P fimbriae, capsule and aerobactin characterize colonic resident Escherichia coli

Resident and transient Escherichia coli strains from the colonic microflora of 13 Swedish schoolgirls were analysed for carriage of genes encoding a r ange of adhesins (P, type 1 and S fimbriae, Dr haemagglutinin and three var ieties of the P fimbrial papG adhesin) and other virulence traits (K1 and K 5 capsule, haemolysin and aerobactin) using multiplex PCR. Forty-four perce nt of the resident clones carried genes for P fimbriae, K1 or K5 capsule, a nd aerobactin, compared with only 3 % of transient clones (P < 0.0001). The P-fimbriated clones most often had the class II variety of the P-fimbrial adhesin gene papG and this adhesin was significantly associated with persis tence of a strain. S fimbriae and type 1 fimbriae were equally common in re sident and transient strains. The results indicate that not only P fimbriae , but also, certain capsules and the ability to produce the siderophore aer obactin might contribute to persistence of E. coli in the large intestine.