Screening of uropathogenic Escherichia coli for expression of mannose-selective adhesins: importance of culture conditions.

I surveyed the prevalence of mannose-sensitive adherence factors (adhesins) in uropathogenic Escherichia coli isolates by using several rapid screening tests based on the agglutination of stained yeast cells. Mannose-sensitive adhesin activity was demonstrated best for bacteria grown in aerobic static broth cultures. Under these conditions, the majority of the strains from patients with significant bacteriuria (55[85%] of 181 isolates) or upper urinary tract infections (19[79%] incidence of mannose-sensitive adhesion activity was detected for strains cultured on solid medium. Thus, only 26 (51%) of 51 fresh isolates from cases of significant bacteriuria appeared to have mannose-sensitive adhesin activity when they were tested directly on the primary isolation medium (MacConkey agar), whereas after serial static broth subculturing, 45 (88%) of these strains were active. Many of the nonagglutinating weakly agglutinating strains detected were also nonmotile. Various other enterobacteria showed strong agglutinating activity toward the yeast cells, and in most cases these reactions were blocked by mannose. However, a few notable exceptions were found.