Diagnostic Challenges in Nocardia Keratitis

Nocardia keratitis after small incision lenticule extraction (SMILE)

We report the case of a female patient in her late 20s who visited the clinic with concerns about poor vision, redness, watering and a burning sensation in her left eye 2 weeks after undergoing a small incision lenticule extraction. She had no history of systemic illness or immunosuppressed status. On slit lamp examination, she was found to have corneal stromal infiltrates in the interface at multiple locations. Given the clinical diagnosis of microbial keratitis, corneal scraping of the interface infiltrate was performed and sent for microbiological examination revealing gram-positive, thin, beaded filaments that were acid-fast positive and later identified by growth in culture media as Nocardia species. This case was managed successfully with the use of topical amikacin and systemic trimethoprim-sulfamethoxazole with complete resolution of infection.

A case of disseminated nocardiosis with orbital apex involvement and endophthalmitis

Nocardia is a rare cause of ocular infections and most commonly occurs secondary to trauma. Systemic Nocardiosis may have ocular involvement in rare cases. We report a case of disseminated nocardiosis with orbital apex involvement and endophthalmitis in an immunocompromised patient. The patient presented with respiratory sepsis, and later developed complete ptosis and ophthalmoplegia in the left eye. This was on the background of treatment with high-dose prednisolone. Magnetic resonance imaging showed enhancement of the entire clivus, extending into the left orbital apex and cavernous sinus. The patient was initially treated empirically for CNS tuberculosis. Bronchoscopic cultures returned positive for Nocardia farcinica, and the patient was treated with trimethoprim/sulfamethoxazole and weaned off previous corticosteroids.

Herpes simplex keratitis: A brief clinical overview

The aim of our minireview is to provide a brief overview of the diagnosis, clinical aspects, treatment options, management, and current literature available regarding herpes simplex keratitis (HSK). This type of corneal viral infection is caused by the herpes simplex virus (HSV), which can affect several tissues, including the cornea. One significant aspect of HSK is its potential to cause recurrent episodes of inflammation and damage to the cornea. After the initial infection, the HSV can establish a latent infection in the trigeminal ganglion, a nerve cluster near the eye. The virus may remain dormant for extended periods. Periodic reactivation of the virus can occur, leading to recurrent episodes of HSK. Factors triggering reactivation include stress, illness, immunosuppression, or trauma. Recurrent episodes can manifest in different clinical patterns, ranging from mild epithelial involvement to more severe stromal or endothelial disease. The severity and frequency of recurrences vary among individuals. Severe cases of HSK, especially those involving the stroma and leading to scarring, can result in vision impairment or even blindness in extreme cases. The cornea's clarity is crucial for good vision, and scarring can compromise this, potentially leading to visual impairment. The management of HSK involves not only treating acute episodes but also implementing long-term strategies to prevent recurrences and attempt repairs of corneal nerve endings via neurotization. Antiviral medications, such as oral Acyclovir or topical Ganciclovir, may be prescribed for prophylaxis. The immune response to the virus can contribute to corneal damage. Inflammation, caused by the body's attempt to control the infection, may inadvertently harm the corneal tissues. Clinicians should be informed about triggers and advised on measures to minimize the risk of reactivation. In summary, the recurrent nature of HSK underscores the importance of both acute and long-term management strategies to preserve corneal health and maintain optimal visual function.

Atypical microbial keratitis

Atypical microbial keratitis refers to corneal infections caused by micro-organisms not commonly encountered in clinical practice. Unlike infections caused by common bacteria, cases of atypical microbial keratitis are often associated with worse clinical outcomes and visual prognosis. This is due to the challenges in the identification of causative organisms with standard diagnostic techniques, resulting in delays in the initiation of appropriate therapies. Furthermore, due to the comparatively lower incidence of atypical microbial keratitis, there is limited literature on effective management strategies for some of these difficult to manage corneal infections. This review highlights the current management and available evidence of atypical microbial keratitis, focusing on atypical mycobacteria keratitis, nocardia keratitis, achromobacter keratitis, and pythium keratitis. It will also describe the management of two uncommonly encountered conditions, infectious crystalline keratopathy and post-refractive infectious keratitis. This review can be used as a guide for clinicians managing patients with such challenging corneal infections.

