Attachment of Proteus mirabilis to human urinary sediment epithelial cells in vitro is different from that of Escherichia coli.

The in vitro attachment of 335 Proteus mirabilis strains from various human sources to human urinary tract epithelial cells was measured. No significant difference in adhesive capacity was found between P. mirabilis strains isolated from the blood of 89 patients with bacteremia, the stools of 36 healthy subjects and 56 patients with diarrhea, and the urine of 62 adults and 92 children with bacteriuria. High mean adhesion values were observed in all groups. The P. mirabilis strains attached only to squamous cells and not to transitional epithelial cells, whereas most of the Escherichia coli strains tested attached to both cell types; strains from patients with acute pyelonephritis attached more often than those from patients with acute cystitis or asymptomatic bacteriuria. The attachment of P. mirabilis to squamous epithelial cells was high about day 15 of the menstrual cycle of the epithelial cell donor, but low at the beginning and the end of the cycle. In contrast, the attachment of E. coli to squamous and transitional epithelial cells did not vary significantly with the menstrual cycle of the cell donor. Differences in adhesion characteristics of E. coli and P. mirabilis may relate to the differences in clinical appearance of urinary tract infections produced by the two organisms.