UTIs ppt

Learning Outcomes

  • Describe different types of urinary tract infections (UTIs).

  • Outline risk factors for UTIs.

  • Describe diagnostic tests for determining UTIs.

  • Discuss bacteria commonly found in the urinary tract.

  • Explain virulence mechanisms of uropathogenic E. coli.

  • Describe pathogenesis in catheter-associated UTIs.

Definitions

  • Urinary Tract Infection (UTI): Symptomatic infection within the urinary tract.

  • Asymptomatic Bacteriuria: Significant bacteria presence in urine with no symptoms, defined as > 100,000 mL-1 of a single species in a mid-stream urine sample.

  • Lower UTIs: Affect the bladder (cystitis) or urethra (urethritis).

  • Upper UTIs: Affect the kidneys (pyelonephritis) or ureters (ureteritis).

Types of UTIs

  • Uncomplicated UTIs: Occur in individuals with normal urinary tracts.

  • Complicated UTIs: Associated with abnormalities or factors like urinary obstruction or indwelling catheters.

  • Recurrent UTIs: Can be a relapse with the same organism or reinfection with a different one.

Epidemiology and Prevalence

  • UTIs account for approx. 1-3% of GP visits.

  • 1 in 3 women has had a UTI by age 24.

  • Asymptomatic bacteriuria prevalence in women can range from 2-10% during pregnancy.

  • Higher incidence in older women than men due to anatomical and physiological factors.

Risk Factors

Iatrogenic/Drugs

  • Indwelling Catheters: Provide access for bacteria to the bladder.

  • Antibiotic Use: Disrupts normal flora, allowing colonization by uropathogens.

  • Spermicides: Can irritate and facilitate E. coli attachment.

Behavioral

  • Frequent Sexual Intercourse: Increases risk of introducing bacteria into the urinary tract.

Anatomic/Physiologic

  • Female Anatomy: Shorter urethra increases risk.

  • Pregnancy: Changes in urinary tract anatomy can promote bacterial growth.

Genetic/Physiological

  • Family tendency and susceptible uroepithelial cells may lead to higher UTI rates.

Pathogenesis

  • Colonization Process: Uropathogenic E. coli must attach to the urinary tract lining, using adhesins like fimbriae and pili.

  • Bacteria colonize urethra -> bladder -> potentially kidneys under certain conditions.

  • Pyelonephritis: Inflammatory response leading to acute kidney injury can occur if bacteria ascend to the kidneys.

Common Bacteria in UTIs

  • Uropathogenic E. coli (UPEC): Most common cause of uncomplicated and complicated UTIs.

  • Other potential pathogens include Klebsiella, Staphylococcus saprophyticus, and Proteus species.

Diagnostic Tests

  • Chemical Tests/Dipstick: Used to assess for leukocytes, nitrites, and presence of blood, pH, etc.

  • Quantitative Urine Culture: Determines the presence of bacteria, essential for formal diagnosis.

Urinary Symptoms to Test

  • Dysuria: Painful urination.

  • Pyuria: White blood cells in the urine indicating infection.

  • Haematuria: Blood in the urine.

Uropathogenic E. coli Virulence Mechanisms

  1. Adhesion: Using fimbriae to firmly attach to the urinary tract, escaping from urine flow.

  2. Survival: Siderophores scavenge iron, essential for bacterial growth in iron-limited environments.

  3. Toxicity: Production of toxins causing inflammation and damaging host tissue.

Pathogenesis in Catheter-Associated UTI

  • Initial Attachment: Mediated by mannose-resistant Proteus-like pili.

  • Urease Production: Increases urine pH, aiding biofilm development.

  • Toxin Production: Includes haemolysin and proteases causing cell and tissue damage.

Antimicrobial Resistance

  • Rise in antibiotic-resistant UPEC strains highlights the need for effective management strategies.

WHO Priority Pathogens for Antibiotic Research

  • Critical: Acinetobacter baumannii, carbapenem-resistant Enterobacteriaceae.

  • High: Methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecium.

Summary

Understanding the pathogenesis and epidemiology of UTIs is crucial for effective diagnosis and treatment. Identification of virulence factors in causative pathogens helps in developing targeted therapeutic strategies.