**16. Conclusions**

A wide range of UPEC VFs have been established epidemiologically or experimentally (*in vivo*) as being important in UTI pathogenesis. No single VF profile has been proven to be important in causing any particular UTI syndrome. Indeed, studies have suggested that UTI pathogenesis is multiply determined. Thus, intervention strategies based on VF genes might have to involve multiple targets, which would offer the extra advantage of protection against a wide range of UTI syndromes. This observation, which is in agreement with previous studies, provides evidence that VF repertoire is as, or more, important than phylogenetic background for predicting pathogenic behavior in UPEC.

The prevalence of antibiotic resistance among human urine *E. coli* isolates has risen substantially in recent years, especially to first line agents such as fluoroquinolones and trimethoprimsulphamethoxazole. Furthermore, multidrug-resistant *E. coli* ST131 has shown rapid global dissemination among humans and animals, which has coincided with the general increase in resistance among *E. coli* clinical isolates. A better understanding of the microbiological basis for the emergence of UPEC antibiotic resistance is necessary for guiding efforts aimed at interrupting this process. Further studies on ST131 are clearly needed to explain its impressive emergence so that control measures can be devised and implemented.
