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Can Vet J. Nov 2007; 48(11): 1155–1158.
PMCID: PMC2034423

Language: English | French

Actinomyces endophthalmitis and pneumonia in a dog

Abstract

Actinomyces endophthalmitis and pneumonia were diagnosed in a young rottweiler that was presented with lethargy, weight loss, right blepharospasm, and ocular discharge. The affected eye was enucleated, and the pneumonia was treated successfully with systemic antibiotics.

Résumé

Endophtalmie et pneumonie à actinomyces chez un chien. Une endophtalmie et une pneumonie à actimoyces ont été diagnostiquées chez un jeune Rottweiler qui avait été présenté pour léthargie, perte de poids, blépharospasme droit et écoulement oculaire. L’œil affecté a été énucléé et la pneumonie traitée avec succès par antibiothérapie systémique.

(Traduit par Docteur André Blouin)

A 37.0 kg, 18-month-old, male rottweiler was presented to the veterinary teaching hospital at the Western College of Veterinary Medicine with a history of right ocular discharge, weight loss, lethargy, and anorexia. The vaccinations against infection with distemper, hepatitis, parainfluenza, parvo- and rabies viruses were current; there was no travel history; and the dog lived with 1 other healthy rottweiler on a farm in Saskatchewan.

Case description

Physical examination revealed a fever (40.4°C) and lethargy, bilateral mucopurulent ocular discharge, right conjunctival hyperemia and chemosis, and corneal edema. The neuro-ophthalmic examination was incomplete in the right eye due to the corneal edema and hypopyon that precluded visualization of the iris, pupil, and posterior segment (Figure 1). The right palpebral and oculocephalic reflexes were present; the right menace response was negative. Results from the neuro-ophthalmic examination of the left eye were normal [menace response, palpebral, oculocephalic, and direct and indirect (right > left) pupillary light reflexes]. Schirmer tear tests (Schirmer Tear Test Strips; Alcon Canada, Mississauga, Ontario) were 25 and 20 mm wetting/min, in the right and left eyes, respectively. Applanation tonometry (Tonopen XL; Biorad Ophthalmic Division, Santa Clara, California, USA) estimated the intraocular pressures at 15 and 18 mmHg in the right and left eyes, respectively. Biomicroscopic (Osram 64222; Carl Zeiss Canada, Don Mills, Ontario) examination confirmed hypopyon, diffuse corneal edema, and 1 mm of limbal corneal vascularization in the right eye. Biomicroscopic and indirect ophthalmoscopic (Heine Omega 200; Heine Instruments Canada, Kitchener, Ontario) examinations of the left eye failed to identify any abnormalities. Fluorescein staining (Fluorets; Bausch & Lomb Canada, Markham, Ontario) was completed on each cornea and examination with cobalt-blue-filtered light and a biomicroscope did not identify any stain uptake. A complete blood (cell) count revealed mild leukocytosis 17.4 × 109/L (reference range, 4.8 to 13.9 × 109/L) with a regenerative left shift, segmented neutrophils 11.48 × 109/L (reference range, 3 to 10 × 109/L), bands 0.17 × 109/L (reference range, 0.0 to 0.1 × 109/L), and a monocytosis 2.96 × 109/L (reference range, 0.08 to 1.0 × 109/L). A serum biochemical panel revealed low urea 3.3 mmol/L (reference range, 3.5 to 11.4 mmol/L), mildly elevated total protein 73 g/L (reference range, 55 to 71 g/L), low albumin (A) 22 g/L (reference range, 28 to 38 g/L), high globulin (G) 51 g/L (reference range, 23 to 37 g/L), low A/G ratio 0.43 (reference range, 0.73 to 1.49), and elevated sorbitol dehydrogenase 6.0 U/L (reference range, 0.0 to 4.0 U/L). A urinalysis revealed a specific gravity of 1.044 and 3 + protein. Blood gas analyses and clotting profile prothrombin time/partial thromboplastin times (PT/PTT) were within normal reference ranges. Thoracic radiographs indicated a large area of consolidation of the right middle lung lobe (Figure 2). The preliminary clinical diagnoses were right endophthalmitis and pneumonia. The laboratory findings were consistent with a bacterial infection. However, fungal endophthalmitis and pneumonia, and systemic neoplasia with pulmonary or intraocular metastasis were also considered as differential clinical diagnoses. To differentiate these etiologies, a transtracheal wash (TTW) and right vitreous paracentesis were completed. General anesthesia is usually recommended prior to vitreous paracentesis; however, given the presence of pneumonia and the dog’s poor systemic condition, a TTW and vitreous aspirate were attempted with only sedation and topical ocular anesthesia. An IV catheter was placed into a cephalic vein and the dog