TABLE 1.

Effect of lp56 on survival and proliferation of B. burgdorferi clones 5A1 (lp56⁻) and 5A19 (lp56⁺) in capillary-inoculated ticks^a

B. burgdorferi B31 isolate	Values for effects determined in expt 1
	Before mouse feeding			After mouse feeding
	No. of positive nymphs/total fed nymphs	Mean no. of spirochetes per field ± SD	P	Mouse	No. of positive nymphs/total fed nymphs	Mean no. of spirochetes per field ± SD	P
5A1 (lp56−)	5/5	0.64 ± 0.17		S327	14/14	41.84 ± 21.88
				S328	4/5
			0.13020	S329	6/6		0.000001
5A19 (WT)	5/5	0.48 ± 0.13		S330	12/12	92.83 ± 39.51
				S331	4/4
				S332	8/8

^aCulture positivity and mean number of spirochetes per field were determined 24 to 25 days after capillary inoculation (before mouse feeding group) or 7 days after mouse feeding (after mouse feeding group). Three and 10 fields were counted for each fed and unfed tick, respectively. Mean values of spirochetes per field were averaged over the total number of fed ticks in the three mice of each group. Student's t test was used to evaluate statistical significance. All mice were culture positive at all tissue sites examined after feeding.