Microbiology of UTI Flashcards

1
Q

In a normal urinary tract, where is the urine sterile and where might it pick up bacteria?

A

Sterile - kidney, ureter, bladder

Distal urethra is colonised by bowel flora (coliforms & enterococci)

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2
Q

Define UTI

A

Presence of bacteria in urine which is causing clinical infection

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3
Q

Define lower and upper UTI

A

Lower UTI - infection confined to bladder (cystitis)

Upper UTI - infection involving ureters +/- kidney (pyelonephritis)

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4
Q

Define complicated UTI

A

UTI associated with systemic sepsis OR stones OR urinary tract abnormality

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5
Q

Define bacteriuria

A

Bacteria in the urine

Nb - common in elderly people with catheters & does not always denote infection

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6
Q

Cystitis is infection of the bladder. T/F

A

False - inflammation of the bladder; infection is one cause but there are others

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7
Q

Who is at highest risk of UTI?

A

Women
Catheterised patients
Patients with structural abnormalities of the urinary tract

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8
Q

Why are women more at risk of UTI?

A

Shorter & wider urethra
Proximity of urethra to anus
Increased risk with sexual activity & pregnancy

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9
Q

Describe ascending infection

A
Bowel bacteria on perineal skin -->
Urethra -->
Bladder -->
Ureter -->
Kidney
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10
Q

Describe bloodstream infection

A

Bacteraemia/septicaemia –>

Kidneys (multiple small abscesses)

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11
Q

What organisms commonly cause UTI?

A

E.coli
Klebsiella
Enterobacter

(more rarely proteus & other coliforms)

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12
Q

What are the features of UTI commonly associated with Proteus?

A

Calculi formation

Foul smelling urine

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13
Q

How does proteus cause the formation of renal stones?

A

Produces urease which breaks down uric acid into ammonia –> higher blood pH –> formation of salts

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14
Q

What are enterococci? Name two

A

Types of streptococci which live within the GI tract

Enterococci faecalis and faecium

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15
Q

What types of staph can cause UTI? State whether they are coagulase positive or negative

A
Staph. saphrophyticus (neg)
Staph aureus (pos)
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16
Q

Who gets staph. saphrophyticus infection?

A

Women of child bearing age

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17
Q

Pseudomonas aeruginosa is a gram negative bacillus of the coliform family. T/F

A

False - not a coliform

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18
Q

What is pseudomonas aeruginosa infection associated with?

A

Catheterisation

Instrumentation

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19
Q

How is pseudomonas aeruginosa infection treated?

A

Ciprafloxacin (resistant to other oral antibiotics)

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20
Q

What are the clinical symptoms and signs of UTI?

A

Dysuria
Frequency
Nocturia
Haematuria

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21
Q

What are the clinical symptoms and signs of UTI with upper tract involvement?

A

Fever
Rigors
Flank/loin pain

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22
Q

What is important to remember about collecting urine samples? How is this overcome?

A

Bacterial contamination from the perineum is common on first samples.
Midstream specimen of urine (MSSU)

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23
Q

Describe how midstream specimen of urine is collected

A
Perineum/meatus is washed with sterile saline
Sterile foil bowl given to patient
First pass urine on toilet
Mid urine collected in bowl
Last pass urine on toilet
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24
Q

Apart from MSSU, how else can urine be collected? When are these indicated

A

Clean catch - children & elderly
Bag urine - babies
Catheter specimen urine - catheter in
Suprapubic aspiration - outflow obstruction

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25
Q

List one drawback and one positive about bag urine collection?

A

Often contaminated with bowel flora

Negative culture results are reassuring

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26
Q

Which two containers can be used for urine collection? State the timeframes in which they should be delivered to the lab, respectively

A

Boricon container - 24 hours (preservative)

Sterile universal container - 2 hours

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27
Q

Which results on dipstick urine testing would indicate infection?

A

Leukocyte (WBC in urine)
Nitrite (bacteria in urine)
Blood
Protein

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28
Q

Which bacterias will not test positive for nitrites on dipstick?

A

Enterococci (which is absolutely fabulous because they’re a common pathogen)

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29
Q

Which two tests can be done on the urine in a laboratory? When are these indicated?

A

Microscopy - urgent cases (look for pus, bacteria & red cells)
Culture - significant bacteraemia suspected

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30
Q

Describe Kass’s criteria for defining urine culture results. Who does this criteria apply to?

A

> 10^5 organisms/ml - probable UTI

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31
Q

Mixed growth in urine culture is not significant as UTIs are usually caused by one infecting organism. T/F

A

True - single organism in large majority of patients but may not stand true for those who are catheterised or who have structural abnormalities

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32
Q

What are ESBL producing bacteria?

A

Extended spectrum beta lactamase producing bacteria (i.e bacteria resistant to all cephalosporins and most penicillins)

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33
Q

Which antibiotics may be useful against ESBL producing bacteria?

A

Nitrofurantoin (oral)
Temocilin (IV)
(& others)

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34
Q

What are carbapenemase producing enterbacteria (CPE)?

A

Gram negative coliform bacilli that are resistant to Meropenem (i.e all current antibiotics)

35
Q

How does CPE resistance spread? What are some strains associated with?

A

Plasmids

Travel to indian sub-continent

36
Q

What are the features of an antibiotic useful in treating UTI?

A

Excreted in high concentrations in urine
Few side effects
Oral

37
Q

How long a course of antibiotics should be given to uncomplicated lower UTI’s in women?

A

3 days

38
Q

What are the first line antibiotics for UTI?

A

Amoxicillin (IV or oral)
Trimethoprim (oral or IV cotrimoxazole)
Nitrofurantoin (oral)
Gentamicin (IV)

39
Q

What are the second line antibiotics for UTI?

