UTIs Flashcards
What percentage of kids have UTIs?
~5% of girls and 1% of boys have a UTI before 5 y.o.
What are the stats for women and UTIs?
~50% of women report at least one UTI by 50 years
Sexually active women have one UTI every 2 years
What is acute cystitis?
Inflammation of the urinary bladder
What is Pyelonephritis?
Inflammation of the urinary bladder and kidneys
What is sterile pyuria?
Pus in the urine with a negative culture
What are the sterile areas of the urinary tract?
The kidneys, ureter and bladder
Does the urethra have bacteria in it?
Yes - it has a microbiota
What is the source of most UTIs?
The microbiota (E. Coli is predominant and it the predominant cause of UTI)
What percentage of community acquired UTIs are caused by: E. coli Proteus species Staph. saprophyticus Other
80
5
10
5
What percentage of hospital acquired UTIs are caused by: E. coli Proteus species Staph. saprophyticus Other
40
10
2
48
What are the other bacteria which cause UTIs?
Other GNRs: Klebsiella, Enterobacter, Serratia, Pseudomonas.
G+ bacteria: Enterococcus, other Staphylococcus.
With regard to CMV why is the urinary tract important?
The patient may have asymptomatic shedding (i.e. they may transmit the virus through urine)
How do bacteria access the urinary tract?
Most infections are ascending (i.e. from commensals in the distal urethra)
They can make their way up into the bladder and then occasionally to the kidneys
What bacteremias can cause UTIs?
Requires systemic infections
• Staph. aureus (renal abscess)
• Salmonella Typhi
• TB
What type of epithelium is present in the urinary tract?
Transitional epithelium
What is the benefit of having transitional epithelium in the urinary tract?
It resists bacterial colonisation
Do bacteria grow in urine?
Many do not like this medium
What are the elements of innate immunity of the UT?
Transitional epithelium
Many bacteria do not grow in urine
Constant flushing of urine and regular bladder emptying plays a key role in resistance to infection
What are the effects of constant flushing of urine from the bladder?
Bacteria cannot reach sufficient numbers to activate virulence mechanisms.
Those who cannot empty their bladder completely are much more susceptible
What are females more commonly affected by UTIs?
Shorter urethra
Infection comes from the perineum and female urethra essentially opens in the perineum
Sexual intercourse massages bacteria up the female urethra
What may protect against UTIs in infant boys?
Circumcision
What is thought about the colonisation of the distal urea with regard to UTIs?
Suggested that the higher the level of colonisation the more susceptible to infection
What are some abnormal host factors which contribute to UTIs?
Incomplete bladder emptying
Catheterization
What are some causes of incomplete bladder emptying?
Structural abnormality (congenital, tumour, pregnancy, stone, enlarged prostate). (May be first evidence in a child - always investigate boys girls are allowed a couple)
Functional abnormality (neurological conditions, vesico-ureteric reflux - urine pushed up the ureters)
What allows bacteria to adhere to the bladder?
Type 1 pili
(Almost all E. Coli can produce these)
PAP pili - these allow for good adhesion to the transitional epithelium
What the role of flagella in UTI causing bacteria?
It allows for motility - perhaps to reach the kidneys
Bacteria which are more likely to produce UTIs do what with the epithelium?
Can invade transitional epithelium and form intracellular communities
What is a biofilm?
A community of microbes within a matrix
What are biofilms usually made out of?
Polysaccharides
What are siderophores?
These are compounds with very high affinity for iron
Which bacteria is noted for producing urease?
Proteus sp
What does urease do?
It changes the pH of urine and promotes the formation of struvite stones
Where are PAP effective?
In the kidneys
Where are flagella effective?
In the ureter
Where are type 1 pili effective?
In the bladder
Are filaments produced by E.Coli a virulence factor?
Yes - some evidence
How is UTI diagnosed?
- History and physical examination
- Imaging
- Collect appropriate samples
- Interpret lab report
What comes up in the history of someone with a UTI?
Pain
Frequency
Urgency
(it is hard to distinguish between upper and lower UTI - fever is an indication)
When is a person with a UTI imaged?
Usually only done in people who we do not expect to get a UTI
What samples are collected to test for UTIs?
Urine in most cases
Blood - if pyelonephritisis suspected
What is the most common urine sample?
A midstream urine sample (only collect middle bit of urine, not end or start)
What are some other types of urine samples?
- Catheter/nephrostomy sample
- Bag sample (in babies - not very helpful)
- Suprapubic aspirate (paediatrics - needle directly into bladder)
Where is urine for analysis collected from the catheter?
From the catheter itself
What examinations are done of urine samples?
- Microscopy
- Count
- Quantitative culture for bacteria
- Susceptibility testing
What are the pathologists looking for in microscopy?
WBC, RBC, epithelial cells, casts, crystals, microorganisms incl. parasitic forms
What parasite infects the bladder?
Flatworm - fluke
What is the level of WBC in the urine for it to be considered an infection?
> 10^5/ml
Could also be due to stones or tumours or other inflammatory processes
What is the normal squamous epithelial presence in a urine sample?
0 - any present = not well collected sample
What is one colony forming unit?
One bacterium before culturing
What is the infectious level of colony forming unit/ml?
> 10^5 CFU/ml is strongly suggestive of infection (especially if only one species isolated)
What is the CFU threshold for urine taken from the catheter?
> 10^2 CFU/ml
What is the CFU threshold for urine taken via suprapubic aspirate?
0 - should be sterile
How quickly should urine samples be transported to the lab?
Less than 1 hour
Or can be kept at less than 4 degrees for a period of up to 18 hours
What is sterile pyuria?
No growth with WBC consistently >10^5/ml
What are the causes of sterile pyuria?
- non-infectious conditions
- partial treatment
- difficult to grow bacteria, e.g., TB
What is a treatment for uncomplicated cystitis?
Alkalanise urine (check pH first)
Why is alkalanising the urine helpful?
It may stop burning
The burning on micturition is due to the acid which the bacteria are producing
Why does the pH need to be checked before the alkalanising the urine?
Proteus species produces ammonia during its growth and thus the urine will already be alakaline. Making it more so may precipitate the formation of struvite stones
What is the recomended treatment for uncomplicated cystitis?
Trimethoprim OR cephalexin OR co-amoxyclav OR nitrofurantoin
How long is the recommended treatment dosage for uncomplicated cystitis?
5 days [women & children] or 7 days [men]
If a child less then 2 y.o. has a UTI what needs to happen?
Need to check for UT abnormality
A girl may allow one but a boy = none
What drugs are used to treat pyelonephritis?
co-amoxyclav OR cephalexin OR trimethoprim
How long do we treat for in Pyelonephritis?
10-14 days
How is sepsis treated?
If severe sepsis, use ampi/amoxycillin + gentamicin
When is asymptomatic bacteriuria treated?
In pregnancy (it is associated with prem delivery and other obstetrics complications)
What is used to treat women with asymptomatic bacteriuria in pregnancy?
cephalexin OR co-amoxyclav OR other
What is considered to be a recurrent UTI in women?
> 2 UTIs in 6 months
most are reinfections i.e. not relapse
What causes recurrent UTIs?
Genetic predisposition
Behaviour: intercourse, spermicide, incontinence, etc
How can reccurent UTIs be managed?
Change behaviour; ↑ fluid intake; postcoital voiding Antimicrobial prophylaxis (different regimes)/early intervention
What is the normal level of WBC in the urine?
What is the normal level of RBC in the urine?
What is the normal colony forming unit/ml?
