L75 – Urinary Tract Infections Flashcards by Max Kam

Female: male ratio of UTI?

Female:male – 30:1

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What is associated with most hospital acquired UTI?

30-40% of all hospital-acquired infections (HAI):

often associated with use of catheters causing UTI

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UTI in adult men is rare unless what condition occurs?

Obstruction of urethra from benign prostatic hyperplasia (BPH), e.g. in elderly

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What is the main host defense against UTI?

Flushing effect of urine:

> > Emptying the bladder flushes out bacteria in bladder, urethra

> > Anything that interferes with flushing increases risk of UTI

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What host defense decreases the severity and chance of UTI complications?

Immunity decreases severity, chance of complication:
 Humoral
 Cell-mediated

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Action of bacteria causing infection to bladder?

1) adhere
2) colonize on urinary orifice
3) infect and ascent from urethral opening to bladder in retrograde manner

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UTI pathogens are usually found where?

mostly enteric / skin, e.g. fecal flora

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What is UPEC?

Uropathogenic

Escherichia coli

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Whats ExPEC?

Extraintestinal pathogenic E.coli

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Apart from E.coli, name some other UTI bacteria?

Klebsiella pneumoniae

Proteus mirabilis

Pseudomonas aeruginosa

Staphylococcus saprophyticus

Enterococcus faecalis

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Name some roles of virulence factors in UTI bacteria?

Adherence

Toxin

Immune evasion

Iron acquisition

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2 structures of bacteria used to adhere to mucosa?

Pili/ fimbriae

Adhesins

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What is the structure that UPEC uses to adhere to mucosa?

Type 1, pyelonephritis-associated (P) fimbriae

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Give 2 examples of immune evasion structure used by UPEC?

lipopolysaccharide, capsular

polysaccharides

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Give 2 examples of toxins secreted by UPEC?

hemolysin, aerobactin protease

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What is the role of flagella in UPEC?

flagella provides mobility > ascending infection

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Give 2 sources of E.coli that can cause UTI?

extraintestinal pathogenic E. coli:

1) contaminated / raw / improperly cooked food
2) retail chicken meat products, eggs

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If E.coli has no zoonosis potential, what is expected from a resistance profile between human and poultry bacteria?

expect human-susceptible to cluster with human-resistant,

poultry -susceptible to cluster with poultry- resistant

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What is the resistance profile of E. coli that causes UTI? What does this imply?

expect human-susceptible to cluster with human-resistant, but not seen in this
case - human and poultry strains mix

suggests route of transmission can be from
poultry-resistant / poultry-susceptible

> > E. coli has zoonosis potential

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What factors predispose UTI?

Length of urethra

Mechanical factors causing trauma to mucosa

Genetic factor e.g. density of bacterial receptors

Hormonal effect on mucosa

Underlying disease

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Explain how length of urethra affects risk for UTI?

Length of urethra before reaching bladder:

long in male, short in female

Females are at much higher risk

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Give examples of mechanical factors causing trauma to mucosa, casuing UTI?

 Sexual intercourse

 Trauma

 Contraceptive diaphragm (compress posterior part of
urethra&raquo_space; help ascent of bacteria)

 Catheter

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Explain the effect of hormones on mucosa?

menopause: hormones (especially estrogen) decreases

> > atrophy of mucosa facilitate bacterial adherence

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Explain how pregnancy can lead to increased spreaad of UTI?

Pregnancy:
» dilatation, decreased peristalsis of ureter

> > compress on urethra and incompletely emptying

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What is neurogenic bladder and what are the sonsequences?

bladder dysfunction (flaccid or spastic) caused by neurologic damage Risk of serious complications (eg, recurrent infection, vesicoureteral reflux, autonomic dysreflexia)

factors that can cause poor emptying of bladder?

 Neurogenic bladder |  Pregnancy

How does urinary catheter increase spread of UTI?

nidus (focus of infection) for persistence

How does stones increase UTI spread?

Obstruction of urethra >> impaired flushing

How does diabetes increase risk of UTI?

immune incompetence

What causes reflux which increases chances of UTI?

