Nocardia asteroides is a widespread soil organism, capable of causing opportunistic human disease.1·2 Nocardia has been reported as a rare cause of keratoconjunctivitis, corneal ulcer, or endophthalmitis in adult patients.3'6 Pediatrie infections caused by this organism, and particularly ocular infections, are very uncommon.7 We wish to describe the occurrence of a corneal abscess caused by Nocardia asteroides in a young child that developed after a penetrating ocular injury.
A 5-year-old boy presented to the ophthalmologic emergency room shortly after being struck in his right eye by the thorn of a palm tree. On examination the left eye was intact. The visual acuity in the right eye was hand motion with full light projection. Pathologic eye findings included conjunctiva! injection., a 5-raillimeter corneal perforation, and a total hyphema in the anterior chamber. The patient underwent suturing of the cornea and in the following days the hyphema reabsorbed and the fimdus appeared normal. The patient was discharged on dexametdaeone, gentamicin, atropin, and indometacin drops four times a day.
On the follow-up examination, a normal healing process without pain was observed, the visual acuity was count fingers at 2 m, and cells were detected in the anterior chamber. Administration of local steroids and antimicrobials were continued.
Four weeks after the cornea was sutured, the patient presented with a painful photophobic right eye. Examination revealed a corneal ulcer with a 3-millimeter intrastromal corneal infiltrate (Fig 1). Corneal scrapings were taken for microscopy and culture, and the sutures in the infected area were removed. The patient was given a subconjunctival injection of gentamicin and cefàmyzine, and also the same two medications were given by way of drops hourly. Corneal scrapings showed multiple branchings, beaded gram positive rods, suggestive of a Nocardia species (Fig 2). The organism grew in pure culture on routine solid media after 48 hours of aerobic incubation. The organism was nonmotile and weakly acid fast by the modified Ziehl Neelsen stain. It hydrolyzed urea but it did not hydrolyze caseine, tyrosine, xanthine, starch, gelatin, or esculin. It reduced nitrate and produced acid from glucose, but not from other carbohydrates, including lactose, mannitol, maltose, sorbitol, inositol, and trehalose. Biochemical reactions identified the recovered organism as Nocardia asteroides.
The patient was treated with topical trimethoprimsulfamethoxazole hourly from the commercial intravenous solution (trimethoprim, 16 mg/mL and sulfamethoxozole, 80 mg/mL) and oral trimethoprim-sulfamethoxazole (160/ 800 mg) twice daily. Despite this therapeutic regimen the infiltrate enlarged and the cornea became thinner in the area of the ulcer. Because of the danger of imminent perforation, a corneal graft was performed. The eye became stable, the pain resolved, and a bactériologie culture taken from the anterior chamber was sterile. The patient was discharged and systemic and local treatment with trimethoprim-sulfamethoxazole were continued for 6 weeks.
Six months after the corneal graft was carried out, the visual acuity was 6/21 and the corneal graft appeared clear.
Nocardiae are aerobic, nonencapsulated, nonsporeforming, partially acid-fast, gram-positive bacilli of the order Actinomycetes.1 Nocardiae species are distributed widely in the environment and live in soil and composting vegetation, only accidentally infecting humans.2
Nocardia enters the body by inhalation or by direct inoculation to the skin following trauma. A localized pulmonary or subcutaneous tissue infection usually follows. Bloodborne dissemination of the organism with development of metastatic lesions in the central nervous system, eyes, or bone may occur, especially in immunocompromised hosts.2 In addition, direct involvement of the eye has also been described following accidental trauma or surgery, causing keratitis, corneal ulcer, and endophthalmitis.3-6
Over the years, the sulfonamides alone, or in combination with trimethoprim, have remained the recommended standard drug therapy for human nocardiosis. Sulfonaraide treatment should be continued for at least 6 weeks after the disease has completely cleared.8·9 Recent in vitro studies suggest that doxycycline and amoxicillinclavulanic acid may be potentially useful in the treatment of human nocardiosis.8'9 It should be noted, however, that antibiotic susceptibility testing of Nocardiae is technically difficult and in vitro results may not be reliable predictors of clinical response.
FIGURE 1: 3 x 3-millimeter intrastromal corneal infiltration with white-yellowish discharge.
Nocardiae are a rare cause of pediatrie disease.7 A comprehensive review of the literature covering the 1895 to 1982 period found 51 pediatrie cases, of which only 3 had ocular involvement.7 In the patient herein described, slow, relentless enlargement of the corneal abscess was observed, despite administration of antimicrobial therapy. It is highly probable that Nocardia organisms were inoculated directly into the corneal epithelium by the soil-contaminated palm tree thorn. Local corticosteroid therapy and the presence of corneal sutures possibly added to the progression of the infection and thinning of the cornea, which ultimately required an emergency corneal transplantation. Identification of the organism as a Nocardia species resulted in modification of the therapeutic regimen and administration of specific antimicrobials, which apparently contributed to the control of the infection and the success of the corneal graft.
FIGURE 2: Gram's stain of corneal-scrapping specimen showing thin, gram-positive rods, suggesting Nocardia species.
Nocardiae are rarely responsible for ocular infections. However, in patients with a history of penetrating eye injury caused by soil-contaminated material, who present with a slowly-progressing infection unresponsive to routine antimicrobial drugs, the possibility of nocardiosis should be kept in mind. Careful examination of corneal scraping specimens and performance of bacteriological cultures are mandatory to establish the correct diagnosis and administer adequate antibiotic therapy.
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2. Beaman BL, Buraside J, Edwards B, Causey W. Nocardial infection in the United States, 1972-1974. J Infect Dis. 1976; 134:286-289.
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