Microbiology of the urinary tract Flashcards
Ex of lower urinary tract infection:
Cystitis
Urethritis
Places of acquisition of UTIs
Community acquires
Nosocomial
Route of acquisition:
Ascending
Haematogenous
Risk factors for UTIs:
- Female sex
- Sexual activity
- Diabetes mellitus
- Urinary stasis
- Urinary retention
- Not fully emptying bladder
- Urinary catether
- Congenital abnormalities
- Reflux
Most common bacterial cause of UTI:
E.coli
E.coli:
Gram negative, rod shaped
Other bacterial causes:
Proteus species
Enterobacter
Staphlococci
Fungi causes:
Candida
Viral causes;
- Adenoviruses
- BK, JC viruses
Adenoviruses are associated with:
Haemorrhagic cystitis
BK and JC viruses:
Associated with infection and graft failure in patient following kidney transplant
Parasitic infection that can cause UTI:
Schistosoma haematobium
Ex of upper urinary tract infections:
Pyelonephritis
Innate host defences against UTI:
- Urine flow and mictuition
- Urine pH, osmolarity and urea
Active host defences against UTI:
- Secretory IgA
- Mucosal defences
Why are females more likely to get UTIs?
Shorter urethra
Urethra closer to anus
Bacteria and lower UTI in pregnancy can cause:
- Lower birth rate
- Premature delivery
- Increased perinatal morbidity
- Increased risk of developing pyelonephritis
Pyelonephritis in pregnancy:
- Lower birth weight
- Prematurity
- Foetal loss
What is screened for during pregnancy?
Asymptomatic bacteriuria
Common symptoms of cystitis:
Frequency
Urgency
Dysuria
What is usually absent or low in cystitis?
- Systemic symptoms
- Fever
Symptoms of UTI in infants:
Fussy, reduced feeding, failure to thrive
Symptoms of UTI in elderly:
Normal signs may be absent, sudden onset of confusion
Symptoms of pyelonephritis:
- Frequency, urgency, dysuria
- Loin pain
- Fever
- Rigors
- Renal angle tenderness
- Nausea, vomiting
Diagnosis of UTI:
- Urinealysis
- Urine microscopy
- Urine culture
Urinealysis to look for:
Protein, blood leukocyte esterase, nitrites
Leukocyte esterase may be … due to …
False negative
Taking antibiotics, high glucose in urine
Nitrites are formed by:
Gr- bacteria
Why might nitrities be falsly negative?
- Some bacteria don’t product
- Low numbers of bacteria
Urine microscopy looks for:
WBCs, epithelial cells, red cells, casts
Gold standard for diagnosis:
Urine culutre to look for organism and sensitivities
Urethral syndrome:
symptoms with negative urine cultures
Why might someone have clinical features but negative urine cultures?
- Too few bacteria
- Culturing wrong organisms
- Non-infective inflammation
- STI (chlamydia, gonorrhoea)
Uncomplicated UTI:
Lower UTI in young, otherwise fit woman
Management of uncomplicated UTI:
- Good hydration
- Short course of antibiotics if indicated
Antibiotics used for UTI:
Trimethoprim: cheap, active against most uropathogens of uncomplicated UTI
Nitrofurantoin: high urine conc
Nitrofuratoin cannot be used on:
Proteus species
Upper urinary tract infection
Amoxicillin and uncomplicated UTIS:
High rates of resistance
Recurrent UTI:
> 3 UTIs annually
Management of recurrent UTI:
- voiding post-intercourse
- Double voiding
- HRT
- Prophylactic antibiotics
Way of getting a sterile urine sample:
Suprapubic aspirate
Diagnosing UTI in children:
<3mnths: less reliance on dipstick
3mnths-3yrs: microscopy and culture like adult
3 yrs+: lukocytes esterase and nitrites
What does a UTI in a child may indicate?
Congential abnormality, should image
Treatment of lower tract infections in a child:
- Amoxicillin, trimethoprim, cephalexin
Treatment of mild UUTI in child:
Co-amoxiclav
Treatment of severe UUTI in child:
Cefotaxime, gentamicin
