Effect of relative centrifugal forces and centrifugation times on recovery of Mycobacterium tuberculosis.

ABSTRACT

Background: Tuberculosis (TB) is one of the major cause of morbidity and mortality worldwide, affecting one third of world’s population and the incidence is much higher in South-East Asia (India and China together account for nearly 40% of the global TB cases) Objectives: The current study was designed to evaluate the efficacy of relative centrifugal forces (RCFs) and various centrifugations times (CTs) on recovery of Mycobacterium tuberculosis (MTB) from sputum specimens pre-inoculated with MTB. Materials & Methods: For this study, direct acid fast bacilli (AFB) smear negative sputum specimens were randomly collected, which were further subjected to sterilization ( by autoclaving at 1210 C for 15 min ) and then seeded with MTB. Afterwards, these sputum specimens were subjected to centrifugation (in a cold centrifuge) at various RCFs and CTs. After centrifugation, supernatants and sediments were inoculated on LJ media and incubated at 370 C with daily monitoring for 8 weeks. Results: In the current study, as the RCFs (6000xg) and CTs ( 25 min and 20 min) were increased, the growth detection time exponentially decreased (9 and 11 days) and culture grades (4+) were increased when cultured from the sediments. However, the recovery rates of MTB from the supernatant fluids were constantly decreased as RCFs and CTs increased. Conclusion: The current study concluded that a higher RCF of 6000xg and CTs of 20 and 25 min could effectively detect the tubercle bacilli from the sputum specimens more efficiently than other lower RCFs and CTs.