Sequence microdiversity at the ribosomal RNA operons of Escherichia coli pyelonephritogenic strains

Objective To determine whether Escherichia coli strains isolated from patie nts with uncomplicated acute pyelonephritis can be distinguished from those isolated from patients with complicated acute pyelonephritis on the basis of the genetic background. Methods In total, 103 E. coli strains isolated from patients with acute pye lonephritis (59 uncomplicated pyelonephritis (UAP) and 44 complicated pyelo nephritis (CAP)) were characterized by RFLP of the intergenic spacer region 16S-23S rRNA, the presence of three alternative sequences found in the pol ymorphic V6 loop of the 16S rRNA gene, the presence of the pap gene, and an tibiotic susceptibility. Results At similarity levels of 70%, four RFLP groups (alpha1, alpha2, beta 1 and beta2) were discerned. Strains from UAP were statistically significan t for a RFLP, with a strong association with the presence of the pap gene, V6-I sequence and antibiotic multisensitivity. Strains from CAP randomly be longed to the alpha or beta RFLP groups, with a very low presence of the pa p gene, and random presence of V6 sequences, and were multiresistant to ant ibiotics. When the CAP strains were distributed according to underlying pat hology, non-obstructive cases had RFLP and V6 polymorphisms similar to thos e of UAP cases, while obstructive cases were clearly distinct. Conclusions UAP and non-obstructive CAP E. coli strains are sensitive to an timicrobials, show a high level of the pap gene and belong to the selective , homogeneous and highly protected molecular alpha2 group, where no recombi nations, deletions or insertions are present. On the contrary, obstructive and vesicorenal reflux E. coli strains show significant antimicrobial resis tance, high intercistronic heterogenicity (wide presence of block nucleotid ic substitutions, deletions or insertions) and significantly lower virulenc e.