Lecture 12 - UTI

Question 1

Describe the pathway that a urinary tract infection undertakes.

Answer 1

Ascending pathway

Urethritis goes via the ureter, then cystis in the bladder and pyelenephritis in the Kidneys which is dangerous.

Question 2

What is the first infection rate in women?

Answer 2

40-50%

Question 3

What is the second infection rate in women?

Answer 3

25%

Question 4

What is the third infection rate in women and how long after the previous UTI will it occur?

Answer 4

3% and within 6 months of treatment.

Question 5

How would you treat UTI?

Answer 5

Antibiotics - costly and dirupts normal flora

Question 6

How would you know when the patient is cured of UTI?

Answer 6

When urine is sterile and there is no symptoms - until then you have to use constant antibiotics.

Question 7

Name the most dangerous symptom of UTI and what does it signify?

Answer 7

Flank pain - Pain in your back or side, usually on only one

side at about waist level. Indicates a Kidney infection.

Question 8

Name the symptoms of UTI?

Answer 8

• Dysuria - Pain or burning during urination
• Frequency - More frequent urination (or waking up at
night to urinate)
• Urgency - The sensation of not being able to hold urine
• Hesitancy - The sensation of not being able to urinate
easily or completely
• Cloudy, bad smelling, or bloody urine
• Lower abdominal pain
• Mild fever (less than 39°C), chills, and “just not feeling
well” (malaise)
• Nausea and vomiting

Question 9

How do you analyse the urine?

Answer 9

Take mid stream urine as to not get any endogenous flora and maintain the urine around 4 degrees Celsius thus not allowing contaminants to grow.

Then do a dip stick test and Gram stain and a light microscopy test.

Question 10

How does a dipstick test work?

Answer 10

Has certain fields that change colour.

• Main thing is check for nitrites which are released by bacteria. If the stick section turns positive it goes pink.
• Then check for leukocyte esterase presence whcich also goes pink if it is abundant. L.esterase is released from leukocytes indicating the presence of bacteria.
• If there is elevated protein then it means it is released from damaged epithelial tissue.

Question 11

Describe how you would culture the UTI bacteria?

Answer 11

Culture it in CLED agar.
Full form - cysteine lactose electrolyte Deficient Agar.
Cysteine - need for UPEC
Lactose is fermented by bacteria - blue to yellow ph if fermented
Electrolytes aren’t there so that the colonies of Proteus spp don’t move.
So if you have more than 10^5 CFU/mL (10^8 CFU/L) then = infection
if you have less than 10^4 - 10^5 CFU then you have urethral or vaginal contamination.
* 10^4 to 10^5 CFU/mL = evaluate with clinical information

Question 12

What is the full form of the IMViC test

Answer 12

Indole, Methyl red, Vogues Proskauer, Citrate

Question 13

Describe the IMViC test.

Answer 13

Indole: breakdown of tryptophan to indole
Methyl red: fermentation of glucose to large amounts of stable acidic products Vogues Proskauer: detects digestion of glucose toacetylmethylcarbinol Citrate: use of citrate as a sole Carbon source

Question 14

What happen in the IMViC test if E-coli is present?

Answer 14

++–. E-coli doesn’t uuse citrate as a carbon source.

Question 15

What happen in the IMViC test if Klebsiella is present?

Answer 15

–++

Question 16

What are the source of UTI?

Answer 16

Faecal origin

Question 17

How do you transmit UTI?

Answer 17

*Proximity effect - short urethra - women
*Men only have greater chances when they get an enlarged prostate.
• Hospital acquired via catheters.
• Hematogenous infections (<3%) – infection of kidneys with bacteria from blood (S. aureus, Salmonella spp.)

Question 18

How do bacteria in the urinary tract get washed away?

Answer 18

they must adhere to uroepithelium or the pressure for urine when peeing can wash it away

Question 19

What prevent bacteria from being washed away in the urinary tract?

Answer 19

Pili
• Type 1 (fim) pili common to all Enterobacteriaceae - Bind to mannose residues in glycoproteins
- Important for bladder colonisation.
• Some strains possess P-pili
- bind to globobiose, important for colonisation of kidney.
• Ascending route of infection.

Question 20

How do bacteria evade the immune system?

Answer 20

There are 2 pathways.
First the bacteria has to get into the cell and into the CD63+ vesicle.
1- the bacteria can then become an intracellular bacterial community and cause recurrent infection
2 - the bacteria can become a Quiescent intracellular reservoiur and cause recurrent infection or become intracellular bacterial community.

Question 21

How do bacteria proliferate in the UT?

Answer 21

• Acquisition of iron via siderophore secretion - scavengers to find iron

• siderophore receptors
• Haemolysins (lyse red blood cells)
• haemoglobin receptors

Question 22

How do bacteria damage the UT?

Answer 22

Secrete -
•  Haemolysins are cytolytic    toxins
•  CNF1 is cytotoxic toxin
•  LPS is proinflammatory
 - Inflammation of the bladder, damage to epithelium

Question 23

What is the ESBL strain?

Answer 23

• Resistant to many beta lactams
- Penicillins
- Cephalsporins
- Carbapenems (often last drug for eg Pseudomonas,
Acinetobacter).
• Encoded by plasmids in GNB species
• Especially found in travellers to India

Question 24

How do you manage ESBL strain?

Answer 24

• Screening and cohorting
• Treat with polymyxin B or E (colistin)
• Cationic polypeptide antibiotics
• Disrupt membranes
• Old antibiotic discarded because of renal toxicity, reconsidered where it is the only one that works.
• Monitor renal polymyxin toxicity (15% of patients).
- Serum urea or creatinine
• Monitor patient recovery
So pretty much you use high collateral damage antibiotics to see if the patient is able to cope with it.