DETECTION AND CHARACTERIZATION OF THE FIMA GENE OF ESCHERICHIA-COLI O157-H7

An expected 850-bp DNA fragment containing fimA, the structural gene f or type 1 fimbriae, and flan king sequences was amplified from 39 (of 46) pathogenic and commensal strains of Escherichia coil using the pol ymerase chain reaction (PCR). Restriction fragment length polymorphism (RFLP) analysis of the amplified products showed 13 HinPI and four Sa u961 restriction profiles among these 39 E. coil strains, revealing th e polymorphic nature of this allele. A unique RFLP pattern was shared by E. coil 0157:H7, 0157:H- and a few 055 serotype strains. DNA sequen ce analysis of the fimA region demonstrated that E. coil 0157:H7 strai n 933 and 0157:H- strain E32511 contained identical DNA sequences that were distinct from other E. coil strains, especially a 16-bp sequence 5' to fimA that was conspicuously absent only in E. coil 0157 strains . Exploiting these differences, a PCR assay was developed that amplifi es a 936-bp fragment from all E. coil 0157:H7 strains examined to date . This PCR assay offers a simple, rapid, and reliable means to detect E. coil strains of the 0157:H7 serotype. (C) 1997 Academic Press Limit ed.