Rapid culture of Mycobacterium tuberculosis on blood agar in resource limited setting.

INTRODUCTION

Sputum samples collected at a teaching hospital of Jodhpur, were processed at Desert Medicine Research Centre, Jodhpur. The aim was to assess the time required for primary isolation of Mycobacterium tuberculosis (Mtb) on locally prepared sheep blood agar slants as compared to Löwenstein-Jensen (LJ) medium.

METHODS

Equal volume of homogeneous inoculums prepared from smear positive sputum samples processed with the N-acetyl L-cysteine sodium hydroxide method was inoculated on slants of locally prepared 7% sheep blood agar and LJ medium. These were incubated at 37 degrees C and were observed daily for growth visible with naked eyes. Time taken in growth of Mtb was compared.

RESULTS

LJ medium recovered 68 of 70 isolates (97.1%) as compared to 66 by blood agar (94.2%). The difference was not significant. Mean time to detect macroscopic colonies of Mtb on blood agar was 13.6 + or - 5.2 days as compared to 20.4 + or - 5.1 days on LJ medium (p=0.0001). More colonies were observed on blood agar than on LJ medium.

CONCLUSION

Blood agar slants may be a good substitute of LJ medium for rapid detection of Mtb from sputum in resource limited settings. It may save about one third of the time.