Urinary tract infections Flashcards by Meghan May

Commensals are primarily comprise bacterial species, and are often referred to as an individuals “normal flora”, what is their mechanism

compete for resources with more virulent organisms

produce their own AMPs

keep innate immune cells in a“attentive” state

lower vaginal pH

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species are of particular significance to protection of female urinary tract.

Lactobacillus

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Role of lactobacillus in the vagina

decrease the vaginal pH through lactic acid production, generating H2O2

• occupy the chemical resources that would otherwise be available for exploitation by pathogenic organisms

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Although the urinary and genital tracts are in close proximity to one another, it is important to differentiate between the two as the defenses along the______are more limited in scope.

urinary tract

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Defenses present in the urinary tract

o Physical force of urine flow

o Exfoliation
o Antimicrobial Proteins

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What two and antimicrobials are present in the urinary tract

Antimicrobial peptides

Tamm-Horsfall protein

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With the exception of the____, innate and adaptive leukocytes are absent from the lower urinary tract during times of health.

urethra

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The flow of urine physically prevents the ascension of pathogens up the urinary tract but there are many sources of flow obstruction:

Congenital abnormality

Urethral stricture

Uretheral stone

Neurogenic dysfunction

Obstruction of any part of the

urinary tract by cancer

Benign prostatic hyperplasia

or cancer of the prostate

Cystocele

Pregnancy

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The points where the ureters attach to the bladder __________ act as one-way valves to prevent urine from backing up toward the kidneys

(ureterovesical junction, UVJ)

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The physical force of urine flow, and the pressures that accompany it, require the lower urinary tract epithelia to be elastic.The epithelium of the bladder and urethra is_______; folds and sliding cells allow stretching.

TRANSITIONAL

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How does exfoliation help protect the vagina

o Exfoliated bladder cells are epithelial cells sloughed from the surface of the urinary tract.

o This serves as a defense against pathogens, “ejecting” them into the urine for removal.

o The appearance of exfoliated cells in the urine is a sign of urinary tract infection

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the infectious agent (e.g. E coli) moves up to kidneys from the urethra. Most common form of UTI.

Ascending:

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: associated with a structural or functional abnormality of the GU tract, or the presence of a comorbidity, which increases the risks of acquiring an infection or of failing therapy.

uncomplicated UTI

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What is the most common uropathogenic agent in adults

E.Coli

UPEC (use type 1 pili to adhere to bladder epithelium)

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Most common UTI causing species in children

enterobacter

klebsiella

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most common non socomial UTI agent

pseudomonas aeruginosa

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How does the bladder respond to UTI

The body responds to UTI by both exfoliation and neutrophil recruitment

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Bladder inflammation is the consequence of ________ into the bladder

o painful urination

o lower abdomen discomfort, low- grade fever, pelvic pressure, and frequent urination

o diagnosed by presence of leukocytes in urine

leukocyte infiltration

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The activation of neutrophils results in degranulation and release __________, which is used as a diagnostic for UTI

leukocyte esterase

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UTIs are most commonly diagnosed using a ______that measures several aspects of urine chemistry (see Reference slide)

______are the most common treatment for UTI, the selection and efficacy of which depends on:

the causative species

the ability to concentrate in the urine well

“dipstick”

Antibiotics

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– for individuals who frequently develop UTI following coitus, these may be taken prophylactically

Coital prophylaxis

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The ability to UPEC to reside in___ is a cause of recurrent UTI

calculi

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Lower tract UTI (bladder, prostate, urethra) - Mainly bladder =_____

Upper tract UTI (kidney, ureter)
- Mainly kidney =________

cystitis

pyelonephritis

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Female >> Male
___% of women will develop a UTI in their lifetime
___% of nosocomial (hospital-acquired) infections are UTIs
___% of gram –ve bacteremias/year in the hospital setting start as UTIs.

