Pulmonary nocardiosis (PN) is an uncommon infection seen typically in immunocompromised (IC) patients. Definitive diagnosis depends on culture of nocardia along with a clinical presentation suggestive of PN. As nocardia species can grow slowly and mimic other infections, we investigated the performance of respiratory sampling in confirming this diagnosis.

Methods: Microbiologic data from 1994-2015 was reviewed for any expectorated sputum (ES), bronchoalveolar lavage (BAL), or tissue biopsy. Records of patients identified were reviewed for evidence of PN and analyzed. Two way ANOVA was used to assess differences among clinical sampling and culture techniques.

Results: 112 episodes of PN occurred in 109 patients; 73% were IC, most commonly due to organ transplant (30%). Sufficient data was available for 88. 49 had ES analysis. 52 underwent BAL +/- transbronchial biopsy (TBBx; 25 cases), 18 had percutaneous biopsy (PBx). Initial ES confirmed diagnosis in 63% (31/49), and increased to 76% when multiple patient ES were included. 43% (21/49) were suspected on the basis of organism morphology on direct smear (Gram, fungal or acid fast bacilli (AFB) stain)). In culture, 23% (10/44) were positive by bacterial, 71% (12/37) by fungal, 50% (30/37) by AFB. Of 52 patients with BAL, 23% (12/52) had a suspected diagnosis by smear, with diagnosis by culture in 77% (40/52); 15/47 (32%) positive on bacterial, 35/48 (73%) on fungal, 8/50 (16%) on AFB. TBBx overall sensitivity was 47% (9/19) by culture and secured diagnosis in only 2 additional patients. PBx confirmed diagnosis in 82% (14/17) by culture; 47% (8/17) had a suspected diagnosis by direct smear and 10/17, 14/17 and 4/13 in positive bacterial, fungal or AFB cultures, respectively. Diagnostic yield by ES was not statistically inferior to BAL, BAL+TBBx or PBx, but discordance between diagnostic methods was high. Diagnostic yield by fungal culture was significantly greater (p = <.05) than by bacterial or AFB.

Conclusion: PN should be suspected in the IC patient with pneumonia. In the appropriate clinical scenario, diagnostic assessment with ES and bronchoscopy or percutaneous biopsy is suggested for adequate exclusion of the disease. Fungal culture significantly increases diagnostic yield for this bacterial infection. Given possible delay in definitive diagnosis and suboptimal sensitivity of culture, development of sensitive and rapid molecular diagnostic tests is needed.

CITATION INFORMATION: Wray D, Win S, Heincelman M, Steed L, Cantey J. Diagnosis of Pulmonary Nocardiosis: A Single Center Study. Am J Transplant. 2016;16 (suppl 3).

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