Urinary Tract Infections - Robinson & Guralnick Flashcards Preview

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Flashcards in Urinary Tract Infections - Robinson & Guralnick Deck (55):

Name four ways in which commensals contribute to host defense of the urinary tract.

  1. Compete with pathogens for resources
  2. Produce AMPs (bacteriosins)
  3. Keep innate immune cells in "attentive" state
  4. Lower vaginal pH.


What commensal genus comprises a significant proportion of the vaginal flora in a healthy woman?

How do species of this genus protect the host?


  • Compete for resources with pathogens
  • Decrease vaginal pH via lactic acid production
  • Produce H2O2


What host defenses exist within the urinary tract itself?

What defenses are notably absent from the urinary tract during times of health?

N.B. Urinary tract defenses are more limited than in the genital tract

  • Physical force of urine fow
  • Exfolitation of epithelial cells
  • AMPs
    • Produced by most epithelia along the urinary tract
  • Innate and adaptive leukocytes are absent from the lower urinary tract during times of health


What AMP of particular significance acts in the urinary tract?

Where is this AMP produced?

Tamm-Horsfall Protein (TMP)

Prevents adhesion of uropathognic E. coli (UPEC) to urinary epithelium

Produced in the kidney Loop of Henle


As urine flow physically prevents the ascension of pathogens up the urinary tract, impaired flow is a risk factor for UTI.

How many causes of impaired urine flow can you think of?

[Memorizing this is likely low-yield]

  • Congenital abnormality
  • Urethral stricture
  • Urethral stone
  • Neurogenic dysfunction
  • Mass obstruction, e.g. cancer
  • BPH or prostate cancer
  • Cystocele
  • Pregnancy
  • Likely several others


What parts of the urinary tract act as one-way valves to prevent urine flow from backing up toward the kidneys?

Ureterovesical junctions

The points where the ureters attach to the bladder


The physical force and pressure of urine flow necessitates that the lower urinary tract epithelia be what?


TRANSITIONAL epithelium!


  1. The appearance of bladder epithelial cells in the urine are a sign of what process?
  2. What is driving this process?

  1. Exfoliation - defense against pathogens, ejects them into the urine
  2. Presence of exfoliated cells in urine indicates a UTI!


  1. Where does an ascending UTI originate from?
  2. Where does a descending UTI originate from?

Which is more common?

  1. Ascending: Pathogen moves up toward the kideys from the urethra
    • Most common form by far
  2. Descending: Due to hematogenous spread
    • Only ~5% of UTIs


What is the difference between a complicated versus an uncomplicated UTI?

  • Uncomplicated
    • A simple, run of the mill UTI (essentially, anthing that is not complicated)
  • Complicated
    • Associated with one of the following:
      • Structural abnormality
      • Functional abnormality
      • Presence of a comorbidity
    • Increases the risk of acquiring an infection or of failing therapy
    • More prone to become disseminated, resulting in sepsis or even death


What are the most significant risk factors for UTI in the following age groups?

  1. Children up to 15yo
  2. 16-35yo
  3. >35yo

  1. Anatomic GU abnormalities
  2. Sexual intercourse, diaphragm use
  3. Surgery, prostate obstruction, catheterization, incontinence


What is the major reason women are more susceptible to UTIs?

Women have a shorter urethra (~4cm) than men (~20cm)


What is/are the most common causative organism(s) of UTIs in:

  1. Adults?
  2. Children?
  3. Hospital inpatients? (nosocomial)

  1. Uropathogenic E. coli (UPEC)
  2. Klebiella spp. and Enterobacter spp.
  3. Pseudomonas aeruginosa


What structure of UPEC allows the bacteria to adhere to bladder epithelia?

Type 1 pili


Following infection, the bladder can recruit neutrophils, causing inflammation.

  1. How does bladder inflammation present?
  2. How can bladder inflammation be diagnosed via urinalysis?

  1. Symptoms:
    • Painful urination
    • Low grade abdominal discomfort
    • Low grade fever
    • Pelvic pressure
    • Frequent urination
  2. Diagnosed by presence of leukocytes in urine


What is leukocyte esterase?

