Reproduction of the Escherichia coli peritonitis syndrome in laying hens

Figures & data

Table 1.  E. coli peritonitis syndrome in egg-producing brown layers after E. coli administration by different routes

			Experiment
	E. coli dose^a (10^x CFU per hen)	Egg yolk inoculation^b	1	2	3	4	5	1 to 5
Age at inoculation (weeks)			23	26	28	23	33	23 to 33
Age at end of experiment (weeks)			27	29	30	25	35	27 to 35
Inoculation route
Intravenous	7.6 to 8.9	Yes	6/7^c	–^d	–	–	–	41/49 (84%)^A
		No	6/7	3/7^A	–	14/14^B	12/14
Intraperitoneal	8.7 to 8.9	Yes	7/7	–	–	–	–	16/21 (76%)^A,B
		No	5/7	4/7	–	–	–
Intratracheal	8.7 to 9.1	Yes	7/7	–	–	–	–	55/69 (80%)^A
		No	6/7	11/14	10/14	13/14	8/13
Intravaginal	8.7 to 8.9	Yes	3/7	–	–	–	–	28/57 (49%)^B
		No	4/8	1/14^A	–	10/14^B	10/14^B
Oral	8.7 to 8.9	Yes	3/7	–	–	–	–	7/56 (13%)^C
		No	2/7	0/14	–	2/14	0/14
Aerosol 1×^e	5.1 to 5.7^f	No	–	–	7/14	9/14	10/14	32/56 (57%)^B
Aerosol 4×^g	6.2	No	–	–	6/14	–	–
Intraperitoneal (placebo)	BPW	Yes	0/7	–	–	–	–	0/21 (0%)^C
		No	0/7	0/7	–	–	–
Intratracheal (placebo)	BPW	No	–	–	0/7	0/7	0/7	0/21 (0%)^C
Data with identical superscript uppercase letters do not differ significantly (P≥0.01). Within the same inoculation route, only the indicated data with different subscript upper case letter differ significantly (P<0.01). ^aThe E. coli dose was administered in a volume of 1 ml per hen for all inoculation routes, except aerosol exposure where each time a volume of 100 ml 1:2 in BPW-diluted E. coli culture was used per isolator (isolator volume = 1.34 m^3). ^bBacteriological sterile egg yolk (25 ml) was injected intraperitoneally per hen just prior to E. coli inoculation. ^cNumber of hens with E. coli peritonitis syndrome (E. coli septicaemia and/or peritonitis) out of number of hens examined. ^dNot done. ^eExposure time was 30 min. ^fCalculated inhaled dose per hen. ^gExposed to four nebulizations generated with intervals of 2 h.

Figure 1.  Restriction endonuclease digestion patterns obtained by PFGE of re-isolated E. coli from Experiments 3, 4 and 5 (n=5 re-isolates per experimental group; two re-isolates of orally inoculated birds of Experiment 4 were not tested) were considered genetically indistinguishable compared the inoculum strain. The two control isolates A and B originating from two different field outbreaks of EPS appeared to be genetically unrelated to the former isolates. IVAG, i.v., aerosol 1×, i.t. and aerosol 4× denote the inoculation or exposure routes by order of appearance in the figure, which are intravaginal, intravenous, aerosol once, intratracheal and aerosol four times, respectively. The dendrogram was constructed based on Dice similarity comparison of fragment profiles followed by UPGMA analysis.