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MICRO ADYA > Microbiology 10 - Urinary Tract Infections > Flashcards

Microbiology 10 - Urinary Tract Infections Flashcards

1
Q

Which organism is the most common cause of UTI in structurally normal people

What increases the virulence of E. Coli?

A

E coli O serotype-

Virulence factors e.g. P-fimbriae - allows them to attach to the epithelium and ascend to the bladder or the kidneys

NB: most UTIs are caused by a single bacterium (if you get mixed, tends to be in structurally abnormal urinary tract)

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2
Q

What is the empirical antibiotic treatment for pyelonephritis?

A

Co-amoxiclav +/- gentamycin

Amikacin is also recommended as most ESBLs are sensitive

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3
Q

When is it iimportant to treat bacteruria and why?

A

Usually it is not a cause for concern, but in pregnant women it can lead to complications- hence must treat.

complications- LBW, prematurity, pre-eclampsia

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4
Q

What is a complicated UTI?

A

infection in a urinary tract with functional or structural ABNORMALITIES

iatrogenic- indwelling catheters, stents

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5
Q

WHat is the second most common cause of UTIs in women?

A

Staphlococcus saprophyticus

It has virulence Pfimbriae- allows it to ascend

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6
Q

Which organism tends to affect structurally abnormal kidney tracts and is associated with kidney stones?

A

Proteus Mirabilis

*also Klebsiella

PK

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7
Q

Which organism causes UTIs in the presence of prosthetic material eg longterm indwelling catheter?

A

Staph epidermidis - usually a common skin commensal

**another coagulase negative staph (like saprophyticus)

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8
Q

Which organisms are implicated in recurrent UTIs? What properties do they share?

A

These organisms can adhere to prosthetic material like indwelling catheters eg pseudomonas

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9
Q

What makes ascending infection likely?

A
  • structural abnormlaities eg VUR- allows urine to reflux into ureters and possibly kidneys
  • bacterial factors - E Coli and S. Saprophyticus have virulence factors –> adherence to epithelium enables ascent
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10
Q

In females where do bacteria tend to colonise before they cause UTIs?

A
  • vaginal introitus
  • periurethral area
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11
Q

What can cause staph aureus to be present in urine? Thus what must you do if you find staph aureus in urine?

A

a) poorly taken sample - contaminant in perineal/ groin area: REPEAT SAMPLE
b) endocarditis / bacteraemiea/emboli –> spread of staph aureus to the kidneys–>bladder–> urine
* SIGN OF STAPH AUREUS ABSCESS IN THE KIDNEY: TAKE BLOOD CULTURES

NB: staph aureus does NOT ASCEND the urinary epithelium as it doesn’t have virulence factors

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12
Q

How does the route of spread of gram positive and gram negative organisms differ?

A

Gram negatives- ascend the urinary epithelium (eg E Coli )

Gram positives - spread haematogenously (eg staph auerus)

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13
Q

What are the two main renal tract abnormalities that can cause UTIs?

A
  1. obstruction - can be extrarenal or renal:
    * Obstruction INHIBITS the normal flow of urine >>> stasis** >>> **increasing susceptibility to infection
  2. reflux - VUR in children: maintaining a residual pool of infected urine in the bladder after voiding >>> cause scarring of kidneys
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14
Q

Symptoms of UTIs in <2yo?

A

Failure to thrive

Vomiting

Fever

**basc very non-specific

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15
Q

Symptoms of lower UTI?

A
  • frequency
  • dysuria
  • small amounts of turbid urine
  • suprapubic heaviness OR pain
  • Sometimes haematuria
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16
Q

What does presence of fever in UTI indicate?

A

Only get fever in UPPER UTI

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17
Q

Symptoms of an upper UTI

A
  • Fever (sometimes with rigors)
  • Flank pain
  • lower tract symptoms (e.g. frequency, urgency and dysuria)
    • lower UTI may precede upper UTI by 1-2 days as the infection ascends
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18
Q

SYmptoms of UTI in older patients

A

mainly ASYMPTOMATIC

Symptoms of upper tract infection are often atypical

e.g. vague abdominal pain, change in mental status

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19
Q

IVX for UTIs

What else do you need to do for complicated UTIs?

