An atypical weakly haemolytic strain of Brachyspira hyodysenteriae is avirulent and can be used to protect pigs from developing swine dysentery

Table 4 Shedding of B. hyodysenteriae in the faeces of pigs in experiment 2 as detected by culture on selective media

Pig group	Pig number	Culture results: days after first day of inoculation with MU1^a							Culture results: days after first day of challenge with five virulent strains^b										Median (post cocktail)
Pig group	Pig number	8	11	15	18	22	25	29	7	10	14	17	21	24	28	31	35	38	Median (post cocktail)
A	1	0	0	0	1^d	1^d	0	0	0	0	0	0	0	0	0	0	0	0	0
	2	0	0	0	0	1^d	1^d	1^d	1^d	1^d	1^d	0	0	0	0	0	0	0	0
	3	0	0	1^d	1^d	1^d	1^d	1^d	0	0	0	0	0	0	0	0	0	0	0
	4	0	0	0	0	1^d	1^d	0	0	0	0	0	0	0	0	0	0	0	0
	6	0	0	1^d	1^d	1^d	1^d	1^d	1^d	1^d	1^d	1^d	1^d	0	0	0	0	0	0.5
	7	0	0	0	1^d	1^d	1^d	1^d	0	0	0	0	0	0	0	0	0	0	0
	10	0	0	0	0	0	1^d	1^d	1^d	0	0	0	0	0	0	0	0	0	0
	15	0	0	0	0	1^d	0	1^d	0	0	0	0	0	0	0	0	0	0	0
	16	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	18	0	0	0	1^d	1^d	1^d	0	0	0	0	0	0	0	0	0	0	0	0
	22	0	0	0	0	1^d	1^d	0	0	0	0	0	0	0	0	0	0	0	0
	26	0	0	0	0	1^d	0	0	0	0	0	0	0	0	0	0	0	0	0
Median^c		0	0	0	0	1	1	0.5	0	0	0	0	0	0	0	0	0	0	0
B	5	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	9	0	0	0	1^d	1^d	1^d	1^d	1^d	0	0	0	0	0	0	0	0	0	0
	12	0	0	0	0	0	1^d	1^d	0	0	0	0	0	0	0	5	5	Dead	0
	14	0	0	0	0	1^w	0	0	0	0	0	0	0	0	0	0	4	5	0
	19	0	0	1^d	1^d	1^d	1^d	1^d	1^d	1^d	1^d	0	0	0	0	0	0	0	0
	23	0	0	0	1^d	1^d	1^d	1^d	1^d	1^d	1	1	1	0	0	0	0	0	0
	24	0	0	0	0	0	1^d	0	1^d	1^d	1^d	0	1	0	0	0	0	0	0
	25	0	0	0	1^d	0	1^d	1^d	1^d	1^d	1^d	0	0	0	0	0	0	0	0
	27	0	0	0	0	1^d	1^d	0	0	0	0	0	0	0	0	0	0	0	0
	29	0	0	1^d	1^d	1^d	1^d	1^d	0	0	0	0	0	0	0	0	0	0	0
	32	0	0	0	0	1^d	0	1^d	1^d	1^d	1^d	0	0	0	0	0	0	0	0
	33	0	0	1^d	1^d	1^d	0	0	0	0	0	0	0	0	0	0	0	0	0
Median^c		0	0	0	0.5^#	1^##	1^##	1^#	0.5	0	0	0	0	0^#	0	0^#	0^##	0^#	0^##
C	8	0	0	0	0	0	0	0	0	0	0	0	0	5	5	5	5	Dead	0
	11	0	0	0	0	0	0	0	0	0	0	0	0	0	0	5	5	5	0
	13	0	0	0	0	0	0	0	0	0	0	0	0	0	5	5	5	5	0
	17	0	0	0	0	0	0	0	0	0	5	5	5	5	Dead	Dead	Dead	Dead	5
	20	0	0	0	0	0	0	0	0	3	5	5	5	5	Dead	Dead	Dead	Dead	5
	21	0	0	0	0	0	0	0	0	0	4	5	5	5	Dead	Dead	Dead	Dead	4.5
	28	0	0	0	0	0	0	0	0	0	0	0	0	5	5	5	5	Dead	0
	30	0	0	0	0	0	0	0	0	5	5	5	Dead	Dead	Dead	Dead	Dead	Dead	5
	31	0	0	0	0	0	0	0	0	0	0	0	0	5	5	5	5	Dead	0
	34	0	0	0	0	0	0	0	0	0	0	0	0	0	0	5	5	5	0
	35	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	5	5	0
	36	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Median^c		0	0	0	0^#	0^##	0^##	0^#	0	0	0	0	0	5^#	2.5	5^#	5^##	5^#	0^##

Group A was only experimentally inoculated with weakly haemolytic B. hyodysenteriae strain MU1. Group B was inoculated with MU1 and subsequently challenged with a mixture of five virulent field strains of B. hyodysenteriae. Group C was only challenged with the virulent strains.
Dead—indicates pig that developed dysentery and was removed for pm.
^aCulture score: 1 to 5, extent of growth on selective agar plates; 0, no growth.
^bGroup A exposed to MU1 and not challenged with the cocktail of strains.
^cMedians for groups A and B that were significantly different in a Mann–Whitney test are marked with asterisks (* p < 0.05; ** p < 0.01). Medians for groups B and C that were significantly different in a Mann–Whitney test are marked with hashes (^#p < 0.05; ^##p < 0.01).
^dGrowth of weakly haemolytic B. hyodysenteriae (MU1). All others were strongly haemolytic.

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