Microbiology Flashcards
(114 cards)
1
Q
Urine in what areas is usually sterile?
A
Kidneys
Ureters
Bladder
2
Q
What microbes are commensals in the lower urethra?
A
Coliforms
Enterococci
Anaerobes (rarely cause UTI)
3
Q
What is cystitis?
A
Infection in bladder (Lower UTI)
4
Q
What is an upper UTI?
A
Infection involving ureters
5
Q
What is pyelonephritis?
A
An upper UTI involving the kidneys
6
Q
What is a complicated UTI?
A
UTI complicated by:
- Sepsis - Abnormality/Stones
7
Q
What effect does a complicated UTI have on treatment?
A
Requires a longer antibiotics course
8
Q
When might bacteruria not be an infection?
A
In the elderly
Patients with catheters
9
Q
Why are females much more prone to UTIs?
A
Short and wide urethra
Urethral opening close to anus
10
Q
What can increase the risk of UTIs?
A
Sex
Pregnancy
11
Q
Why do posterior urethral valves increase the UTI risk?
A
Incomplete bladder emptying:
-> Urine stasis -> Infection
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
13
Q
How can a descending UTI occur?
A
- Patient with bacteraemia/sepsis
- Bacteria seeded in kidney
- Multiple small abscesses -> Bacteruria
14
Q
What are coliforms?
A
Rod-shaped, gram negative, non-spore forming, facilitative anaerobes
15
Q
What is the most common causal organism in UTIs?
A
E. coli (70%)
16
Q
What other coliforms can cause UTIs?
A
Klebsiella sp
Enterobacter sp.
Other
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
18
Q
Proteus sp. UTIs have what other distinguishing feature?
A
Foul smelling
19
Q
What are Enterococcus sp?
A
Types of Strep. living in the GI tract
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
21
Q
Who gets UTIs caused by Staphylococcus saphrophyticus?
A
Women of child-bearing age
22
Q
Why is Pseudomonas not a coliform?
A
Strictly aerobic
23
Q
What are Pseudomonas UTIs associated with?
A
Catheters
Urinary tract instrumentation
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
25
What symptoms suggest an upper UTI?
Fever
Loin pain
Rigors
26
What urine is likely to be infected in obtaining a urine sample?
1st urine (collects commensals from perineum and lower urethra)
27
What (ideally) needs to be carried out before obtaining a MSSU?
Wash perineum and urethral meatus with saline:
| - Not antiseptic (May kill bacteria)
28
When would a clean catch urine sample be used?
In children and elderly when MSSU can't be obtained
29
In what individuals is a bag urine sample used?
Babies
30
What do you do if there is a positive culture from a bag urine sample?
Suprapubic specimen must be taken
31
When would you take a catheter specimen of urine?
If signs/symptoms of UTI
32
What is the best container for containing urine for transport?
Boricon container:
- Contains boric acid
- > Stops bacterial multiplication for ~24 hours
- Red top
33
If a universal sterile container is used to transport urine samples, how soon must it reach the lab?
In 2 hours
34
What does a positive leukocyte esterase mean on urine dipstick?
Indicates WBC in urine
35
What might give a false positive result on leukocyte esterase on dipstick?
Catheter
36
What does a positive nitrite result on urine dipstick mean?
Bacteruria
37
Why do bacteria cause a positive nitrite result on urine dipstick?
Nitrate is reduced to Nitrite
38
What bacteria cause a positive nitrite result?
Coliforms
39
What bacteria do not cause a positive nitrite result?
Enterococcus
40
Ideally, when should a MSSU only be sent?
If dipstick is positive and there are symptoms
41
When is urine microscopy used?
If it is an urgent case
42
What should you look for in urine microscopy?
Polymorphs (pus cells)
Bacteria
+/- RBCs
43
What is a significant urine culture result according to the Kass' Criteria?
>100,000 (10^5) organisms/ml
44
What is a insignificant urine culture result according to the Kass' Criteria?
45
If on urine culture there are 10^4 organisms/ml, what might this indicate?
Contamination?
| UTI?
46
If there are only 10^4 organisms/ml on urine culture what should you do?
