UTIs Flashcards
What is the classical presentation of UTI?
Lower abdominal pain
Frequent and urgent need to urinate
Little urine
What is another name for UTI?
Acute cystitis
What is a UTI?
Bacterial infection of the bladder
What is a rare complication of a UTI?
Can ascend to the kidneys causing pyelonephritis
What are diagnostic methods of UTIs?
Dipsticks
Examining urine characteristics
Microscopy
Culture
Why are antibiotic sensitivity tests important when treating UTIs?
Many uropathogens are resistant to common antibiotics
UTI is one of the most common infectious diseases in the world
TRUE or FALSE
TRUE
Why are UTIs more common in women than men?
Outside environment is closer to the female anatomy
Urethra is much shorter in women than men
Easier for pathogens to reach the bladder in females
Bacteria present in faeces or skin of the perineum of the anus may find their way to the distal urethra
What proportion of females in the UK will develop a UTI at some point in their life?
Up to half of all women in the UK
What proportion of men develop a UTI in the UK yearly?
1 in 2000 healthy men
What is the length of the urethra in women?
4-5 cm
What is the length of the urethra in men?
20-25 cm
What are common causes and risk factors of UTIs in males?
Enlarged prostate
Kidney stones
Catherisation
Weakened immune system
Diabetes
How does an enlarged prostate increase the risk of developing UTIs in males?
Prevents the bladder from fully emptying
Causes urine to stagnate
Allows bacteria to multiply
How does diabetes increase the risk of developing UTIs in males?
Glucose which may be present in the urine supports the growth of bacteria
What are common causes and risk factors of UTIs in females?
Factors which prevent full emptying of the bladder
Catherisation
Weakened immune system
Diabetes
Being sexually active
Spermicide
What are factors that prevent full emptying of the bladder in females?
Kidney stones
Using contraceptive diaphragm
Are UTIs sexually transmitted diseases?
No
How does being sexually active increase chances of developing UTIs?
Sex can irritate the urethra
Allows bacteria to enter more easily
How does spermicide increase the chances of developing UTIs?
Can irritate the vagina and reduce its immune defences
Is voided urine sterile?
Yes
Sterile or have low levels of bacteria
How does the vagina prevent bacterial contamination of the urethra?
Immune defences
Flushing with urine - bladder is constantly washed out and emptied
What has recent evidence showed about the environment of the bladder?
Originally thought there was no bacteria in the bladder
Recent work shows bladder may normally harbour some bacteria
Can now see them due to molecular techniques like sequencing and PCR
What is cystitis?
Infection and inflammation of the bladder
Causes the discomfort and pain associated with UTIs
What is pyelonephritis?
Infection can spread from the bladder via the ureters to infect the kidneys
Happens in minority of patients
What is the main symptom of pyelonephritis?
Pain in the lower back
What are possible complications of pyelonephritis?
Renal failure
Septimcaemia
What percentage of all nonconsomial infections are UTIs?
40%
Which population is particularly at risk of developing UTIs?
Catherised
Undergo cystoscopy
What is the sample taken to test for UTIs?
Midstream specimen of urine
First 20 ml of urine should be passed into the toilet and a sample should be collected midstream into a sterile container
Why should a midstream specimen of urine be collected for UTI testing?
Prevent the initial urine from picking up bacteria from the skin
What volume of urine is required for UTI testing?
5-10 ml of urine
How should the patient prepare before taking urine sample?
Patient should wash around their genital area first with soap and water
When is lab testing of urine not necessary?
If patient is in pain/ cloudy urine
What does a dispstick urinalysis indicate?
Presence of several markers of urinary tract
What are the key features of UTI that show up on dispstick urine test?
Leukocytes
Nitrites
Blood
Glucose
Urobilinogen
Why is a nitrite dipstick urine test inaccurate?
Not all bacteria produce nitrites
Only gram negative
Break down urine to form nitrite
What is pyuria?
Presence of pus in the urine
Why are urobilinogen levels elevated in YTI?
