Urinary Tract Infections
Meral Sönmezoğlu
Division of Infectious Diseases
Yeditepe University Hospital
Learning objectives UTI’s




Epidemiology
Pathogenesis
Risk Factors
Types of cystitis


Evaluation
Therapy
Urinary System
Based on: Mader, S., Inquiry Into Life, McGraw-Hill
Anatomy of
the Kidney
Based on: Mader, S., Inquiry Into Life, McGraw-Hill
Nephron
Based on: Mader, S., Inquiry Into Life, McGraw-Hill
Urine moves from the collecting
ducts through the kidney pelvis to
the ureter
Based on: Mader, S., Inquiry Into Life, McGraw-Hill
Urine moves from the kidneys, through
the ureters to the bladder and finally
through the urethra
Based on: Mader, S., Inquiry Into Life, McGraw-Hill
Epidemiology UTI’s

UTIs are the second most common cause for prescription
of antibiotics

Most infections are limited to the lower urinary tract

30 times more likely
in young women than
young men

Incidence in men rises
dramatically after age 50
Women may have more UTIs than men
because:
1) they have a shorter urethra, allowing quicker access to
the bladder
2) the urethral opening is nearer the anus
3) intercourse may result in UTIs in women
Based on: Harvard Medical School Family Health Guide
Relative frequency of nosocomial
(hospital-acquired) infections
Site
% of total
Urinary tract
34
Surgical wound
17
Bloodstream
14
Pneumonia
13
Other
21
Pathogenesis UTI’s
Bacteria travel:
 Ascending route via the
urethra 95%
 Hematogenous (kidney->
bladder)



Endocarditis
Tuberculosis
Direct (connection bowelbladder)
Bacterial factors



Inoculum size
Virulence
Adherence


E. coli adhere to
urothelial cells
Proteus, Providencia
adhere to lumen of
catheter material
Virulence
Host factors
Infection
No infection
Host defense mechanisms

Mechanical



Interference


Normal bacteria flora (meatus)
Chemical



Dilution and flow of urine
Length of urethra
Osmolality and pH of urine
Prostatic fluid
Anti-adherence mechanisms in bladder


Urinary immunoglobulins
Mucosal antibacterial activity

Risk factors UTI’s (I)
Alteration/introduction of bacteria






Antibiotics
Spermicides
Vaginal atrophy (age)
Sex
Insertive rectal sex
Inserting toys
Patient education:
Void after intercourse,
Proper wiping, front to back
once
Risk factors UTI’s (II)

Urinary stasis



Neurologic bladder
Reflux into the ureters (pregnancy)
Obstruction




Diabetes mellitus


Congenital anatomical abnormalities
Prostate hypertrophy (age)
Stones, tumor
Glycosuria
Foreign materials



Stones
Stents
Catheters
Pathogenesis of cystitis
UTI’s

Uncomplicated cystitis


Complicated UTI’s




Risk factors
When to look for causes
Interpret UA, dipstick, urine cx
Asymptomatic bacteriuria
Catheter-related issues

Prudent use of antibiotics
Types of urinary tract problems



Asymptomatic bacteriuria
Dysuria
Cystitis



Complicated UTI




Acute uncomplicated cystitis
Recurrent cystitis
Pyelonephritis
UTI’s in men, pregnant women, children
Prostatitis
Other



Catheter associated UTI
Candida in urine
Sterile pyuria
Definitions (I)

Asymptomatic bacteriuria:




isolation of a specified quantitative count of
bacteria
in an appropriately collected urine specimen
obtained from a person without symptoms or
signs referable to urinary infection
Acute uncomplicated UTI (cystitis):



symptomatic bladder infection
characterized by frequency, urgency, dysuria or
suprapubic pain
in a woman with a normal genitourinary tract
Definitions (II)

Acute nonobstructive pyelonephritis:





renal infection
characterized by costovertebral angle pain
often with fever
sometimes with bacteraemia
Complicated urinary tract infection:



may involve the bladder or kidneys
symptomatic urinary infection
in individuals with functional or structural
abnormalities of the urinary tract
What can the laboratory do with a
sample of urine?

Urinalysis


Microscopy
Dipstick

Quantitative culture

Specialized cultures (TB, fungi)
Urine dipstick

Leukocyte esterase: rapid
screening test for detecting
pyuria


Patients with symptoms and
negative LE should have a
urine microscopic
examination for pyuria
Urinary nitrite


Nitrite is formed when
bacteria reduce the nitrate
that is normally found in the
urine
False negatives common, but
false positives are rare
The whys and how's of urinary
tract organism quantification

Bladder urine is sterile
Distal urethra is not sterile

How can we differentiate:



bladder bacteria (pathogens) from
urethral bacteria (contaminants)?
What is a positive culture?