was sedated with acepromazine (Atravet; Wyeth Ayerst Canada, Guelph, Ontario), 0.06 mg/kg body weight (BW), IV, and hydromorphone (Hydromorphone HP; Sandoz Canada, Boucherville Quebec), 0.07 mg/kg BW, IV, and topical ocular anesthesia was induced with 1 drop of 0.5% proparacaine (Alcaine; Alcon Canada). The transtracheal wash and right vitreous paracentesis were completed without complications. Cytological evaluation of the TTW revealed a mixture of degenerate neutrophils, mononuclear cells, and respiratory epithelial cells. The vitreous aspirate was purulent, and cytologic examination revealed degenerate neutrophils and macrophages that contained an abundance of intracellular bacteria and were surrounded by extracellular bacteria, including long thin filaments, cocci, and short rods, which confirmed septic endophthalmitis (Figure 3). Urine, whole blood, TTW, and vitreous fluid were submitted for anaerobic/aerobic bacterial culture. Ultrasonography of the globe was considered but not completed because of the results from the cytologic examination of the TTW and the vitreous paracentesis. The diagnoses were septic endophthalmitis and pneumonia. This dog was nebulized with sterile saline, coupaged q8h, and administered ampicillin (Nov-Ampicillin; Novopharm, Toronto Ontario), 22 mg/kg BW, PO, q8h, and enrofloxacin (Baytril; Bayer, Toronto, Ontario), 10 mg/kg BW, PO, q24h, during the remainder of hospitalization to ensure broad spectrum antimicrobial therapy against the varied bacteria observed cytologically, and until results from the bacterial culture and sensitivity testing were available. Septic endophthalmitis carries a risk for ascending optic neuritis and an associated meningitis and encephalitis, if bacteria migrate proximad in the optic nerve; therefore, right enucleation was recommended. The dog was premedicated with hydromorphone (Hydromorphone HP; Sandoz Canada), 0.1 mg/kg BW, IV, and diazepam (Diazepam Inj; Sandoz, Canada), 0.2 mg/kg BW IV; general anesthesia was induced with propofol (Rapinovet; Schering Canada, Pointe Claire, Quebec), 2 mg/kg BW, IV, and maintained via inhalation isoflurane (Aerrane; Baxter, Mississauga, Ontario). The right eye was enucleated without complication via a transconjunctival approach, then immersion-fixed in buffered formaldehyde, and submitted for routine sectioning and light microscopic examination. The dog improved over the next 3 d and thoracic radiographs were repeated. A significant decrease in the area of lung consolidation was evident, and 5 d after initial hospitalization, the dog was discharged with instructions to the owner to administer ampicillin (Nov-Ampicillin; Novopharm), 22 mg/kg BW, PO, q8h for 60 d. The dog recovered completely and 1 y later has regained his body weight. Results from the culture of the TTW and the vitreous aspirate confirmed the prescence of an Actinomyces sp. The species could not be classified by the laboratory because of limited resources. The Actinomyces sp. was sensitive to the following antibiotics: amikacin, amoxicillin/clavulanic acid, ceftiofur, cephalothin, clindamycin, gentamicin, penicillin, tetracycline, and trimethoprin/sulfa, but resistant to enrofloxacin. Results from the TTW culture also revealed a few bacteria of the Acinetobacter sp.; these were sensitive to amikacin, chloramphenicol, enrofloxacin, tetracycline, and trimethoprin/sulfa, but resistant to amoxicillin/clavulanic acid, ampicillin, ceftiofur, cephalothin, clindamycin, gentamicin, and penicillin. The urine culture revealed the presence of an alpha Streptococcus sp. The Streptococcus sp. was sensitive to amoxicillin/clavulanic acid, ampicillin, ceftiofur, cephalothin, chloramphenicol, clindamycin, enrofloxacin, gentamicin, penicillin, and trimethoprin/sulfa, but resistant to amikacin and tetracycline. Bacterial growth was not apparent on blood culture. Light microscopic examination of the fixed globe revealed anterior synechiae and a corneal perforation with a rupture in Descemet’s membrane near the inferior limbus. Inflammatory debris within the anterior chamber consisted of blood, fibrin, and abundant degenerate neutrophils that occasionally contained gram-positive filamentous bacteria. The iris, ciliary body, cornea, anterior vitreous, and suprachoroid were infiltrated with moderate numbers of degenerate neutrophils, while the posterior vitreous and retina had minimal neutrophil infiltration. Light microscopic abnormalities were not detected in the lens, optic nerve, sclera and episclera, and orbital tissues. The morphologic diagnoses were an Actinomyces sp. endophthalmitis, keratitis, and corneal perforation.