Due to haemolytic processes
How does the presence of blood show up in a urine dipstick test?
Haemoglobin released from haemolysed RBC causes a colour change from yellow to green
Intact red cells cause intense green speckles
What are the advantages of urine dipstick analysis?
Quick
Cheap
What are the disadvantages of urine dipstick tests?
Leukocyte esterase misses some geniune infections
- Especially if they are subacute
- Not very specific
Nitrite test is only applicable to bacterial species that reduce nitrate
- E. coli
What is an example of uropathogen that does not reduce nitrates?
Enterococcus
What happens if urine dipstick test shows up negative with the presence of UTI symptoms?
Further tests are warranted
What are macroscopic inspections we can do of urine?
Turbidity - indicates pyuria
Haematuria
Foul smell
What causes the turbidity of the urine?
Neutrophils
Recruited to the site of infection in the bladder
What is observed during microscopic inspection of urine?
Light microscope
Inspected for presence of white and red blood cells
Normally present in very low numbers
When high = strongly indicative of UTI
What is the third lab test we can do on urine to identify UTI?
Culture
How is culture used to diagnose UTI?
Confirmates and identifies bacterial infection
By culturing the urine on an agar plate
How is a culture carried out
A volume of 1-10μl of urine is spread on agar plate
Placed in an aerobic incubator at 37 degrees for 24 hours
Viable bacteria present will grow into colonies
How is culture used to diagnose UTI?
Count the bacterial colonies
What is an example of a modification of culture used in labs to identify bacterial species in urine?
Chromogenic agar
Imparts different colony colours to different uropathogens
Useful to distinguish what type of bacteria you have
Where are sources of bacteria in urine?
From the skin may be introduced during the urine sample collection
Distal urethra
Bladders
Does presence of bacteria in urine immediately indicative of UTI?
No
Small numbers of bacteria in urine is normal
What is the threshold for significant bacteriuria in many european countries?
10^5 bacteria/ ml urine
Why do some countries have lower thresholds for significant bacteriuria?
Recognise that an arbitrary cutoff of 10^5 may not make sense for all patients
Arbitrary threshold would exclude a proportion of the population with the disease
What are non-acute symptoms indicative of low-count UTI?
Frequency
Urgency
Incontinence
What percentage of acute UTIs is E.coli responsible for?
E. coli
What are most acute UTIs characterised by?
Caused by a single type of bacteria
What may mixed bacterial growth be indicative of?
Contamination during sample collection
UTIs cannot be caused by mixed bacterial growths
TRUE or FALSE
FALSE
Mixed growths can be significant
Especially in chronic or subacute UTI
What is the disk diffusion method?
Test to see if the pathogen being treated is sensitive to abtibiotics
When are disk diffusions carried out?
When urine culture finds a significant bacteriuria
Why are disk diffusion methods carried out?
To determine the specificity or resistance of the strain to a range of antibiotics
How do you carry out a disk diffusion method?
Colonies are picked from the first culture plates
They are re-inoculated onto a new agar plate
Antibiotics impregnated in paper discs are placed on the agar plate
How long are disk diffusion agar plates incubated?
48 hours
How do we use the results of the disk diffusion method to conclude sensitivity of the bacteria to antibiotics?
Look at zone of inhibition
If the disk is secreting antibiotic that forms a zone of inhibition = bacteria is sensitive to it
What is a disadvantage of bacterial culturing?
Takes time
Delay diagnosis and treatment
Can take up to 2 days
When a UTI is strongly inspected following microscopy, the initial culture step can be missed out
Move straight on to antibiotic sensitivity testing
What are examples of automated microbial identification and antimicrobial susceptibility testing systems (AST) being used?
Biotyper
BD Phoenix
What is a biotyper?
Microbial identification system based on protein signatures
Matrix-assisted laser desorption ionization
Time of flight mass spectrometry
What is a form of treatment of UTIs?
Empirical use of antibiotics
Take any broad-range antibiotic and hope it works
