Background In urology and nephrology units the rate of urinary tract infections and its complication is one of the main infective causes of mortality and morbidity. Early and prompt antibiotic therapy based on the knowledge of the prevalent microorganisms can help reduce this rate. The objective of the study was to assess the microbiology and rate of bacteremia causing urinary tract infections in the urology and nephrology unit of our institute. Methods This was retrospective study over 4 month period (July to October 2010); 103 paired urine and blood samples from urology and nephrology unit received in the clinical laboratory were analyzed. Microbiological data was retrieved from laboratory data base. Cultures were performed using standard microbiological methods. Organisms were identified using routine biochemical tests. Antibiotic susceptibility testing was performed with Kirby-Bauer disc diffusion method using Clinical laboratory standard institute (CLSI) standards. Results Significant bacteriuria was found in 68% and 31% had only bacteremia. E.coli was the most commonly isolated organism from blood and urine culture, 60% were extended spectrum beta lactamases producers. About 14% of the patient had concordant organisms in blood and urine cultures and were labeled as urosepsis, while 6% patients had disconcordant results with different organisms in blood and urine and 8% had negative urine culture and positive blood cultures. Conclusion Rates of urinary tract infection are high and lead to bacteremia in one third of the patients and can be reduced with stringent infection control practices. Key Words Bacteremia, Urinary Tract Infection, Urology. Introduction Urinary tract infection (UTI) is one of the major causes of Corresponding Author: Muhammad Zeeshan, Department of Microbiology, Sindh Institute of Urology and Transplantation (SIUT), Karachi, Pakistan. E-mail: dr.zeeshan1@gmail.com morbidity and mortality throughout the globe especially in hospitalized patients. 1 Systemic infection or bacteremia complicating UTI happens in patients with underlying risk factors that include urinary tract instrumentation (e.g., catheterization, cystoscopy), anatomic abnormalities, urine out flow obstruction or poor bladder emptying, immunocompromised population such as post renal transplant, diabetic and chemotherapy recipients. 2 Bacteria can enter the bladder with the insertion of the catheter, through the catheter lumen, or from around the outside of the catheter. A biofilm develops around the outside of the catheter and on the uroepithelium. Bacteria enter this biofilm, which protects them from the mechanical flow of urine, host defenses, and antibiotics, making bacterial elimination difficult. 3 About 15 % of UTI patients have bacteremia at the time of presentation to the hospital and the source of 20% of hospitalacquired bacteremia is the urinary tract. The mortality associated with this condition is about 10%. 4,5 The microbiological spectrum of uropathogens are changing in urology unit with increasing incidence of Gram positive organisms such Enterococcus faecalis, Staphylococcus aureus, however members of family Enterobacteracea are still the predominant pathogen. 6 Pathogens causing Bacteremia in Patients with Urinary Tract Infection in Urology and Nephrology Units of a Tertiary Care Hospital in Karachi, Pakistan Sadaf Baqai, Muhammad Zeeshan, Saleem Hafeez, Syed Kashif Raza, Parpoola Kumari Department of Microbiology, Sindh Institute of Urology and Transplantation, Karachi, Pakistan Abstract ORIGINAL ARTICLE