A
  • Bloods
    • FBC- WCC
    • CRP
    • U&Es
  • MSU for MC&S
    • Microscopy: look for RBC and WBC
    • Culture
    • Sensitivities- disc diffusion \

Complicated UTIs:

  • renal ultrasound
  • IV urography
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20
Q

how do you make sure there’s no contamination of MSU sample?

A

midstream urine sample

Look for presence of squamous epithelial cells (from the urethra) - these look like FRIED EGG CELLS under microscope

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21
Q

What does the presence of fried egg cells on microscopy suggest?

A

Contamination with squamous epithelial cells from the urethra

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22
Q

When do you ask elderly/frail people to do a urine sample

A

ONly if they are symompatic and are able to collect a urine sample

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23
Q

What are the indications to send a urine sample for culture?

A
  • over 65 if symptomatic and antibiotic given
  • pregnancy
  • suspected pyelonephritis or sepsis
  • suspected UTI in men
  • failed Abx Tx or persistent sx
  • recurrent UTI
  • prescribing Abx in someone with a urinary catheter
  • abnormalities of genitourinary tract
  • renal impairment
  • care home resident
  • hospitalisation for >7 days in last 6m
  • recent travel to a country with increased resistance
  • previous UTI resistant
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24
Q

How do you define recurrent UTI?

