Urinary Tract Infections

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Urinary Tract Infections

• Dr. Ross Davidson
• Rm 309, MacKenzie Building
• QE II HSC
• ph 473-5520

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UTI

• UTI - common affliction for which patients seek
  medical attention
• UTI can occur from infancy through old age
• more common in females than males 20
  of all females will experience a UTI during their
  lifetime

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UTIDefinitions

• The term UTI represents a wide range of
  clinical syndromes
• Bacteriuria the presence of bacteria in urine
  - does not necessarily imply infection
• Asymptomatic bacteriuria presence of bacteria in
  the urinary tract in the absence of symptoms
• - clinical significance controversial outside
  certain patient populations
• - pregnant women
• - patients
  undergoing invasive procedures
  of the urinary tract

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UTIDefinitions

• Cystitis UTI presumed to be confined to the
  bladder - painful/burning urination -
  urgency or frequency - absence of symptoms or
  physical signs suggesting inflammation at other
  sites within the urinary tract
• Note clinical criteria are notoriously
  inaccurate in identifying the actual anatomic
  site of infection

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UTIDefinitions

• Pyelonephritis clinical diagnosis which implies
  a more invasive infection- inflammation of the
  kidney and renal pelvis is assumed to be present
  when patients have pain or tenderness involving
  the flank, together with other clinical or
  laboratory evidence of UTI-fever, nausea,
  chills, malaise, headache, etc

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UTIDefinitions

• Prostatitis inflammation / infection of the
  prostate gland - may present as acute
  or chronic
• Intrarenal abscess / perinephric abscess
  collection of pus in the kidney or in the soft
  tissue surrounding the kidney

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UTIDefinitions

• Complicated infections
• - underlying abnormality that predisposes
  patient to UTI or makes UTI more difficult
  to treat effectively
• Recurrent Infections Relapse - recurrence of
  infection by same organism after discontinuation
  of treatment Reinfection - recurrence of
  infection by a different organism after
  discontinuation of treatment

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UTIPathogenesis

• UTI usually due to patients own intestinal flora
  - ascending route of infection -
  organisms enter the urinary tract in a retrograde
  fashion via the urethra
• Complicating factors such as catheters,
  nephrostomy tubes, surgery, urinary stones, etc
  - allow organisms to enter and persist in
  urinary tract - alter the typical spectrum
  of organisms - may have multiple etiologies

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UTIPathogenesis

• Elderly patients - incontinant
  - functionally impaired
  - postmenopausal changes
  - neurological alterations
• Pregnant women - altered anatomy
• Hematogenous route
  - endocarditis, bacteremias, tuberculosis
  - disseminated infections

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UTIEtiology

• Majority of UTI are due to a single pathogen
• The Enterobacteriaceae responsible for 90 of all
  UTI- gram negative bacilli- facultatively
  anaerobic- common intestinal flora
• Escherichia coli most commonly isolated pathogen
  80 of all UTI

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Community-Acquired UTI
E.coli
S.epi gm - enterics
Enterococcus
Proteus
S.saprophyticus
K.pneumoniae
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Uro-pathogens

• E.coli, Klebsiella spp.-intrinsic gut
  organisms-highly motile-produce fimbriae (pili)
  gtgtattachment
• Proteus, Morganella, Providencia- urease
  producing organisms- increases urinary pH -
  leads to crystal formation gtgtbiofilmsgtgtcolonizati
  on of cathetergtgtprotects bacteria from host
  defenses antibiotics

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Nosocomial UTIcatheter associated
Short Term
Long Term
E.coli
E.coli
Enterobacter
Proteus
Enterococcus
Candida
Proteus
Providencia
S.aureus
Morganella
Pseudomonas
Pseudomonas
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Urinalysis

• usually have increased numbers of WBC
• leukocyte esterase test is often positive
• nitrate test is often positive

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Urinalysis

• Urine culture significant bacteriuria usually
  defined as gt 105 bacteria / ml. (108 / litre)
• lower numbers may be significant in children and
  in catheter collected specimens

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Specimen collection

• Should all patients with a suspected UTI be
  cultured?
• Community acquired vs nosocomial?
• Should all isolates be identified?Susceptibility
  testing?

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Specimen collection

• Clean catch mid stream specimens - most
  frequently used method - urethra cleaned prior
  to collection - first void urine allowed to
  pass to clear urethra - mid-stream collected in
  sterile container
• Collection bags (children) - used in young
  children lacking bladder control - often
  contaminated - most meaningful result is a
  negative culture

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Specimen collection

• Suprapubic aspiration / straight catheters -
  invasive - specimen obtained directly from
  bladder
• Indwelling catheters - urine obtained by
  inserting needle into catheter or through
  diaphram - preferable to obtain specimen from
  new catheter, rather than old catheter

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Specimen transport

• Sent to and processed by lab as quickly as
  possible- Require method of collection
  time of collection
  patients antibiotics
• Specimens not received by lab in 1-2 hours MUST
  be refridgerated
• Urines not received within 24 hours or not
  refridgerated will be rejected by laboratory

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Antimicrobial Therapy

• Empiric Therapy - based on most probable
  pathogens - local rates of resistance -
  acute infection vs chronic - reinfection or
  relapse - indwelling catheter etc

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Antimicrobial Therapy

• cystitis - usually responds to 3 days of
  treatment
• uncomplicated pyelonephritis - 2 weeks treatment
• complicated infections / prostatitis - 6 weeks
• IV antibiotics may be required in seriously ill
  patients, but oral drugs usually effective