L75 – Urinary Tract Infections Flashcards Preview

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Flashcards in L75 – Urinary Tract Infections Deck (90)
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1
Q

Female: male ratio of UTI?

A

Female:male – 30:1

2
Q

What is associated with most hospital acquired UTI?

A

30-40% of all hospital-acquired infections (HAI):

often associated with use of catheters causing UTI

3
Q

UTI in adult men is rare unless what condition occurs?

A

Obstruction of urethra from benign prostatic hyperplasia (BPH), e.g. in elderly

4
Q

What is the main host defense against UTI?

A

Flushing effect of urine:

> > Emptying the bladder flushes out bacteria in bladder, urethra

> > Anything that interferes with flushing increases risk of UTI

5
Q

What host defense decreases the severity and chance of UTI complications?

A

Immunity decreases severity, chance of complication:
 Humoral
 Cell-mediated

6
Q

Action of bacteria causing infection to bladder?

A

1) adhere
2) colonize on urinary orifice
3) infect and ascent from urethral opening to bladder in retrograde manner

7
Q

UTI pathogens are usually found where?

A

mostly enteric / skin, e.g. fecal flora

8
Q

What is UPEC?

A

Uropathogenic

Escherichia coli

9
Q

Whats ExPEC?

A

Extraintestinal pathogenic E.coli

10
Q

Apart from E.coli, name some other UTI bacteria?

A

Klebsiella pneumoniae

Proteus mirabilis

Pseudomonas aeruginosa

Staphylococcus saprophyticus

Enterococcus faecalis

11
Q

Name some roles of virulence factors in UTI bacteria?

A

Adherence

Toxin

Immune evasion

Iron acquisition

12
Q

2 structures of bacteria used to adhere to mucosa?

A

Pili/ fimbriae

Adhesins

13
Q

What is the structure that UPEC uses to adhere to mucosa?

A

Type 1, pyelonephritis-associated (P) fimbriae

14
Q

Give 2 examples of immune evasion structure used by UPEC?

A

lipopolysaccharide, capsular

polysaccharides

15
Q

Give 2 examples of toxins secreted by UPEC?

A

hemolysin, aerobactin protease

16
Q

What is the role of flagella in UPEC?

A

flagella provides mobility > ascending infection

17
Q

Give 2 sources of E.coli that can cause UTI?

A

extraintestinal pathogenic E. coli:

1) contaminated / raw / improperly cooked food
2) retail chicken meat products, eggs

18
Q

If E.coli has no zoonosis potential, what is expected from a resistance profile between human and poultry bacteria?

A

expect human-susceptible to cluster with human-resistant,

poultry -susceptible to cluster with poultry- resistant

19
Q

What is the resistance profile of E. coli that causes UTI? What does this imply?

A

expect human-susceptible to cluster with human-resistant, but not seen in this
case - human and poultry strains mix

suggests route of transmission can be from
poultry-resistant / poultry-susceptible

> > E. coli has zoonosis potential

20
Q

What factors predispose UTI?

A

Length of urethra

Mechanical factors causing trauma to mucosa

Genetic factor e.g. density of bacterial receptors

Hormonal effect on mucosa

Underlying disease

21
Q

Explain how length of urethra affects risk for UTI?

A

Length of urethra before reaching bladder:

long in male, short in female

Females are at much higher risk

22
Q

Give examples of mechanical factors causing trauma to mucosa, casuing UTI?

A

 Sexual intercourse

 Trauma

 Contraceptive diaphragm (compress posterior part of
urethra&raquo_space; help ascent of bacteria)

 Catheter

23
Q

Explain the effect of hormones on mucosa?

A

menopause: hormones (especially estrogen) decreases

> > atrophy of mucosa facilitate bacterial adherence

24
Q

Explain how pregnancy can lead to increased spreaad of UTI?

A

Pregnancy:
» dilatation, decreased peristalsis of ureter

> > compress on urethra and incompletely emptying

25
Q

What is neurogenic bladder and what are the sonsequences?

A

bladder dysfunction (flaccid or spastic) caused by neurologic damage

Risk of serious complications (eg, recurrent infection, vesicoureteral reflux, autonomic dysreflexia)

26
Q

factors that can cause poor emptying of bladder?

A

 Neurogenic bladder

 Pregnancy

27
Q

How does urinary catheter increase spread of UTI?

A

nidus (focus of infection) for persistence

28
Q

How does stones increase UTI spread?

A

Obstruction of urethra&raquo_space; impaired flushing

29
Q

How does diabetes increase risk of UTI?

