The influence of growth media on the morphology and in vitro adherence characteristics of gram-negative urinary pathogens.

We studied the adherence of 3 groups of gram-negative urinary pathogens, grown in different culture media, to human uroepithelial cells obtained from healthy females (controls) and from female patients with recurrent urinary tract infection, using an in vitro adhesion assay and electron microscopy. Morphologic examination and mannose sensitivity testing of the uropathogens grown in urine showed that they expressed extracellular structures similar to those found in infected urine in vivo. However, the production of various bacterial extracellular structures responsible for adhesion can be enhanced or decreased when the same uropathogens are grown in media other than urine, resulting in an alteration of the mean adherence of the uropathogens to uroepithelial cells. Brain Heart Infusion broth enhances the production of fimbriae, Modified Vogel and Bonner's Medium enhances the production of exopolysaccharides, and yeast nitrogen base decreases the production of both. These studies suggest that bacterial extracellular structures should be examined morphologically prior to in vitro adhesion assays and that urine is the medium of choice for studying the adherence characteristics of various urinary pathogens in vitro.