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* \_\_\_\_\_\_ = painful urination–\> Burning, stabbing, “peeing shards of glass” * _______ = needing to urinate often–\> It hurts to hold urine

Dysuria Urinary frequency

\_\_\_\_\_\_\_= blood in urine – Gross(visible)–more concerning.Can’t necessarily attribute it to UTI (needs further investigation) – Microscopic

Hematuria

Symptoms of bladder infection

• Dysuria – Burning, stabbing, “peeing shards of glass” • Urinary frequency Urinary urgency Suprapubic pain/discomfort/pressure Cloudy/smelly urine Hematuria

Differential Diagnosis of Dysuria

UTI Diet related irritants Urethritis Vulvitis/vaginitis Stones/foreignbody Atrophy Recent intercourse Interstitial cystitis and other inflammatory conditions

* Flank/back pain * High fever, chills * Headache * Nausea/vomiting * Maybe septic shock * +/- cystitis symptoms

Pyelonephritis (kidney infection) Symptoms

: UTI in healthy patient with normal urinary tract – Young to middle age female with “run of the mill” UTI (often triggered by sex)

Uncomplicated UTI

: UTI associated with factors that predispose to bacterial infection and decrease efficacy of therapy – These infections are more prone to become disseminated resulting in sepsis and even death

Complicated UTI

What are some causes of Abnormal GU tract

– Urinary obstruction (BPH, scar tissue, stone) – Urinary stasis (incomplete bladder emptying, diverticulum) – Vesicoureteral reflux (backwashing of urine from bladder to ureters/kidneys – mainly a pediatric issue) – Foreignbody(catheter,stone) – Neurogenicbladderwithhighpressures(e.g.spinalcordinjury)

Immunocompromised/unhealthy host – Diabetes, transplant patients, chronic steroids • Multi-drug resistant bacteria These are both examples of:

causes of complicated UTI

Chemical strip analysis (urine dipstick) can screen for:

– Good screening test for urinary blood, pus (leukocytes), bacteria, pH, specific gravity (ie concentration), protein, glucose

– Definitive test for blood (RBC) and pus (leukocytes) – Can have false positive dipsticks so they should be confirmed with

microscopic analysis

Detects pyuria (pus or WBC in urine) UTIs usually have pyuria

UA Dipstick: Leukocyte Esterase (LE)

DDx of pyuria seen with leukoctye esterase test

• Pregnancy * Vaginalinfection * Inflammation from bladder or kidneys or adjacent organs • Tumors * Stones * Non-bacterial cystitis

Sensitivity and specificity of leukocyte esterase test

Sensitivity is HIGH Specificity is LOW

Produced by action of bacteria on dietary nitrates through nitrate reductase (converts nitrates to nitrites) Specificity: HIGH (66%-99%) – Low false positive rate for UTI Sensitivity: LOW (29%-92%) – False negative rates

UA Dipstick: Nitrites

Nitrites have low sensitivty for testing. Why and what are important testing tips?

– False negative rates • Not all bacteria have the enzyme nitrate reductase • Nitrate to nitrite conversion takes 4-6 hours – First AM void is best \*\*\*\*+ve nitrite test likely rules in UTI but a –ve nitrite test doesn’t rule out UTI

Dipstick test detects the peroxidase activity of erythrocytes

UA Dipstick: Blood (microscopic hematuria)

What are some concerns for using Blood analysis with UA dipstick : microscopic hematuria

Potential false +ves: – Myoglobin and Hemoglobin can catalyze this reaction Need microscopy for confirmation Microhematuria noted in 50% of women with acute UTI

Can persist up to one week after successful treatment of UTI but if persistent beyond this: – 5-22% will have serious urologic disease • 0.5-5% will have a GU malignancy

microscopic hematuria

Reason to obtain urine culture and sensitivity

To determine growth of bacteria from urine sample – Identification and quantification of bacterial species – Determining sensitivities to various antibiotics (to guide therapy)

Three specimen collection methods for urine

Clean catch voided specimen * Easiest but most prone to contamination – Catheterized specimen * Less risk of contamination but more invasive – Suprapubic aspirate • Less risk of contamination but more invasive

Organism responds to antibiotic and will likely respond to treatment with a standard antibiotic dosage

Sensitive

At standard antibiotic doses organism may or may not respond – Organism may be eradicated if: high Abx concentrations at the site (in urine) of infection higher than normal dosage is used

Intermediate (I)

Organism won’t respond to antibiotic – Physiologic concentrations required to overcome resistance would cause toxicity in humans

Resistant (R)

Antibiotics are mainstay for UTI tx, what do we need to keep in mind when prescribing antibiotics?

