Lecture 8 - Urinary tract infections Flashcards
Describe the infection rate of UTIs
High infection rate, very common disease with 175 million cases per year worldwide
How many women and men will experience a UTI in their lifetimes?
40-50% of women
10-12% of men
what statistics show that UTIs are a recurrent disease?
25% of women experience a second UTI, and 3% of women will experience a third UTI within 6 months of the initial UTI
what is the more serious illness that can stem from UTIs?
pyelonephritis, infection spreads to kidneys
What is the main treatment for UTIs?
Antibiotics
what are the cons of treating UTIs with antibiotics?
- they can be costly
- can disrupt normal flora (surfacing of other infections)
- promotes drug resistance
what marks the treatment endpoint of UTIs?
when there is a sterilisation of urine and a loss of symptoms,
- not an eradication of the pathogen, which leads to relapse
what are the signs and symptoms of a moderate UTI?
- frequency of urination increases
- dysuria (pain while urinating)
- hesitancy
- urgency
what are the signs and symptoms of a more severe UTI?
- hematouria
- pyelonephritis (kidney infection with flank pain)
- systemic effects such as vomiting and fever
who is most commonly infected with community acquired UTIs and what is the pathogen that causes it?
mainly young women
mainly UPEC (Uropathogenic Escherichia coli)
who is most commonly infected with hospital acquired UTIs and what is the pathogen that causes it?
device related so could be anyone
UPEC but also other organisms
- higher drug resistance
what does the urine look like of someone with a UTI?
cloudy due to bacteria
smelly
sometimes with blood if more severe
what is cystitis?
inflammation of the bladder that happens during a UTI
what is urinalysis
- the process of collecting an analysing urine to detect for bacteria
describe the process of urinalysis
Midstream urine specimen collection and analysis
- clean perineal area and don’t use first bit of urine
- analyse immediately or store at 4ºC to reduce contamination of the sample
how can the UTI urine sample be contaminated with bacteria we aren’t looking for?
by passing through the lower urinary tract and skin, the urine picks up other bacteria and fungi
what is the dipstick test?
dipstick into a urine sample of someone suspected to have a UTI
what is a positive reading of a dipstick test?
- testing positive for nitrites (bacteria change NO3- to NO2-)
- positive for leukocyte esterase (indicates presence of WBC)
what would urine sediment microscopy show?
- WBCs such as neutrophils
- bacteria everywhere coz its literal pee
- transitional epithelial cells from bladder
what would a gram stain of a urine sample of someone with a UTI show?
gram negative bacilli and the presence of neutrophils.
- this can conclude UTI is due to a gram negative rod since we can see the neutrophil phagocytosing the rod
what is the main bacteria that causes community acquired UTIs?
- escherichia coli
responsible for up to 95% of UTI cases in community
what are the five less common bacteria that can cause a community acquired UTI?
- Proteus mirabilis (-ve rod)
- Klebsiella pneumoniae (-ve rod)
- Staphylococci saprophyticus (+ve cocci)
- enterobacter (HA)
- pseudomonas (HA)
what are the main bacterias that cause hospital acquired UTIs?
- E. coli (31%)
- other enteric bacteria such as
Klebsiella and enterobacter - proteus, pseudomonas enterococci and staph
how can we diagnose E.coli or Klebsiella and enterobacter using culture?
CLED agar
- Cysteine (requirement of some UPEC)
- Lactose (UPEC are lactose fermenters, and agar will turn yellow)
- Electrolyte Deficient (prevents swarming of proteus so we can actually see how many colonies we have)
do psuedomonas and proteus ferment lactose?
no, so the blue indicator will remain blue
what is enumeration of a urine sample?
If we have a sufficient sized sample, we can see if we have significant bacteruria (>10^5 CFU/mL or 10^8 CFU/L) which is greater than what we expect from normal flora
what does CFU stand for?
colony forming units
if a patient had 10^4 to 10^5 CFU/mL, then what should we do?
evaluate with clinical information
how can we test to see if we have E coli present of whether we have Klebsiella or enterobacter?
E coli gives ++– on IMViC tests
Enterobacter and Klebsiella give the reverse: –++
or spectroscopy
what is the source and transmission of the bacteria causing UTIs?
- fecal origin
- community acquired (more common in females due to ‘proximity effect’ and in older men due to statis)
- hospital acquired via catheters
what is the proximity effect?
the entry of the urethra is closer to the anus in females than males
who are at risk of UTIs?
- sexualy active women
- women with previouse UTIs
- ABs that disrupt flora
- urinary catheter
- underlying disease leading to stasis in the bladder (such as prostatic hypertrophy in men)
what are the key virulence factors?
- adhesins (pili)
- immune evasion (flagella, capsule)
- Iron acquisition
- Lipid A for inflammation
- toxins such as alpha hemolysin and cytotoxic necrotising factor
describe the pili in the bacteria that cause UTIs
type 1 pillus (aka fimbriae) is common to all enterobacteria
- bind to mannose residues in glycoproteins
P pillus for colonisation of the kidney
what does it mean if a UTI is an ascending infection vs a haematogenous infection?
goes from bladder into kidney from ureter, or from blood to kidney.
how are UTIs a recurrent infection
bacteria remain and grow in cells until there is enough for them to leave and cause an acute infection
for mild cases of UTIs, are antibiotics required?
if the patient is healthy, then we shouldn’t use antibiotics due to resistance concerns
if symptoms get worse or persist then we should
or if case is moderate to severe
what is recommended treatment for people with a mild UTI?
- fluids, pain relief
- advice for future around hygiene
which antibiotic is usually effective against UTIs
amoxil
if a patient has a recurring UTI and the used amoxil last time and wants amoxil again, what should we do?
- advise her to use trimethoprim or ciprofloxacin (a non-beta lactam AB) due to bacteria likely having grown resistance to that AB.
