Table 1.

Different patterns of serotypes and virulence genes, and in vivo virulence assessment of APEC isolates.

Serial No.	Isolate Code No.	Serotype	Virulence Gene Content	In Vivo Virulence Assays
				SPF 1-day-old Chicks a	SPF ECEs b
1	9	O115	iss	L	H
2	16	O115	iss + iutA	L	H
3	41	O158	iss + fimH	M	H
4	50	O158	iss + fimH + iutA	L	H
5	28	O114	iss + iutA	M	H
6	54	O114	iutA	L	H
7	5	O125	iss	H	H
8	2	O27	iss	M	H
9	7	O55	iss + fimH	L	H
10	39	O55	iss + iutA	H	H
11	15	O20	iss + iutA	L	H
12	32	O142	iss + iutA	L	H
13	49	O15	iss	L	H
14	Control c	-	-	-	-
15	Control negative d	-	-	-	-

^a SPF 1-day-old chicks (n = 5) were inoculated with each sample subcutaneously and were observed for 7 days post-infection to record the mortality rate. H: highly virulent (highly pathogenic isolates produced mortality or severe lesions including pericarditis, perihepatitis, air sacculitis, and liver necrosis in more than 50% of the challenged chicks), M: moderately virulent (were nonlethal and produced lesions in fewer than 50% of the inoculates), L: low virulent (produced no mortality and only occasional lesions in the air sacs) [20]. ^b 10-day-old SPF ECEs (n = 10) were inoculated with each sample via the allantoic sac route and were observed for 6 days post-inoculation to record the mortality rate. H: highly virulent strain resulted in mortality rate of >29% of ECEs; M: moderately virulent strains reported 10–29% mortality, and L: low virulent strains induced <10% mortality [13,21]. ^c Control for each assay (1-day-old chicks or ECEs) were sham inoculated with saline by the same route and dose; neither mortality nor post-mortem lesions were observed. ^d Control negative for each assay (1-day-old chicks or ECEs were not inoculated).