May start Abx based on a “best guess” (empiric treatment) of which will be sensitive using hospital/clinic data on most commonly cultured organisms and antibiotic sensitivities – Must factor in prior use of antibiotics (a recently used antibiotic may not be effective because of development of bacterial resistance) • Want high Abx concentrations in urine (see handout)

Duration of treatment determined by degree of illness, complicated vs uncomplicated UTI – For **uncomplicated** UTI in healthy female: – For **complicated** UTI:

typically 3-5d course of Abx (sometimes up to 7d) Must correct any structural or functional urinary tract abnormality (eg relieve obstruction) and treat with Abx for at least 7d and often longer (10-14d)

• Basic UTI evaluation = H&P, UA & C&S ± Blood testing: –\_\_\_\_ – to see if elevated WBC (may be sign of more serious infection) – Basic chemistry • Creatinine – estimate of\_\_\_\_ function (Abx dosing) • Electrolytes

CBC renal

when do we need to get imaging?

* Complicated UTIs :But not always – Predisposing factors :GU anomalies or Hx of stones * Lack of response to appropriate therapy • Recurrent pyelonephritis Use kidney/bladder ultrasound or CT scan (CT is better at identifying stones)

\_\_\_\_\_from bacteria outside the urinary tract (ie a new infection) •\_\_\_\_\_ of bacteria in a focus within the urinary tract (ie same infection as before; didn’t resolve)

Reinfection Persistence

Causes of Bacterial persistence

Inadequate/inappropriate/incomplete antibiotic therapy Stones/foreign bodies Chronic bacterial prostatitis (infection harbored in prostate) Urethral diverticula Fistula (abnormal connection between epithelialized structures (eg. colon to bladder – colovesical fistula) Urinary stasis – Poor bladder emptying (e.g. BPH, weak detrusor) – Vesicoureteralreflux

Management of Recurrent UTI

Use Abx (typically at lower than therapeutic dosing e.g. half strength) taken on a daily or every other day basis to prevent symptomatic recurrence **Prophylaxis**: prevention of UTI from outside re-infection **Suppression**: prevention of UTI from bacterial persistence (eg have a known focus of infection but it can’t be removed)

Recommended antibiotics for long term prophylaxsis

– NTF 50 mg QHS – Bactrim SS 1 tab QHS – Trimethoprim 100 mg QHS – Cipro 100 mg or 250 mg QHS • Would reserve for more complicated UTIs or failure with above regimens

– Converted to formaldehyde and ammonia in acidic urine (need pH\<6) – Found in combination with other acids

Methenamine salts

three non antibiotic prophylaxis options for UTIs

methenamine salts, cranberry juice, ascrobic acid or Vit C

What pts are at risk for asymptomatic bacteriuria: +ve urine culture but no symptoms = bacterial colonization

Elderly women (especially in care homes) Pregnancy Diabetes Use of catheters (intermittent, indwelling) Spinal cord injury (often due to use of catheter)

We generally don't tx asymptomatic bacteriuria,why? and when would we want to?

1) treatment doesn’t reduce incidence of symptomatic UTI 2) it recurs soon after treatment stopped 3) overuse of Abx risks bacterial resistance Exception; pregnancy; treat to prevent preterm labor

25 y.o. healthy female complains of “burning when I urinate for past 3 days. Tried drinking lots of cranberry juice which helped a little but still having the burning and having to urinate often” No history of UTIs, no hematuria Sexually active on “the pill” • Unremarkable physical exam What do you do?

Check urinalysis!

You note your pt has an acute bacterial UTI options to tx: Nitrofurantoin for 14 days Bactrim for 3 days Cipro for 7 days Amoxicillin for 7 days

bactrim for 3 days (only need 3-5 days)