Molecular Identification and Susceptibility Pattern of ClinicalNocardiaSpecies: Emergence ofNocardia crassostreaeas an Agent of Invasive Nocardiosis

Abstract

BACKGROUND:Nocardiaspecies are rare, opportunistic organisms that cause disease in both immunocompetent and immunocompromised individuals.OBJECTIVE: To investigate the clinical presentations of variousNocardiainfections based on the 16S ribosomal RNA gene of the isolate, as well as related risk factors and susceptibility patterns to antimicrobial agentsMETHODS: Thirteen patients with a diagnosis of nocardiosis were included in the present study. SevenNocardiaspecies were identified by 16S ribosomal RNA. Susceptibility testing was performed using six antimicrobial agents.RESULTS: Five patients were immunocompromised, and eight were immunocompetent with predisposing factors including cystic fibrosis, tuberculosis and ophthalmic infections.Nocardiacaused pulmonary infections in eight patients (61.5%), invasive systemic infections in three patients (23%) and local (ophthalmic) infections in two patients (15.4%). In the patients with pulmonary disease, nocardiosis was caused by six species (Nocardia cyriacigeorgica,Nocardia otitidiscaviarum,Nocardia farcinica,Nocardia carnea,Nocardia testaceaandNocardia asiatica). The seventh species identified in the present study wasNocardia crassostreae.DISCUSSION:N crassostreaeis a multidrug-resistant organism that was reported to be an emerging human pathogen causing invasive nocardiosis in a patient with non-Hodgkin’s lymphoma.N farcinicawas isolated from blood in a patient with breast cancer. None of theNocardiaisolates were resistant to linezolid. OneN otitidiscaviarumisolate was a multidrug-resistant organism. All patients in the present study were treated with the appropriate antibiotics and their condition resolved without further sequelae.CONCLUSIONS: The present study is the first report onN crassostreaeas a human pathogen. The detection of multidrug-resistant species necessitate molecular identification and susceptibility testing, and should be performed for allNocardiainfections. Nocardiosis manifests various clinical features depending on theNocardiaspecies and underlying conditions.