Review Article International Journal of Medical Microbiology and Tropical Diseases, January-March,2016;2(1): 10-18 10 Adhesins of Uropathogenic Escherichia coli (UPEC) Sabitha Baby 1 , Vimal Kumar Karnaker 2,* , Geetha R K 3 1 Assistant Professor, 3 Professor & HOD, Dept. of Microbiology, Karuna Medical College, Palakkad, Kerala, India 2 Professor & HOD, Dept. of Microbiology, KSHEMA, NITTE, Mangalore, Karnataka, India *Corresponding Author E-mail: vimalkarnaker@yahoo.co.in Abstract Uropathogenic Escherichia coli (UPEC) is the main pathogen associated with urinary tract infections namely cystitis, pyleonephritis and infectious complications. As a commensal, E.coli is mostly harmless in the gut. Some strains diverge and become more pathogenic. They express multiple virulence factors and invade the urinary tract (UT). The important ones are the ‘adhesins’ or specialized proteins with sticky ends, which help to break the inertia of urinary bladder mucosa and help to attach to them. Host immune response trigger inflammatory reactions, resulting in symptoms of urinary tract infections (UTI). Recent studies help to get updated information about the molecular mechanisms behind the adhesins. This knowledge is helpful for better understanding of the pathogenesis of UTI which can then be applied to epidemiological research. It also helps to understand the revolutionary trends, to help with better prognosis and to devise new methods in lab diagnosis & vaccine development. This review is intended to unravel the molecular components that makeup the adhesions of UPEC. Key words: Adhesins, AFA, Curli, CUP, Pap, SFA, UPEC Introduction Escherichia coli (E.coli) are highly versatile organisms. The commensal E.coli peacefully exists in mammalian gut niche. It is a successful competitor at this crowded site. There are other highly evolved strains among E.coli that cause broad spectrum of infections with the help of virulence factors. Expression of these factors are through the genetic elements that can be mobilized into different groups to form new combinations. Only the successful combinations persist long to become a Pathotype.(A group of strain of a single species that can cause common disease using a common set of virulence factors)(1). E.coli is categorized into Diarrhoeagenic E.coli, the pathotype associated with enteric/diarrhoeal diseases, the Uropathogenic E.coli (UPEC), causing UTIs and E.coli causing Sepsis/meningitis, Meningitis associated E.coli (MNEC). The E.coli causing infections outside intestine is also termed as Extra Intestinal Pathogenic E.coli (ExPEC). The six categories among diarrhoegic E.coli include enteropathogenic E.coli (EPEC), enterohaemorrahagic E.coli (EHEC), entero invasive E.coli (EIEC), enterotoxigenic E.coli (ETEC) and diffusely adherent E.coli (DAEC). Pathotypes of Diarrhoeagenic E.coli give rise to gastroenteritis but not any infection outside intestine. The ExPEC will exist in gut without consequence but will disseminate and colonize other niches causing disease (2). UTI is defined as the presence of significant number of pathogenic organisms in urinary tract, along with symptoms, while recurrent UTI can be defined as two or more episodes within six months or three or more episodes in one year(3). UPEC are responsible for more than 90% of UTI, in both sexes. E.coli is the primary cause for community acquired UTI (70-90%) and to a large part of nosocomial UTIs(50%), accounting for substantial medical costs and morbidity worldwide(4). The women & children are more prone. The incidence of UTI in women increases with age and has a peak in the twenties(5). Sexually active women aged 20-40years and postmenopausal women older than 60 years are the two populations at highest risk of UTI. The life time risk of symptomatic UTI among women has been found to be 60%(6). Factors such as shortness of urethra, sexual activity, contraceptives, estrogen deficiency, diabetes, obstructing lesions and genetic factors such as blood group secretor status increase a woman’s likely-hood of contracting UTI(7). The prevalence of asymptomatic bacteriuria (ABU) in healthy women has shown to increase with age by about 1% in age group 5 to 14 while about 20% in elderly living in community. In ABU carrier state E.coli strains exist without symptoms. For many groups ABU screening is not beneficial, while for other groups like pregnant women and people undergoing traumatic genitourinary procedures ABU screening is useful for better outcome(8). It is believed that the primary reservoir for UPEC is the intestine and that E.coli get introduced into the urethra (ascending hypothesis). E.coli strains colonize the bladder after travelling from gut to reach vaginal and periurethral area will cause cystitis, the common form of UTI. It is marked with dysuria, frequency, burning sensation& pain. UTI can proceed from bladder, via ureters to the kidney to cause pyleonephritis. It can damage the kidneys and result in kidney failure. This is associated with flank pain, fever, nausea and vomiting and may even progress to septicemia. Pyleonephritis is less common type of symptomatic UTI than cystitis(3).