TABLE 3.

Comparison of in vivo and in vitro IBCs

IBC characteristicCharacteristic present:
In vivoIn vitro
Forms as dense aggregate of coccoid bacteriaYesYes
Is cytosolicYesNo
Forms 6-24 h postinfectionYesYes
Secretes polysaccharideYesNTa
Stains for antigen 43YesYes
Is deficient as fimH mutantYesYesb
Requires leuX and surAYesNT
Upregulates iron acquisition systemsYesYes
  • a NT, not tested.

  • b The fimH mutant formed IBCs, but significantly fewer than wild-type UPEC.