A

immune incompetence

30
Q

What causes reflux which increases chances of UTI?

A

Incompetent ureterovesical valves (functional / anatomical)

31
Q

How does bacteria in urinary tract reach blood?

A

Bladder > kidney > blood

32
Q

Summarize all the factors that increases spread of UTI

A

Immune incompetence

Foreign body obstruction

Dilation and decreased peristalsis of ureter

Poor emptying

Reflux

33
Q

Virulence factor that causes inflammation?

A

Lipopolysaccharide

34
Q

Explain how UTI increases formation of kidney stones?

A

Some bacteria in urine produces urease

Urease converts urea to NH3 and raises urine pH

Normally acidic urine becomes alkaline, causing salts to precipitate

> > form stones

35
Q

2 classes of UTI?

A

Uncomplicated and complicated

36
Q

What is the most dominating pathogen to cause UTI?

A

UPEC

37
Q

Definition of uncomplicated UTI?

A

Infection in a structurally and neurologically normal urinary tract

Affect healthy individuals

38
Q

Which organs are involved in uncomplicated UTI?

A

Bladder and kidney

39
Q

Definition of complicated UTI?

A

UTI associated with factors that compromise the urinary tract or host defense (e.g. urinary obstruction, neurogenic bladder…etc)

40
Q

What can cause recurrent infection>?

A

Relapse or Reinfection

41
Q

Differentiate relapse from reinfection?

A

Relapse = same bacterial strain persist to infect

Reinfection = new infection by a different organism / strain

42
Q

What is urosepsis?

A

sepsis caused by UTI

43
Q

Symptoms of acute pyelonephritis?

A

High fever, loin pain

44
Q

Difference between acute pyelonephritis and glomerulonephritis?

A

glomerulonephritis: mainly autoimmune

Acute pyelonephritis: caused by bacterial infection

45
Q

Which patients are likely to have perinephric abscess? What is it?

A

Spread from kidney to adjacent fascia

In patient with underlying disease, e.g. poorly
controlled diabetes mellitus

46
Q

What is cystitis?

A

Inflammation of Bladder lining (e.g. mucosa, urine; not outside)

47
Q

Symptoms of cystitis?

A

urinary urgency and frequency, dysuria, suprapubic discomfort

48
Q

What constitutes asymptomatic bacteriuria?

A

No symptoms but diagnosed in laboratory diagnosis

49
Q

Symptoms of acute and chronic prostatitis?

A

Acute = fever, perineal pain

Chronic= non-specific and hard to diagnoser

50
Q

What is pyuria?

A

inflammatory response due to infection > abnormally high number of WBC /
leukocytes

51
Q

How is pyuria detected?

A

Use urine strip:

Leukocyte esterase (from host) react with substrates in strip to produce purple
color
52
Q

How may results from urine strip be wrong?

A
  • Some drugs (e.g. cephalexin), high glucose level may interfere with chemical reaction =
    false-negative results
  • Positive result may occur from contamination of specimens by vaginal discharge
53
Q

What is the nitrite detection test for? How does it work?

A

Some bacteria possess nitrate reductase
> can reduce nitrate (NO3-) in urine to nitrite (NO2)

> nitrite reacts with substrates in strip to produce uniform pink color

54
Q

Give 2 reasons why the nitrite detection test is not definitive for UTI ?

A

 Some bacteria (e.g. enterococcus) do not have the enzyme for reducing nitrate to nitrite

 Urine may not be retained in the bladder for long enough for bacteria to reduce nitrate (e.g. frequent
voiding)

55
Q

How to differentiate contamination / genuine

bacteriuria?

A

use quantitation / semi-quantitative culture

56
Q

Explain how the count of bacteria can be used to differentiate infection from contamination?

A

Cut threshold cut-off

Infected women (significant bacteriuria): >= 10^ 5 bacteria/mL of urine

57
Q

Why do uninfected women still have bacteria in urine?

A

because urine passes through the portion of mucosal surface in urethra that is colonized by
commensals

58
Q

What is the medium for UTI?

A

cysteine lactose electrolyte deficient (CLED) agar

59
Q

Why is CLED used?

A
inhibits swarming (no expression of motility in
bacteria)

> > create localized, colony morphology

** hence why blood agar is not used **

60
Q

What is the positive and negative results for CLED agar?

A

+ve = ferment lactose = yellow

-ve = doesnt ferment lactose = white

61
Q

Give 2 methods to put urine on agar culture to detect bacterial load?

A

Standard calibrated loop

Dip paper strip vertically to line > touch urine to agar surface

62
Q

What is the cfu indicating significant growth of bacteria?