Repeat specimen
47
In a patient who is not catheterised, what does urine culture usually show?
Single organism
| >10^5 organisms/ml of pure growth
48
If there is mixed growth on urine culture, even if >10^5 organisms/ml, what does this mean?
Usually insignificant unless they have urinary tract abnormalities
49
What does ESBL stand for?
Extended Spectrum β-Lactamase
50
ESBL-producing bacteria are resistant to what?
All cephalosporins
| Almost all penicillins
51
What is the ESBL-producing gene carried on and what is it usually carried with?
On a plasmid with other resistance genes:
- Gentamicin
- Ciprofloxacins
52
What oral antibiotics may be useful in treating ESBL-producing bacteria?
Nitrofurantoin
Pivmecillinam
Fosfomycin
53
What IV antibiotics may be useful in treating ESBL-producing bacteria?
Temocillin
Meropenem
Ertapenem
54
What is a possible source of ESBL-producing bacteria?
Imported chicken:
- Antibiotics used as growth factors
- > Resistance
55
What are Carbapenemase-Producing Enterobacteriaceae?
Gram-negative bacilli (coliforms) that are resistant to meropenem:
- Essentially resistant to all antibiotics
56
What are Carbapenemase-Producing Enterobacteriaceae associated with?
Travel to the Indian sub-continent
57
What are the features of an ideal antibiotic used for UTIs?
Excreted in high concentrations in the urine:
- If metabolised in liver -> Useless
Oral
Inexpensive
Few side effects
58
What length of treatment is usually adequate for an uncomplicated, lower UTI in women?
3 days
59
When is a urine sample sent in uncomplicated, lower UTIs in women?
If they have a second UTI relatively soon after the 1st
60
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)
Co-amoxiclav (It is second line)
61
When is second line treatment initiated in the treatment of UTIs?
If resistant to >=1 of the 1st line treatments
62
Which of the following is not a second line treatment of UTIs:
- Pivmecillinam (PO)
- Temocillin (IV)
- Cefalexin (PO)
- Ciprofloxacin (PO/IV)
- Vancomycin
Vancomycin
63
How many antibiotics are often tested for sensitivities?
12-20
64
Approximately how many antibiotics are reported back to doctors?
~4 (more if resistant)
65
Is amoxicillin safe in pregnancy?
Yes
66
What is amoxicillin useful for?
Enterococcus faecalis
Some coliforms:
- 50% of E. coli are now resistant
- Not great empirical treatment
67
How does Trimethoprim work?
Inhibits bacterial folic acid synthesis:
- Dihydrofolate -> Tetrahydrofolate
- > Dihydrofolate Reductase inhibited
68
When is Trimethoprim not safe in pregnancy and why?
1st trimester:
| - Inhibits folic acid synthesis -> Spina bifida
69
Why is Trimethoprim recommended for UTI with prostatitis?
Good [urine] and [prostate]
70
What two antibiotics form PO/IV Co-trimoxazole?
Sulphamethoxazole + Trimethoprim
71
What is a serious side effect of using Co-trimoxazole?
Stevens-Johnson Syndrome
72
Which of the following is not reliably covered by Trimethoprim:
- Most coliforms
- Enterococci
- Staph aureus
- MRSA
- Proteus sp
- Pseudomonas
Proteus sp.
| Pseudomonas
73
When is Nitrofurantoin useful? Why is it useful here?
In lower UTI:
| - Effective [urine] only reached in bladder
74
Why should nitrofurantoin be avoided in late pregnancy?
Can cause neonatal haemolysis
75
When else should nitrofurantoin be avoided?
Breastfeeding
| Kids
76
Which of the following is not covered by nitrofurantoin:
- Most coliforms
- Proteus sp.
- Enterococci
- Staph aureus
- MRSA
- Pseudomonas
Proteus sp.
| Pseudomonas
77
Why must gentamicin be avoided?
Can affect:
- Hearing
- CN VIII
- Kidneys
78
What is the dose of gentamicin?
7mg/kg once daily IV
79
After giving a dose of gentamicin, what follow up is needed?
Measure blood levels 6-14hrs later
80
Which of the following is not covered by gentamicin:
- Most coliforms
- Pseudomonas sp.