Incompetent ureterovesical valves (functional / anatomical)

How does bacteria in urinary tract reach blood?

Bladder > kidney > blood

Summarize all the factors that increases spread of UTI

Immune incompetence Foreign body obstruction Dilation and decreased peristalsis of ureter Poor emptying Reflux

Virulence factor that causes inflammation?

Lipopolysaccharide

Explain how UTI increases formation of kidney stones?

Some bacteria in urine produces urease Urease converts urea to NH3 and raises urine pH Normally acidic urine becomes alkaline, causing salts to precipitate >> form stones

2 classes of UTI?

Uncomplicated and complicated

What is the most dominating pathogen to cause UTI?

UPEC

Definition of uncomplicated UTI?

Infection in a structurally and neurologically normal urinary tract Affect healthy individuals

Which organs are involved in uncomplicated UTI?

Bladder and kidney

Definition of complicated UTI?

UTI associated with factors that compromise the urinary tract or host defense (e.g. urinary obstruction, neurogenic bladder...etc)

What can cause recurrent infection>?

Relapse or Reinfection

Differentiate relapse from reinfection?

Relapse = same bacterial strain persist to infect Reinfection = new infection by a different organism / strain

What is urosepsis?

sepsis caused by UTI

Symptoms of acute pyelonephritis?

High fever, loin pain

Difference between acute pyelonephritis and glomerulonephritis?

glomerulonephritis: mainly autoimmune Acute pyelonephritis: caused by bacterial infection

Which patients are likely to have perinephric abscess? What is it?

Spread from kidney to adjacent fascia In patient with underlying disease, e.g. poorly controlled diabetes mellitus

What is cystitis?

Inflammation of Bladder lining (e.g. mucosa, urine; not outside)

Symptoms of cystitis?

urinary urgency and frequency, dysuria, suprapubic discomfort

What constitutes asymptomatic bacteriuria?

No symptoms but diagnosed in laboratory diagnosis

Symptoms of acute and chronic prostatitis?

Acute = fever, perineal pain Chronic= non-specific and hard to diagnoser

What is pyuria?

inflammatory response due to infection > abnormally high number of WBC / leukocytes

How is pyuria detected?

Use urine strip: ``` Leukocyte esterase (from host) react with substrates in strip to produce purple color ```

How may results from urine strip be wrong?

- Some drugs (e.g. cephalexin), high glucose level may interfere with chemical reaction = false-negative results - Positive result may occur from contamination of specimens by vaginal discharge

What is the nitrite detection test for? How does it work?

Some bacteria possess nitrate reductase > can reduce nitrate (NO3-) in urine to nitrite (NO2) > nitrite reacts with substrates in strip to produce uniform pink color

Give 2 reasons why the nitrite detection test is not definitive for UTI ?

 Some bacteria (e.g. enterococcus) do not have the enzyme for reducing nitrate to nitrite  Urine may not be retained in the bladder for long enough for bacteria to reduce nitrate (e.g. frequent voiding)

How to differentiate contamination / genuine | bacteriuria?

use quantitation / semi-quantitative culture

Explain how the count of bacteria can be used to differentiate infection from contamination?

Cut threshold cut-off Infected women (significant bacteriuria): >= 10^ 5 bacteria/mL of urine

Why do uninfected women still have bacteria in urine?

because urine passes through the portion of mucosal surface in urethra that is colonized by commensals

What is the medium for UTI?

