TABLE 1.

Incidence of diarrhea and clinical symptoms after oral challenge of Aotus nancymaae with escalating doses of S. flexneri 2a strain 2457T and homologous rechallenge^a

Group	Treatment (dose [CFU])	Primary challenge				Homologous rechallenge
		No. of animals	Incidence (%) of diarrheab	Incidence (%) of clinical symptomsc	P valued	No. of animals	Incidence (%) of diarrhea	Incidence (%) of clinical symptoms	P value
1	S. flexneri 2a 2457T (5 × 109)	8e	25	50	0.558	8e	25	38	0.145
2	S. flexneri 2a 2457T (5 × 1010)	9	56	56	0.057	7e,f	43	71	1.000
3	S. flexneri 2a 2457T (5 × 1011)	9	100	100	0.0001	8f	38	50	0.321
4	PBS	10	10	10		10	50	80

^aThe groups of Aotus nancymaae monkeys were challenged with S. flexneri 2a strain 2457T, treated with 1 × 10¹¹ CFU of S. flexneri 2a 2457T, and then rechallenged with a homologous strain.

^bDiarrhea was defined as at least one loose-watery stool on at least two consecutive days during the observation period (10 days).

^cClinical symptoms of Shigella-induced gastroenteritis were defined as evidence of Shigella colonization (PCR or isolation) and either (i) an episode of diarrhea, (ii) blood in the stool (occult, gross, or melena) for two consecutive days, or (iii) death.

^dThe P values were calculated by Fisher's exact test compared to control group inoculated with PBS.

^eOne animal excluded from data analysis due to diarrhea for 2 days prior to challenge.

^fOne animal euthanized after the primary challenge.