A simple, efficient and cost-effective method for medium- to longterm maintenance and storage of Mycobacterium abscessus complex organisms

Abstract

Traditional culture of non-tuberculous mycobacteria (NTMs) has involved egg-based formulations (Lowenstein-Jensen medium, Ogawa Egg medium) or defined media (Middlebrook formulations), which have disadvatages of composition complexity, availability and cost. Previously, the commercial agar formulation, Standard Plate Count (SPC) agar [Yeast extract 2.5 g/L, pancreatic digest of casein 5.0 g/L, glucose 1.0 g/L, agar 15.0 g/L, pH 7.0 ± 0.2 at 25 °C] has been shown to be an effective solid medium for the enumeration and laboratory manipulation of Mycobacterium abscessus complex organisms. Given its relative simplicity, commercial availability and inexpensive cost, we wished to evaluate its utility for the medium- to longterm maintenance/storage of these organisms. M. abscessus complex organisms (n = 33), were inoculated onto SPCA slopes and stored undistubed in the dark at ambient temperature for six months. Following this, slopes were broken out and culture of the NTM attempted. All slopes maintained NTM culture viability and were able to initiate growth six months later. We therefore advocate the cost-effective employment of SPCA slopes for the medium- to longterm maintenance of M. abscessus organisms, without the need for complex media, availability of sterile blood and requirements for continuous -80 °C freezing.