L75: Urinary Tract Infections Flashcards Preview

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Flashcards in L75: Urinary Tract Infections Deck (19)
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1
Q

Epidemiology of UTI

A
  • Adult women: 25% by age 30
  • Adult men: rare
  • Female to male = 30:1
  • 30-40%: Hospital-acquired due to use of catheters
  • bacteraemia, chronic renal failure, renal stones
2
Q

Host defences in UTI

A
  1. Flushing effect of urine
  2. Humoral immunity
  3. Cell-mediated immunity
3
Q

Host-microbe interaction

A
  1. Entry
  2. Adhesion / Colonisation
  3. Spread + Multiplication
  4. Damage
4
Q

Microbe entry in UTI

A
Microbial factors:
- Ascend from urethra
- Enteric / Skin bacteria:
—> E. coli (UPEC/ExPEC)
—> Staphylococcus saprophyticus
—> Enterococci
—> Proteus mirabilis
5
Q

Host factors in microbial entry

A
  • Length of urethra
  • Mechanical factors (catheter, trauma)
  • Genetic factors
  • Hormonal effect (atrophic effect)
  • Underlying disease
6
Q

Virulence factors of main uropathogens

A
  1. Adherence (pili, adhesin)
  2. Toxin
  3. Immune evasion (capsule, elastase)
  4. Iron acquisition
7
Q

UPEC / ExPEC virulence factors

A
  1. Type 1 and P Fimbriae
  2. LPS (Lipid A+ polysaccharide (O-antigen + Core))
  3. Capsular polysaccharide
  4. Toxin:
    - Hemolysin
    - Aerobactin
    - Protease
8
Q

Microbial spread in UTI

A
  • Bladder —> kidney —> blood
    1. Reflux (Incompetent ureterovesical valves)
    2. Poor emptying (neurogenic bladder)
    3. Dilatation / Decreased peristalsis of ureter (Pregnancy)
    4. Nidus for persistence (Catheter)
    5. Obstruction (stones)
    6. Immune incompetence (DM)
9
Q

Microbial damage in UTI

A
  1. Polysaccharide capsule: inhibit phagocytosis
  2. LPS: inflammation
  3. Haemolysin: tissue damage
  4. Urease: stone formation (urea —> NH3: precipitation of salt due to ↑ pH)
10
Q

***Uncomplicated UTI vs Complicated UTI

A

Uncomplicated UTI:

  • Infection in structurally and neurologically normal UT / Health individuals
    1. UPEC
    2. S. saprophyticus
    3. K. pneumoniae
    4. Enterococcus

Complicated UTI:

  • Compromised UT/ host defence / Infection in men, pregnant women, children
    1. UPEC
    1. Enterococcus
      1. K. pneumoniae
    1. Candida spp.
11
Q

***UTI syndrome

A
  1. Acute pyelonephritis (high fever, loin pain)
  2. Perinephric abscess (extension of pus through renal capsule into perinephric tissue)
  3. Cystitis (frequency, dysuria, suprapubic discomfort)
  4. Prostatitis (fever, perineal pain)
  5. Asymptomatic bacteriuria
  6. Urethritis
    * ** glomerulonephritis is autoimmune (x infection)
12
Q

Recurrent, Relapse, Reinfection, Urosepsis

A

Recurrent: relapse / reinfection

Relapse: same bacterial stain, consequence of bacterial persistence

Reinfection: new infection by a different strain

Urosepsis: sepsis caused by UTI

13
Q

Microbiological diagnosis

A
  1. Bacteria culture (pyruria, significant bacteriuria)
    —> Quantitation / Semi-quantitative culture
    - differentiate contamination / genuine bacteriuria
    - standard loop
    - paper strip
    - dip slide
    - CLED agar (Cystiene, Lactose, Electrolyte Deficient agar: prevent Proteus swarming —> isolation and differentiation of urinary microbes)
  2. Urine dipstick
    —> Nitrite detection
    - reduce nitrate to nitrite
    - pink colour
    - for Staphylococcus, Enterobacteriaceae, Proteus, Pseudomonas
    - negative does not rule out: bacteria do not have the enzyme / urine not retained long enough
    —> Leukocyte detection
    - leukocyte esterase
    - purple colour
    - drugs may interfere with chemical reaction: false negative
    - contamination / vaginal discharge: false positive
14
Q

Interpretation of significant bacteriuria

A
  • Suprapubic tap urine: any growth
  • Indwelling urine catheter: >10^5 cfu / ml plus symptoms
  • Pediatric urine bag: >10^5 cfu / ml (caution)
  • Clean-catch urine: >10^5 cfu / ml (caution)
  • Mid-stream urine: >10^5 cfu / ml x 2 sample if no symptoms

Symptomatic patients without >10^5 cfu / ml:

  • uncomplicated cystitis
  • male patients
  • pure growth (E. Coli) —> lower colony counts but may still be clinically significant
15
Q

Specimen collection

A
  1. Avoid cleaning with antiseptic (false negative)
  2. Whip in backward direction

False positive:

  • heavy colonisation of vagina
  • delayed transport
16
Q

Treatment of bacteriuria

A
  • NO symptom = NO treatment
  • since common in elderly, debilitated
  • no urine culture if no symptom
  • giving antibiotic may selective for resistant bacteria
  • recurrence common after treatment

Asymptomatic but still need treatment:

  1. Pregnant women
  2. Before urological operation
  3. Children < 5 (when associated with vesicoureteric reflux)
17
Q

Recurrent UTI

A
  • **- 1 in 10 women
  • most do NOT have structural abnormality
  • behavioural factors
  • receptive uroepithelial cells / colonisation by “stick strain” E. coli
  • Urological evaluation not needed unless Recurrent + >= 1 red flag signs:
    1. Haematuria (between infection)
    2. Pyelonephritis
    3. Obstructive symptoms
    4. Urea-splitting bacteria
    5. Urine stone
    6. Severe diabetes
18
Q

Acute Prostatitis

A

Risk factors:

  • unprotected anal intercourse
  • catheter use
  • prostate biopsy

Symptoms:

  • Dysuria, frequency
  • High fever
  • Urinary retention
  • Tender prostate

Culture: yield pathogen >10^5 cfu / ml (often E. coli)

19
Q

Chronic bacterial prostatitis

A
  • Relapsing UTI by same organism
  • causes: instrumentation, dysfunctional voiding, retrograde spread into prostatic duct
  • Positive 4/2 glass test
  • 4 glass test (1 log higher count): collect 1st 10ml voided urine after prostatic massage
    —> difficult to perform, limited sensitivity for gram +ve
  • 2 glass test: collect semen, repeat if ejaculate yield gram +ve bacteria
    —> easier to perform, better sensitivity for gram +ve

Accepted pathogens

  • E. coli
  • Enterobacteriaceae
  • Enterococci
  • P. aeruginosa

Treatment: 6 weeks antibiotics

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