Nocardia infection following ocular surface surgery

OBJECTIVE

To investigate the clinical characteristics and treatment outcomes of Nocardia infection after ocular surface surgery.

METHODS

This is a retrospective study. Eight cases of culture-proven Nocardia infection, which developed within 1 month after ocular surface surgery were included. Demographics and clinical history of patients were investigated.

RESULTS

There were 8 eyes (2 left and 6 right) of 8 patients (5 males and 3 females), aged 27-65, with a median age of 52.9 years. Three cases underwent pterygium excision, three were subjected to conjunctival flap covering, and two were treated with lamellar corneal transplantation. The time interval between previous surgery and the onset of symptoms varied from 7 to 28 days (mean = 20.5 ± 7.13 days). All the cases presented grey-white infiltrates at the surgical incision site while appearing with six corneal ulcers and two conjunctival ulcers. Filaments of Nocardia were founded by confocal microscopy in two of the five cases. All responded poorly to medical therapy. Seven of the eight cases were treated with reoperation. Nocardia infection recurred in three cases after reoperation, and one was eviscerated.

CONCLUSIONS

Surgical trauma is a risk factor for ocular Nocardia infection. Nocardia infection should be suspected when secondary infection occurs in a surgical incision with an atypical clinical presentation. The use of corticosteroids may influence the efficacy of drugs. Complete removal of lesions may lower the recurrence of Nocardia infection with poor drug treatment effects.

Nocardia keratitis presenting as an anterior chamber ball of exudates and its management

A man in late 40s presented with corneal ulcer of the right eye of 1 month duration. He had a central corneal epithelial defect measuring 4.6×4.2 mm with an underlying 3.6×3.5 mm anterior to mid stromal patchy infiltrate and 1.4 mm hypopyon. Gram stain of the colonies on chocolate agar showed presence of confluent thin branching, gram-positive beaded filaments, which were positive after 1% acid fast stain. This confirmed our organism to be Nocardia sp. Topical amikacin was started but continued worsening of the infiltrate and presence of a ball of exudates in the anterior chamber, prompted the use of systemic trimethoprim-sulfamethoxazole. There was a dramatic improvement in the signs and symptoms, with complete resolution of infection over a period of 1 month.

A Case of Nocardia africana-Related Keratitis

Nocardia spp. are gram positive, aerobic, weakly acid-fast bacteria. Nocardia spp. keratitis is a rare ocular infection classically described following corneal injury or vegetative and soil exposure. However, keratitis caused by Nocardia africana had never been reported in the literature. We first reported a 70-year-old male who had a traumatic ocular injury to his left eye a month ago. With his complaint of left eye pain, reduced vision, and light sensitivity, the slit-lamp biomicroscopy showed the superficial multi-lobulated epithelial infiltration located at the inferior cornea with a positive fluorescein stain. Microscopic workup from corneal specimens demonstrated dry and chalky white colonies on blood agar and Lowenstein-Jensen media resembling Nocardia spp. The MALDI-TOF MS analyses using VITEK® MS exhibited N. africana. The corneal lesion was treated with 2% amikacin topical eye drops and responded well. The careful history-taking, precise clinical examinations, and meticulous microscopic assessment were the cornerstones of diagnosis. Definite diagnosis and timely treatment were essential to prevention of ocular morbidity in N. africana.

Case Report: First Case of Endophthalmitis Caused by an Emerging Pathogen: Nocardia huaxiensis

Nocardia endophthalmitis is a relatively uncommon form of endophthalmitis seen in clinical patients. In general, Nocardia endophthalmitis tends to carry a poor prognosis. Here, we report a 3-year-old child who was admitted to the hospital due to a rupture of the left eye. The suturing and anterior chamber formation were performed immediately. Approximately, 16 days after the operation, massive whitish plump and tufted exudates gathered in the pupil area and at the bottom of the anterior chamber, and the child was diagnosed with endophthalmitis. The infection was initially considered to be caused by fungal pathogens for that the hyphae and spores were observed in the smear. However, the isolate obtained after 4 days of culturation was identified as actinomycetes using MALDI–TOF. We further classified it as Nocardia huaxiensis by next-generation sequencing (NGS) based on the MinION platform. Amikacin and sulfamethoxazole tablets were used to control the infection and the ocular inflammation subsided gradually. Intraocular lens (IOL) implantation is planned to be performed at an appropriate future time to improve his vision. Nocardia endophthalmitis is rare and usually caused by ocular trauma or surgery. In conclusion, Nocardia huaxiensis should be considered as an emerging pathogen and deserves more attention.

