P017

1:Laboratory of Microbiology and Virology, University Hospital “Maggiore della Carità”, Novara, Italy; 2:Department of Infectious Diseases, University Hospital “Maggiore della Carità”, Novara, Italy

Mycobacterium nebraskense is a yellow pigmented, slow growing nontuberculous mycobacterium species with limited documented cases. M. nebraskense infections were first described in 2004 in Nebraska (from 5 patients). Only 14 additional cases have been reported in the literature, to the best of our knowledge. Here, we present our 4 cases (between 2009 and 2015) of patients who had M. nebraskense isolated from respiratory secretions: 3 were oncologic patients with solid tumours whereas 1 with acute myeloid leukemia. For all patients bronchoalveolar lavage was sent to our laboratory for mycobacteria research. All samples were first decontaminated with NAC-PACᵀᴹ Red (AlphaTec®-USA) then submitted to microscopic examination, amplification assays and cultured on solid (Löwenstein-Jensen, Becton Dickinson-BD) and liquid (MGIT 960-BD) medium incubated at 35-37°C, for 56 days. Microscopic examination, after Kinyoun staining, was negative for acid-fast-bacilli (AFB) in all four cases. The amplification test for M. tuberculosis complex (BD ProbeTecᵀᴹ) resulted negative in all cases and the culture on Lowenstein-Jensen too. In the four cases the presence of AFB in the liquid medium was detected after 32, 42, 36 and 53 days respectively. The identification of M. nebraskense was carried out with the use of the MALDI-TOF MS (Bruker). Species identification were confirmed by gene sequencing (16S rRNA). None of the patients started a treatment because of severe clinical conditions and all died few months later. The exact presentation of infection, disease progression, and treatment have not been described well, continued surveillance will be needed to determine its frequency and optimum treatment.