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Year 2 - Renal (DP) > Microbiology > Flashcards

Microbiology Flashcards

1
Q

Urine in what areas is usually sterile?

A

Kidneys
Ureters
Bladder

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2
Q

What microbes are commensals in the lower urethra?

A

Coliforms
Enterococci
Anaerobes (rarely cause UTI)

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3
Q

What is cystitis?

A

Infection in bladder (Lower UTI)

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4
Q

What is an upper UTI?

A

Infection involving ureters

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5
Q

What is pyelonephritis?

A

An upper UTI involving the kidneys

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6
Q

What is a complicated UTI?

A

UTI complicated by:

 - Sepsis
 - Abnormality/Stones
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7
Q

What effect does a complicated UTI have on treatment?

A

Requires a longer antibiotics course

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8
Q

When might bacteruria not be an infection?

A

In the elderly

Patients with catheters

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9
Q

Why are females much more prone to UTIs?

A

Short and wide urethra

Urethral opening close to anus

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10
Q

What can increase the risk of UTIs?

A

Sex

Pregnancy

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11
Q

Why do posterior urethral valves increase the UTI risk?

A

Incomplete bladder emptying:

-> Urine stasis -> Infection

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12
Q

What is the most common route of UTI? What route does it take?

A

Ascending infection

Bowel bacteria -> Perineal skin -> Lower urethra -> Bladder -> Ureters -> Kidneys

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13
Q

How can a descending UTI occur?

A
  1. Patient with bacteraemia/sepsis
  2. Bacteria seeded in kidney
  3. Multiple small abscesses -> Bacteruria
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14
Q

What are coliforms?

A

Rod-shaped, gram negative, non-spore forming, facilitative anaerobes

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15
Q

What is the most common causal organism in UTIs?

A

E. coli (70%)

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16
Q

What other coliforms can cause UTIs?

A

Klebsiella sp
Enterobacter sp.
Other

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17
Q

What are Proteus sp. UTIs associated with? How do they cause this?

A

Stone formation:

 - Produce ureases
 - Urea broken down into ammonia
 - Urinary pH rises
 - Precipitates salt formation
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18
Q

Proteus sp. UTIs have what other distinguishing feature?

A

Foul smelling

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19
Q

What are Enterococcus sp?

A

Types of Strep. living in the GI tract

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20
Q

Which of the following is antibiotic sensitive and which can be resistant and difficult to treat:

  • Enterococcus faecalis
  • Enterococcus faecium
A

Faecalis:
- Antibiotic sensitive
Faecium:
- Can be resistant and difficult to treat

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21
Q

Who gets UTIs caused by Staphylococcus saphrophyticus?

A

Women of child-bearing age

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22
Q

Why is Pseudomonas not a coliform?

A

Strictly aerobic

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23
Q

What are Pseudomonas UTIs associated with?

A

Catheters

Urinary tract instrumentation

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24
Q

What is the only antibiotic that can treat Pseudomonas UTIs and what does this increase the risk of?

A

Ciprofloxacin:

- Increased risk of C. diff

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25
Q

What symptoms suggest an upper UTI?

A

Fever
Loin pain
Rigors

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26
Q

What urine is likely to be infected in obtaining a urine sample?

A

1st urine (collects commensals from perineum and lower urethra)

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27
Q

What (ideally) needs to be carried out before obtaining a MSSU?

A

Wash perineum and urethral meatus with saline:

- Not antiseptic (May kill bacteria)

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28
Q

When would a clean catch urine sample be used?

A

In children and elderly when MSSU can’t be obtained

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29
Q

In what individuals is a bag urine sample used?

A

Babies

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30
Q

What do you do if there is a positive culture from a bag urine sample?

A

Suprapubic specimen must be taken

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31
Q

When would you take a catheter specimen of urine?

A

If signs/symptoms of UTI

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32
Q

What is the best container for containing urine for transport?

A

Boricon container:

 - Contains boric acid
           - > Stops bacterial multiplication for ~24 hours
 - Red top
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33
Q

If a universal sterile container is used to transport urine samples, how soon must it reach the lab?

A

In 2 hours

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34
Q

What does a positive leukocyte esterase mean on urine dipstick?

A

Indicates WBC in urine

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35
Q

What might give a false positive result on leukocyte esterase on dipstick?

A

Catheter

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36
Q

What does a positive nitrite result on urine dipstick mean?

A

Bacteruria

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37
Q

Why do bacteria cause a positive nitrite result on urine dipstick?

A

Nitrate is reduced to Nitrite

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38
Q

What bacteria cause a positive nitrite result?

A

Coliforms

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39
Q

What bacteria do not cause a positive nitrite result?

A

Enterococcus

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40
Q

Ideally, when should a MSSU only be sent?

A

If dipstick is positive and there are symptoms

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41
Q

When is urine microscopy used?

A

If it is an urgent case

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42
Q

What should you look for in urine microscopy?

