The Incidence of Clostridium Tetani in the Soil of Calcutta

Sixty samples of soil collected from different areas were examined for the presence of Clostridium tetani. The samples were collected during the pre-monsoon hot weather and the methods employed in the isolation and study of the cultures we're on the lines found satisfactory by Fildes (1925a and b). A summary of the methods employed is outlined below :? Approximately 2 to 3 c.cm. of ground-up soil were added to 10 c.cm. of freshly-prepared bloodbroth (nutrient broth enriched with 2 per cent ?f pepsin digest of blood). The tubes were well shaken and incubated under a3robic conditions at 37?C. for four days. On the fifth day two big loopfuls of inoculum were removed from the tubes and inoculated into the condensation water ?f peptic-blood-agar slopes (which had been kept upright in the incubator overnight in order to allow of sufficient drying of the surface of the medium). The inoculated blood-agar slopes, Were incubated under anaerobic conditions in Mcintosh and Fildes' jar at 37?C. for four days. Any growth occurring at the apex of the slope Was examined and subcultured into the condensation water of another tube and incubated anaerobically. C. tetani under these conditions grows a rapidly-spreading film on the surface of the medium and the fact that this character of spreading growth is more pronounced in the case ?f this bacterium than with other anierobes was taken advantage of by Fildes in his method of isolation of C. tetani in pure culture. Although m the majority of the isolations the second tube showed a pure growth of C. tetani (a fine transParent filamentous growth often difficult to detect with the naked eye) a third tube was inoculated from the topmost area of growth. If now the growth appeared to be contaminated, Purification was done by inoculating further tubes of peptic-blood-agar slopes in the same Way. In certain strains of tetanus bacilli no spores were seen even after four days' incubation. This delayed formation of spores at first