Anaerobic orbital cellulitis and septicemia in a dog - NCBI

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Anaerobic orbital cellulitis and septicemia in

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B. Keith Collins, Cecil P. Moore, Richard R. Dubielzig, William R. Gengler A four-year-old, 37 kg, intact male German Shepherd dog was referred to the University of Wisconsin Veterinary Medical Teaching Hospital for evaluation of episodic left periorbital swelling. The owner stated that the dog had suffered blunt trauma to the head one month prior to the first episode, but the circumstances were unclear. Three episodes of diarrhea, followed by gradual swelling of the periorbital region, had occurred at two month intervals. Mild protrusion of the globe and pain upon opening the mouth were also noted. In each occurrence, clinical symptoms temporarily subsided with oral ampicillin (Warner Chilcott Laboratories, Morris Plains, New Jersey, USA) (27 mg/kg, ql2h) and prednisone (Schein Pharmaceuticals, Inc., Port Washington, New York, USA) (0.5 mg/kg, ql2h) initially, followed by a reduction of the prednisone dosage by one-half at three day intervals. The total duration of therapy in each occurrence was ten days. The dog had marked left periorbital swelling which precluded detailed ophthalmic examination. Blepharedema, chemosis, and scant serosanguineous ocular discharge were noted and were consistent with orbital cellulitis. Pitting edema was present along the left side of the muzzle. The right eye was normal. Pain was elicited when the dog's mouth was opened for examination. Physical examination was otherwise unremarkable except for splenomegaly. The rectal temperature was 38.9°C. Diagnostic evaluation included a complete blood count (CBC), serum biochemistry profile, and urinalysis. The CBC revealed a white blood cell (WBC) count of 14 x 109/L with a mild neutrophilia. Serum alanine amino transferase (ALT) was elevated (198 U/L, normal range = 4-66 U/L). Remaining test results were unremarkable. Because prior therapy with ampicillin had only transiently resolved the problem, oral

sulfadiazine/trimethoprim (Tribrissen, Wellcome Animal Health Division, Burroughs Wellcome ComCan Vet J 1991; 32: 683-685

Department of Surgical Sciences (Collins, Moore) and Department of Pathobiological Sciences (Dubielzig), School of Veterinary Medicine, University of Wisconsin, Madison, Wisconsin, USA 53706; Animal Clinic of Verona (Gengler), Verona, Wisconsin, USA 53593. Present address of Dr. B.K. Collins and Dr. C.P. Moore: W227 University Teaching Hospital, University of Missouri, Columbia, Missouri, USA 65211. Can Vet J Volume 32, November 1991

pany, Kansas City, Missouri, USA) was prescribed (15 mg/kg, ql2h). By the next morning, the dog's temperature had increased to 41.1 °C. Tachycardia (140/min) and rapid respirations (60/min) were present. A scant mucopurulent discharge was visible at the left nares. Cytological evaluation of the nasal exudate revealed moderate numbers of degenerate neutrophils and a few bacteria. The periorbital swelling was more pronounced, the area was painful to the touch, and there was edema of the entire face, muzzle, and proximal cervical region. Attempts to identify an orbital abscess by digital palpation and fine needle aspiration of the periorbital region were unsuccessful. A second CBC was unremarkable. Aseptically collected blood samples were placed in separate containers of Columbia broth (Vacutainer, Becton Dickinson Vacutainer Systems, Becton Dickinson and Company, Rutherford, New Jersey, USA) and were submitted for aerobic and anaerobic bacterial culture. Buffered aspirin (Ascriptin, William H. Rorer Inc., Fort Washington, Pennsylvania, USA) (17 mg/kg, PO single dose) was administered as an antipyretic; the fever decreased to 39.5°C within four hours. Sulfadiazine/trimethoprim was discontinued and aqueous ampicillin (Polyflex, Bristol Laboratories, Division of Bristol-Myers Company, Syracuse, New York, USA) was initiated (20 mg/kg, SC q8h). Dexamethasone (Dexasone, Tech America Group, Inc., Elwood, Kansas, USA) was administered (0.1 mg/kg IM single dose) to decrease facial and periorbital

swelling. Skull radiographs were taken under general anesthesia. Marked soft tissue swelling of the left orbit was observed with no bony changes. On oral examination, there was mild swelling of the buccal mucosa caudal to the upper left last molar tooth. The mucosa was incised and retrobulbar drainage attempted. Although no exudate was present, a firm lobular mass, suspected to be zygomatic salivary gland, was observed to extrude through the incision. Because of the gland's abnormally caudal location, it was biopsied to rule out the possibility of neoplasia or infection. Surgical exploration of soft tissue overlying the left frontal bone revealed a pocket of purulent exudate. Aerobic and anaerobic bacterial cultures of the exudate were collected using commercially available swabs (Culturette, Becton Dickinson Microbiology Systems, Becton Dickinson and Company, Cockeysville, Maryland, USA). The pocket was flushed with a mixture 683

