Pulmonary infection by Nocardia spp. has been recognized for the past 100 years. The number of cases of pulmonary nocardiosis reported in the literature is increasing, and in some cases, a diagnosis is reached even postmortem. This increase is partly due to the growing number of patients with depressed cellular immunity. The diagnosis of this infection, which has a high rate of mortality, is usually delayed, due to a nonspecific clinical-radiological presentation and the difficulties in cultivating the bacteria. This review analyzes the current situation, in order to better understand this infection and enhance awareness and clinical suspicion that would lead to further specific microbiological studies and treatment.The number of case series in the literature is increasing. This development may be due to an absolute increase in the number of immunocompromised patients, but also to improvements in laboratory techniques and molecular methods to detect nocardiosis.It is important to keep in mind, and suspect the presence of pulmonary nocardiosis in the immunodepressed patients with clinical pulmonary infection. Furthermore, the laboratory should be notified when Nocardia is suspected in a clinical specimen so that measures can be taken to optimize recognition and recovery of the organism.

Pulmonary nocardiosis often occurs among immunocompromised patients, especially in those with impaired cell immunity related to AIDS and transplant. As the number of patients receiving transplant, the occurrence of pulmonary nocardiosis may also increase. Radiologic characteristics of this entity have not been well documented. In present study, CT findings of clinical confirmed pulmonary nocardiosis were retrospectively reviewed in order to understand CT features of pulmonary nocardiosis.Electronic databases of Shenzhen People's Hospital, Shenzhen, China, and the Third People's Hospital of Longgang District, Shenzhen, China were searched for patients with definitive diagnosis of pulmonary nocardiosis and available CT images. Nine patients were founded and they were included in this retrospective analysis. Clinical presentations at diagnosis and related medical history were recorded. CT images were retrospectively reviewed by two radiologists in consensus.The patients consisted of seven men and two women with a median age of 47 years (range, 20-73 years). There were three immunocompromised patients and six immunocompetent patients. The latter included two patients had history of bronchiectasis. The symptoms at the diagnosis were nonspecific of fever, cough, sputum, dyspnea, chest pain, and hemoptysis. CT findings included: lung consolidation (n=8) with cavitation in three cases and foci of decreased enhancement in one patient who had contrast-enhanced CT, nodules/masses (n=6) with cavitation in two patients, ground-glass opacity (n=4), centrilobular nodules (n=4), pleural effusion (n=4), bronchiectasis (n=4), interlobular septal thickening (n=3), interlobular reticular opacity (n=3), lymph node enlargement (n=2), halo sign (n=2) and mucoid impaction (n=1).Lung consolidation and nodules/masses are the most common findings, but CT findings of pulmonary nocardiosis are diverse and nonspecific. In some clinical background, such as immunocompromised patients or with some underlying lung diseases, consolidation or nodules/masses with cavitation may suggest the possibility of pulmonary nocardiosis.

Pulmonary nocardiosis is a rare but severe infection caused by Nocardia species. This study aimed at describing the clinical characteristics and prognosis of pulmonary nocardiosis.An observational, retrospective study was undertaken of patients diagnosed with pulmonary nocardiosis over a 13-year period at the Kinki-Chuo Chest Medical Center, Osaka, Japan.Seven patients with airway nocardial colonization and 59 patients with pulmonary nocardiosis were identified, one of whom had disseminated nocardiosis. Patients with pulmonary nocardiosis were predominantly male patients (73%), with a mean age of 66 (range, 15-88) years. New-onset cough and dyspnea were the most common manifestations (76%). Although 52 (88%) patients had at least one underlying pulmonary disease, most patients did not appear to be systemically immunocompromised. The predominant abnormality on chest computed tomography in pulmonary nocardiosis was airspace consolidation (52%), sometimes associated with cavitation. Multivariate Cox proportional-hazards analysis revealed the following significant and independent risk factors for overall mortality: age >68 years (hazard ratio [HR], 4.7; 95% confidence interval [CI], 1.6-14; p=0.05), pulmonary aspergillosis (HR, 8.8; 95% CI, 2.4-33; p=0.01), and trimethoprim/sulfamethoxazole (TMP-SMZ) resistance (HR, 4.3; 95% CI, 1.6-11; p=0.04).Clinicians should be aware that pulmonary nocardiosis can occur even in immunocompetent patients, especially those with an underlying pulmonary disease. In pulmonary nocardiosis, older age, pulmonary aspergillosis, and TMP-SMZ resistance are associated with increased risk of mortality.© 2013 Published by The Japanese Respiratory Society on behalf of The Japanese Respiratory Society.

The recent explosion of newly described species of Nocardia results from the impact in the last decade of newer molecular technology, including PCR restriction enzyme analysis and 16S rRNA sequencing. These molecular techniques have revolutionized the identification of the nocardiae by providing rapid and accurate identification of recognized nocardiae and, at the same time, revealing new species and a number of yet-to-be-described species. There are currently more than 30 species of nocardiae of human clinical significance, with the majority of isolates being N. nova complex, N. abscessus, N. transvalensis complex, N. farcinica, N. asteroides type VI (N. cyriacigeorgica), and N. brasiliensis. These species cause a wide variety of diseases and have variable drug susceptibilities. Accurate identification often requires referral to a reference laboratory with molecular capabilities, as many newer species are genetically distinct from established species yet have few or no distinguishing phenotypic characteristics. Correct identification is important in deciding the clinical relevance of a species and in the clinical management and treatment of patients with nocardial disease. This review characterizes the currently known pathogenic species of Nocardia, including clinical disease, drug susceptibility, and methods of identification.

Nocardia, a gram-positive bacillus with the microscopic appearance of branching hyphae, can produce considerable disease in the appropriate host. The taxonomy of Nocardia continues to evolve; more than 50 species have been described. Early recognition and effective therapy are imperative to achieve successful outcomes. Although nocardiosis typically occurs in patients with cell-mediated immunosuppressive conditions, infection may occasionally develop in immunocompetent patients as well. This review addresses the microbiology of Nocardia, risk factors for infection, clinical presentations, and management strategies.Copyright © 2012 Mayo Foundation for Medical Education and Research. Published by Elsevier Inc. All rights reserved.