Performance of bioMérieux Lowenstein-Jensen slopes in plastic tube packaging, compared to existing phenotypic methods, for efficient recovery of the Mycobacterium tuberculosis complex.

Purpose: Lowenstein-Jensen (LJ) medium used for cultivating Mycobacterium tuberculosis (MTB) is marketed in glass packaging. Breakage of glass slope is a major biosafety risk, especially during processing and storage, which gets magnified in large laboratories. We evaluated the performance of new bioMérieux (bMx) LJ slopes in plastic packaging, compared to bMx glass LJ medium and Becton Dickinson Mycobacterial Growth Indicator Tube (MGIT), for MTB recovery.

Methodology: Consecutive pulmonary/extra-pulmonary samples (n=240) were processed using routine methods of decontamination, inoculation and incubation.

Results: Plastic LJ slopes detected all 213 true-positive cases. The mean time-to-growth detection was 17.97 days for plastic LJ slopes, compared to 18.08 and 13.53 days for glass LJ slopes and MGIT, respectively. No statistically significant difference was observed between the two LJ slopes (P< 0.05). Both LJ slopes had a sensitivity and specificity of 100%, with respect to MGIT.

Conclusion: Plastic LJ slopes are a good alternative to the traditional glass slopes. The medium quality did not differ with the packaging material. Increased surface area of these slants allowed enhanced growth, and the clear plastic material allowed accurate recording of growth. The wide mouth of these containers eased inoculation. Increased biosafety, by elimination of breakage risk, is the biggest advantage of this modification.