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Haemophilus influenzae is a rare cause of corneal ulceration, usually associated with previous corneal damage. To ensure appropriate treatment, the organism must first be identified by cultures in enriched media. We describe a case of keratitis caused by H influenzae associated with two risk factors—herpetic keratitis and atopic keratoconjunctivitis.
A 43 year old Hispanic male presented with 1 week of redness, blurred vision, pain, burning, and itching in the left eye. Past ocular history was remarkable for bilateral epithelial and interstitial herpetic keratitis and atopic keratoconjunctivitis with a previous shield ulcer in the left cornea. The patient was not using any medications at the onset of the current episode. He had a history of anhidrotic ectodermal dysplasia and atopic dermatitis since birth. On examination, uncorrected visual acuity was 20/100 in the left eye. The skin of the eyelids was wrinkled, thickened, and hyperpigmented bilaterally with madarosis of the lashes. The conjunctiva had a mild papillary reaction on the right and a severe reaction on the left, with giant papillae in the superior tarsal area. In the left eye, corneal sensation was markedly decreased and a central corneal epithelial defect of 1.0 × 0.5 mm was present with an underlying anterior stromal infiltrate measuring 2.5 × 1.5 mm (Fig 1). Scant keratic precipitates and a small hypopyon were also present.
Scrapings of the corneal ulcer were taken and inoculated on blood and chocolate agar as well as in thioglycollate broth. Viral cultures and polymerase chain reaction (PCR) were also performed to rule out the possibility of a recurrent herpes simplex infection. They were subsequently negative. The patient was started on ofloxacin and fortified cefazolin (50 mg/ml) drops every hour. He was also started on oral aciclovir 800 mg five times a day. On the fourth day, corneal cultures were positive with a heavy growth of H influenzae sensitive to ofloxacin (Fig 2). On the sixth day of treatment, uncorrected visual acuity improved to 20/30, the stromal infiltrate decreased to 1 × 1 mm, with a small epithelial defect, and there was no hypopyon. A supratarsal injection of dexamethasone was given and topical prednisolone acetate 1% three times a day was added. The papillae regressed and the corneal lesion healed completely, leaving a central scar with a deep stromal vessel.
H influenzae is a tiny Gram negative coccobacillus that is an uncommon cause of corneal ulceration. In most series it accounts for less than 2% of all corneal ulcers.2, 3, 5, 7, 8, 10 It is a common cause of acute bacterial conjunctivitis, especially in children.9 Unlike Staphylococcus aureus, Streptococcus pneumoniae, and other bacterial causes of conjunctivitis, H influenzae seldom produces corneal ulceration. This is in marked contrast with H egyptus ocular infections where peripheral ulcers, infiltrates, and phlyctenules are commonly seen as complications of conjunctivitis. For H influenzae to infect the cornea, there must be an epithelial defect. Most of the reported cases of H influenzae keratitis have been associated with specific risk factors such as contact lens wear, application of cyanoacrylate glue, or systemic debilitating diseases.1, 4, 6 In this case, the patient had two significant risk factors—severe atopic keratoconjunctivitis and herpetic keratitis. Despite the negative results of the viral cultures and HSV-DNA PCR, we cannot rule out the possibility that a viral aetiology played a part in this case. Also, it seems likely that complications from the patient's atopic disease, delayed the healing of the ulcer.
H influenzae is a fastidious organism that needs media enriched with nicotinamide adenine dinucleotide (NAD), such as chocolate agar for growth. It will not grow in blood agar, unless there are also colonies of Staphylococcus aureus, which provide NAD. In that situation, H influenzae will then grow as satellite colonies around the Staphylococcus aureus. This case illustrates the importance of utilising chocolate agar as well as blood agar to make an aetiological diagnosis.
In conclusion, H influenzae is a rare cause of corneal ulceration, which can occur in patients with previous corneal damage from diseases such as herpetic keratitis and atopic keratoconjunctivitis. To ensure appropriate treatment the organism must first be identified by cultures in enriched media.