Neisseria sicca: A Rare Cause of Bacterial Conjunctivitis

Background

Neisseria-associated conjunctivitis is a rare cause of bacterial conjunctivitis in adults, with Neisseria gonorrhoeae as the primarily identified infectious strain. Here, we present a rare case of bacterial conjunctivitis due to Neisseria sicca in a 34-year-old man with no prior medical or ocular history. Our patient presented with ocular pain, copious discharge, and erythema consistent with the more commonly seen Neisseria gonorrhoeae, although without a socio-sexual history consistent with this infection. The patient was empirically treated, and cultures revealed the much rarer Neisseria species. This is the second reported case of Neisseria sicca conjunctivitis, and the first reported case to have corneal involvement [1].

Case Report

The patient presented to our Emergency Department with left periorbital edema, ocular pain, and copious ocular discharge. As per the patient’s self-report, symptoms began 3 days prior to hospital presentation, with foreign-body sensation, and progressed to ocular erythema, edema, and purulent discharge by the next day. He reported subjective fever, and denied sick contacts, ocular trauma, and sinusitis. He endorsed monogamous, unprotected sexual activity with his wife. Visual acuity on initial presentation was 20/30-2 OD and 20/50 OS. On slit lamp biomicroscopy, the patient’s left eye had eyelid edema, diffuse conjunctival injection, and chemosis, with frequent re-accumulation of mucopurulent material (Figure 1). The right eye was within normal limits. There were no conjunctival adhesions, corneal epithelial defects, corneal ulceration, or corneal thinning seen on initial presentation.

Bacterial conjunctivitis was suspected due to the rapidity of onset and purulence. Neisseria species was high in the differential diagnosis because of the severity and clinical presentation, despite the patient’s self-reported sexual monogamy. Ocular cultures were taken and preliminary results grew gram-negative diplococci. Complete blood count and HIV testing were also performed and results were within normal limits. The patient was treated with intramuscular ceftriaxone for suspected gonococcal infection and oral azithromycin for chlamydia coverage, was started on moxifloxacin eye drops every 2 h, and was advised to perform saline irrigation at home.

One day following treatment, the patient showed interval improvement with decreased chemosis, discharge, and increased overall comfort. With the interval reduction of conjunctival chemosis, a peripheral 1 mm by 2 mm sickle-shaped corneal epithelial defect with thinning was revealed (Figure 2). Given the overall clinical improvement, the patient was given a second dose of intramuscular ceftriaxone, advised to protect the cornea with an eye shield, and maintained daily monitoring as an outpatient. The patient had continued improvement with full resolution of keratoconjunctivitis over 1 week. The final eye culture resulted Neisseria sicca/subflava species. Cultures were performed with the Rapid ID NF test (produced by Remel). Susceptibility studies were not performed.

Discussion

Neisseria-associated conjunctivitis as a whole is an uncommon occurrence in adults; it is more commonly associated with neonates, with transmission occurring via transference from mothers during vaginal delivery [2]. More common causes of bacterial conjunctivitis in adults include staphylococcal species, Streptococcus pneumoniae and Haemophilus influenzae [3]. However, hyperacute bacterial conjunctivitis with the presence of ocular pain and edema, as in our patient, is more consistent with the rarer Neisseria gonorrhoeae ocular infection. Among Neisseria species, Neisseria sicca conjunctivitis is exceedingly rare. Neisseria sicca is a known colonizer of the human nasopharynx, and is a known opportunistic pathogen in immunocompromised hosts [4]. Neisseria sicca is rarely identified to be pathogenic in immunocompetent hosts. To date, there is only 1 other reported case of Neisseria sicca-associated conjunctivitis, in which a 79-year-old woman with no prior ocular history also presented with left eye purulence and injection, and was successfully treated with netilmicin eye drops [1]. In comparison to our patient’s case, the disease onset and course were less severe, limited to conjunctivitis without corneal involvement, and responded to topical treatment alone.

Conclusions

Overall, this case highlights how the traditionally non-pathogenic strains of Neisseria subspecies can be associated with pathogenicity in immunocompetent hosts, and its ocular manifestations can present with a range of features. Any case of bacterial conjunctivitis with severe features, regardless of sexual history or other risk factors, should be treated with a high suspicion for Neisseria species.