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25 Cards in this Set
- Front
- Back
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Learning objectives
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Cite the bacterial factors that contribute to the pathogenesis of UTIs
Cite the host factors that contribute to the pathogenesis of UTIs Know the major differences between the microbiology of community-acquired vs nosocomial UTIs Understand the role of urinalysis and quantitative urine cultures in the diagnosis of UTI Understand why males with UTI need to have further evaluation for anatomic abnormalities Know the differences in duration of therapy for cystitis, pyelonephritis, and prostatitis |
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UTI background
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UTIs are the most common infection encountered in the outpatient setting
Common problem in hospitalized patients, particularly those with urinary catheters Clinical manifestations differ based on affected portion of urinary tract Treatment regimen differs based on anatomic location of infection |
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Bacteriuria
Pyuria Cystitis Complicated UTI Pyelonephritis Prostatitis |
Bacteriuria: ≥10^5 organisms per milliliter
Pyuria: >10 wbc per high power field Cystitis: inflammation/infection of the bladder Complicated UTI: anatomic, functional or pharmacologic factors (also men and catheter) that predispose the patient to persistent infection recurrent infection or treatment failure Pyelonephritis: infection of kidney Prostatitis: infection of prostate |
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UTI Pathogenesis: Bacterial factors (7)
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1. Increased bacterial adherence to uroepithelial cells
-Mediated via fimbria (also called pili) -Two important types in E. coli --Type 1 fimbriae --P fimbriae 2. Resistance to serum cidal activity -Evades normal host defenses 3. Hemolysin production -Cell toxin, important in pyelonephritis 4. Ability to synthesize essential amino acids -Guanine, arginine and glutamine required for bacterial growth in urine 5. Urease production (Proteus mirabilis) -Important in pyelonephritis and urolithiasis 6. Bacterial motility -Ascend against urine flow 7. Endotoxin production -Decreases ureteral peristalsis |
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Type 1 and P fimbriae
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Seen in E.coli
Type 1 fimbriae (mannose-sensitive) -Adhere to mannosylated proteins on uroepithelial cells, can be detached by exposure to mannose -Bacterial tropism for bladder (cystitis) P fimbriae (mannose-resistant) -Adhere to glycophospholipids embedded in outer surface of plasma membrane of uroepithelial cells -Tropism for upper urinary tract (pyelonephritis) TMP-SMX reduces synthesis and expression of fimbria adhesion molecules |
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Different E.coli strains
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Pyelonephritis
-76% P fimbriae -60% produce hemolysin Most cystitis, asymptomatic bacteruria, and fecal flora don't have P fimbriae and hemolysis |
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UTI Pathogenesis: Host factors (6)
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1. Obstruction or reflux
-Urethral stenosis -Posterior urethral valves -Kidney stones -Polycystic kidney disease -Spinal cord injury or neurogenic bladder (incomplete bladder emptying) -Prostatic hypertrophy -Pregnancy 2. Short urethra (10-20% of women will develop a symptomatic UTI in their lifetime 3. Bacterial colonization of vagina (periurethra) 4. Sexual intercourse -Facilitates movement of bacteria from anterior urethra to bladder -Trauma to urethra -Diaphragm use (can cause urethral trauma) -Spermacide use (inhibit lactobacillus) 5. Bladder catheterization (bypasses urethra) -100% of patients will have bacteriuria within 3 days of catheter placement 6. Susceptibility of renal medulla -High ammonia concentrations inactivate complement -High osmolality inhibits migration of PMNs |
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UTI microbiology: community vs nosocomial
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Outpatient setting:
-E. coli is #1 -Followed by Klebsiella and Proteus spp. Inpatient setting: -E. coli still #1 -Microbiology is more diverse, other GNR #2 -Pseudomonas and Candida |
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UTI microbiology: other points
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UTIs are most often caused by a single organism
-Polymicrobial infections more likely to occur in those with structural abnormalities of the urinary tract Staphylococcus saprophyticus accounts for 5-15% of UTIs in young, sexually active females Staphylococcus epidermidis is an important nosocomial pathogen |
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Cystitis clinical manifestations
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Dysuria
Frequency Urgency Suprapubic pain |
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Pyelonephritis clinical manifestations
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Fever
Chills Flank pain Costovertebral angle tenderness Nausea and vomitting Hypotension Tachycardia Plus: symptoms of cystitis may be present |
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Asymptomatic bacteriuria clinical manifestations
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Bacteria in the urine with NO symptoms
