L10: Microbiology of the urinary tract Flashcards
5 symptoms of UTI
polyuria dysuria urgency suprapubic discomfort fever low grade/ absent
symptoms of UTI in infants (2)
failure to thrive
poor feeding
symptoms of UTI in elderly
absent signs
sudden confusion
symptoms of pyelonephritis (4)
loin pain
fever
rigors
renal angle tenderness
7 risk factors for UTI
female anatomical abnormality functional abnormality catheterisation pregnancy foreign body urinary tract surgery
why is female sex a risk factor
shorter urethra
urethra opens into introitus
closer to anus
what does catheterisation lead to
biofilm formation
what happens in pregnancy increase UTI risk (3)
dilated ureters
incomplete bladder emptying
gestational glycouria
what are UTIs in pregnancy associated with
low birth rate
premature
perinatal morbidity
what will eventually happen to all catheters
get colonised
can you have a UTI with negative urine cultures
YES- 50% of women
reasons for a negative urine culture with a UTI (4)
- low bacteria count
- fastidious bacteria don’t grow on culture
- non-infective inflammation
- Sexually transmitted pathogens
commonest bacteria cause of UTI
E.coli
where does E.coli live normally
in bowel
what E.coli can cause UTIs
uropathogenic E.coli (UPEC)
what do UPECs have to enable UTIs
virulence factors for urinary tract
3 non-bacterial cause of UTI
viruses
mycobacterium tuberculosis
parasitic infection
what are BK and JC viruses associated with
infection and graft failure in patients following kidney transplant
most common route of UTI acquisition
ascending from urethra to bladder to kidney
less common UTI acquisition route
haematogenous
UTI from urethra to bladder=
cystitis
UTI from bladder to kidney=
pyelonephritis
4 host defences of UTI
urine flow
urine osmolarity/ pH/ organic acids
secreted sIgA
mucosal defences
3 UPEC virulence features
type 1 fimbriae
type p fimbriae
bacterial capsule
what is type p fimbriae associated with
pyelonephritis
what is type 1 fimbriae associate with
cystitis causing strains
what is bacterial capsule associated with
pyelonephritis causing strains
what does type 1 fimbriae bind to
mannose residue on bladder endothelial cells membrane
what do type p fimbriae bind to
glycolipid residues on host cells
E.coli gram stain=
negative
other gram negative causing UTIs
proteus species
commonest proteus species
proteus mirabilis
how is proteus protected
it produces magnesium ammonium phosphate stones which surround it
what is changed on a urinalysis with UTI
protein
blood
leucocyte esterase
nitrites
most specific signs for UTI
nitrites
leucocyte esterase
what is urinalysis good at
ruling out UTI (negative predictive value)
what is a Negative predictive value
is the probability that subjects with a negative screening test truly don’t have the disease.
what is urinalysis bad at
ruling in UTI
how do you avoid urine specimen contamination
midstream urine specimens
what acid is placed in urine samples
boric acid
what does boric acid do
stuns the bacteria
what suggests contamination in a urine sample
epithelial cells
colour of E.coli in CLED agar
yellow
colour of proteus in CLED agar
pale blue
in children how are UTIs thought of
complicated
2 managements of UTIs
good hydration
antibiotics (if indicated)
antimicrobial active against most agents of uropathogens
Trimethoprim
trimethoprim affect on bacteria =
bacteriostatic
treatment of lower UTIs in children (3)
amoxicillin
trimethoprim
cephalexin
treatment of upper UTIs in children
co-amoxiclav
treatment of severe UTIs in children
cefotaxime
gentamicin
