Tropism in bacterial infections: urinary tract infections

Tropism describes the phenomenon by which commensal and pathogenic bacteria are restricted to certain hosts, tissue and cell types. This review was done to shed light on the initiating factors in bacterial disease, more particularly those responsible for urinary tract infections.

The literature was reviewed on the tropism of several common bacterial infections with an extensive evaluation of tropism at the molecular level in urinary tract infections.

Interaction of bacteria with certain tissues, cells and molecules is described. Initially, bacterial adhesion occurs via bacterial fimbriae in the case of gram-negative bacteria, while gram-positive bacteria adhere more frequently via extracellular polysaccharides. Urinary tract infections occur most frequently because of adherence via P-fimbriae of Escherichia coli. P-fimbriae are important in cystitis as well, while type 1 fimbriae and nonfimbrial adhesins may also be responsible for its initiation.

The usual initiating mechanism in bacterial infections involves bacterial adhesion to specific molecules on cell surfaces, followed by invasive disease. The tip proteins of P-fimbriae of Escherichia coli lead to the initiation of urinary tract infection. Understanding the molecular events responsible may lead to development of a vaccine to prevent urinary tract infection.