A

Polymorphs (pus cells)
Bacteria
+/- RBCs

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43
Q

What is a significant urine culture result according to the Kass’ Criteria?

A

> 100,000 (10^5) organisms/ml

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44
Q

What is a insignificant urine culture result according to the Kass’ Criteria?

A
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45
Q

If on urine culture there are 10^4 organisms/ml, what might this indicate?

A

Contamination?

UTI?

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46
Q

If there are only 10^4 organisms/ml on urine culture what should you do?

A

Repeat specimen

47
Q

In a patient who is not catheterised, what does urine culture usually show?

A

Single organism

>10^5 organisms/ml of pure growth

48
Q

If there is mixed growth on urine culture, even if >10^5 organisms/ml, what does this mean?

A

Usually insignificant unless they have urinary tract abnormalities

49
Q

What does ESBL stand for?

A

Extended Spectrum β-Lactamase

50
Q

ESBL-producing bacteria are resistant to what?

A

All cephalosporins

Almost all penicillins

51
Q

What is the ESBL-producing gene carried on and what is it usually carried with?

A

On a plasmid with other resistance genes:

 - Gentamicin
 - Ciprofloxacins
52
Q

What oral antibiotics may be useful in treating ESBL-producing bacteria?

A

Nitrofurantoin
Pivmecillinam
Fosfomycin

53
Q

What IV antibiotics may be useful in treating ESBL-producing bacteria?

A

Temocillin
Meropenem
Ertapenem

54
Q

What is a possible source of ESBL-producing bacteria?

A

Imported chicken:

 - Antibiotics used as growth factors
           - > Resistance
55
Q

What are Carbapenemase-Producing Enterobacteriaceae?

A

Gram-negative bacilli (coliforms) that are resistant to meropenem:
- Essentially resistant to all antibiotics

56
Q

What are Carbapenemase-Producing Enterobacteriaceae associated with?

A

Travel to the Indian sub-continent

57
Q

What are the features of an ideal antibiotic used for UTIs?

A

Excreted in high concentrations in the urine:
- If metabolised in liver -> Useless
Oral
Inexpensive
Few side effects

58
Q

What length of treatment is usually adequate for an uncomplicated, lower UTI in women?

A

3 days

59
Q

When is a urine sample sent in uncomplicated, lower UTIs in women?

A

If they have a second UTI relatively soon after the 1st

60
Q

Which of the following is not a 1st line antibiotic for UTIs:

  • Amoxicillin (PO/IV)
  • Co-amoxiclav (PO/IV)
  • Trimethoprim (PO/IV [as Cotrimoxazole])
  • Nitrofurantoin (PO)
  • Gentamicin (IV)
A

Co-amoxiclav (It is second line)

61
Q

When is second line treatment initiated in the treatment of UTIs?

A

If resistant to >=1 of the 1st line treatments

62
Q

Which of the following is not a second line treatment of UTIs:

  • Pivmecillinam (PO)
  • Temocillin (IV)
  • Cefalexin (PO)
  • Ciprofloxacin (PO/IV)
  • Vancomycin
A

Vancomycin

63
Q

How many antibiotics are often tested for sensitivities?

A

12-20

64
Q

Approximately how many antibiotics are reported back to doctors?

A

~4 (more if resistant)

65
Q

Is amoxicillin safe in pregnancy?

A

Yes

66
Q

What is amoxicillin useful for?

A

Enterococcus faecalis
Some coliforms:
- 50% of E. coli are now resistant
- Not great empirical treatment

67
Q

How does Trimethoprim work?

A

Inhibits bacterial folic acid synthesis:

 - Dihydrofolate -> Tetrahydrofolate
           - > Dihydrofolate Reductase inhibited
68
Q

When is Trimethoprim not safe in pregnancy and why?

A

1st trimester:

- Inhibits folic acid synthesis -> Spina bifida

69
Q

Why is Trimethoprim recommended for UTI with prostatitis?

A

Good [urine] and [prostate]

70
Q

What two antibiotics form PO/IV Co-trimoxazole?

A

Sulphamethoxazole + Trimethoprim

71
Q

What is a serious side effect of using Co-trimoxazole?

A

Stevens-Johnson Syndrome

72
Q

Which of the following is not reliably covered by Trimethoprim:

  • Most coliforms
  • Enterococci
  • Staph aureus
  • MRSA
  • Proteus sp
  • Pseudomonas
A

Proteus sp.

Pseudomonas

73
Q

When is Nitrofurantoin useful? Why is it useful here?

A

In lower UTI:

- Effective [urine] only reached in bladder

74
Q

Why should nitrofurantoin be avoided in late pregnancy?

A

Can cause neonatal haemolysis

75
Q

When else should nitrofurantoin be avoided?

A

Breastfeeding

Kids

76
Q

Which of the following is not covered by nitrofurantoin:

  • Most coliforms
  • Proteus sp.
  • Enterococci
  • Staph aureus
  • MRSA
  • Pseudomonas
A

Proteus sp.

Pseudomonas

77
Q

Why must gentamicin be avoided?

