A naturally occurring nucleotide polymorphism in the orf2/folc promoter is associated with Streptococcus suis virulence

Table 1 Virulence of complemented S. suis strains in germfree piglets; all strains contained a plasmid (pCOM1) with or without insert

						Clinical index of the group			No. of pigs in whichS. suiswas isolated from
Strain	No. of pigs	Dose (CFU)	Mortality^a(%)	Mean no. of days till death	Morbidity^b(%)	Specific^csymptoms	Non-specific^dsymptoms	Fever index^e	CNS	Serosae^g	Joints
S735-pCOM1-V[10]	4	106	100	1	100	100**	100**	38*	4	4	4
S735-pCOM1-orf2[10]	4	106	100	1	100	100**	66**	29	4	4	4
S735-pCOM1-folC[10]	4	106	0	11	0	4	21	1	0	0	0
S735-pCOM1	4	106	0	11	0	0	21	5	0	0	0
S735-pCOM1-V[10]f	5	106	100	1	100	100**	100**	60*	5	5	5
S735-pCOM1-V[S735]f	5	106	20	15	100	43**	38	25	1	1	1
S735-pCOM1f	5	106	20	16	60	14	11	12	1	0	0
T15-pCOM1-V[10]	5	106	0	14	16	4	16	13	1	1	1

V[10]/V[S735]: original 3kb fragment from strain 10 or strain S735 that was selected from library; orf2[10]: orf2 from V[10]; folC[10]: orf3 from V[10]encoding dihydrofolate synthase.
^aPercentage of pigs that died due to infection or had to be killed for animal welfare reasons.
^bPercentage of pigs with specific symptoms.
^cPercentage of observations for the experimental group in which specific symptoms (ataxia, lameness of a least one joint and/or stillness) were observed.
^dPercentage of observations for the experimental group in which non-specific symptoms (inappetite and/or depression) were observed.
^ePercentage of observations for the experimental group of a body temperature of >40C.
^fPrevious experiments (Smith et al., 2001) were re-analyzed to allow for statistical comparison between experiments, this re-analysis required new stringent definitions of specific and aspecific symptoms as indicated in materials and methods.
*p ≤0.05 compared to S735-pCOM1.
**p ≤0.01 compared to S735-pCOM1.
^gSerosae are defined as peritoneum, pericardium or pleura.

ISSN: 1471-2180