The use of in vivo confocal microscopy in fungal keratitis - Progress and challenges

Fungal keratitis (FK) is a serious and sight-threatening corneal infection with global reach. The need for prompt diagnosis is paramount, as a delay in initiation of treatment could lead to irreversible vision loss. Current "gold standard" diagnostic methods, namely corneal smear and culture, have limitations due to diagnostic insensitivity and their time-consuming nature. PCR is a newer, complementary method used in the diagnosis of fungal keratitis, whose results are also sample-dependent. In vivo confocal microscopy (IVCM) is a promising complementary diagnostic method of increasing importance as it allows non-invasive real-time direct visualization of potential fungal pathogens and manifesting infection directly in the patient's cornea. In numerous articles and case reports, FK diagnosis by IVCM has been evaluated, and different features, approaches, sensitivity/specificity, and limitations have been noted. Here, we provide an up-to-date, comprehensive review of the current literature and present the authors' combined recommendations for fungal identification in IVCM images, while also looking to the future of FK assessment by IVCM using artificial intelligence methods.

Nocardia keratitis: amikacin nonsusceptibility, risk factors, and treatment outcomes

PURPOSE

To report the increasing trends in Nocardia keratitis species diversity and in vitro antibiotic susceptibility, to demonstrate contact lens wear as a risk factor, and to report visual acuity outcomes after treatment.

METHODS

A retrospective clinical case series was performed at a single academic referral center which identified 26 patients with culture-confirmed Nocardia keratitis between 2014 and 2021. A combination of conventional microbiology and molecular techniques were used to identify isolates. Antibiotic susceptibilities were determined using both commercial and in-house laboratory methods. Microbiology and electronic medical records were used to characterize patients' clinical profiles.

RESULTS

Patients' median age was 32.5 years with a 2:1 male to female ratio. Eighty-four percent (n = 21/25) of patients were diagnosed within two weeks of symptom onset. Nocardia amikacinitolerans (n = 11/26) was the most recovered Nocardia isolate among study patients. Sixty-four percent (n = 16/25) of all isolates, including all 11 N. amikacinitolerans isolates, were resistant to amikacin. All isolates were susceptible to trimethoprim sulfamethoxazole. Contact lens wear was the leading identified risk factor (n = 23/26) in this population. Median time to resolution was 44 days (n = 23, range: 3-190 days). Seventy-one percent of patients (n = 15/21) had a final visual acuity of 20/40 or better.

CONCLUSION

Amikacin resistant Nocardia isolates were the majority in the current study. Trimethoprim sulfamethoxazole may be the preferred alternative antibiotic treatment based on in vitro susceptibilities. Contact lens wear was the major risk factor for Nocardia keratitis in South Florida. Overall visual acuity treatment outcomes of patients were favorable.

Rose Bengal and Riboflavin Mediated Photodynamic Antimicrobial Therapy Against Selected South Florida Nocardia Keratitis Isolates

Purpose

To examine and compare the efficacy of in vitro growth inhibition using rose bengal and riboflavin photodynamic antimicrobial therapy (PDAT) for Nocardia keratitis isolates.

Methods

Nocardia asteroides complex, Nocardia amikacinitolerans, and Nocardia farcinica species were isolated from patients with confirmed Nocardia keratitis. Isolates were tested against three experimental groups: (1) no photosensitizer/no irradiation, (2) photosensitizer/no irradiation, and (3) photosensitizer/irradiation. Each isolate was prepared in suspension to a concentration of 1.5 × 10⁸ CFU/mL. Bacterial suspensions were mixed with water or prepared 0.1% photosensitizer solution for a final bacterial concentration of 1.5 × 10⁷ CFU/mL. Aliquots of 1 mL were plated on 5% sheep blood agar. Rose bengal and riboflavin PDAT plates were irradiated for 15 minutes with a 525- or 375-nm custom 6-mW/cm² powered light source for a total fluence of 5.4 J/cm². All experimental groups were repeated in triplicate. Plates were incubated in a 35°C non-CO₂ incubator for 96 hours and photographed. Percent inhibition was evaluated using LabVIEW-based software.

