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Journal of Clinical Microbiology, July 2008, p. 2339-2344, Vol. 46, No. 7
0095-1137/08/$08.00+0     doi:10.1128/JCM.02476-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Tuberculosis Diagnosis and Multidrug Resistance Testing by Direct Sputum Culture in Selective Broth without Decontamination or Centrifugation ^,

Louis Grandjean,^1, Laura Martin,^1, Robert H. Gilman,^1,2,3 Teresa Valencia,¹ Beatriz Herrera,¹ Willi Quino,¹ Eric Ramos,¹ Maribel Rivero,¹ Rosario Montoya,¹ A. Roderick Escombe,^1,2,5 David Coleman,⁴ Denis Mitchison,⁴ and Carlton A. Evans^1,2,3,5*

Laboratorios de Investigación y Desarrollo, Departamento de Microbiología, Facultad de Ciencias, Universidad Peruana Cayetano Heredia, Lima, Perú,¹ Asociación Benefica Prisma, Lima, Perú,² Department of International Health, Johns Hopkins Bloomberg School of Hygiene and Public Health, Baltimore, Maryland,³ Department of Medical Microbiology, St. George's Hospital Medical School, London, United Kingdom,⁴ Wellcome Centre for Clinical Tropical Medicine and Department of Infectious Diseases and Immunity, Imperial College London, Hammersmith Hospital Campus, London, United Kingdom⁵

Received 24 December 2007/ Returned for modification 16 February 2008/ Accepted 23 April 2008

Tuberculosis culture usually requires sputum decontamination and centrifugation to prevent cultures from being overgrown by contaminating bacteria and fungi. However, decontamination destroys many tuberculous bacilli, and centrifugation often is not possible in resource-poor settings. We therefore assessed the performance of Mycobacterium tuberculosis culture with unprocessed samples plated directly by using tuberculosis-selective media and compared this procedure to conventional culture using centrifuge decontamination. Quadruplicate aliquots of strain H37RV were cultured in 7H9 broth with and without selective antimicrobials and after centrifuge decontamination. The subsequent comparison was made with 715 sputum samples. Split paired sputum samples were cultured conventionally with centrifuge decontamination and by direct culture in tuberculosis-selective media containing antibiotics. Centrifuge decontamination reduced tuberculosis H37RV colonies by 78% (P < 0.001), whereas direct culture in tuberculosis-selective media had no inhibitory effect. Similarly, in sputum cultures that were not overgrown by contaminants, conventional culture yielded fewer tuberculosis colonies than direct culture (P < 0.001). However, the sensitivity of conventional culture was greater than that of direct culture, because samples were less affected by contamination. Thus, of the 340 sputum samples that were tuberculosis culture positive, conventional culture detected 97%, whereas direct culture detected 81% (P < 0.001). Conventional and direct cultures both took a median of 8.0 days to diagnose tuberculosis (P = 0.8). In those direct cultures that detected drug resistance or susceptibility, there was a 97% agreement with the results of conventional culture (Kappa agreement statistic, 0.84; P < 0.001). Direct culture is a simple, low-technology, and rapid technique for diagnosing tuberculosis and determining drug susceptibility. Compared to that of conventional culture, direct culture has reduced sensitivity because of bacterial overgrowth, but in basic laboratories this deficit may be outweighed by the ease of use.

Published ahead of print on 30 April 2008.

Supplemental material for this article may be found at http://jcm.asm.org/.

L.G. and L.M. contributed equally to the article.