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.

Assessment of eye length changes in accommodation using dynamic extended-depth OCT.

It has been suggested that accommodation induces increases in axial eye length which could contribute to the development of myopia. However, it is debated whether changes in eye length occur during accommodation as the degree of change varies widely across literature. In this study, an extended-depth optical coherence tomography (OCT) system that provides dynamic whole eye biometry was utilized to assess changes in lens thickness (LT) and axial eye length (AEL) in young subjects responding to step disaccommodation stimuli of amplitude 2D, 4D, and 6D. The decrease in lens thickness with disaccommodation was strongly correlated with stimulus amplitude. No statistically significant changes in AEL during accommodation were observed.