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Updated: Sep 1, 2025
A Microscopic Phenotypic Assay for the Quantification of Intracellular Mycobacteria Adapted for High-throughput/High-content Screening
Published on: January 17, 2014
Comparison of Mycobacterium tuberculosis complex Yield and Contamination Rates using Lowenstein-Jensen with and
A Okumu1, K McCarthy2, J Orwa1
1Kenya Medical Research Institute (KEMRI) Center for Global Health Research, Kisumu, Kenya.
Background:
While molecular methods have been recently endorsed for diagnosis of tuberculosis (TB), mycobacterial culture remains the gold standard. Lowenstein-Jensen (LJ) is often used for the cultivation of Mycobacterium tuberculosis complex (MTBC); however contamination often renders a subset of cultures useless. We compared the MTBC yield and contamination rate of processed sputum inoculated on LJ with antibiotics (LJ PACT) to LJ without antibiotics (LJ).
Methodology:
Sputum samples were obtained from people living with HIV enrolled in a TB screening study in western Kenya, processed using NALC/NaOH-Na citrate, then inoculated on LJ PACT and LJ media. Cultures were evaluated weekly with growth identified as acid-fast bacilli by Ziehl-Neelsen bright-field microscopy. MTBC and nontuberculous mycobacteria (NTM) were identified by immunochromatographic and line probe assays.
Results:
A total of 700 sputum samples were cultured on both LJ PACT and LJ between March and June 2012. Of those cultured on LJ PACT, 29 (4.1%) grew MTBC, 613 (87.6%) were negative, 12 (1.7%) grew NTM, and 46 (6.6%) were contaminated; on LJ, 28 (4%) grew MTBC, 553 (79%) were negative, 9 (1.3%) grew NTM, and 110 (15.7%) were contaminated. The difference in contamination on LJ PACT and LJ was statistically significant (p<0.0001), while the difference in MTBC growth was not (p=0.566).
