The biology of cystitis: Host and bacterial factors

Cystitis is caused by a relatively small number of bacterial species. To co lonize and grow in the urinary tract, these organisms have developed and ac quired special properties (virulence factors) that allow them to overcome t he defences of the urinary tract, particularly clearance by urine flow. The se virulence factors are unlikely to be required during transmission from h ost to host, and sometimes their constitutive expression may actually be di sadvantageous. Such factors are therefore regulated by the environment and in a coordinate manner to ensure their most appropriate expression for the conditions encountered. This review focuses on the biology of the urinary t ract and the bacterial properties necessary to cause cystitis. The regulati on of virulence factors at the different stages of the infection is conside red, and a general model for the pathogenesis of urinary tract infection is proposed.