of sterile saline and povidone solution (Betadine, The Purdue Frederick Company, Norwalk, Connecticut, USA) and a penrose drain was installed. On digital palpation, the frontal bone was roughened, and was therefore biopsied. Postoperative therapy included ampicillin injection as administered previously and warm orbital compresses ql2h. A reduced blink reflex was anticipated postoperatively, so a neomycin/ polymyxin/bacitracin ophthalmic ointment (Neosporin, Burroughs Wellcome Company, Kansas City, Missouri, USA) was applied to the left eye q6h to maintain corneal lubrication. Histopathological evaluation of the bone biopsy revealed necrotic areas of bone as well as suppurative inflammatory infiltrates. This was consistent with bacterial osteomyelitis. Evaluation of the biopsied tissue observed to extrude from the buccal mucosa was confirmed as normal salivary gland. One day postoperatively, facial swelling was reduced and the fever had resolved. Ampicillin was continued, and prednisone (Deltasone, Upjohn Company, Kalamazoo, Michigan, USA) was initiated (1.0 mg/kg, PO ql2h). Periorbital swelling continued to decrease, and the dog was discharged from the hospital one week following initial presentation. Oral medications included ampicillin (Omnipen, Wyeth Laboratories, Philadelphia, Pennsylvania, USA) (20 mg/kg, q8h) and prednisone (Deltasone, Upjohn Company) (0.5 mg/kg, ql2h) initially, followed by a reduction of the prednisone dosage by one-half after four days. Topical therapy of the left eye was continued. Aerobic bacterial cultures were negative, and anaerobic cultures were pending. Aerobic bacterial cultures were performed using tryptic soy agar with 50o defibrinated sheep blood and chocolate agar plates incubated at 35-37°C in 5%/o CO2 and 95%o air. An additional MacConkey plate was incubated in air at 35-37°C. Anaerobic cultures were performed using prereduced blood agar plates and thioglycollate broth in an anaerobic chamber at 35-37°C. Anaerobic bacterial isolates were identified by characteristic Gram stain and colony morphologies, differential plate media, and biochemical reactions. One reexamination nine days later, there was mild swelling of the left periorbital area. A central corneal erosion of the left eye was present secondary to a reduced blink reflex and exposure keratitis; the reduced blink reflex was attributed to continued eyelid swelling and possible disruption of terminal palpebral nerve fibers at the time of surgery. Pupillary light reflexes were normal, and the dog appeared to have normal vision. Ophthalmoscopic examination was unremarkable. Anaerobic bacterial cultures had yielded Bacteroides fragilis from the blood and orbit, Fusobacterium nucleatum from the blood, and Peptostreptococcus sp. from the orbit. Following the procedure of Wilkins and Thiel for anaerobic susceptibility testing (1), two of the bacterial isolates were sensitive to penicillin, but the Fusobacterium nucleatum was resistant to penicillin and ampicillin. All three pathogens were sensitive to chloramphenicol which then was prescribed (Anacetin, Bio-Ceutic Division, Boehringer Ingelheim Animal Health Inc., St. Joseph, Missouri, USA) (70 mg/kg, PO q8h). Prednisone and ampicillin were 684

discontinued, and topical therapy of the left eye was continued as before. On reexamination three weeks later, there was complete resolution of the periorbital swelling. The central corneal erosion had healed. Anisocoria was present with the left pupil dilated and unresponsive to direct light stimulation. The left optic papilla appeared small but had normal color, and retinal vasculature was unremarkable. Chloramphenicol therapy was continued for an additional three weeks, and the ophthalmic medication was discontinued. Skull radiographs performed eight weeks after initial examination were unremarkable. All medication was discontinued. The dog had not suffered a recurrence when reexamined one year later, but the left eye was blind. Funduscopic examination revealed a small optic papilla, attenuated retinal vasculature, and increased tapetal reflectivity consistent with optic neuropathy and/or retinal degeneration.

Three of the bacterial genera reported most often in anaerobic infections, Bacteroides spp., Fusobacterium spp., and Peptostreptococcus spp., were isolated from the orbit or blood in this case Orbital cellulitis and retrobulbar abscess are usually characterized by acute onset, variable exophthalmos, periorbital swelling, fever, and pain. We refer the reader to a recent review (2) for differential diagnoses of exophthalmia. Commonly cited causes of orbital cellulitis/abscess include trauma, foreign body penetration through the oropharynx or facial skin, abscessation of the molar teeth, sinus infection, and hematogenous spread from other locations (2). Foreign bodies which penetrate the buccal mucosa are perhaps most often implicated, but they are seldom identified (3). Anaerobic orbital infection secondary to foreign body penetration from the oropharynx is plausible, as anaerobes are natural flora in this site. The orbit may be predisposed to anaerobic infection simply because of its proximity to the oropharynx (4,5), but reports of such infections are few (6). The present case is noteworthy because it describes a recurrent anaerobic orbital cellulitis with concurrent septicemia. In two published accounts of orbital abscess, the causative organism(s) were not identified (3,7). In a recent review of anaerobic infections, the orbit was mentioned in only one of 36 cases (6). Anaerobic infections are typically polymicrobial. Three of the bacterial genera reported most often in anaerobic infections, Bacteroides spp., Fusobacterium spp., and Peptostreptococcus spp., were isolated from the orbit or blood in this case (4-6). The relationship between orbital cellulitis and retrobulbar abscess is unclear. Although retrobulbar abscess may progress to orbital cellulitis, or vice versa, the two may occur as separate entities. Exophthalmia is typically more profound with retrobulbar abscess than orbital cellulitis. Also, surgical drainage through the buccal mucosa is more likely to yield exudate with Can Vet J Volume 32, November 1991

