment success rate due to its ability to remain in the pouches for a longer period of time than aqueous solutions (1,18). It has proven to be a useful way to achieve high concentrations of penicillin at the site of infection, while minimizing systemic absorption (1,18,19). It was therefore believed that similar effects could be achieved with its use in the case reported here, which was refractory to conventional therapies for sinusitis. Similar benefits were noted in this case, as there was complete resolution of clinical signs and there was no endoscopic evidence of sinusitis within 1 wk of initiating the topical therapy. There are no reports of adverse effects related to instillation of antimicrobials into the paranasal sinuses. In addition, no adverse effects were noted in this case, and the gelatin/penicillin mixture appears to be safe and effective in cases of guttural pouch empyema (1).

In conclusion, this report highlights the challenges that can be associated with the treatment of chronic sinusitis secondary to dental disease. Rapid culture and sensitivity testing and copious sinus lavage are essential for effective treatment. In addition, the use of appropriate intra-sinus antimicrobials may also help to improve the treatment outcome. To the authors’ knowledge, this is the first report of intra-sinus gelatin/penicillin therapy as an adjunct treatment for chronic sinusitis. This therapy may represent a unique additional therapy for complex sinusitis cases involving susceptible bacteria.