≥10^5 cfu/mL = positive urine culture It does NOT prove infection; it is just a number to state that the culture is unlikely due to contamination Pyuria also is not predictive on its own It is the presence of symptoms AND pyuria AND bacteruria that denotes infection |
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Treatment of asymptomatic bacteriuria in the elderly
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Multiple prospective randomized clinical trials have shown no benefit
No improvement in “mental status” No difference in the number of symptomatic UTIs No improvement in chronic urinary incontinence No improvement in survival |
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Treatment of asymptomatic bacteriuria
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Screen and Treat ASB in 2 scenarios:
-Pregnancy -Patients undergoing urologic procedure in which bleeding is anticipated Children Otherwise, DO NOT TREAT |
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Urethritis: clinical manifestations and causes
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Primary symptom: burning on urination
No frequency or urgency Urine culture colony counts lower Causes: -Chlamydia trachomatous and Neisseria gonorrhoeae (purulent discharge from the urethra) -Ureaplasma urealyticum -noninfectious (trauma, allergic and chemical) |
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Prostatitis: clinical manifestations, PE findings, treatment
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Fevers, Chills
Dysuria Urinary frequency Bladder outlet obstruction can occur PE: high fever, may appear septic, moderate tenderness of suprapubic region Rectal exam: exquisitely tender and diffusely enlarged prostate Prostatic massage contraindicated ABX Therapy should be prolonged (4-6 weeks) as most abx do not penetrate well into acidic, lipophilic environment of the prostate |
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UTI: diagnosis
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Symptoms plus pyuria on urine dipstick or urinalysis
Urine dipstick: leukocyte esterase is rapid, sensitive U/A required for evaluation of complicated UTI -Centrifuge x 5 min at 2000 rpm -Examine the sediment at high power - > 10 WBC/hpf = pyuria - White blood cell casts can be seen in pyelonephritis |
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Urine gram stain
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Should be performed in all pts with suspected pyelonephritis
> 1 bacteria/hpf correlates with > 10^5 organisms/ml In combination with pyuria and symptoms = infection |
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Urine culture
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Should be performed in all patients EXCEPT young, sexually active women with suspected cystitis
-Recurrent UTI -Pyelonephritis -Catheter-associated urinary tract infection Urine in the bladder is normally sterile, but urethra and periurethral areas are very difficult to sterilize, particularly in woman Statistically differentiate using quantitative culture of midstream clean-voided urine |
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Anatomic investigations
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All upper tract disease
Relapse or failure to improve after appropriate abx therapy Preschool girls after their second UTI UTI in males of any age |
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Anatomic investigations: diagnostic tests
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Ultrasonography - sensitive, specific, inexpensive and safe. Test of choice.
CT scan - To exclude the diagnosis of perinephric abscess (no response to 48 hrs therapy in a patient with pyelonephritis) Intravenous pyelogram - after abnormal ultrasonogram |
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Uncomplicated cystitis: treatment
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Short course therapy (3-5 days)
-Nitrofurantoin -Trimethoprim-Sulfamethoxazole (TMP-SMX) -Ciprofloxacin β-lactams are an alternative (3-7 days) (don't need to memorize list): -Amoxicillin-clavulanate -Cefdinir -Cefaclor -Cefpodoxime |
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When not to use short course therapy
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Males
Upper tract symptoms (pyelonephritis) Recurrent or relapse of symptoms > 7 days of symptoms |
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Treatment of pyelonephritis
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All patients should have urine culture and susceptibility test performed
Adjust antibiotics based on the results 7-14 days of antibiotics -Intravenous ceftriaxone -Oral if nontoxic and able to tolerate p.o. --Ciprofloxacin --TMP-SMX |
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Prevention of UTI
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Sexually active women should void immediately after intercourse
Post-coital prophylaxis can be considered in sexually active women with recurrent UTIs -TMP-SMX -Nitrofurantoin Cranberry juice or concentrated tablets may be effective in preventing cystitis (particularly in elderly women) Intravaginal estrogen may be effective in preventing cystitis in elderly women with atrophic vaginitis Long-term antibiotic prophylaxis -NOT effective -Causes antibiotic resistance In-and-out straight catheterization preferable to indwelling catheterization in patients who are unable to void on their own |