retrobulbar abscess, but such exudate was not observed in this case. We could not determine the inciting cause of orbital cellulitis in this dog. Septicemia may have been primary or secondary to the orbital infection, and the same may be true of the prior history of diarrhea. Radiographic studies failed to demonstrate bony orbital involvement, although histological examination confirmed osteomyelitis. Bacteria may gain access to the bone marrow through direct extension of soft tissue infection, trauma, surgical intervention, or hematogenously. Trauma has been suggested as the most common cause of osteomyelitis in domestic animals (8), and there was a history of trauma in the case reported herein. Surgical drainage is often required in anaerobic infections of tissue (5,8), as antibiotic therapy alone may be insufficient. Although a sulfonamide/trimethoprim preparation has been reported effective in vitro against anaerobes (9), a similar preparation was ineffective in this case. Ampicillin (or amoxicillin) has good efficacy in most anaerobic infections with the exception of those caused by Bacteroides fragilis and some other Bacteroides spp. The fact that a temporary or incomplete response to ampicillin was observed in this case was attributed to resistance of the Fusobacterium nucleatum, as the Bacteroides fragilis and the Peptostreptococcus sp. were sensitive to penicillins. Chloramphenicol is also effective against many anaerobes (5), and susceptibility testing indicated its effectiveness against all anaerobes isolated in this case. Complete resolution of orbital cellulitis did not occur until chloramphenicol therapy was begun. The routine use of corticosteroids in the treatment of septic orbital cellulitis is controversial. Corticosteroid therapy was initiated in this case in an effort to diminish orbital inflammation and possible adverse sequelae which include impaired orbital circulation and/or necrosis, uveitis, optic neuritis or neuropathy, retinitis, and retinal detachment (2,10,11). Nevertheless, funduscopic abnormalities and visual deficits of the left eye were observed in this case. The present case emphasizes the need to distinguish anaerobic bacterial orbital cellulitis from other septic and nonseptic orbital inflammatory syndromes. Clinical recurrence is typical of sterile inflammatory syndromes which may be responsive to steroids (10,1 1). Recurrent orbital swelling characterized by an inital response to antibiotic/corticosteroid therapy may characterize deep orbital infections. Surgical exploration with biopsy of deep orbital tissues and anaerobic cultures of blood and orbital tissues were necessary for diagnosis and appropriate therapy in this case. cvJ

References 1. Wilkins TD, Thiel T. Modified broth-disk method for testing the antibiotic susceptibility of anaerobic bacteria. Antimicrob Agents Chemother 1973; 3: 350-356. 2. McCalla TL, Moore CP. Exophthalmos in dogs and cats Part II. Compend Contin Educ Pract Vet 1989; 11: 911-924. 3. Rosenthal JJ. Surgical treatment of chronic retrobulbar abscess. Vet Med Small Anim Clin 1973; 6: 663-668. 4. Dow SW, Jones RL. Anaerobic infections. Part I. Pathogenesis and clinical significance. Compend Contin Educ Pract Vet 1987; 9: 711-720. 5. Dow SW, Jones RL. Anaerobic infections. Part II. Diagnosis and treatment. Compend Contin Educ Pract Vet 1987; 9: 827-839. 6. Dow SW, Jones RL. Anaerobic bacterial infections and response to treatment in dogs and cats: 36 cases (1983-1985). J Am Vet Med Assoc 1986; 189: 930-934. 7. Koch SA, Buell BE. Medial orbital abscess in a collie dog. J Am Vet Med Assoc 1970; 156: 1905-1906. 8. Walker RD, Richardson DC, Bryant MJ, Draper CS. Anaerobic bacteria associated with osteomyelitis in domestic animals. J Am Vet Med Assoc 1983; 182: 814-816. 9. Indiveri MC, Hirsh DC. Susceptibility of obligate anaerobes to trimethoprim/sulfamethoxazole. J Am Vet Med Assoc 1986; 188:46-47. 10. Kennerdell JS, Dresner SC. The nonspecific orbital inflammatory syndromes. Surv Ophthalmol 1984; 29: 93-103. 11. Rootman J, Nugent R. The classification and management of acute orbital pseudotumors. Ophthalmology 1982; 89: 1040-1048.

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