Figure 1
The right eye of a young rottweiler with diffuse corneal edema, mucopurulent ocular discharge, conjunctival hyperemia, and chemosis.
Figure 2
A ventrodorsal thoracic radiograph of a young rottweiler with right middle lung lobe consolidation.
Figure 3
Cytologic smear of the vitreous aspirate. Note the degenerate neutrophils and macrophages with intra- and extracellular bacteria. (Wrights Geimsa stain, bar = 25 μm)

Discussion

Actinomycosis is usually diagnosed in middle-aged, large breed, outdoor dogs; when the skin and subcutaneous tissues are involved, it is often characterized by draining fistulous tracts, if the chest cavity is involved, pythorax (1). Actinomyces spp. are endogenous, saprophytic, gram-positive, anaerobic organisms found within the oropharynx of dogs and cats (2,3). Risk factors for an Actinomyces sp. infection in humans include dental caries, head trauma, abdominal surgery, recent tooth extraction, chronic osteomyelitis, and chronic otitis (4,5). The pathogenesis in dogs usually involves inhalation or ingestion of grass awns or penetration of skin and soft tissue by a foreign body. Once an Actinomyces sp. infects these tissues, granulomas and draining fistulous tracts develop (13,68). The cervicofacial region, pulmonary parenchyma, pleura, pericardium, retroperitoneal space, limbs, and subcutaneous tissues are the most commonly affected areas (69). Abscesses, draining fistulous tracts, and granulomas that develop can be misinterpreted as neoplasms on radiographs or ultrasonograms (1,2). The tentative diagnosis is based on cytological identification of gram-positive branching coccobacilli obtained from draining fistulas. The diagnosis is confirmed by light microscopy and anaerobic culture (10,11). However, Actinomyces spp. require anaerobic sample collection and culture. The organism’s growth is slow and to demonstrate them, several days to weeks on a plate of blood agar or enriched thioglycolate media in the presence of 5% to 10% carbon dioxide are often required (4). Sulfur granules may be seen in tissue sections and draining fistulas. These granules are composed of branching, filamentous, gram-positive bacteria surrounded by homogenous, brightly eosinophilic material known as Splendore-Hoeppli material (4,10). However, the presence of sulfur granules is not specific, and can be found with similar organisms, such as Nocardia spp. (11).

To our knowledge, this is the first report of an Actinomyces sp. endophthalmitis in a dog. It is logical to assume that the pathogenesis for this dog’s pneumonia and endophthalmitis were related. Primary intraocular infection, secondary to a penetrating corneal foreign body that induced acute endophthalmitis and septicemia, which then spread to the lung, is most plausible. There was light microscopic confirmation of a corneal perforation. Postoperative contamination of the corneal incision with an Actinomyces sp. has been reported in humans following cataract surgery (1216). Similarly, microbial contamination of the anterior chamber of dogs has been reported during cataract surgery (17,18). However, despite the marked anterior segment sepsis, most of the posterior segment of this globe was relatively spared, except for the anterior vitreous. This supports the pathogenesis of an acute endophthalmitis that originated in the cornea and anterior chamber. In contrast, the pneumonia was of longer duration and well established, based on the history, clinical signs, and radiographs. The pneumonia may have predisposed the dog to the septicemia and then the anterior uveitis and acute endophthalmitis. The pathogenesis of the endophthalmitis and pneumonia in this case remain unresolved.

All humans reported with an Actinomyces sp. endophthalmitis have been treated by vitrectomy and intravitreal and sub-conjunctival injections of antibiotics, steroids, or both, and all regained their vision following this therapy (1216). This dog’s corneal opacity precluded a vitrectomy, so an enucleation was recommended to ensure that ascending septic meningitis was precluded. A transconjunctival enucleation was recommended, as the clinical diagnosis was endophthalmitis. A transpalpebral enucleation was considered and not completed, as there was no clinical evidence of orbital involvement (exophthalmos, third eyelid prolapse). Transconjunctival enucleation is an easier and quicker surgery that leaves more orbital tissues, which then scarify and decrease postenucleation orbital sagging that is common after transpalpebral enucleation. Successful treatment of systemic actinomycosis involves prolonged (4–6 wk) administration of systemic antibiotics (13). Beta-lactam antibiotics, such as penicillin or ampicillin, are the antibiotics of choice for Actinomyces spp. infections (19). The following are other effective antibiotics: erythromycin, clindamycin, tetracycline, minocycline, doxycycline, chloramphenicol, first generation cephalosporins, and ceftrixone (19). This dog was treated with ampicillin and enrofloxacin to ensure broad spectrum coverage initially, as we were concerned of septicemia with an unknown organism. We continued to treat with enrofloxacin because of the urinary infection with streptococcus and the continued improvement during hospitalization. After the results of the cultures and sensitivity testing became available and the dog was improving rapidly and ready for discharge, the enrofloxacin was discontinued and the dog remained on therapy with ampicillin. CVJ

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