Classic definition:
> 105 cfu/ml

With symptoms:
> 103 cfu/ml

90% chance of
actual infection
Etiologic agents
Community acquired-UTI







E. coli (25%)
Enterococcus spp (16%)
P. aeruginosa (11%)
Candida spp. (8%)
K. pneumoniae (7%)
Enterobacter spp. (5%)
Proteus mirabilis (5%)
Community-Acquired UTI
E.coli
S.epi &
gm - enterics
Enterococcus
Proteus
K.pneumoniae S.saprophyticus
Microscopy

A true UTI is accompanied by

Pyuria



Lack of epithelial cells


>5/ mm³ indicates contamination
Only one bacterial species (monoculture)


>10 leukocytes/mm³ of uncentrifuged urine
unless catheter in place
>105 cfu
Do not culture urine unless


Indicated AND
Abnormal UA
Dysuria

Dysuria can be caused by

Vaginitis -no pyuria and <102 cfu/ml)
Candida
 Trichomonas
 atrophy of vaginal tissues


Urethritis –pyuria and <102 cfu/ml, gradual
Chlamydia
 Neisseria gonorrhoeae


Cystitis – pyuria and >103 cfu/ml, onset abrupt
Asymptomatic bacteriuria why screen?

Screening of asymptomatic people for
bacteriuria is only appropriate to prevent
adverse events



In pregnancy (Gp B strep)
Prior to urologic surgery
Undesirable outcomes associated with therapy:




Antimicrobial resistance
Adverse drug effects
Costs
C. difficile associated disease
Asymptomatic bacteriuriaHealthy, premenopausal women



Bacteriuria increases risk for symptomatic UTI
Not associated adverse outcomes
Treatment of asymptomatic bacteriuria
neither decreases frequency of symptomatic
infection
 nor prevents further episodes of asymptomatic
bacteriuria


Screening for and treatment of asymptomatic
bacteriuria is not indicated
Asymptomatic bacteriuria - Pregnant
women




20-30 fold increased risk of pyelonephritis
during pregnancy
More likely to experience premature delivery
and to have low birthweight infants
Treatment of bacteriuria decreases above
risks
Screen for bacteriuria by urine culture at
least once in early pregnancy and treat for
3-7 days if positive
Asymptomatic bacteriuria Elderly institutionalized subjects

No decrease in rate of




symptomatic infection
improvement in survival
chronic GU symptoms with Abx therapy
Screening and treatment of asymptomatic
bacteriuria in elderly institutionalized
residents of long-term care facilities not
recommended
Asymptomatic bacteriuria –
Patients with indwelling catheters



Antimicrobial therapy not associated with
decrease in rate of symptomatic infection
High incidence of recurrence, usually with
more resistant organisms
Asymptomatic bacteriuria or funguria
should not be screened for or treated in
patients with indwelling urethral catheter
Acute uncomplicated UTI
(cystitis)

Symptoms




Dysuria, frequency,
urgency
Initial and terminal
hematuria
Suprapubic discomfort
Low-grade fever may
occur

Diagnosis

Dipstick or microscopy



Culture



Exclude other causes


STD
Vaginitis
Nitrite positive
Positive LE/WBC
(>10 WBC’s)


Not routinely necessary
Carefully obtained
clean catch
104-5 cfu/ml
1 bacterial species only
Acute uncomplicated UTI
(cystitis)

Bacteria




E. coli in 80-90%
Staph. saprophyticus in 5-15%
Proteus and Klebsiella species
Adult female


No anatomic/functional/immunologic
abnormalities
Non-pregnant
Acute uncomplicated UTI Therapy

Resistance varies




30% resistant to amoxicillin
1-20% to nitrofurantoin
5-15% to TMP-SMX
Recommend: course of



TMP-SMX as first choice (3 days)
Fluoroquinolone as second (3 days)
Nitrofurantoin (7 days)

Does not penetrate in kidney
Recurrent Cystitis

Relapse: same organism in <2 weeks

Suggests uneradicated focus



Abx resistance
Non compliance
Reinfection - may be same or different
organism: Interval >2 weeks
Hygiene/wiping
 Post-coital
 Vaginal atrophy
 Post-void residual (prolapse)

Management: Recurrent UTI


Patient-initiated therapy: multiple 3 day
courses of antibiotics to be started by the
patient at onset of sx
Post-menopausal women: symptomatic
relief with topical estrogen -helps to
“normalize” protective flora
Further Studies / Referral





