TABLE 2.

Distribution of iro genes among APEC and avian fecal commensal isolates according to lethality class

Lethality classaNo. (%) of E. coli isolates
APECAvian fecal commensal
Totaliro positivebTotaliro positiveb
LC1222203 (91)c11 (100)
LC23824 (63)126 (50)
LC33817 (45)193 (16)
Total298244 (82)d3210 (31)
  • a Lethality classes were defined by lethality in 1-day-old chicks as follows: LC1, 50% lethal dose (LD50) of <108 CFU; LC2, LD50 of ≥108 CFU; LC3, not lethal at ≥108 CFU (14).

  • b Positive PCR amplification of the iroB and iroN genes.

  • c iro sequences were significantly associated with APEC isolates from LC1 as compared to APEC isolates from LC2 or LC3 (P < 0.0001) using Fisher's exact test.

  • d iro sequences were significantly associated with APEC isolates relative to environmental isolates (P < 0.0001) using Fisher's exact test.