- Staph aureus
- MRSA
- Enterococci
Enterococci
81
In what infection is gentamicin most useful in?
Gram negative sepsis
82
Gentamicin can only be prescribed for 3 days, this means 3 doses should be given. True or false?
False
| Eg. in CKD, a dose may be given every 36hrs ie. 2 doses in 3 days
83
What is Pivmecillinam?
Esterified form of mecillinam
84
When is Pivmecillinam most useful?
Uncomplicated lower UTI
85
Why are pivmecillinam and temocillin active against ESBL-producing bacteria?
Very β-lactamase stable
86
What bacteria does Pivmecillinam not have activity against?
Gram positives
| Pseudomonas
87
Is pivmecillinam safe in pregnancy?
No
88
When is temocillin useful?
If gentamicin can't be given:
| - In urosepsis if renal function too poor
89
True or false, temocillin is just as effective as gentamicin?
False (it is less effective)
90
What bacteria does temocillin not have activity against?
Gram positives
| Pseudomonas
91
What class of drugs does Cefalexin belong to?
1st generation oral cephalosporins
92
Is Cefalexin safe in pregnancy?
Yes
93
When is Cefalexin reported?
If amoxicillin and trimethoprim resistant
94
What are the risks of using Cefalexin?
Increased risk of C. diff
| High risk of UTI recurrence
95
Which of the following bacteria does Cefalexin not cover:
- Most coliforms
- Enterococci
- Pseudomonas
- Staph aureus
- MRSA
Enterococci
Pseudomonas
MRSA
96
What are the benefits of using Co-Amoxiclav?
Cheap
Effective
Safe in pregnancy
97
What is the main disadvantage of using Co-Amoxiclav?
C. diff risk
98
Which of the following bacteria is not covered by Co-Amoxiclav:
- Most coliforms
- MRSA
- Staph. aureus
- Enterococci
- Pseudomonas
MRSA
| Pseudomonas
99
How does Ciprofloxacin work?
Inhibits bacterial DNA gyrase:
| - Prevents 'DNA' supercoiling
100
In what patients is Ciprofloxacin not safe? Whys is it not safe?
Kids
Pregnancy
- Damages cartilage
101
What bacteria is Ciprofloxacin useful against?
Pseudomonas (Only PO useful against Pseudomonas)
Almost all coliforms
Some Enterococci
102
What is the empirical treatment of female lower UTI?
Trimethoprim OR Nitrofurantoin:
| - PO for 3 days
103
What is the empirical treatment of male, uncatheterised UTIs?
Trimethoprim OR Nitrofurantoin:
| - PO for 7 days
104
What is the empirical GP treatment for complicated UTIs or pyelonephritis?
Co-amoxiclav OR Co-trimoxazole for 14 days
105
What is the empirical hospital treatment for complicated UTIs or pyelonephritis?
Amoxicillin (for Enterococci) AND Gentamicin IV (for coliforms) for 3 days
106
What is the empirical hospital treatment for complicated UTIs or pyelonephritis in a penicillin-allergic patient?
Co-trimoxazole AND Gentamicin
107
How many organisms are present on urine culture in asymptomatic bacteriuria?
>10^5 organisms/ml
108
How does asymptomatic bacteriuria appear on urine microscopy?
No pus cells
109
Why are antibiotics prescribed in pregnant women with asymptomatic bacteriuria?
To prevent:
- Pyelonephritis (20-30%)
- Intra-Uterine Growth Retardation (IUGR)
- Prematurity
110
What can cause an abacterial cystitis/urethral syndrome?
```
Early UTI
Urethral trauma ('Honeymoon cystitis')
Urethritis due to:
- Chlamydia
- Gonorrhoea
```
111
What are some features of abacterial cystitis?
Symptoms of UTI
Pus cells in urine
No significant growth on culture
112
How can symptoms be reduced in abacterial cystitis?
Alkalinising the urine
113
When should a UTI in catheterised patients be treated?
If >10^5 organisms/ml AND symptomatic
114
What can unnecessary antibiotics cause in catheterised patients?
Colonisation with resistant strains
