A fter vaccin atio n w ith th e live P F stra in of T rypanosom a cruzi, 194 blood cultures were perform ed in 143 mice, 9 dogs, 5 Cebus m onkeys and 7 h u m a n subjects.Some of these blood cultures were sim ultaneously done w ith xenodiagnosis, subinoculation in baby mice a n d /o r cu ltu re of viscerae.The trypanosom es isolated from th e few positive cases (6,1% ) were in capable of infecting baby mice were considered as cases of im m unotolerance. All th e oth er tests were negative.This work intends to d em o n strate th ro u g h blood cultures, xenodiagnosis, sub inoculations an d culture of viscerae, th e avirulence of th e P F stra in of T rypano som a cruzi (20) in laboratory anim als and h u m an s (6,8,12,18) .
MATERIAL AND METHODSThe m ajo rity of anim als described in th is com m unication have already been used in several experim ents perform ed in th e last four years by one of us (6 -2 0 ), a com m on face being th a t all of th em h a d been vaccinated w ith th e PF stra in w ith th e doses m entioned in Table 1.They la te r h a d blood culture w ith or w ithout one or several of th e tests specified above.164 anim als w ere used; 143 w hite mice, 9 dogs, 5 Cebus m onkeys an d 7 h u m an beings in w hich 194 blood cultures were p e rfo rm e d .The culture m edium used was th a t of W arren, as described by one of us (1 ) . T he tests were realized 8,15,20, 30, 45, 60, 90, 120, 150, 180, 270 an d 510 days a fte r vac cin atio n . In some groups tests w ere m ade only once in one of these periods b u t in o thers in more th a n one period or in all of th em as was th e case w ith th e h u m an subjects.Among th e mice th a n h a d only blood cultures, th e am ount of to ta l blood or se ru m used was 0,4 to 0,7 ml for each test tube of culture m edium .W hen more th a n one te st was p e r form ed on mice, th a t am ount was only 0,2 m l. In h u m a n subjects, dogs and m on keys, th e q u an tity of to ta l blood or blood serum (th e la te r in accordance w ith S tro u t's tech n iq u e-23) was always 0,5 m l for each te st tube.T he resu lts of th e blood cultures were always recorded on th e 30th. day as a blind te s t since th e tech n ician h a d no knowledge of the origin of th e m aterial u n d er ex am ination.The xenodiagnosis w ad done by th e use of 4th. in sta r nym phes of R hodnius * U S P . F a c u ld a d e d e M ed icin a de R ib e irã o P rê to . S ão P a u lo . B ra sil. ** D e p a rta m e n to d e C iê n c ia s B io ló gicas. F a c . F a r . O d o n t. R ib e irã o P rê to .R ecebid o p a ra p u b lic a ç ã o em 14-12-1971.
