INFECTIONS OF URINARY TRACT

• Urinary tract infections


  Among the most commonly encountered infections

  
• Community acquired UTI


  • More common in women
  • Mostly uncomplicated
• Community acquired UTI is more common in women due to the shorter urethra and the proximity of the anal opening to the urethral orifice in females
• Hospitalized patient UTI


  • Usually develops as a complication of prolonged urethral catheterization
  • Harder to treat as most are resistant to various antibiotics
• Urinary tract protection


  • Frequent flushing action of urination
  • Constant sloughing of the epithelium
  • Acidity of normal urine inhibits the growth of many microorganisms

  
• Routes of bacteria reaching the kidneys

  • Through the bloodstream
  • Ascending infection from the lower urinary tract
• The most common route is by ascending infection
• Predisposing factors to UTI

  • Gender
  • Mechanical factors
  • Metabolic disorders
  • Anatomic abnormalities of the urinary tract

  
• Common etiologic agents of UTI

  • Enterobacteriaceae (Escherichia coli, Klebsiella pneumoniae)
  • Staphylococcus saprophyticus
  • Enterococci (Enterococcus faecalis)
  • Opportunistic pathogens (Pseudomonas, Proteus, Serratia)

  
• Less common etiologic agents of UTI

  • Bacteria (S. aureus, Corynebacterium, Lactobacilli)
  • Yeast (Candida)
  • Viruses (Adenovirus type 2)
• Escherichia coli


  • Gram negative bacillus that is part of the normal microbial flora of the human body, specifically the colon
  • Infections are endogenous
  • Improper washing after defecation is a factor that promotes entry into the urinary tract, most specially in women due to the proximity of the urethral orifice to the anal opening
  • The most common cause of community acquired UTIs

  
• Proteus mirabilis


  • Gram negative bacilli that are members of the family Enterobacteriaceae
  • Produces urease which causes alkalinization of urine, making the patient more prone to development of urinary stones
  • The second most common cause of community acquired UTI and a major cause of nosocomial infections

  
• Serratia spp.


  • Gram negative bacilli that belong to the family Enterobacteriaceae
  • Major entities in nosocomial infections
  • Almost all infections caused by these organisms are associated with underlying disease, changing physiological patterns, immunosuppressive therapy, or mechanical manipulations of the patient
  • The most frequently isolated species is Serratia marcescens which produces a bright red pigment called prodigiosin
• Enterococcus faecalis


  • Part of the normal enteric flora, belonging to the family Enterobacteriaceae
  • Grow in 6.5% NaCl and are more resistant to penicillin G
  • The most common among the Enterococci
  • Frequent causes of nosocomial infections, particularly in intensive care units
  • Transmitted from one patient to another primarily from the hands of hospital personnel
  • In urinary tract infections, enterococci are usually cultured along with other species of bacteria

  
• Staphylococcus saprophyticus


  • Gram positive coccus and a common cause of urinary tract infections in sexually active young women
  • A common colonizer of the urinary tract

  
• Pathogenesis of UTI


  1. Infecting organism is derived from the patient's own fecal flora

  2. Bacteria can reach the kidneys through the bloodstream or from the lower urinary tract (ascending infection)

  3. Ascending infection is the most common cause of clinical pyelonephritis

  4. Infection begins with colonization of the distal urethra and introitus by the invading organism

  5. Organism then ascends to the urinary bladder

  6. Instances that can cause incomplete voiding of the urine can lead to urine stasis, allowing the bacteria to further multiply

  7. Chronic infection leads to ascent of the organism to the kidneys, leading to the development of an upper urinary tract infection

  
• Portions of the urinary tract that may be involved in the infection

  • Urethra (urethritis)
  • Urinary bladder (cystitis)
  • Kidneys and its tubules (pyelonephritis)

  
• Cystitis


  • Inflammation of the urinary bladder
  • The most common type of urinary tract infection
  • Most commonly caused by E. coli

  
• Urethritis


  • Inflammation of the urethra
  • Organisms involved are usually sexually transmitted, the common causes of which are Neisseria gonorrhoeae and Chlamydia trachomatis (non gonococcal urethritis or NGU)

  
• Pyelonephritis


  • Inflammation of the kidneys, particularly of the tubules
  • The most frequent cause is E. coli
  • Most often is the result of an ascending infection, but the offending organism may also reach the kidneys through the bloodstream
• Complications of UTI include bacteremia and septic shock, severe renal damage, or end stage chronic pyelonephritis leading to renal failure
• Common clinical manifestations of urinary tract infections

  • Lower urinary tract infection: Urethritis, Cystitis, Urethrocystitis
  • Upper urinary tract infection: Acute Pyelonephritis

  
• Urinalysis


  • One of the oldest clinical laboratory procedures
  • Involves gross observation and assessment of general appearance of urine, dipstick analysis, and microscopic examination of formed elements in urine
  • One of the most commonly performed laboratory tests
  • Appropriate specimen collection is important

  
• Urine collection methods


  • Clean voided mid stream technique
  • Suprapubic aspiration
  • Diagnostic catheterization
  • From an in dwelling catheter
  • During cystoscopy, ureteral catheterization or retrograde pyelography

  
• The usual practice is to use the clean voided mid stream technique
• Urine culture


  • The best method to diagnose urinary tract infection
  • Urine collection follows the same principles as in doing a routine urinalysis
  • Specimen should be examined within 15 minutes of collection to avoid false positive results
  • Colony count of 100,000/mL or more in a clean voided mid stream specimen indicates significant bacteriuria
  • Colony count less than 1,000/mL represents contamination
  • Colony count between 1,000 and 100,000/mL and a single microbial species represents possible or probable infection

  
• Treatment of UTI


  • Any antibiotic eliminated by the kidney and to which the organism is susceptible can be used effectively and safely
  • Culture and susceptibility testing are important for pyelonephritis and complicated cases, and when the patient is not responding to the antibiotic therapy
  • For uncomplicated infection with E. coli, the recommended drug of choice is Trimethoprim Sulfamethoxazole given 3-7 days
  • For infections with Proteus and Pseudomonas, Fluoroquinolone is the antibiotic of choice
  • In cases of acute pyelonephritis, Fluoroquinolones or third generation cephalosporins may be given for a period of 3-10 days
  • Increased water intake is also often advised to avoid dehydration