Week 6: UTI ID Flashcards
What type of bacteria cause most UTIs? What % of the time is it this type?
Normal enteric flora, 95%. Note: these are not the species that cause GI disease.
What is ABU?
Asymptomatic bacteriuria. UTI minus symptoms.
First line antimicrobials for uncomplicated UTI for men vs women
Men: Fluoroquinolone or TMP-SMX
Women: Nitrofurantoin or TMP-SMX
Therapy for complicated UTIs
Individualized, based on culture results
Natural barriers to harmful pathogens in urinary tract (4)
acidity of urine, act of urination -> desquamation, mucosal lining, urethral sphincter
What percent of UTIs occur by bacteria ascending the urethra? How do the rest occur?
90%. Rest are hematogenous.
What makes a UTI complicated?
underlying factors -> predisposed to ascending bacterial infection e.g. catheter, anatomic abnl, obstruction of urine flow, poor bladder emptying.
How do antibiotic and spermicide use make UTI more likely?
Change vaginal flora allowing for overgrowth of E. coli.
Pathogen most common for acute uncomplicated UTI. What percent of the time? How does it accomplish this?
E. coli 75%. Special attachment factors for transitional epithelium
____ is the #2 cause of uncomplicated UTI and accounts for ___%, more frequent in ________.
Staphylococcus saprophyticus, 5-15%, younger women
5-10% of uncomplicated UTIs caused by what other enteric organisms?
Klebsiella, Proteus, Enterococcus, Citrobacter.
Most common cause of complicated UTI
E. coli
Other causes of complicated UTI
Aerobic and facultative anaerobic gram neg rods inc: Klebsiella, Proteus, Citrobacter, Acinetobacter, Morganella, and Pseudomonas. Gram Pos: enterococci and staph aureus. Yeasts. (prob don’t need to know all these, just that there are many).
E. coli virulence factors contributing to UTI
Surviving low pH + surface adhesions. P fimbriae: hair-like protein interacting w renal epithelial cells, important in pyelonephritis and subsequent bloodstream invasion. Type 1 pilus (fimbria): all e. coli possess, not all express, mediate binding to uroplakins on bladder uroepithelial cells.
How does Sulfamethoxazole work?
Inhibits PABA to DHF via dihydropteroate synthetase
How does Trimethoprim work?
Inhibits conversion of DHF to THF via dihydrofolate reductase
How do the fluoroquinolones work?
Bind topo II/DNA gyrase –> tension -> double strand breaks
How does nitrofurantoin work?
Bacterial nitrofuran reductase reduces the drug -> damage or inactivate ribosomal proteins
How does urine chemistry block colonization? (3)
Acidity, lysozyme (breaks down peptidoglycan), lactoferrin (binds iron to prevent microorganisms from scavenging it)
How do the epithelial cells of the urinary tract prevent colonization?
Surface proteins differ from those of GI tract - prevents most enteric from gaining a foothold
What adaptive immune response defends the urinary tract?
Secretory IgA (requires previous exposure)
How does normal flora of the urinary tract prevent pathological colonization?
Physical barrier
What are the 3 major threats to the urinary system?
Microorganisms moving from GI to urinary tract, catheters, immune system malfunction -> glomerulonephritis
Cause of urine cloudiness in UTI (2)
Bacteria and WBCs
