Table 4. B. burgdorferi ruvA and ruvB mutants survive well in ticks, but do not establish long-term infection in mice following tick-mediated inoculation.

B. burgdorferi Strain	Unfed Ticks			Fed Ticks			Mouse Tissues
	Positive Cultures	Mean no. of spirochetes per field±SD	p value (Mutant vs. WT)	Positive Cultures	Mean no. of spirochetes per field±SD	p value (Mutant vs. WT)	Positive Cultures
ruvA mutant	9/10	0.93±0.42	0.77	24/24	27.3±16.2	0.841	0/12
ruvB mutant	9/10	1.41±0.44	0.17	24/25	12. 4±7.6	0.053	0/12
5A18NP1	8/10	1.06±0.33		26/26	24.4±24.1		12/12

I. scapularis nymphs were inoculated with the ruvA mutant T11P01A01, the ruvB mutant T03TC051, or the parental strain 5A18NP1 by capillary feeding, as described in Materials and Methods. Ticks were held for 21–25 days and cultured for B. burgdorferi either before or immediately after feeding on 3 C3H/HeN mice. The mice used for feeding were euthanized 4 weeks afterwards, and heart, bladder, ear, and tibiotarsal joint tissue specimens were utilized for B. burgdorferi culture. Spirochetes were quantified by direct immunofluorescence either in flat or fed ticks. One half of each tick was used for culture and the other half for immunofluorescence. Statistical significance (p<0.05) was assessed by ANOVA.