A
Pivmecillinam (oral)
Temocillin (IV)
Cefalexin (oral)
Co-amoxiclav (IV, oral)
Ciprofloxacin (IV, oral)
40
Q

Is amoxicillin safe in pregnancy?

A

Yes

41
Q

Which organisms will amoxicillin treat?

A
Enterococci faecalis 
Some coliforms (50% are resistant)
42
Q

How does trimethopram work?

A

Inhibits bacterial folic acid synthesis

43
Q

Is trimethopram safe in pregnancy?

A

Avoid in first trimester (3 months)

44
Q

What is co-trimoxazole a combination of?

A

Trimethopram and sulphamethoxazole

45
Q

What risk do sulphonamides carry?

A

Stevens Johnsons syndrome (i.e toxic epidermal necrolysis)

46
Q

Which organisms will trimethopram treat?

A

Most coliforms
Staph aureus
MRSA

NOT pseudomonas

47
Q

In which clinical presentation of UTI is nitrofurantoin useful? Why?

A

Lower uncomplicated UTI

Only reaches effective concentrations in bladder urine

48
Q

Is nitrofurantoin safe in pregnancy?

A

Avoid in late pregnancy (neonatal haemolysis) , breast feeding and in children

49
Q

Which organisms will nitrofurantoin treat?

A

Most coliforms
Staph aureus
MRSA

NOT proteus or pseudomonas

50
Q

Is gentamicin safe in pregnancy?

A

No

51
Q

What does gentamicin toxicity cause? How common is this?

A

Renal toxicity
8th cranial nerve damage (deafness and balance issues)

Narrow therapeutic index - must be carefully monitored

52
Q

How is gentamicin administered? What then must be checked?

A

Once daily IV infusion (7mg/kg)

Must check blood levels 6-14 hours later

53
Q

Which organisms will gentamicin treat?

A

Most coliforms
Staph aureus
MRSA

NOT enterococci

54
Q

When is gentamicin clinically indicated? How long for?

A

Severe gram negative (i.e coliform) sepsis

NO MORE THAN 3 DAYS

55
Q

Pivmecillinam is useful in what clinical context?

A

Lower uncomplicated UTI

56
Q

What bugs is pivmecillinam effective against?

A

Resistant coliforms

57
Q

What bugs is pivmecillinam NOT effective against?

A

Strep
Staph
Pseudomonas
Enterococci

58
Q

Can pivmecillinam be used in pregnancy?

A

Nope

59
Q

Which bugs is temocillin effective against? Which is it NOT effective against?

A

Resistant coliforms

Strep
Staph
Enterococci
Pseudomonas

60
Q

Temocillin is useful in which clinical context?

A

Complicated UTI/urosepsis where the patients renal function isn’t good enough to introduce gentamicin

61
Q

Can cefalexin be used in preganancy?

A

Yes

62
Q

Why is cefalexin not used if it can be avoided?

A

Broad spectrum antibiotic increases risk of c.diff infection

63
Q

Which organisms do cefalexin treat?

A

Coliforms

Staph

64
Q

What is co-amoxiclav?

A

Combination of amoxicillin and clavulanic acid

65
Q

Is co-amoxiclav safe in pregnancy?

A

Yes

66
Q

Which organisms does co-amoxiclav treat? Why is it not used more often?

A

Staph
Coliforms
Enterococci

C.diff infection risk

67
Q

When is ciprofloxacin not used?

A

Young children

Pregnant woman

68
Q

Why is ciprofloxacin not used more often?

A

C.diff infection risk because broad spectrum antibiotics

69
Q

Which organisms does ciprofloxacin treat? Why is worth remembering about this antibiotic?

A

Pseudomonas
Coliforms
Enterococci
Only ORAL agent that treats pseudomonas

70
Q

How is female lower UTI treated?

A

Trimethoprim OR
Nitrofurantoin orally
3 days

71
Q

How is uncatheterised male UTI treated?

A

Trimethoprim OR
Nitrofurantoin orally
7 days

72
Q

How is a complicated UTI/pyelonephritis treated in the community?

A

Co-amoxiclav OR
Co-trimoxazole
14 days

73
Q

How is a complicated UTI/pyelonephritis treated in the community?

A

Amoxicillin/co-trimoxazole AND gentamicin
3 days
Step down treatment

74
Q

When can you diagnose asymptomatic bacteraemia?

A

> 10^5 organisms/ml
Asymptomatic patient
NO pus in the urine

75
Q

How is asymptomatic bacteraemia treated?

A

It isn’t - especially not in old people

76
Q

How is asymptomatic bacteraemia treated in a pregnant woman? What happens if you don’t treat?

A

Antibiotics
May develop into pyelonephritis –>
Intra-uterine growth retardation (IUGR) or premature labour

77
Q

What is abacterial cystitis/urethral syndrome?

A

UTI symptoms
Pus in urine
No significant growth in culture

78
Q

What can the cause of abacterial cystitis?

A

Early phase of UTI
Urethral trauma
Chlamydia/gonorrhoea causing urethritis

79
Q

What is honeymoon cystitis?

A

Urethral trauma due to vigorous sexual intercourse

80
Q

How can urethral syndrome be treated?

A

Alkalising the urine for symptomatic relief

81
Q

Does catheterisation increase the incidence of UTI? What increases the risk?

A

Yes

Increasing length of catheter

82
Q

When should catheterised patients be given antibiotics?

A

> 10^5 organisms/ml

Symptomatic

83
Q

Giving unnecessary antibiotics to catheterised patients causes what?

A

Colonisation of catheter with increasingly resistant organisms