A

> 1 x 10^5 Colony count per mL of urine

63
Q

Name other agar (not CLED) for detecting urine bacterial load?

A

McConkey agar:

incubate for 24h> determine
the number of bacteria

64
Q

Name ways to collect urine ?

A

MSU (mid-stream urine)

Clean-catch urine (baby)

Pediatric urine bag

CSU (indwelling urine catheter)

Suprapubic tap urine

65
Q

What is the bacterial cfu in suprapubic tap urine sample?

A

Any growth = UTI

Not the usual 10^5 colonies per mL

66
Q

Which symptomatic patients might not produce urine with 10^5 cfu/ml?

A

 Women with uncomplicated cystitis

 Male patients

67
Q

Under what circumstance does low cfu still count as clinically significant?

A

If the colony is pure growth (esp. E.coli)

68
Q

2 reasons for urine samples to produce false positive results?

A

Heavy colonization of vagina

Delay transport >2h

69
Q

Give one reason how a urine sample creates false negative result?

A

Cleaning with antiseptic > contaminate urine and lower bacterial load

70
Q

No UTI symptom = no urine culture and treatment except in which 3 cases?

A

 Pregnant women (if not treated: 20-30% risk of progression to acute pyelonephritis)

 Before urological operation (e.g. transurethral resection of enlarged prostate gland)

 Children (age <5 years), with vesico-ureteric reflux of urine back into kidney (e.g. valve defect)

71
Q

Asymptomatic bacteriuria is common is which patients?

A

Elderly, debilitated

72
Q

Most recuurent UTI is caused by what?

A

Behavioral factors

Most do not have structural abnormality

73
Q

What host or microbe factor can increase chances of recurrent UTI?

A
  1. Unusually receptive uroepithelial cells; or

2. Colonization by ’stick strains’ of E. coli

74
Q

What criteria is needed for urological evaluation in young women, which in not routine or cost-effective?

A
2 things needed:
1) Recurrent UTI 
\+
2) Any one of the following conditions:
-Hematuria between infections 
-Pyelonephritis 
-Obstructive symptoms 
-Urea-splitting bacteria 
-Urinary calculi 
-Severe diabetes
75
Q

Risk factors for acute bacterial prostatitis?

A

Unprotected anal intercourse

Indwelling urinary catheter use

Prostate biopsy

76
Q

What are the clinical presentations of Acute bacterial prostatitis (ABP)?

A

High fever + septic shock

Dysuria and urinary frequency

Urinary retention

Very tender prostate

77
Q

What causes urinary retention in ABP?

A

Obstruction from acute edema of prostate

78
Q

What is the urine culture cfu?

A

> = 10^5 cfu/ml

79
Q

What are the 2 tests to confirm Chronic bacterial prostatitis?

A

Positive 4 glass or 2 glass test

80
Q

What causes chronic bacterial prostatitis?

A

Relapsing UTI by the same organism

81
Q

Name the 4 bacteria that are accepted pathogens for acute and chronic bacterial prostatitis?

A

E. coli (70%)

Enterobacteriaceae

Pseudomonas aeruginosa

Enterococci

82
Q

What are some associated conditions of chronic bacterial prostatitis?

A

Retrograde spread of bacteria into prostatic ducts

Dysfunctional voiding

Previous instrumentation (e.g. ultrasound probe)

83
Q

Is ultrasound good for diagnosis of bacterial prostatitis?

A

Ultrasound imaging is not indicative (confused with BPH)

84
Q

Treatment of CBP?

A

Treatment: 6-12 weeks antibiotics

85
Q

What are in the 4 samples in the 4 glass test/ Stamey’s technique? Which samples have pathogen ?

A
  1. VB1 = first 10mL urethral urine voided
  2. VB2 = mid-stream culture
  3. Expressed prostatic secretion (EPS)
  4. VB3: first 10mL voided after massage

3rd and 4th samples have bacteria

86
Q

What induces EPS release from prostate?

A

Massage prostate for ~1 min

87
Q

Limitation of 4 glass test for CBP?

A

 Difficult to perform
 Limited sensitivity for
Gram-positive

88
Q

What is in the 2 samples of the 2 glass test? which one contains bacteria?

A

VB1: 1st voided 10mL urine

Semen bacteria

89
Q

Why is semen collected in 2 glass test?

A

Repeat if ejaculate yields Gram-positive bacteria:

Ejaculate comes from seminar vesicle, passes through prostate
» carries infective organism

90
Q

Why is the 2 glass test better than 4 glass?

A

 Easier to perform

 Better sensitivity for Gram-positive

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