What does it signify?

  • A protein released during the degranulation of activated leukocytes
  • Signifies pyuria (pus or WBC in urine)


Other than sensitivity of the pathogen, what is an important factor to consider when prescribing antibiotics for a UTI?

Ability of the antibiotic to concentrate in the urine well


What is coital prophylaxis?

Antibiotics prescribed to individuals who frequently develop a UTI following coitus.

Meant to be taken prophylactically before coitus takes place to prevent a possible UTI.


What is a critical factor in determing how effective the treatment of a complicated UTI will ultimately be?

Whether or not the underlying anatomical or functional issue is resolved!


UPEC's ability to reside where is a cause of recurrent UTIs?

Urinary calculi (stones!)


Challenge Card! [Thanks for the idea, Tim! Muahahaha...]

1. If a urinalysis dipstick test shows alkaline urine in the presence of UTI symptoms and positive leukocyte esterase, what is the likely causative agent?

2. If you carried out the dipstick testing in question for this case, what else would you likely notice about the urine?

1. A urea-splitting bacteria such as Proteus.

The bacteria splits urea into CO2 and ammonia, causing a rise in the urine's normally acid pH.

2. The urine would likely smell rancid due to the ammonia odor


For the purposes of UTIs, what is considered a "lower tract UTI"?

An "upper tract UTI"?

Lower: Infection of the bladder, prostate, or urethra.

Upeer: Infection of the kidney or ureter.


What is a UTI that mainly involves the bladder called?

What about one that mainly involves the kidney?

Bladder: Cystitis

Kidney: Pyelonephritis


  1. What percentage of women will develop a UTI during their lifetime?
  2. What percentage of nosocomial infections are UTIs?
  3. What percentage of hospital-presenting bacteremias each year start as a UTI?

  1. 60%
  2. 40%
  3. 40%


What are six symptoms of cystitis?

  • Dysuria (painful urination)
    • Burning, stabbing, "peeing glass shards"
  • Urinary frequency
  • Urinary urgency
  • Suprapubic pain/discomfort/pressure
  • Cloudy and/or smelly urine
  • Hematuria


What possible symptom of UTIs is particularly concerning and needs to be worked up to ensure the UTI is the actual source of the symtom?

Gross (visible) hematuria


Your patient presents with painful urination. Before you assume a UTI is to blame: what is the differential diagnosis of dysuria?

  • UTI
  • Diet-related irritants
  • Vulvitis/Vaginitis
  • Stones/foreign body
  • Atrophy
  • Recent intercourse
  • Interstitial cystitis and other inflammatory conditions


What are the symptoms of pyelonephritis?

  • Flank or back pain
  • High fever, chills
  • Headache
  • Nausea/vomiting
  • Septic shock possible
  • +/- symptoms of cystitis?


Name 5 anatomic or functional abnormalities of the GU tract that predispose an individual to complicated UTIs. Which one is mainly a pediatric issue?

  1. Urinary obstruction (BPH, scarring, stones)
  2. Urinary stasis (incomplete emptying, diverticulum)
  3. Vesicoureteral reflux (mainly a pediatric issue)
  4. Foreign body (catheter / stone)
  5. Neurogenic bladder with high pressures


Other than structural or functional abnormalities, what else can predispose an individual to complicated UTIs?

  • Immunocompromised or unhealthy host (incl. severe diabetes)
  • Multi-drug resistant bacteria


Name seven characteristics of urine that a urine dipstick test is good for measuring.

  1. Urinary blood
  2. Pus (leukocytes)
  3. Bacteria
  4. pH
  5. Specific Gravity (concentration)
  6. Protein
  7. Glucose


What is the definitive test for blood and pus in the urine?

Why is it more definitive than a urine dipstick?

