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YR5 Microbiology > Urinary Tract Infections > Flashcards

Urinary Tract Infections Flashcards

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1
Q

Define bacteriuria.

A

Presence of bacteria in the urine.

Not always symptomatic (esp. in elderly)

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2
Q

Define cystitis.

A

Inflammation of bladder, often caused by infection.

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3
Q

What is an uncomplicated urinary tract infection?

A

Infection in a structurally + neurologically normal urinary tract.

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4
Q

What is a complicated urinary tract infection?

A

Infection in a urinary tract with functional or structural abnormalities (inc. pregnancy, indwelling catheters + calculi).

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5
Q

Summarise the epidemiology of UTIs.

A

Prevalence of bacteriuria in young nonpregnant women is 1-3%.

Up to 40% to 50% of females will experience a symptomatic UTI during their life.

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6
Q

What is the most common causative organism of acute UTIs? What feature allows for this?

A

E. Coli

Virulence factors allow them to ascend epithelium of urinary tract + evade host defences.

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7
Q

Other than E coli, name 5 organisms that can cause UTIs? What are they associated with?

A

Proteus mirabilis: affinity for those with calculi

Klebsiella aerogenes: catheterised (adhere to plastic)

Enterococcus faecalis

Staphylococcus saprophyticus: VF allow ascent, young healthy women

Staphylococcus epidermis: instrumentation, prosthetic material

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8
Q

What is the pathophysiology of recurrent urinary tract infections?

A

In recurrent UTIs esp. in presence of structural abnormalities, the relative frequency of infection caused by Proteus, Pseudomonas, Klebsiella, + Enterobacter species and by enterococci + staphylococci increases greatly.

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9
Q

What are antibacterial host defences in the urinary tract?

A

Urine: Osmolality, pH, organic acids

Urine flow + micturition: flushes out

Urinary tract mucosa: Bactericidal activity, cytokines

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10
Q

What is the pathophysiology of ascending UTI?

A

Urethra is usually colonized with bacteria.

Female urethra is short + is in proximity to warm moist vulvar + perianal areas, making contamination likely.

Organisms that cause UTI in women colonize the vaginal introitus + periurethral area before urinary infection results.

Once within the bladder, bacteria may multiply + pass up ureters, esp. if vesicoureteral reflux is present, to the renal pelvis + parenchyma

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11
Q

How can renal tract abnormalities contribute to UTIs?

A

Obstruction inhibits flushing out, resulting stasis allows bacteria to multiply + cause infection

Catheter enables ascent without VF for adherence to urinary epithelium

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12
Q

What are the extra renal mechanical causes of obstruction?

A

Valves, stenosis, or bands

Calculi

Extrinsic ureteral compression from a variety of causes e.g. gravid uterus

Benign prostatic hypertrophy

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13
Q

What are neurogenic malfunctions which can lead to obstruction?

A

Diabetic neuropathy

Spinal cord injuries

Poliomyelitis

Tabes dorsalis

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14
Q

How can Vesicoureteral reflux contribute to UTIs?

A

Perpetuates infection by maintaining a residual pool of infected urine in the bladder after voiding.

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15
Q

What is the haematogenous route and how does it contribute to UTIs?

A

Kidney is frequently the site of abscesses in patients with S. aureus bacteremia or endocarditis or both

In humans, infection of the kidney with gram -ve bacilli rarely occurs by the hematogenous route.

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16
Q

What are symptoms of UTIs in infants < 2y?

A

Nonspecific:

Failure to thrive

Vomiting

Fever

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17
Q

What are symptoms of UTIs in children over 2 years?

A

More likely to display localized Sx:

Frequency/ “accidents”

Dysuria

Abdominal or flank pain

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18
Q

What are symptoms of lower UTI?

A

Frequent + painful urination of small amounts of turbid urine.

+/- suprapubic heaviness or pain.

+/- bloody urine or shows a bloody tinge at end of micturition.

Fever usually absent in infection limited to lower tract.

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19
Q

What are symptoms of upper UTI?

A

Fever (+/- rigors)

Flank pain

+/- lower tract Sx: frequency, urgency, + dysuria

(sometimes antedate fever + upper tract Sx 1-2d)

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20
Q

What symptoms may present in upper tract infections in older people?

A

Atypical:

Abdo pain

Change in mental status: confusion, off legs

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21
Q

What are appropriate investigations for an uncomplicated UTI?

A

Urine dipstick

MSU for urine microscopy, culture + sensitivities

Bloods: FBC, UE, CRP (inflammatory markers + renal function)

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22
Q

How should catheterised patients with no systemic features and a positive MC+S be treated?

A

Nothing, bacteriuria is common in catheterised patients

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23
Q

What are methods of sampling?

A

Midstream clean catch (MSU): preferred

Catheterisation.

Suprapubic aspiration.

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24
Q

What is this, and what is it a sign of?