Renal US- least invasive
VCUG- best study to detect vesicourethral reflux
CT / MRI
IVP
According to Fihn, NEJM (July 17,2003),
imaging studies are not necessary unless
there are other sx ie. hematuria.
Complicated UTI
(Everyone/everything else)



Child, male, pregnant female
Kidney involvement, 2nd bacteraemia
Abnormality




Anatomy, function, immunology
Urologic procedure
Catheterization
Unusual or resistant organisms
Acute pyelonephritis

Usually E. coli
Obtain urine culture
 If hospitalized obtain blood cultures


Mostly an ascending infection

Disease severity


Mild
Life threatening urosepsis
Acute pyelonephritis -Therapy

Mild to moderately ill patients




Severely ill patients




TMP-SMX (bactrim) amox/clav, cefuroxime or fluoroquinolone
Patients usually improve in 48-72 hours
Treat for 1-2 weeks
Ampicillin + aminoglycoside
IV therapy until patient afebrile for 48-72 hours
Treat for 2 weeks
If fever persists and all children and men:

Renal US, CT or MR ± IVP


Look for perinephric abscess
Exclude urinary obstruction
Cystitis in males

Young men (rare in men under 50)



Older men




Calculi
Enlarged prostate (obstruction)
Chronic prostatitis
Organisms differ



Anatomic abnormalities
Anal insertive sex, toys
E. coli accounts for 40-50%
Proteus and Providencia species accounting for next most
frequent cause
Most common cause of relapsing UTI is chronic bacterial
prostatitis
UTI’s in males
(other than pyelonephritis)

Urethritis (STI’s)




Gonorrhea
Chlamydia
Ureoplasma
Prostatitis


Same organisms as above
For older males (in addition to above):


Gram negative rods
Enterococci
Acute prostatitis




Fever, chills
Dysuria, pain
Marked local tenderness
Excellent penetration by most antibiotic
classes-easily cured

Complications


Prostatic abscess
Chronic prostatitis
Chronic prostatitis

Chronic pain
Dysuria
Recurrent “UTI’s” – same organism

Poor antibiotic penetration-difficult to treat





Biofilm
Calculi
Preferred agents


Fluoroquinolones
TMP-SMX
Role of the catheter in UTI

Conduit


Internal lumen
Migration of bacteria along
external surface

Foreign body

Biofilm formation



Protects from host defense
Protects from antibiotics
Incomplete emptying
Complications in catheterized
patients

Bacteriuria is universal
Providencia stuartii (24%)
Proteus (15%)
E. coli (14%)
Pseudomonas (12%)

Pyuria is common from bladder irritation

Cannot diagnose UTI unless:


Fever (cured often with cath change alone)
Pyelonephritis
Prevention of catheter-related UTI’s

Avoid catheterization




Avoid extrinsic contamination of system


Early removal
Replace catheter frequently
Intermittent cath far superior
Closed catheter drainage
Unproven benefit


Antiseptics in drainage bag
Antibiotics will decrease bacteriuria and then lead
to recolonization with resistant organisms
Candida in the urine

Most candiduria occurs in patients with
indwelling catheters



Risk factor is prior antibiotics
Removal of the catheter results in
clearance of most candiduria
Oral fluconazole or amphotericin B
bladder irrigation eliminate candiduria
short-term

no more effective than no therapy
Only indications for treatment of
asymptomatic candiduria

Urinary tract obstruction (fungus ball)

Neutropenia

Renal transplant recipient

Urologic procedure in next 48-72 hours
Sterile pyuria
1.
Antibiotic pre-treatment kills bacteria
(Culture negative)
2.
Organisms that don’t grow on commonly
used culture media


Tuberculosis
Fungi
Genitourinary tuberculosis
From:
Johnson and Feehally,
Comprehensive Clinical
Nephrology, 2000, Elsevier
Genitourinary tuberculosis



Hematogenous seeding can occur in
cortex and forms granuloma
Seeding in the medulla
In both sites




Granulomas form
Caseation
Erosion into collecting system
Further spread to ureters, bladder,
prostate…
Health Education




Correct technique for obtaining clean
catch!
Avoid bladder irritants: caffeine,
carbonated beverages, aspartame, ETOH,
spicy foods.
Hygiene: wipe front to back.
Avoid bubble baths, scented products
(pads, tampons, soaps, feminine sprays).
Health Education







Showers instead of baths.
Void at regular intervals, do not hold it all day.
If sexually active, void after intercourse.
Push fluids.
Avoid constipation.
Take all of meds!!!
White toilet tissue, white cotton underwear.