Clinical significance, antimicrobial susceptibility and molecular identification of Nocardia species isolated from children with cystic fibrosis

Nocardia is an opportunistic pathogen that causes respiratory infections in immunocompromised patients. The aim of this study was to analyze the epidemiology, clinical significance and antimicrobial susceptibility of Nocardia species isolated from eight children with cystic fibrosis. The isolated species were identified as Nocardia farcinica, Nocardia transvalensis, Nocardia pneumoniae, Nocardia veterana and Nocardia wallacei. N. farcinica was isolated in three patients and all of them presented lung affectation with a chronic colonization and pneumonia. N. farcinica showed resistance against gentamicin, tobramycin, cefotaxime, but was susceptible to trimethoprim-sulfamethoxazole and amikacin. N. transvalensis, which was isolated from two patients, showed an association with chronic colonization. N. transvalensis was resistant to tobramycin and amikacin, but susceptible to ciprofloxacin, trimethoprim-sulfamethoxazole and cefotaxime. N. veterana, N. pneumoniae and N. wallacei were isolated from three different patients and appeared in transitory lung colonization. N. veterana and N. pneumoniae were susceptible to imipenem, trimethoprim-sulfamethoxazole, amikacin, tobramycin, and cefotaxime. N. wallacei was resistant to amikacin, tobramycin, imipenem, and trimethoprim-sulfamethoxazole and susceptible to ciprofloxacin and cefotaxime. All the isolates were identified up to species level by 16S rRNA gene sequencing. The presence of Nocardia in the sputum of patients with cystic fibrosis is not always an indication of an active infection; therefore, the need for a treatment should be evaluated on an individual basis. The detection of multidrug-resistant species needs molecular identification and susceptibility testing, and should be performed for all Nocardia infections.