Table 2.

Tropism of B. burgdorferi sl DNA in mice organs by two modes of infection (inoculation by needle vs. 120 h female tick attachment) analyzed 38 days post-infection.

B. burgdorferi sl strains	Type of infection	Mouse organs
		Brain	Heart	Back skin	Ankle	Muscle	Spleen	Liver	Bladder	Mesentery	Lymph node
		% of organ infected	% of organ infected	% of organ infected	% of organ infected	% of organ infected	% of organ infected	% of organ infected	% of organ infected	% of organ infected	% of organ infected
B31	Inoculation	0*	40	100a$	100c£	ND	ND	ND	80	ND	ND
	Tick bite	40	40	40	40	40	60	20	80	40	20
BRE-13	Inoculation	83*	0§	67	50	ND	ND	ND	100	ND	ND
	Tick bite	85+	57b	85	71	40	60	40	85+	20	85+
N40	Inoculation	0*	0§	60	100c£	60d	0	0	60d	60d	100e
	Tick bite	0+	0	100	14	0	0	0	0+	0	0+
PBi	Inoculation	100f*	100g§	0$	0£	ND	ND	ND	67	ND	ND
	Tick bite	14	0	57b	43	57	71	71	71	0	43
IBS-5	Inoculation	40	80	80	80	ND	ND	ND	60	ND	ND
	Tick bite	43	28	100	43	28	43	71	43	28	43
Stat	Inoculation	p < 0.0003	p < 0.0002	p < 0.005	p < 0.004	–	–	–	NS	–	–
Stat	Tick bite	p < 0.018	NS	NS	NS	NS	NS	NS	p < 0.016	NS	p < 0.017

Mice were infected with the various strains/species of Borrelia burgdorferi sl either by needle injection of 10⁵ Borrelia/mouse or by tick bite during 120 h (see Figure 1). Mice were dissected 38 days after beginning of tick attachment. DNA was extracted as described in the Material and Methods section and a specific nested PCR was performed. The percent of organs found infected in the mice analyzed was reported according to the type of infection (inoculation/tick bite). 5–7 mice were used for each experiment. Statistical comparisons of organ infection between Borrelia strain after infection (inoculation or tick bite) are presented in bold:

^*BRE-13 = PBi > B31 = N40;

^§PBi > BRE-13 = N40;

^$B31 > PBi;

^£B31 = N40 > PBi;

⁺BRE-13 > N40. Statistical comparison of organ infection between inoculation and tick bite:

^ap < 0.04;

^bp < 0.03;

^cp < 0.004;

^dp < 0.017;

^ep < 0.0005;

^fp < 0.002;

^gp < 0.0003. ND, not done. NS, non-significant.