Conversion of Coccidioides immitis from a mycelial form to spherules using the 'agar-implantation method'.

The morphological conversion of Coccidioides immitis in vivo was observed using the agar-implantation method. Short hyphae implanted into the peritoneal cavity of mice swelled gradually and many septa appeared in them after 48 hours. As the implantation period advanced, these arthroconidia swelled and then broke up into spherical cells at the 72nd hour. On the other hand, arthroconidia implanted into the peritoneal cavity of mice also swelled and became immature spherules within 72 hours. During the 96th hour a few of the spherules reached a stage of maturity. They were filled with numerous endospores. The agar-implantation method is therefore a useful for the demonstration of spherules of C. immitis.