Revisiting Nocardiosis at a Tertiary Care Institution: any Change in Recent Years?

Abstract Objective To analyze relevant changes in incidence, clinical and microbiological characteristics of nocardiosis over the last 24 years at our institution. Materials/methods We reviewed the clinical records of patients with nocardiosis (2006-2018) and compared them to our previous cohort (1995-2006). Nocardia isolates were identified by 5’-end-16S-rRNA-gene-PCR targeting the first 500bp of the gene and sequencing. Susceptibility tests were determined by broth microdilution (CLSI guidelines). Results Forty-two patients (64.3%male) with nocardiosis were evaluated in the recent cohort-COPD(51.2%), corticosteroid therapy (43.9%) and cancer (31.7%). The incidence of nocardiosis varied from 6.3 to 7.1/100,000 admissions (p = 0.62) with a decrease in HIV patients (27%vs.4.9%,p = 0.01) and SOT recipients (18.9%vs.2.4%,p = 0.01). Cases with pulmonary involvement increased (70.3%vs.90.5%,p = 0.04). Nocardia species were similar-the most common: N.cyriacigeorgica (32.4%vs.40.5%,p = 0.49) and N.farcinica (24.3%vs.14.3%,p = 0.39). Antibiotic resistance remained stable: cotrimoxazole (10.8%vs.5.7%,p = 0.68), imipenem (5.4%vs.5.6%,p = 1.0)-amikacin and linezolid-100% active. No differences were found in breakthrough-nocardiosis (21.6%vs.9.8%,p = 0.21) or related-mortality (21.6%vs.21.4%,p = 1.0). The multivariate analysis confirmed that nocardiosis caused by N.farcinica is a risk factor for poor outcome (p = 0.045). Conclusions Nocardiosis incidence remains stable, affecting mainly elderly patients with chronic respiratory conditions and those under corticosteroid treatment. Infections in HIV and SOT patients have practically disappeared. Pulmonary affection remains the most common localization. Nocardiosis caused by N. farcinica is apparently a risk factor for poor clinical outcome.