Week 4 - A(1) - Microbiology of Urinary tract infections Flashcards
Name the two gram negative cocci Which organism most commonly causes epididymitis?
Neisseria gohnorrhea and meningitidis Chlaymdia trochomatis is the most common cause of epididymitis
What part of the urinary tract is normally colonised with bacteria?
The lower end of the urethra is normally colonised with bacteria
The presence of mirco-organsims in the urinary tract causing clinical infection What is this?
A urinary tract infection
What is the difference in structures affect by upper vs lower urinary tract infection?
Lower UTI denotes symptoms confined to the bladder and down (cystitis) Upper UTI denotes symptoms affecting the ureter +/- pyelonephritis
What are some of the causes of a complicated UTI?
Sepsis or urinary tract abnormalities or stones
What is cystitis?
It is the inflammation of the bladder - not always due to infection
Bacteriuria = the presence of bacteria in the urine however does not always mean infection What two sets of patients is this most important in?
Does not always mean infection especially in catheterised patients or patients or elderly patients
Urinary tract infection (UTI) is common Why is it more common in women rather than men?
Woman have a shorter urethra than men and a closer proximity of the urethral opening to anus
What are two types of abnormalities of the urinary tract that can increase the chance of UTI? Also catheterised patients are more at risk
Patient with a horseshoe kidney or posterior urethral valves
What is the commonest route of urinary tract infection? Starts of with the bacteria from the bowel and can potentially end up reaching the kidney
This is ascending infection Bacteria from the bowel - perineal skin - urethra - bladder - ureter - kidneys
If there is bacteria in the bloodstream, this can be filtered into the kdineys causing infection What is the classical thing described in bacterial bloodstream infection?
Can cause multiple small abscesses
What are the most common types of organism causing UTI? What is the most common organism?
Gram negative bacilli - coliforms are the most common type Escherichia coli is the most comon UTI causing organism (accounts for 70% of cases)
Apart from E.coli, name 4 other UTI causes and name which is not a coliform?
Can have klebsiella, enterobacter, proteus, enterococcus Also can have pseudomonas aerguinosa causing an infection and this is not a coliform
Name a UTI causing organism that is non-lactose fermenting with a positive oxidase test Is this organism a coliform?
Pseudomonas aerguinsa This organism is not a coliform
What is the proteus organism associated with the formation of?
Associated with the formation of stones - struvite stones
What is the characteristic smell of proteus organisms?
has a foul smelling burnt chocolate odour
Proteus has a characteristic swarming culture – multiple concentric ring What can this cause the blockage of?
It can cause the blockage of catheters
Describe the features of proteus organism eg * what it causes to form, * what it smells like, * what it looks like on agar plate * and how does it increase urinary pH therefore increasing preciptation of salts?
Causes the formation of struvite (triple phosphate) stones Has a foul burnt chocolate smell has a characterisitc swarming culture Protease produces the enzyme urease which breaks down urea into ammonia increasing urine pH and increasing precipitation of salts
Gram negative bacillus but not a coliform Associated with catheters and UT instrumentation What is this?
This is pseudomonas aerguinosa - non lactose fermenter with a +ve oxidative test
Pseudomonas is resistant to most oral antibiotics except what?
resistant to most oral antibiotics except ciprofloxacin 4C antibiotics are ciprofloxacin, clindamycin, co-amoxiclav, and cephalosproins (ceftriaxone)
What type of organism is enterococcus?
It is a gram positive non-haemolytic streptococci
enterocococcus are types of commensals living in the GI tract There is Enterococcus faecalis and Entercoccus faecium Which is not sensitive to antibiotics?
Eenterococcus faecialis is sensitive to antibiotics Enterococuus faecium is not sensitive and therefore harder to treat if a UTI
a type of coagulase negative staph usually affects women of child bearing age ? What colour a coagulase negative staph on agar?
This is staph saphrophyticus Coagulase negative staph usually appear white on agar
Name the two negative staphlococcal coagulase negative and how do you differentiate beween the two?
Staph epidermis, staph saphrophyticus Novobiocin test Staph saphrophyticus is novobiocin resistant
What are symptoms / signs of a urinary tract infection?
Pain on urination Increased frequency of urination Urgency Haematuria
female sex, history of UTI, diabetes also and obesity Frequency and urgent urination with suprapubic pain Is this cystitis or pyelonephritis?
This is cystitis, suprapubic pain
What are three signs that suggest kidney involvement?
Fever loin pain, rigors
What bacteria is the most common cause of UTI? Which is present where there are catheteries and urinary tract abnormalites? Why has a swariming appearance on blood agar? Which infections woman of child bearing age?
E.coli is the most common cause of UTI Pseudomonas aerguinosa is present where there are catheteries and urinary tract abnormalites Proteus has a swariming appearance on blood agar? Staph saphrophyticus infects woman of child bearing age
Remember: bladder urine is normally sterile, but urine passed via the urethra will be contaminated with bacteria from the perineum or lower urethra Why is it important when taking a urine sample not to take the first urine passed?
It is the most likely to be contaminated
At what stage of urination should the urine sample be taken then?
Take a mid-stream specimen of urine (MSSU)
Ideally when taking a mid stream specimen of urine out, the perineum and urethral meatus are washed with?
Washed with saline and not an antiseptic as this can contaminate Give patient a sterile foil bowl First urine passed into toilet Next part collected in foil bowl Last urine passed in toilet
When is the only time first void urine is useful?
It is useful when looking for STDs as the cause of the infection
What are the two different specimen containers and how long do they last?
Boricon container (red cap) - lasts 24 hours Sterile universal container (white cap) - lasts 2 hours
What does the boricon container contain to stop the bacteria multiplying and therefore preserves for 24 hours?
Contain boric acid which is a preservative to prevent multiplication of the bacteria
If a patient doesnt have any sympotms of a UTI, should you dipstick test? When should you not dipstick test?
Do not dipstick test unless the patient has symptoms of a UTI Do not dipstick test if the patient has a catheter or is elderly
What other things are found in urinalysis in a UTI?
Would find blood, protein and nitrites probably
Why would there be nitirites in a UTI? Which bacteria will not cause nitrite in the urine?
Nitirites - due to bacteria breaking down nitrates to nitrites Enterococcus would not indicate the presence of nitrites in the urine
In catheter and the elderly, if there is symptoms of a UTI, urinalysis is not carried out Instead what is carried out?
Carry on straight to sending a laboratory sample of urine
What is the cornerstone of diagnosis in a urinary tract infection?
Culture of the urine - usually tends to only be one organism causing the UTI
As all urine will contain bacteria , it is the concept of “significant bacteriuria”(bacteria in urine) when looking at culture that will indicate a urinary tract infection What is done in urgent cases? (ie a renal transplant patinet)
Microscopy of the urine looking for polymorphs (pus cells), bacteria +/- RBCs
