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YR5 Microbiology > Urinary Tract Infections > Flashcards

Urinary Tract Infections Flashcards

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
Q

What are these fried egg cells and what is this a sign of?

A

Squamous epithelial cells

Indicative of contamination

26
Q

What are risk factors for sterile pyuria?

A

Prior tx with abx

Calculi

Catheterisation

Bladder neoplasm

TB

Sexually Transmitted Disease

27
Q

What is indicative of a UTI on culture?

A

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
Q

What is the treatment of UTIs in women with uncomplicated UTI and men?

A

Uncomplicated F: Cefalexin 3d

M: Cefalexin 7d

29
Q

What are fungal infections in UTIs and what is the treatment?

A

Most Candida UTIs occur in catheterised

Removal of catheter may cure.

Oral fluconazole is no more effective than no therapy.

30
Q

In which groups is treatment of fungal UTIs indicated?

A

Renal transplant patients

Patients undergoing elective urinary tract surgery.

Should attempt to eliminate/ suppress the candiduria.

31
Q

What is pyelonephritis?

A

Infection of the Kidney.

The greater the no. organisms delivered to kidneys, the greater the chance of infection.

32
Q

What is pyelonephritis commonly associated with?

A

Sepsis

Septicaemia

33
Q

What is the management of pyelonephritis?

A

Requires more aggressive tx.

Broad spectrum Abx.

Co-amoxiclav +/- gentamicin.

34
Q

What are 4 complications associated with pyelonephritis?

A

Perinephric abscess.

Chronic pyelonephritis: scarring + chronic renal impairment

Septic shock

Acute papillary necrosis

35
Q

Can you prophylactically treat UTIs?

A

Controversial

Likely to promote resistance

Adverse effects

36
Q

In which groups is bacteria in the urine worrying?

A

Children: may indicate structural abnormality

Pregnant: may lead to chorioamnionitis

37
Q

Why is a mid-stream urine sample requested?

A

Flushes out commensals from urethra so they don’t contaminate the sample

38
Q

In which patient groups do we consider UTIs as complicated?

A

Men

Pregnant women

Children

Patients hospitalised or in health-care settings (often catheterised)

39
Q

Why is it important to investigate children with UTI?

A

May indicate structural abnormality e.g. vesicoureteric reflux which can cause scarring of the kidney + long term sequelae

40
Q

A UTIs usually caused by single or multiple bacterial species?

A

>95% caused by single species

41
Q

How do expression of different virulence factors in E coli serogroups alter manifestation of infection?

A

Different factors allow different level of ascent so some cause cystitis, some pyelonephritis

42
Q

List 6 intrarenal mechanical causes of obstruction

A

Nephrocalcinosais

Uric acid nephropathy

Analgesic nephropathy

Polycystic kidney disease

Hypokalemic nephropathy

Renal lesions of sickle cell trait or disease

43
Q

What may be indicated by S aureus in urine?

A
  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
Q

How do bacteria cause symptoms in lower UTI?

A

Bacteria cause irritation of urethral + vesical mucosa

45
Q

Why are symptoms when present in elderly often not diagnostic?

A

Noninfected older adults often experience frequency, dysuria, hesitancy, + incontinence.

46
Q

Why should you avoid urine dipsticks for diagnosing UTI in >65s?

A

Less reliable

Majority have bacteruria without infection/ Sx

Abx not indicated, may cause harm e.g. C diff risk

47
Q

What further investigations may be performed in a complicated UTI?

A

Renal USS

Intravenous urography

48
Q

Why are nitrites and leukocyte esterase indicative of UTI?

A

Gram -ve Coliforms reduce Nitrates to Nitrites

Leukocyte esterase: sign of inflammation

49
Q

Why are even carefully collected samples frequently contaminated?

A

Urine in bladder normally sterile

Urethra + periurethral areas v difficult to sterilise even when obtaining with catheter

50
Q

What differentials should be considered to UTI?

A

STI

Thrush

51
Q

How are men investigated differently?

A

Always send MSU for culture

Dipsticks are poor at excluding infection

52
Q

In which 6 groups do you always send a urine culture?

A

>65s if symptomatic + abx given

Pregnancy

Suspected pyelonephritis/ sepsis

Men

Failed abx tx

Recurrent UTIs

53
Q

What is the significance of epithelial cells in a urine sample?

A

Possible improper collection

Urethra: squamous

Bladder: columnar

Squamous presence indicates colonisation/ contamination

54
Q

In the presence of white cells and symptoms but no organisms grown from urine what should you consider?

A

STIs

TB (renal TB not detected in urine cultures)

55
Q

Why does a negative culture not exclude UTI?

A

In reality may be <10^5 bacteria/mL of urine.

56
Q

In which women is short course therapy not appropriate for UTI?

A

Those with hx of UTI caused by Abx-resistant organisms or >7d of Sx.

Increased likelihood of upper tract infection: 7d

57
Q

Which Abx are prescribed for UTI in pregnancy?

A

1st Trim: Nitrofurantoin

2nd + 3rd: Trimethoprim

58
Q

How should UTI in catheterised patients be managed?

A

Remove catheter

Abx

59
Q

Describe the susceptibility of the kidney itself to infection

A

Not uniform:

Medulla: Very few organisms needed to infect

Cortex: 10,000x as many needed

60
Q

Why is imaging performed in pyelonephritis? At what threshold?

A

To identify Calculi or Structural cause

After 1st case: Men + Children

After 2nd case: Women

YR5 Microbiology (23 decks)

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