Microscopic analysis

Dipsticks can have false positives - good to confirm with microscopy before proceeding


  1. What is the DDx of pyuria (pus / WBC in urine)?
  2. What protein in the urine signifies pyuria, again?

  1. DDx
    • Pregnancy
    • Vaginal infection
    • Inflammation from bladder, kidneys, or adjacent organs
    • Tumors
    • Stones
    • Non-bacterial cystitis
  2. Leukocyte esterase


Given that: 

  • UTIs usually have pyruria, but
  • the DDx of pyuria contains several possible diagnoses:
  1. What is the sensitivity of a positive leukocyte esterase (LE) test for UTI?
  2. What is the specificity of a positive LE for UTI?

  1. Sensitivity is HIGH
    • Since most UTIs have pyuria, a negative LE likely rules out UTI
    • High sensitivity = low false negative rate
    • "SnOUT"
  2. Specificity is LOW
    • Since several other conditions can cause pyuria, a positive LE does not specifically indicate a UTI
    • Low specificity = significant false positive rate
    • "SpIN"


If you find nitrites in a UTI patient's urine, what do you know about the causative bacteria?

That the bacteria expresses nitrate reductase

Nitrates --> Nitrites


Given that:

  • Only a bacterial presence would cause production of nitrites, but
  • Not all bacteria have the enzyme nitrate reductase,
  1. What is the sensitivity of +ve urine dipstick nitrites for UTI?
  2. What is the specificity of +ve urine dipstick nitrites for UTI?

  • LOW sensitivity
    • Because not all UTI-causing organisms form nitrites, a negative dipstick nitrites test does not rule out UTI
    • Low sensitivity = significant false negative rate
    • "SnOUT"
  • HIGH specificity
    • Because typically, only a UTI would generate nitrates, a positve dipstick nitrates test strongly suggests UTI
    • High sensitivity = low false positive rate
    • "SpIN"


  1. What does a urine dipstick test for blood actually detect?
  2. What are potential false positive confounds to consider for this test?
  3. What test should be done to confirm a positive test?

  1. Detects peroxidase acitivty of eryhtrocytes
  2. Potential false +ves:
    • Myoglobin and Hb can catalyze the same rxn
      • (Hemoglobinuria could be caused by a hemolytic anemia, for example)
      • (and myoglobinuria could indicate rhabdomyolysis)
  3. Again, for confirmation: Microscopic analysis


What percentage of women with an acute UTI have microhematuria?



  1. How long can microhematuria normally persist after successful treatment of a UTI?
  2. What if the microhematuria persists beyond this point?

  1. 7 days
  2. Concern for serious urologic disease (5-22% of pts with persistent microhematuria)
    • 0.5-5% will have a GU malignancy
    • Requires urologic investigation


Name three urine collection methods used to obtain samples for bacterial cultures. How do they differ?

  1. Clean catch voided specimen
    • Easiest
    • Most prone to contamination
  2. Catheterized specimen
    • Less contamination risk
    • More invasive
  3. Suprapubic aspirate
    • Less contamination risk
    • More invasive


What is considered significant bacteriuria?

How is method of collection a factor of consideration regarding what is a signficant level?

>100,000 (1x105) cfu/mL

If collected by sterile cath or SP aspirate, lower colony counters may still be significant (less chance of contamination), esp. if pt. is symptomatic


Define Sensitive, Intermediate, and Resistant in terms of antiobiotic sensitivty testing of bacteria.

  • Sensitive (S)
    • Organism will likely respond to treatment with standard Abx dosage
  • Intermediate (I)
    • Organism may or may not respond at standard dosage
      • Abx with high urine concentration ability may be needed
      • Higher than normal dosage may be needed
  • Resistant (R)
    • Organism won't respond to the Abx in question
      • Dosage required to overcome resistance would cause toxicity in humans


Name some common agents of uncomplicated and complicated UTIs.

