Isolation and identification of nontuberculous mycobacteria from foods as possible exposure sources

A variety of foods collected from local supermarkets and produce stands wer e examined as possible sources of nontuberculous mycobacterial exposure. Fo od samples were combined with sterile ultrapure water and manually shaken. To remove large particles, the suspensions were filtered through a sterile strainer, centrifuged, and the supernatants were discarded. The food pellet s were stored at -75 degrees C. The pellets were treated with either oxalic acid or sodium hydroxide-sodium citrate solutions to reduce contamination by nonmycobacterial organisms. Decontaminated pellets were cultured on both Middlebrook 7H10C agar and Middlebrook 7H10C agar with supplemental malach ite green. Plates were observed for growth at 2 and 8 weeks. Isolates demon strating acid-fastness were identified to species using polymerase chain re action and restriction enzyme analysis. Nontuberculous mycobacteria (NTM) w ere recovered from 25 of 121 foods. Six different species of NTM were isola ted, the most predominant being Mycobacterium avium.