A

White cells pyuria

Indicative of infection

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25
What are these fried egg cells and what is this a sign of?
Squamous epithelial cells Indicative of contamination
26
What are risk factors for sterile pyuria?
Prior tx with abx Calculi Catheterisation Bladder neoplasm TB Sexually Transmitted Disease
27
What is indicative of a UTI on culture?
Infection: \>,10^5 cfu/mL in bladder urine, so voided urine contains \>,10^5 No infection: sterile bladder urine, with proper collection, voided urine contains \< 10^4
28
What is the treatment of UTIs in women with uncomplicated UTI and men?
Uncomplicated F: Cefalexin 3d M: Cefalexin 7d
29
What are fungal infections in UTIs and what is the treatment?
Most Candida UTIs occur in catheterised Removal of catheter may cure. Oral fluconazole is no more effective than no therapy.
30
In which groups is treatment of fungal UTIs indicated?
Renal transplant patients Patients undergoing elective urinary tract surgery. Should attempt to eliminate/ suppress the candiduria.
31
What is pyelonephritis?
Infection of the Kidney. The greater the no. organisms delivered to kidneys, the greater the chance of infection.
32
What is pyelonephritis commonly associated with?
Sepsis Septicaemia
33
What is the management of pyelonephritis?
Requires more aggressive tx. Broad spectrum Abx. Co-amoxiclav +/- gentamicin.
34
What are 4 complications associated with pyelonephritis?
Perinephric abscess. **Chronic pyelonephritis:** scarring + chronic renal impairment Septic shock Acute papillary necrosis
35
Can you prophylactically treat UTIs?
Controversial Likely to promote resistance Adverse effects
36
In which groups is bacteria in the urine worrying?
Children: may indicate structural abnormality Pregnant: may lead to chorioamnionitis
37
Why is a mid-stream urine sample requested?
Flushes out commensals from urethra so they don't contaminate the sample
38
In which patient groups do we consider UTIs as complicated?
Men Pregnant women Children Patients hospitalised or in health-care settings (often catheterised)
39
Why is it important to investigate children with UTI?
May indicate structural abnormality e.g. vesicoureteric reflux which can cause scarring of the kidney + long term sequelae
40
A UTIs usually caused by single or multiple bacterial species?
\>95% caused by single species
41
How do expression of different virulence factors in E coli serogroups alter manifestation of infection?
Different factors allow different level of ascent so some cause cystitis, some pyelonephritis
42
List 6 intrarenal mechanical causes of obstruction
Nephrocalcinosais Uric acid nephropathy Analgesic nephropathy Polycystic kidney disease Hypokalemic nephropathy Renal lesions of sickle cell trait or disease
43
What may be indicated by S aureus in urine?
1. Colonisation in improper sample 2. S aureus bacteraemia/ endocarditis, emboli can settle in kidney, form abscess, cause excretion into the urine Ix if systemic features e.g. fever, weight loss
44
How do bacteria cause symptoms in lower UTI?
Bacteria cause irritation of urethral + vesical mucosa
45
Why are symptoms when present in elderly often not diagnostic?
Noninfected older adults often experience frequency, dysuria, hesitancy, + incontinence.
46
Why should you avoid urine dipsticks for diagnosing UTI in \>65s?
Less reliable Majority have bacteruria without infection/ Sx Abx not indicated, may cause harm e.g. C diff risk
47
What f**urther investigations may be performed in a complicated UTI?**
Renal USS Intravenous urography
48
Why are nitrites and leukocyte esterase indicative of UTI?
Gram -ve Coliforms reduce Nitrates to Nitrites Leukocyte esterase: sign of inflammation
49
Why are even carefully collected samples frequently contaminated?
Urine in bladder normally sterile Urethra + periurethral areas v difficult to sterilise even when obtaining with catheter
50
What differentials should be considered to UTI?
STI Thrush
51
How are men investigated differently?
Always send MSU for culture Dipsticks are poor at excluding infection
52
In which 6 groups do you always send a urine culture?
\>65s if symptomatic + abx given Pregnancy Suspected pyelonephritis/ sepsis Men Failed abx tx Recurrent UTIs
53
What is the significance of epithelial cells in a urine sample?
Possible improper collection Urethra: squamous Bladder: columnar Squamous presence indicates colonisation/ contamination
54
In the presence of white cells and symptoms but no organisms grown from urine what should you consider?
STIs TB (renal TB not detected in urine cultures)
55
Why does a negative culture not exclude UTI?
In reality may be \<10^5 bacteria/mL of urine.
56
In which women is short course therapy not appropriate for UTI?
Those with hx of UTI caused by Abx-resistant organisms or \>7d of Sx. Increased likelihood of upper tract infection: 7d
57
Which Abx are prescribed for UTI in pregnancy?
1st Trim: Nitrofurantoin 2nd + 3rd: Trimethoprim
58
How should UTI in catheterised patients be managed?
Remove catheter Abx
59
Describe the susceptibility of the kidney itself to infection
Not uniform: Medulla: Very few organisms needed to infect Cortex: 10,000x as many needed
60
Why is imaging performed in pyelonephritis? At what threshold?
**To identify** Calculi or Structural cause After 1st case: Men + Children After 2nd case: Women

YR5 Microbiology (23 decks)

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