A

Can affect:

 - Hearing
 - CN VIII
 - Kidneys
78
Q

What is the dose of gentamicin?

A

7mg/kg once daily IV

79
Q

After giving a dose of gentamicin, what follow up is needed?

A

Measure blood levels 6-14hrs later

80
Q

Which of the following is not covered by gentamicin:

  • Most coliforms
  • Pseudomonas sp.
  • Staph aureus
  • MRSA
  • Enterococci
A

Enterococci

81
Q

In what infection is gentamicin most useful in?

A

Gram negative sepsis

82
Q

Gentamicin can only be prescribed for 3 days, this means 3 doses should be given. True or false?

A

False

Eg. in CKD, a dose may be given every 36hrs ie. 2 doses in 3 days

83
Q

What is Pivmecillinam?

A

Esterified form of mecillinam

84
Q

When is Pivmecillinam most useful?

A

Uncomplicated lower UTI

85
Q

Why are pivmecillinam and temocillin active against ESBL-producing bacteria?

A

Very β-lactamase stable

86
Q

What bacteria does Pivmecillinam not have activity against?

A

Gram positives

Pseudomonas

87
Q

Is pivmecillinam safe in pregnancy?

A

No

88
Q

When is temocillin useful?

A

If gentamicin can’t be given:

- In urosepsis if renal function too poor

89
Q

True or false, temocillin is just as effective as gentamicin?

A

False (it is less effective)

90
Q

What bacteria does temocillin not have activity against?

A

Gram positives

Pseudomonas

91
Q

What class of drugs does Cefalexin belong to?

A

1st generation oral cephalosporins

92
Q

Is Cefalexin safe in pregnancy?

A

Yes

93
Q

When is Cefalexin reported?

A

If amoxicillin and trimethoprim resistant

94
Q

What are the risks of using Cefalexin?

A

Increased risk of C. diff

High risk of UTI recurrence

95
Q

Which of the following bacteria does Cefalexin not cover:

  • Most coliforms
  • Enterococci
  • Pseudomonas
  • Staph aureus
  • MRSA
A

Enterococci
Pseudomonas
MRSA

96
Q

What are the benefits of using Co-Amoxiclav?

A

Cheap
Effective
Safe in pregnancy

97
Q

What is the main disadvantage of using Co-Amoxiclav?

A

C. diff risk

98
Q

Which of the following bacteria is not covered by Co-Amoxiclav:

  • Most coliforms
  • MRSA
  • Staph. aureus
  • Enterococci
  • Pseudomonas
A

MRSA

Pseudomonas

99
Q

How does Ciprofloxacin work?

A

Inhibits bacterial DNA gyrase:

- Prevents ‘DNA’ supercoiling

100
Q

In what patients is Ciprofloxacin not safe? Whys is it not safe?

A

Kids
Pregnancy
- Damages cartilage

101
Q

What bacteria is Ciprofloxacin useful against?

A

Pseudomonas (Only PO useful against Pseudomonas)
Almost all coliforms
Some Enterococci

102
Q

What is the empirical treatment of female lower UTI?

A

Trimethoprim OR Nitrofurantoin:

- PO for 3 days

103
Q

What is the empirical treatment of male, uncatheterised UTIs?

A

Trimethoprim OR Nitrofurantoin:

- PO for 7 days

104
Q

What is the empirical GP treatment for complicated UTIs or pyelonephritis?

A

Co-amoxiclav OR Co-trimoxazole for 14 days

105
Q

What is the empirical hospital treatment for complicated UTIs or pyelonephritis?

A

Amoxicillin (for Enterococci) AND Gentamicin IV (for coliforms) for 3 days

106
Q

What is the empirical hospital treatment for complicated UTIs or pyelonephritis in a penicillin-allergic patient?

A

Co-trimoxazole AND Gentamicin

107
Q

How many organisms are present on urine culture in asymptomatic bacteriuria?

A

> 10^5 organisms/ml

108
Q

How does asymptomatic bacteriuria appear on urine microscopy?

A

No pus cells

109
Q

Why are antibiotics prescribed in pregnant women with asymptomatic bacteriuria?

A

To prevent:

 - Pyelonephritis (20-30%)
 - Intra-Uterine Growth Retardation (IUGR)
 - Prematurity
110
Q

What can cause an abacterial cystitis/urethral syndrome?

A 
Early UTI
Urethral trauma ('Honeymoon cystitis')
Urethritis due to:
     - Chlamydia
     - Gonorrhoea
111
Q

What are some features of abacterial cystitis?

A

Symptoms of UTI
Pus cells in urine
No significant growth on culture

112
Q

How can symptoms be reduced in abacterial cystitis?

A

Alkalinising the urine

113
Q

When should a UTI in catheterised patients be treated?

A

If >10^5 organisms/ml AND symptomatic

114
Q

What can unnecessary antibiotics cause in catheterised patients?

A

Colonisation with resistant strains

Year 2 - Renal (DP) (15 decks)

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