MAPPING OF NONINVASION TNPHOA MUTATIONS ON THE ESCHERICHIA-COLI O-18-K1-H7 CHROMOSOME

The most virulent newborn meningitis-associated Escherichia coli are o f the serotype O18:K1:H7. We previously isolated a large number of E. coli O18:K1:H7 mutants resulting from transposon TnphoA mutagenesis th at fail to invade brain microvascular endothelial cells. We have now d etermined the locations of 45 independent insertions. Twelve were loca lized to the 98 min region, containing a 120 kb segment that is charac teristic of E. coli O18:K1:H7. Another, the previously described inser tion ibe-10::TnphoA, was localized to the 87 min region, containing a 20 kb segment found in this E. coli. These noninvasion mutations may d efine new O18:K1:H7 pathogenicity islands carrying genes for penetrati on of the blood-brain barrier of newborn mammals.