Epidemiology, clinical treatment and outcomes, susceptibility patterns and genotypic analysis of 214 Nocardia strains from multiple centers in Henan Province

Objectives This study aimed to investigate the epidemiology, clinical treatment and outcomes, antimicrobial resistance profiles and genotypic analysis of 214 Nocardia strains collected from 9 hospitals in Henan Province spanning 9 years. Methods Through retrospective analysis of hospitalized patients with nocardiosis, the epidemiological characteristics of 214 Nocardia strains were elucidated. These isolates were identified and subjected to the broth microdilution method for the antimicrobial susceptibility profiles, and the resistance and virulence genes were determined using whole-genome sequencing (WGS). Results Of all strains, 74.8% were collected from lower respiratory tract specimens, and N. cyriacigeorgica was the most commonly isolated species (28%), followed by N. farcinica (24.8%), N. abscessus (7.9%), N. amamiensis (7.9%), N. otitidiscaviarum (7.5%). 93.9% were obtained from in-province patients, and Nanyang City (28.0%) was with the highest isolation rate in Henan Province. Simultaneously, all of the strains were susceptible to linezolid (LZD), and 99.1% susceptible to trimethoprim-sulfamethoxazole (TMP-SMX). The antibiotic resistance profiles of other antibiotics varied tremendously among different Nocardia species. Of all the patients, 108 (50.7%) received TMP-SMX monotherapy or multidrug regimen; moreover, 182 (85.5%) patients recovered after treatment. Notably, 12 antibiotic resistance genes and 11 virulence genes were identified, implicating the complexity of resistance and pathogenicity mechanisms. Meanwhile, the MDR rates for Nocardia species ranged from 68.8% in N. otitidiscaviarum to 17.7% in N. amamiensis. No strains exhibited the XDR and PDR phenotypes. Conclusion This study provides a comprehensive evaluation of the epidemiology, phenotypic and genotypic profiles, and clinical treatment of Nocardia species in Henan, China. TMP-SMX and LZD can be used respectively for the clinical routine and critical treatment of nocardiosis. Particular emphasis is placed on the fact that antibiotic resistance and pathogenicity are species - specific, therefore, the AST of Nocardia isolates should be conducted and standardized, and attempts should be made to monitor its resistance molecular mechanisms.