Urinary tract infections (UTIs) can affect different parts of the urinary tract including the urethra, bladder, and kidneys. UTIs are classified as uncomplicated if occurring in a generally healthy person without structural issues, or complicated if associated with underlying conditions. Escherichia coli is the most common cause of uncomplicated UTIs. Virulence factors like fimbriae and toxins help bacteria adhere and infect the urinary tract. Treatment involves antibiotics administered orally or intravenously depending on severity. Complications can include recurrent infections, kidney damage, low birth weight, and even sepsis.

1. URINARY TRACT INFECTIONS
• Infections of the urinary tract which represents a wide variety of
syndromes including urethritis, cystitis, prostatis and pyelonephitis.
• Classified into:
• Uncomplicated UTI : Infection in healthy female who lacks structural or
functional abnormalities of the urinary tract.
• Complicated UTI: Complicated infections associated with predisposing
lesions of the urinary tract.

2. ETIOLOGY
• The bacteria causing UTIs usually originate from bowel flora of the host.
• The most common cause of uncomplicated UTIs is Escherichia coli, which
accounts for 85% of community-acquired infections.
• Additional causative organisms in uncomplicated infections include
Staphylococcus saprophyticus (5% to 15%), Klebsiella pneumoniae,
Proteus spp., Pseudomonas aeruginosa, and Enterococcus spp. (5% to
10%).

3. PATHOPHYSIOLOGY
ROUTE OF INFECTION
• In general, organisms gain entry into the urinary tract via three possible
routes: the ascending, hematogenous (descending), and lymphatic pathways.
• The female urethra usually is colonized by bacteria believed to originate from
the fecal flora. The short length of the female urethra and its proximity to the
perirectal area make colonization of the urethra likely.
• Bacteria have reached the bladder, the organisms quickly multiply and can
ascend the ureters to the kidneys.
• Infection of the kidney by hematogenous spread of microorganisms usually
occurs as the result of dissemination of organisms from a distant primary
infection in the body.
• There are lymphatic communications between the bowel and kidney, as well
as between the bladder and kidney.

4. HOST DEFENSE MECHANISMS
• The normal urinary tract generally is resistant to invasion by bacteria and is
efficient in rapidly eliminating microorganisms that reach the bladder.
• The urine under normal circumstances is capable of inhibiting and killing
microorganisms.
• The factors thought to be responsible include a low pH, extremes in
osmolality, high urea concentration, and high organic acid concentration.
• Bacterial growth is further inhibited in males by the addition of prostatic
secretions.
• The epithelial cells of the bladder are coated with a urinary mucus or slime
called glycosaminoglycan.
• This thin layer of surface mucopolysaccharide is hydrophilic and strongly
negatively charged.
• When bound to the uroepithelium, it attracts water molecules and forms a
layer between the bladder and urine.

5. BACTERIAL VIRULENCE FACTORS
• The mechanism of adhesion of gram-negative bacteria, particularly E. coli,
is related to bacterial fimbriae that are rigid hair like appendages of the
cell wall.
• Other virulence factors include the production of hemolysin and
aerobactin.
• Hemolysin is a cytotoxic protein produced by bacteria that lyses a wide
range of cells, including erythrocytes, PMNs, and monocytes.
• E. coli and other gram-negative bacteria require iron for aerobic
metabolism and multiplication.
• Aerobactin facilitates the binding and uptake of iron by E. coli.

8. TREATMENT
• Urinary analgesics such as phenazopyridine hydrochloride are used frequently
by many clinicians.
• Conventional therapy consisted of an effective oral antibiotic administered for
7 to 14 days.
• A number of antibiotic regimens have been used as empirical therapy,
including an intravenous fluoroquinolone, an aminoglycoside with or
without ampicillin, and extended-spectrum cephalosporins with or without
an aminoglycoside.
• Other options include aztreonam, the β-lactamase inhibitor combinations
(e.g., ampicillin sulbactam, ticarcillin-clavulanate, and piperacillin-
tazobactam), carbapenems (e.g., imipenem, meropenem, or ertapenem), or
intravenous trimethoprim-sulfamethoxazole.

9. COMPLICATIONS
Complications of a UTI may include:
• Recurrent infections, especially in women who experience two or more UTIs
in a six-month period or four or more within a year.
• Permanent kidney damage from an acute or chronic kidney infection
(pyelonephritis) due to an untreated UTI.
• Increased risk in pregnant women of delivering low birth weight or
premature infants.
• Urethral narrowing (stricture) in men from recurrent urethritis, previously
seen with gonococcal urethritis.
• Sepsis, a potentially life-threatening complication of an infection, especially if
the infection works its way up your urinary tract to your kidneys.