A

2 episodes in 6 months

or 3 episodes in 12 months

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25
How quickly must you culture urine and why?
Within 4 hours as it then increases the chance of false positives.
26
WHat is added to a urine sample before sending for culture, to preserve the sample?
Boric acid- must fill to the correct line: stabilise the bacteria and so avoids overgrowth, preserves cells and prevents false positives \*can also refrigerate the sample
27
What would you do if you found asymptomatic bacteruria after culture?
only treat if pregnant
28
What is the CFU cut off for UTI? (general)
**Path guide:** culture of \>10^4 colony forming units / ml is diagnostic (10^3 for E. coli / S. saprophyticus **Lecture (see picture)**
29
What is the CFU cut off for UTI in strongly symptomatic women?
10^5 CFU/L
30
What do you do if you find mixed growth on culture?
Repeat! As it could be a contaminant or a genuine mixed infection
31
What does RBC found on microscopy mean? and what type of UTI is it seen in more
Can happen in lower or upper UTIs (though it's more common in upper UTIs) \*if you get recurrent haematuria post-infection, refer to urology
32
What is sterile pyuria and what can this indicate (4) ?
When you find WBC but no bacteria on culture Think of: - TB - **_chlamydia_**: inflammation of urethra + other STIs - renal pathology: * **calculi- can cause inflammation** * **Bladder neoplasm / Catheterisation** * The MOST COMMON CAUSE of sterile pyuria is due to **_prior_** **_antibiotic use_**
33
Specific diagnostic points for men
* have lower threshold for concern * consider prostatitis and STIs * always send MSU for culture BEFORE antiobiotics * NB: dipsticks are not accurate at picking up infection * Recurrent UTIs - refer to urology * men \<65 years, if suspected UTI offer mediate treatment and tailor antibiotic based on culture results
34
How does prostatitis present?
Fever Back pain Rectal pain Lower UTI symptoms Prostate tenderness on DRE
35
Diagnostic protocol for UTI in women \<65
36
Do you do a dipstick in \>65 yo?
No- becomes less accurate with age
37
Diagnostic protocol for UTIs in \>65s
\*basc consider other causes before jumping straight to UTI
38
Mnemonic for causes of delirium
PINCH ME Pain Infection Nutrition Constipation Hydration Medication Environment
39
Empirical treatment for UTIs in community and duration
Nitrofurantoin is first line for uncomplicated UTI \*Not trimethorpim because of increasing resistance (a lot of e coli is now resistant to trimethoprim) **\*Short course:** _3 days_ for uncomplicated UTIs in women **\*Longer course in**: _7 days_ for 1) men, 2) women with symptoms \>7 days, 3) women with previous history of UTIs with resistant organisms
40
When must you take nitrifurantoin and why?
After emptying bladder As it stays in bladder, not systemically absorbed
41
Which antibiotics are contraindicated in pregnancy?
Nitrofurantoin- only at term and during breasfeeding - haemoyltic anaemia in babies Trimethoprim- always contraindicated (mainly in first trimester)- neural tube defects
42
Antibiotics for catheter associated UTIs
Unlikely to resolve unless catheter is removed ## Footnote STAT doses of aminoglycoside are recommended and can be given **BEFORE REMOVAL** of an infected catheter Gentamicin (80mg STAT IV/IM) or Amikacin (140mg STAT IV/ IM)
43
Which groups of patients get fungal UTIs?
Generally in people with indwelling catheters Because fungi produce biofilm
44
Treatment of fungal UTIs
PO fluconazole --\> if no improvement then non-liposomal amphotericin B \*NB: difficult to treat as many antifungals don't get excreted by kidneys
45
46
When do you do imaging for pyelonephritis?
All men And women with second presentation of pyelonephritis
47
Overall what features would suggest contamination of urine sample?
Mixed growth Squamous epithelial cells
48
what does mixed growth indicate in UTI
structural abnormality or contamination so repeat sample first
49
groups of people likely to have complicated UTIs
men- should not be having UTI due to long urethra pregnant women- gravid uterus can cause obstruction young children- recurrent UTI can indicate strucutal abnormalities hospitalsed patients i.e. due to indwelling catheters/stents
50
51
common organisms when there is another problem in the urinary tract
- proteus mirabilis: stones - Klebsiella aerogenes- abnormal urinary tracts (i.e. **_stones_**, neurological or anatomical abnormalities) + patients who are catheterised - *Enterococcus faecalis: hospital admited patienets* * *Staphylococcus saprophyticus-* 2nd commonest cause of UTI in young healthy women (but also associated into indwelling lines etc) * *Staphylococcus epidermidis: cause UTI in presence* e.g. instrumentation procedures or long-term indwelling catheterof prosthesis - IATROGENIC
52
extrarenal causes of obstruction that cause UTI
* Valves * Stenosis or bands * Calculi * **Extrinsic ureteral compression** from a variety of causes e.g. BPH or gravid uterus in pregnancy
53
intrarenal causes of obstruction that cause UTI
* Nephrocalcinosis * Uric acid nephropathy * Analgesic nephropathy * Polycystic kidney disease * Hypokalaemic nephropathy * Renal lesions of sickle cell trait or disease
54
neurogenic causes of UTI
* Poliomyelitis * Tabes dorsalis * Diabetic nephropathy * Spinal cord injuries
55
* Further investigation of **complicated UTI/recurrent UTI, UTI in men and children**
* **Renal USS**- see if there is a _structural abnormality_ * **Polycystic kidney disease** * **Nephrocalcinosis** * Valves * Stenosis or bands * Calculi * **Extrinsic ureteral compression** **IV urography**- this is often under guidance of urology
56
when do you do urine culture and sensitivies in women with UTI
only given in recurrent UTIs for women to check sensitivity of antibiotics just in case they have previously developed resistance in previous treatments for UTI
57
why are nitrites specific to UTI and what can indicate if nitire negative but leucocyte positive
* Nitrites are very specific because they are produced by *E. coli* * * **Nitrite**-**negative** and **leukocyte-positive** may **be a UTI caused by a** **non-coliform** bacterium
58
what agar is used for culturing in UTI and what do different organisms appear as
chromogenic agar - to see if growth is mixed or single * **Pink= *E. coli*** * **Blue= *Klebsiella, Enterobacter*** * **Light turquoise= *Enterococcus* (gram positive organisms)**
59
what is worrying about candida. in urine + what should be done
Candida in the urine can also be a sign of candidaemia candida has been seeded into the kidney worrying in young children/ neonates * **USS kidneys to see if there are any candida abscesses in the kidney**
60
complications of pyelonephritis
* Perinephric abscess- may require **drainage** * Chronic pyelonephritis * Scarring * Chronic renal impairment * Septic shock (usually with Gram -ve bacteria) * Acute papillary necrosis

MICRO ADYA (22 decks)

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