**1. Introduction**

Urinary tract infections (UTIs) are among the most common infections encountered worldwide in clinical practice accounting for approximately 150 million cases annually causing heavy burden on health infrastructure [1]. Women, undoubtedly are at greatest risk as compared to males and it is been observed that almost 50% of all women have experienced UTI at least once in their lifetime. The infection may result either due to the pathogenicity of the offending microorganism, host susceptibility or a combination of both. While many different microorganisms are known to cause UTI which includes bacteria, viruses and fungi, bacteria remain the main cause responsible for over 95% of cases. Among bacteria, *Escherichia coli* (*E. coli)* is by far the most frequent cause responsible for nearly 80–90% of the infections [2]. The most common route of infection of *E. coli* is the bacterial colonization of the urethra followed by the ascension to the bladder. Normally, *E. coli* is present as a commensal flora in the lower gastrointestinal tract of

humans, nonetheless, there are a few highly adapted *E. coli* clones present that have acquired specific virulence attributes, which gives them an escalated ability to adapt to new niches and permits them to cause a broad spectrum of disease. Uropathogenic *Escherichia coli* (UPEC) is simply the pathotype of extraintestinal pathogenic *E. coli* which were first isolated from the urine of the patients having UTI. They differed from those cultured from the stool specimens of healthy individuals and those causing diarrhea, hence the term UPEC. UPEC strains possess an abundance of both structural (as fimbriae, pili, flagella) and secreted (toxins, iron-acquisition systems) virulence factors that play an important part in the pathogenesis, however its capability to adhere to host epithelial cells in the urinary tract serves as the most important determinant of pathogenicity [3].
