Urinary tract infection (UTI) refers to microbial infection of any part of the urinary system, including the urethra, bladder, ureters and kidneys. Most UTIs are caused by bacteria that colonize and inflame the mucosal surfaces, leading to symptoms such as dysuria and increased frequency.
Pathogenesis and etiology
The majority of UTIs arise from ascending infection of the lower urinary tract. Uropathogenic Escherichia coli strains are responsible for around 80 % of cases, using fimbriae to adhere to uroepithelial cells and evade urine flow. Other bacteria such as Klebsiella, Proteus, Enterococcus and Staphylococcus saprophyticus contribute to community‑acquired or nosocomial infections. Risk factors include female anatomy, sexual intercourse, indwelling catheters, urinary obstruction and underlying diseases like diabetes. When bacteria ascend from the bladder to the kidneys they can provoke pyelonephritis, which carries a risk of bacteremia. Host defenses involve regular urine flow, antimicrobial peptides and immune responses, but these can be overwhelmed in susceptible individuals.
Clinical manifestations and management
Lower UTIs, such as cystitis and urethritis, commonly present with burning on urination, urgency and suprapubic discomfort, while upper UTIs present with flank pain, fever and malaise. Diagnosis is based on urinalysis showing pyuria and bacteriuria, with culture used to identify the causative organism and guide therapy. Empirical treatment often involves trimethoprim‑sulfamethoxazole, nitrofurantoin or fluoroquinolones, but antimicrobial resistance is an increasing concern. Preventive strategies include adequate hydration, timely catheter removal and, in recurrent cases, prophylactic antibiotics or behavioral interventions.
UTIs are among the most common bacterial infections encountered in primary care. Understanding the pathogenesis, clinical features and risk factors helps in prevention and appropriate management.
Related Terms: Cystitis, Pyelonephritis, Urethritis, Uropathogenic Escherichia coli, Urinalysis