Urinary tract infection is caused by gram-negative bacteria, particularly califorms and affects all parts of urinary tract which consist of ureters, bladder, kidney, urethra and prostate in man through infection. Bacteria get in to urinary tract and infect single or multiple parts of it and thus, cause a urinary tract infection. “Cystitis” is the term used for bladder infection and pyelonephritis is known as kidney infection.
Infections at these various sites may take place simultaneously or separately and may either be asymptomatic which means clear symptoms for infection is absent or be there as one of the clinical syndromes described below.
Infections of the urethra and bladder are often considered superficial infections, where as prostatitis, pyelonephritis, and renal suppuration signify tissue invasion. From a microbiologic perspective, urinary tract infection (UTI) exists when pathogenic microorganisms are detected in the urine, urethra, bladder, kidney, or prostate. In most instances, growth of more than 100000 organisms per milliliter from a properly collected midstream clear urine sample indicates infection. However, significant bacteria in urine are missing in some cases of true UTI. Especially in symptomatic patients in whom clear symptoms can be seen for infection, a smaller number of bacteria (100 to 10000 per mL) may indicate infection. In urine specimens obtained by supra pubic aspiration or “in-and-out” catheterization and in samples from a patient with an indwelling catheter, colony counts of 100 to 10000 per ml generally indicate infection. Conversely, colony counts of more than 100000 per ml of midstream urine are occasionally due to specimen contamination, which is especially likely when multiple bacterial species are found.
Infections that occur again after antibiotic therapy can be due to the persistence of the originally infecting strain as judged by species, arteriogram, serotype, and molecular type or to re infection with a new strain. “Same-strain” recurrent infections that become evident within 2 weeks of cessation of therapy can be the result of unresolved renal or prostatic infection (termed relapse) or of persistent vaginal or intestinal colonization leading to rapid re infection of the bladder. However, this infection can be treated with care and specific treatment.