Lecture 12 - UTI Flashcards
Describe the pathway that a urinary tract infection undertakes.
Ascending pathway
Urethritis goes via the ureter, then cystis in the bladder and pyelenephritis in the Kidneys which is dangerous.
What is the first infection rate in women?
40-50%
What is the second infection rate in women?
25%
What is the third infection rate in women and how long after the previous UTI will it occur?
3% and within 6 months of treatment.
How would you treat UTI?
Antibiotics - costly and dirupts normal flora
How would you know when the patient is cured of UTI?
When urine is sterile and there is no symptoms - until then you have to use constant antibiotics.
Name the most dangerous symptom of UTI and what does it signify?
Flank pain - Pain in your back or side, usually on only one
side at about waist level. Indicates a Kidney infection.
Name the symptoms of UTI?
• 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
How do you analyse the urine?
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.
How does a dipstick test work?
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.
Describe how you would culture the UTI bacteria?
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
What is the full form of the IMViC test
Indole, Methyl red, Vogues Proskauer, Citrate
Describe the IMViC test.
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
What happen in the IMViC test if E-coli is present?
++–. E-coli doesn’t uuse citrate as a carbon source.
What happen in the IMViC test if Klebsiella is present?
–++
What are the source of UTI?
Faecal origin
How do you transmit UTI?
*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.)
How do bacteria in the urinary tract get washed away?
they must adhere to uroepithelium or the pressure for urine when peeing can wash it away
What prevent bacteria from being washed away in the urinary tract?
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.
How do bacteria evade the immune system?
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.
How do bacteria proliferate in the UT?
• Acquisition of iron via siderophore secretion - scavengers to find iron
- siderophore receptors
- Haemolysins (lyse red blood cells)
- haemoglobin receptors
How do bacteria damage the UT?
Secrete - • Haemolysins are cytolytic toxins • CNF1 is cytotoxic toxin • LPS is proinflammatory - Inflammation of the bladder, damage to epithelium
What is the ESBL strain?
• 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
How do you manage ESBL strain?
• 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.
