Rothia aeria: a great mimicker of the Nocardia species.

To cite: Saraya T, Yonetani S, Ogawa Y, et al. BMJ Case Rep Published online: [please include Day Month Year] doi:10.1136/ bcr-2014-206349 DESCRIPTION An 80-year-old man was admitted to our hospital with a 2-week history of an exaggerated productive cough. He had type 2 diabetes mellitus (glycated haemoglobin 8.1%), pancreatic cancer (cT2aN0M1, stage IB) and allergic bronchopulmonary aspergillosis (ABPA) for the past few years. He was treated with antihyperglycaemic drugs and prednisolone (10 mg/day) for ABPA. No pathogens were noted on bronchial lung washing, and his condition gradually improved. However, his sputum Gram stain newly demonstrated abundant Gram-positive filamentous bacteria (figure 1A). Furthermore, 48 h after incubation of sputum with 5% sheep’s blood agar (Eiken Chemical, Tokyo, Japan) at 37°C under 5% CO2, smooth, very small white colonies appeared and when mature they were rough, dry, folded convex and adhered to the blood agar; these were identified as Rothia aeria using Matrix-Assisted Laser Desorption/Ionisation-Time of Flight Mass Spectrometry (MALDI-Tof-MS). R. aeriawas first isolated from an air and water sampler in Russia’s Mir space station and has been detected in the mouths of healthy individuals. It can be mistaken for Nocardia spp (figure 1B, presented as control) due to the morphological similarities, and discrimination between R aeria and Nocardia spp needs further analyses, such as MALDI-Tof-MS and/or 16S rRNA. R. aeria rarely causes respiratory infections, but it should be considered in the differential diagnosis of Nocardia spp, especially in immunocompromised patients who are vulnerable toNocardia infections. Learning points