Isolation of spotted fever group and Wolbachia-like agents from field-collected materials by means of plaque formation in mammalian and mosquito cells.

Three isolations from ticks (Dermacentor occidentalis) of a rickettsia of the spotted fever group and 5 isolations from chipmunk (Eutamias rugicaudus) blood of a Wolbachia-like agent were obtained from plaques formed in Singh's Aedes albopictus (mosquito) and Vero (African green monkey kidney) cell cultures. These organisms could not be isolated by injection of the infected ticks or blood into embryonated chicken eggs, guinea pigs, or voles (Microtus pennsylvanicus), but fluid cultures of Grace's Antheraea eucalypti (moth1 and Singh's A. albopictus cells inoculated with the bloods yielded the Wolbachia-like agent.