From the ophthalmologic point of view, PE caused by a Nocardia species is extremely rare, even though Nocardia species are ubiquitous. In cases caused by very uncommon pathogens, the proper diagnosis and causal treatment of PE can be exceedingly difficult. An incorrect diagnosis is often assumed, and a more common pathogen of mycotic origin is then considered. Because of the delayed causal treatment in these types of cases, significant ocular morbidity, including enucleation of the eye, cannot be prevented in most cases [16, 17].
Very few cases of PE caused by Nocardia species, after a penetrating eye injury, have ever been described in the literature, and to the best of our knowledge, none were caused by Nocardia farcinica; and common injury mechanisms included penetration by a fragment of a windshield, a palm leaf, or a plastic hose [18, 19, 20]. All suggest that Nocardia can apparently grow on smooth surfaces, which fits with one explanation of our patient’s infection, i.e., the initial injury being caused by a razor blade slipping on the car windshield.
As with other infections, immunological status also plays a crucial role in Nocardiosis . This was confirmed by an extensive retrospective study of the relationship between manifestations and outcomes of Nocardia infections relative to the immunocompetence of patients. Of the at least 92 Nocardia species , the most common infectious agents were found to be Nocardia asteroids (73%), Nocardia farcinica (9%), and Nocardia brasiliensis (4%). The majority of patients (60%) were immunosuppressed. No cases of PE were described in patients without immune impairment ; however, it is noteworthy that our patient was immunocompetent.
The mechanism and exact time of the infection in our patient is not clear. During the 6 months post-injury period, the eye was calm. There were no signs of post-traumatic irritation of the eye, the corneal wound healed per primam, and no signs of inflammation were ever noted.
There are two possible explanations for the intraocular penetration of Nocardia farcinica. Our first potential explanation is that the infectious agent penetrated the eye during the primary injury and was encapsulated there, possibly around the injury to the anterior lens capsule. If so, the interval between injury and PE would be 6 months.
Compte et al. described a case in which the interval between an eye injury caused by a palm tree leaflet and the PE was two months. In addition to broad-spectrum antibiotics, the patient was also treated with glucocorticoids during the post-traumatic period, which could have prolonged the interval between the injury and PE. Nocardia kruczakiae was determined as the agent .
Rodriquez-Lozano et al. also described a long interval between the time of injury and the onset of PE. In their patient, a perforating keratoplasty was performed 5 months after the primary injury, and PE caused by Nocardia nova developed one year after the injury. Whether the PE was a consequence of the primary injury or the surgery remained unclear .
Our second potential explanation is that the infectious agent entered the eye at the time of the last corneal sutures removal. If so, this suture was not established intrastromally during the primary suture on the hypotonic eye but instead was guided through the entire thickness of the cornea and into the anterior chamber.
We think the second explanation is more likely. After verification of the pathogen, the patient was reinterviewed and stated that during the hot summer, he repeatedly swam in a natural pond, both before and after the corneal sutures had been removed. Since it is generally accepted that Nocardia is ubiquitous pathogens that can also be present in reservoirs and pools of natural water [8, 9, 10], we assume that Nocardia farcinica adhered to the sutures during swimming and the pathogen was inoculated directly into the anterior chamber during suture extraction. This hypothesis is supported by the fact that no signs of keratitis were found at the time of the anterior uveitis occurrence.
In Nocardia infections, the posterior segment is initially normal or only slightly involved. However, a large proportion of patients (75–83%) show nodules on the corneal endothelium or on the iris. The anterior smooth surface of the lens, in the lower periphery of the posterior chamber, is probably an optimal place for Nocardia species to grow . This agrees with our experience. Initially, nodular exudates began to spread on the corneal endothelium and on the surface of the lens and iris and then spread to the anterior chamber. The posterior segment was also normal.
Nocardia species cultivation is complicated. Hudson et al. described a case of PE with similar manifestations as in our patient. Even a diagnostic pars plana vitrectomy and sectoral iridectomy were performed, with the culture results of the aspirated material being negative. Ultimately, enucleation of the eye was performed, and Nocardia asteroides was found . Our approach, including intraocular surgery with sampling for microbiology, and impeccable processing of biological samples, helped us to determine the causative agent early enough to prevent further spreading of the infection and maintain BCVA 0.5.
The treatment of PE should always be combined with the intravitreal application of broad-spectrum antibiotics, and intraocular surgery since systemically administered antibiotics alone are considered ineffective . As with other cases described in the literature, our patient’s initial therapy with systemic antibiotics only, and even with antifungal drugs was ineffective. Furthermore, the PE signs accelerated after the effect of systemic and subconjunctival corticosteroids wore off.
After determining the infectious agent causing the PE and following the recommendations of the local Department of Microbiology, targeted long-term antibiotic therapy was able to stop the gradual spread of Nocardia farcinica. The surgical trauma associated with lens phacoemulsification and intraocular lens implantation caused neither early nor late exacerbation of the PE. The aqueous humor sample taken for microbiological examination was negative and confirmed long-term stabilization of the intraocular findings.
The success of the diagnosis and subsequent treatment of PE caused by Nocardia species is always based on interdisciplinary cooperation and collaboration with the Department of Medical Microbiology . Consultations on optimal sample collection and the transport of pathological material, as well as proper testing procedures, are crucial. Accurate, early detection of the infectious agent and administration of maximally effective treatments is crucial for obtaining optimal functional and anatomical results. However, our case demonstrates that even when the course and resolution are not straightforward, the final outcome and visual acuity can be very satisfactory.