Effects of storage and transport on the cultivability of mycobacteria

In the course of WHO/UNICEF-assisted tuberculosis surveys carried out in a number of African territories, sputa were microscopically examined for the presence of acid-fast bacilli. Since adequate facilities for performing cultures to confirm the diagnosis of tuberculosis and other mycobacterial infections were not available in these territories, it was necessary to despatch sputum specimens to certain European laboratories for culturing and typing of mycobacteria. However, it was noticed that the number of positive cultures from such sputa was very low, being limited largely to specimens in which acid-fast bacilli were easily demonstrable by microscopy. Specimens containing scanty acid-fast bacilli, or microscopically negative specimens, usually failed to exhibit growth on culture, contrary to the usual observations made with European sputum specimens cultured in European laboratories. As the sputa were mostly taken from new cases with lung pathology, previous treatment could not have been responsible for these poor culture results, and it was thought that the conditions in which the specimens were transported, and possibly also the chemical composition of the containers in which they were stored, might be the cause.In an experiment carried out by the WHO Tuberculosis Research Office, in collaboration with a WHO field team in Africa and the Tuberculosis Research Institute in Prague, pure cultures of the H37 Rv strain and sputa were sent from Prague to East Africa and book in conditions simulating those in which specimens collected by African field teams are routinely sent to European laboratories. The results show that the cultivability of tubercle bacilli is adversely affected by storage and transport.