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APMIS. 1997 Mar;105(3):247-54.

Expression of colonization factor antigen I fimbriae by enterotoxigenic Escherichia coli; influence of growth conditions and a recombinant positive regulatory gene.

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Center for International Health, Gade Institute, University of Bergen, Haukeland Hospital, Norway.


Enterotoxigenic Escherichia coli (ETEC) may spontaneously lose the positive regulatory cfaR gene and thereby the capacity to express colonization factor antigen I (CFA/I). A recombinant plasmid harbouring the cfaR gene was transformed into cfaR-negative mutant ETEC strains. CFA/I expression of wild-type and cfaR-transformed ETEC cultivated in different liquid media was quantified. At 37 degrees C, a high level of CFA/I expression from wild-type and cfaR-transformed strains was observed after growth in CFA broth. Transformation enhanced CFA/I expression only marginally. The transformant cultures showed a considerable variation in CFA/I expression which was paralleled by the proportion of individual bacteria producing CFA/I. This heterogeneity could be explained by a variable tendency to structural CFA/I gene loss among individual cfaR-transformed bacteria.

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