cysteine lactose electrolyte deficient (CLED) agar

Why is CLED used?

``` inhibits swarming (no expression of motility in bacteria) ``` >> create localized, colony morphology ** hence why blood agar is not used **

What is the positive and negative results for CLED agar?

+ve = ferment lactose = yellow -ve = doesnt ferment lactose = white

Give 2 methods to put urine on agar culture to detect bacterial load?

Standard calibrated loop Dip paper strip vertically to line > touch urine to agar surface

What is the cfu indicating significant growth of bacteria?

>1 x 10^5 Colony count per mL of urine

Name other agar (not CLED) for detecting urine bacterial load?

McConkey agar: incubate for 24h> determine the number of bacteria

Name ways to collect urine ?

MSU (mid-stream urine) Clean-catch urine (baby) Pediatric urine bag CSU (indwelling urine catheter) Suprapubic tap urine

What is the bacterial cfu in suprapubic tap urine sample?

Any growth = UTI Not the usual 10^5 colonies per mL

Which symptomatic patients might not produce urine with 10^5 cfu/ml?

 Women with uncomplicated cystitis |  Male patients

Under what circumstance does low cfu still count as clinically significant?

If the colony is pure growth (esp. E.coli)

2 reasons for urine samples to produce false positive results?

Heavy colonization of vagina Delay transport >2h

Give one reason how a urine sample creates false negative result?

Cleaning with antiseptic > contaminate urine and lower bacterial load

No UTI symptom = no urine culture and treatment except in which 3 cases?

 Pregnant women (if not treated: 20-30% risk of progression to acute pyelonephritis)  Before urological operation (e.g. transurethral resection of enlarged prostate gland)  Children (age <5 years), with vesico-ureteric reflux of urine back into kidney (e.g. valve defect)

Asymptomatic bacteriuria is common is which patients?

Elderly, debilitated

Most recuurent UTI is caused by what?

Behavioral factors Most do not have structural abnormality

What host or microbe factor can increase chances of recurrent UTI?

1. Unusually receptive uroepithelial cells; or | 2. Colonization by ’stick strains’ of E. coli

What criteria is needed for urological evaluation in young women, which in not routine or cost-effective?

``` 2 things needed: 1) Recurrent UTI + 2) Any one of the following conditions: -Hematuria between infections -Pyelonephritis -Obstructive symptoms -Urea-splitting bacteria -Urinary calculi -Severe diabetes ```

Risk factors for acute bacterial prostatitis?

Unprotected anal intercourse Indwelling urinary catheter use Prostate biopsy

What are the clinical presentations of Acute bacterial prostatitis (ABP)?

High fever + septic shock Dysuria and urinary frequency Urinary retention Very tender prostate

What causes urinary retention in ABP?

Obstruction from acute edema of prostate

What is the urine culture cfu?

>= 10^5 cfu/ml

What are the 2 tests to confirm Chronic bacterial prostatitis?

Positive 4 glass or 2 glass test

What causes chronic bacterial prostatitis?

Relapsing UTI by the same organism

Name the 4 bacteria that are accepted pathogens for acute and chronic bacterial prostatitis?

E. coli (70%) Enterobacteriaceae Pseudomonas aeruginosa Enterococci

What are some associated conditions of chronic bacterial prostatitis?

Retrograde spread of bacteria into prostatic ducts Dysfunctional voiding Previous instrumentation (e.g. ultrasound probe)

Is ultrasound good for diagnosis of bacterial prostatitis?

Ultrasound imaging is not indicative (confused with BPH)

Treatment of CBP?

Treatment: 6-12 weeks antibiotics

What are in the 4 samples in the 4 glass test/ Stamey's technique? Which samples have pathogen ?

1. VB1 = first 10mL urethral urine voided 2. VB2 = mid-stream culture 3. Expressed prostatic secretion (EPS) 4. VB3: first 10mL voided after massage 3rd and 4th samples have bacteria

What induces EPS release from prostate?

Massage prostate for ~1 min

Limitation of 4 glass test for CBP?

 Difficult to perform  Limited sensitivity for Gram-positive

What is in the 2 samples of the 2 glass test? which one contains bacteria?

VB1: 1st voided 10mL urine Semen *bacteria*

Why is semen collected in 2 glass test?

Repeat if ejaculate yields Gram-positive bacteria: Ejaculate comes from seminar vesicle, passes through prostate >> carries infective organism

Why is the 2 glass test better than 4 glass?

 Easier to perform |  Better sensitivity for Gram-positive

L75 – Urinary Tract Infections Flashcards

(90 cards)