Results

All strains of Nocardia tested with 0.1% rose bengal and irradiated for 15 minutes demonstrated statistically significant inhibition of growth (P < 0.05). No other experimental groups displayed any bacterial inhibition.

Conclusions

Rose bengal is superior to riboflavin PDAT against selected Nocardia isolates. In vivo testing is warranted to investigate the utility of rose bengal PDAT for severe Nocardia keratitis.

Translational Relevance

In vitro results for three clinical strains of Nocardia support the possible use of rose bengal PDAT as a complementary treatment of Nocardia keratitis.

Nocardia keratitis mimicking superior limbic keratoconjunctivitis and herpes simplex virus

Purpose

Nocardia keratitis is a rare type of infectious keratitis and may mimic other corneal diseases and lead to delay in diagnosis. This case illustrates how Nocardia often escapes accurate diagnosis due to its insidious onset, variable clinical manifestations, and unusual characteristics on cultures.

Observation

The patient presented with an epithelial defect and superior pannus and scarring, which was misdiagnosed as superior limbic keratoconjunctivitis (SLK) and herpes simplex virus (HSV) keratitis. Repeat corneal scraping cultures, smears, and conjunctival biopsy were necessary to elucidate the diagnosis. It can be effectively treated with the intravenous preparation of trimethoprim-sulfamethoxazole 80 mg/mL (brand name SEPTRA) used topically as eye drops.

Conclusion

The diagnosis of Nocardia keratitis relies on a high clinical suspicion and a prompt corneal scraping with culture. Due to its potential for rapid resolution with early therapy, it is important to isolate Nocardia early in its disease course.

Importance

Topical amikacin had been the standard of care for Nocardia keratitis for many years. However, recently there is increasing resistance of Nocardia to amikacin. SEPTRA offers an alternative therapy. Nocardia keratitis mimics other infectious and inflammatory etiologies so rapid diagnosis and treatment is critical in the prevention of long-term complications.

Current diagnostic tools and management modalities of Nocardia keratitis

Nocardia species are an uncommon but important cause of keratitis. The purpose of this review is to discus previous published papers relation to the epidemiology, etiology, diagnosis and management of Nocardia keratitis. Nocardia asteroides is the most frequently reported from Nocardia keratitis. Pain, photophobia, blepharospasm and lid swelling are mainly clinical manifestations. Usual risk factors for Nocardia keratitis are trauma, surgery, corticosteroids, and contact lens wear. Several antibiotics were used for treatment of Nocardia infection but according to studies, topical amikacin is the drug of choice for Nocardia keratitis. Topical steroid should not prescribe in these patients. In conclusion, although Nocardia keratitis is rare, early diagnosis and treatment are essential to prevent any scar formation and preserve a good visual acuity.

Isolated Nocardiosis, an Unrecognized Primary Immunodeficiency?

Nocardiosis is an infectious disease caused by the gram-positive bacterium Nocardia spp. Although it is commonly accepted that exposure to Nocardia is almost universal, only a small fraction of exposed individuals develop the disease, while the vast majority remain healthy. Nocardiosis has been described as an "opportunistic" disease of immunocompromised patients, suggesting that exposure to the pathogen is necessary, but a host predisposition is also required. Interestingly, increasing numbers of nocardiosis cases in individuals without any detected risk factors, i.e., without overt immunodeficiency, are being reported. Furthermore, a growing body of evidence have shown that selective susceptibility to a specific pathogen can be caused by a primary immunodeficiency (PID). This raises the question of whether an undiagnosed PID may cause nocardiosis affecting otherwise healthy individuals. This review summarizes the specific clinical and microbiological characteristics of patients with isolated nocardiosis published during the past 30 years. Furthermore, it gives an overview of the known human immune mechanisms to fend off Nocardia spp. obtained from the study of PIDs and patients under immunomodulatory therapies.