[Lecturer said not to memorize - just have a rough idea]

  • Uncomplicated
    • E. coli (80%)
    • S. Saprophyticus
    • ​Klebsiella, Enterobacter, Proteus
    • Salmonella, Shigella
    • G+, incl. S. aureus
  • ​Complicated
    • ​E. coli (20%)
    • Klebsiella, Enterobacter, Proteus
    • Pseudomonas
    • S. aureus, Coag- Staph
    • Yeasts and fungi (Candida)
    • Parasites (Schistosoma)


Other than wanting high Abx concentrations in the urine, what should be considered regarding choice of Abx for a UTI?

Prior use of Abx

A recently used abx may not be effective due to development of resistance


What is the length of a typically course of Abx for treating:

  1. An uncomplicated UTI?
  2. A complicated UTI?

  1. Complicated: Typically 3-5d, up to 7d
  2. Uncomplicated: At least 7d, often 10-14d


When is imaging indicated in the diagnosis and treamtent of UTIs?

  • For complicated UTIs (not always)
  • In pt with known or suspected predisposing factors
    • Structural / Functional GU abnormalities
    • Hx of stones
    • Lack of response to appropriate therapy
    • Recurrent pyelonephritis
  • Not needed for uncomplicated UTIs or uncomplicated pyelonephritis


What imaging modalities are used in the management of UTIs?

  • Ultrasound (simpler)
  • CT (better at identifying stones)


Contrast reinfection vs. persistence of a UTI.

What are these both forms of?

  • Reinfection
    • New infection from bacteria outside the urinary tract.
  • Persistance
    • Same infection as previously; didn't resolve. Consists of bacteria in a focus within the urinary tract.
  • These are both forms of Recurrent UTIs
    • (3-5% of all women, more common in menopause)


What are some causes of UTI bacterial persistence?

Essentially, many of the same structural or functional GU abnormalities that define a complicated UTI and decrease the efficacy of Abx treatment.

  • Stones/foreign bodies
  • Chronic bacterial prostatitis
  • Urethral diverticula
  • Fistula (e.g. colovesical fistula)
  • Urinary stasis
    • Poor emptying
    • Vesicoureteral reflux


Assuming any underlying conditions cannot be managed any further, how are recurrent UTIs medically treated?

Use Abx at lower than therapeutic dosage (~1/2 strength) to prevent symptomatic recurrence. Provides:

  • prophylaxis: prevents outside re-infection
  • suppression: prevention of persistence (e.g. known focus of infection that can't be removed)


Name four Abx recommended as long-term prophylaxis for recurrent UTIs.

  • NTF (Nitrofurantoin) 50mg QHS (quaque hora somni, every night at bedtime)
  • Bactrim SS 1 tab QHS
  • Trimethoprim 100mg QHS
  • Cipro 100mg or 250mg QHS
    • Would reserve Cipro for more complicated UTIs or after failure of above drugs


Typically, how long are prophylactic Abx regimens for recurrent UTIs?

6 months or longer

Often years for pediatric vesicoureteral reflux

UTIs still tend to recur once prophylaxis discontinued


Name three forms of non-antibiotic prophylaxis for the prevention of UTIs and how they work.

  • Methenamine salts
    • Converted to formaldehyde and ammonia in acidic urine (need pH <6)
  • Cranberry juice
    • May help with prevention, results variable
    • From what I can find, contains a protein that prevents bacterial adhesion to the urinary tract
  • Ascorbic acid (Vitamin C)
    • ​Acidifies the urine


A urine test from your patient, not ordered due to a possible UTI, grows significant bacterial cultures. The patient does not complain of any UTI-like symptoms.

What is this called?

When is it treated?

Asymptomatic Bacteriuria

  • Generally: Do NOT treat
    • Treatment doesn't reduce incidence of symptomatic UTIs
    • Recurs soon after treatment stopped
    • Overuse of Abx risks resistance
  • Exception: PregnancyTreat to prevent preterm labor.


Name 4-5 populations of patients in which asymptomatic bacteriuria is more often seen.

  • Elderly women (esp. in care homes)
  • Pregnant women (remember: treat pregnant women!)
  • Diabetes
  • Catheter use
    • Spinal cord injury (often due to catheter use)

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