Urinary tract infection Flashcards
Risk of UTI - facotrs
- host defences
- bacterial virulence
How does an ascending infection start?
- colonisation of perineum and external genitalia
What are the commonest bacterial isolates?
- E.coli > Staphs > Proteus > Klebsiella > Others
Which spp are prone to UTI?
- cats more resistant to UTIs than dogs
- horses and cattle have similar bacteria spp but also get Corynebacterium
- cattle more prone to pyelonephritis
List normal host defence mechanisms
- normal micturition
- anatomical and physiological factors
- mucosal defence barriers
- AM effects of urine
- renal defence mechanisms
Describe normal voiding
- frequent
- complete
- adequate flow
Causes - voiding abnormalities
- urethral obstruction
- spinal dz
- bladder atony
- poor husbandry
Protective urinary physiology
- urethral high pressure zone
- surface characteristics of urethral urothelium
- urethral peristalsis
- prostatic antibacterial fraction (bacteriostatic)
- longer urethral length: males
- ureterovesical valves and ureteral peristalsis
Conditions associated with increased UTI risk
- ectopic ureters
- urethral sphincter mechanism incompetence
- anatomical abnormalities following sx (e.g. perineal urethrostomy)
- urethral trauma (e.g. catherisation)
- disease (neoplasia)
- chemical irritants (cyclophosphamide)
- older cats (urine changes) > younger cats
- DM (glucosuria)
Protective factors - mucosal barrier
- AB production
- surface GAG layer
- intrinsic mucosal AM properties
- bacterial interference
- cell exfoliation
How is urine protective against UTI?
- extreme pH (low or high)
- hyperosmolality
- high (urea)
- organic acids
Pathogenicity of bacteria causing UTI (UPEC)
- avoid flushing action of urine (P- and S-fimbriae)
- complement-resistant –> organophagocytosis-resistant
- haemolysin production and iron-chelating activity
- motility?
Define UPEC
Uropathogenic E. coli
Dx - UTI
- direct urine culture by swab is inappropriate (contaminants –> false positive, requires bacterial account)
- sample: rapid delivery, hold at 4 degrees, boric acid preservative
- blood agar and MacConkey
How does a bacterial count show a UTI?
- > 100,000 CFU/ml = UTI
Define recrudescence/ relapse
= same strain (indicating tx failure)
Define recurrence or reinfection
= new strain (indicating susceptibility of the animal)
Incidence of UTIs in cats/dogs
- variable, about 14% dogs get bacterial UTI during life
- bitches > dogs
- older > younger cats
- usually bacterial
- fungal rare
- viral implicated as causal factor in cats with FLUTD but incidence unknown
Define UTI
= adherence, multiplication and persistence of an infectious agent in the uro(genital) system
Define mircoburia
presence of microbes in urine
Define bacturia
presence of bacteria in urina:
- INFECTION: >10^5/ml
- SUGGESTIVE OF INFECTION: >10^3 (depends on collection methods)
- CONTAMINATION:
Define funguria
presence of fungi in urine
Define pyuria
increased #s WBCs in urine (>5hpf)
- significance depends on method of collection
- cystocentesis >3-5/hpf
- catheter/free catch >5-10 /hpf
- increased WBCs indicate inflammation which may or may not be associated with infection
What do CS depend on?
- predominant site (UUT vs LRT)
- presence of predisposing conditions (cacluli, DM, neoplasia)
CS - UUT (kidneys/ureters)
- renal/lumbar ain
- haematuria
- septicaemia
CS - LUT
- pollakiuria
- stranguria
- dysuria
- inappropriate urination
DX - UTI
- quantitative urine culture
- other tests may suggest but not diagnose a UTI: urinalysis and urine sediment exam, gross appearance and smell
Outline urine sample collection
- best done aseptically to prevent contamination*
- cystocentesis best
- catheterised sample good alternative provided done carefully
- free catch not ideal
- culture (bladder biopsy or urolith) may be useful
- animal shouldn’t have received ABs 5-7d prior to sample
Outline urine sample transport
- sealed sterilised container
- refridgerated
- send asap
- boric acid (bacteriostatic, sometimes used, may not be appropriate)
- follow courrier regulation
- avoid sending on friday
- remember costs and hidden costs
Tx principles - UTI
- ABs (mainstay)
- ideally based on C+S
- may be used empirically (first occurrence, pending results of C+S)
Principles - choosing an AB for UTI
- based on C+S
- bacteriocidal
- excreted in urine –> high concentrations
- no/low risk of toxicity
- easy to administer
- cheap
- good penetration into other related tissue if required (prostate)
- within cascade
- avoid abuse of new/BS ABs
Outline empiric AB use
- appropriate 1st incidence where no underlying cause
- short course (5-7d) of AB predicted to ‘hit’ the most likely bacteria (E.coli, Staph)
- drugs most appropriate (Ampicillin, potentiated amoxicillin, cefalexin, trimethoprim sulphonamide = TMS - latter now less popular)
- use top end of dose range
What to do if UTI signs recur after empiric AB tx?
urine sample + consider further investigation
Indications - therapeutic culture
- UTI associated with high risk morbidity/mortality (prostatitis, pyelonephritis, immunosuppression)
- toxic AB (gentamicin, amikacin)
- signs not improving after 3-5 d after starting tx
- before discontinuing ABs
Indications - surveillance culture
AFTER ABs GIVEN:
- ensure tx success
- if signs recur (same or different organism?)
- concerns about underlying condition which increases UTI risk (FLUTD, urinary incontinence, recessed vulva)
Causes - tx failure - UTI
- infection NOT the cause
- inadequate AB delivery (client factors, animal factors, ineffective drug/delivery)
- AB resistance (intrinsic, acquired)
- undiagnosed/untreated predisposing factors –> superinfection
Actions - poor clinical response to AB for UTI (but you are sure of infection)
Define if culture –>
- no bacterial growth
- growth of same bacteria susceptible to current AB
- growth of same bacteria not susceptible to current AB
- culture of new spp
