Neither Hippurate-negative Brachyspira pilosicoli nor Brachyspira pilosicoli Type Strain Caused Diarrhoea in Early-weaned Pigs by Experimental Infection

Table 1 Pigs inoculated with B. pilosicoli^hipp- strain Br1622, B. pilosicoli type strain P43/6/78 or sterile broth (control). Pathology and results from fluorescent in situ hybridisation are shown.

Pig No.	Inoculum	Necropsy day post-inoculation	Gross pathology¹	Histology		FISH⁴
				Histopathology²	Spiral-shaped bacteria³	1	2
1	Br1622	7	-	+	-	+	-
2	Br1622	9	-	(+)	+	-	-
3	Br1622	11	+	+	++	+	-
4	Br1622	15	++	+	++, s	+	-
5	Br1622	16	++	(+)	-, s	+	-
6	Br1622	17	+	+	++	+	-
7	Br1622	21	+	(+)	++	-	-
8	Br1622	23	++	+	-	-	-
9	P43/6/78	7	+	(+)	+	-	-
10	P43/6/78	9	-	(+)	-	+	-
11	P43/6/78	11	+	(+)	+	-	-
12	P43/6/78	15	++	(+)	++	-	-
13	P43/6/78	16	++	(+)	++	+	-
14	P43/6/78	17	+	+	+	-	-
15	P43/6/78	21	+	(+)	++	+	-
16	P43/6/78	23	++	(+)	-	-	-
17	control	7	-	(+)	-	-	-
18	control	15	+	+	-	+	-
19	control	17	-	(+)	++	+	-
20	control	23	+	+	-	-	-
21	control	9	+	(+)	-	-	-
22	control	11	-	(+)	-	-	-
23	control	21	+	(+)	++	+	-

¹Gross findings in caecum and/or colon. - = normal; + = mucosa slightly hyperaemic; ++ = mucosa hyperaemic and slightly oedematous.
²(+) = diffuse lymphocytic and plasmacytic infiltration in lamina propria, and multifocal accumulation of phagocytic macrophages beneath the epithelial cells of the caecum and/or colon; + = in addition, occasional microabscesses in crypts and/or mild exocytosis of neutrophils.
³Spiral-shaped bacteria in caecum and/or colon in silver-stained sections. - = none; + = very rare or irregularly observed in crypts and/or near tips of villi; ++ = invading through epithelial lining into lamina propria and/or abundantly in crypts; s = Br1622 reisolated from necropsy samples.
⁴Fluorescent in situ hybridisation. Positive (+) and negative (-) results with probes designed for 1 = domain bacteria and genus Leptospira, and 2 = genus Brachyspira, species B. pilosicoli and strain Br1622.

ISSN: 1751-0147