UTI Flashcards
How does normal flora differ along the urinary tract
Kidneys, bladder and prox urethra sterile
- distal urethra and external genital commensal flora
What is the risk of infection related to?
Host defences v bacterial virulence
Most common bacterial isolates in UTIs
- e.coli
- staph
- proteus, strep, klebsiella, enterococcus, others
Are dogs or cats more resistant to UTIs?
Cats
How do pathogens affecting horses and cattle differ to smallies?
Corynebacterium + similar species to smallies
What are cows particularly prone to?
Pyelonephritis (though this may be due to time of tx or assessment of cows cf. smallies)
Outline host defence mechanisms of the urinary tract
- normal micturition
- anatomical and physiological barriers
- mucosal defence barriers
- anti microbial effects of urine
- renal defence mechanism
How is normal micturition defined?
- voiding frequent, complete, with an adequate flow
Clinical conditionss resulting in voiding abnormalities -?
- urethral obstructions
- spinal disease
- bladder atony
- poor husbandry
Outline the protective anatomical and physiological factors
- urethral high pressure zone
- surface characteristics of urethral urothelium
- urethral peristalsis
- prostatic antibacterial fraction
- longer urethral length
- ureterovesical valves and ureteral peristalsis
Clinical conditions that may ^ risk of UTI?
- direct trauma eg. Catheterisation
- ectopic ureters
- urethral sphincter mechanism incontinence
- anatomical abnormalities following surgery eg. Perineal urethrostomy
What are some anti microbial properties of the mucosa?
> protective factors
- antibody
- surface GAGs
- intrinsic mucosal antimicrobial properties (waterproof etc.)
- bacterial interference
- exfoliation of cells
Clinical conditions that affect mucosal defence barriers and pdf UTIs
- trauma eg. Catheters
- disease processes eg. Neoplasia
- chemical irritants eg. Cyclophosphamide
Antimicrobial properties of urine
- extreme of pH (high or low)
- hyperosmolality
- high urea
- organic acids
Which clinical conditions affect urine PDF UTIs?
- older cats d/t poor concentration of urine
- dogs with DM glucosuria
Can anaerobes cause UTIs?
Not commonly
- so restricted range of feacal bacteria cause UTIs as majority are anaerobes
How do uropathogenic E. Coli over come host defences?
- avoid flushing action (S or P-fimbraie)
- complement resistant -> opsonoohagocytosis resistant
- haemolysin production and iron chelation abilities
- motility (some need to be able to move up urinary tract)
How does urine culture differ to normal culture?
- contaminants will give false positive if swab smeared on to agar
- sample must prevent bacterial growth in the urine (rapid transport to lab, hold at 4* c, add boric acid [bacteriostatic])
- 2ul onto blood and onto maconkey
- aerobic incubation, 18hrs
- look for >100,000 CFU/ml to demonstrate UTI (200 colonies from 2ul)
- less than this indicates contaminant
How does uropathogenic e.coli grow on agar?
Grows on blood, more on maconkey, is haemolytic
What is considered to be “no significant growth” ?
-
How does sensitivity testing differ in urine culture?
- higher drug levels than normal disks (because drugs concentrated in the urine)
How does recrudescence differ to recurrence?
Recrudescence or relapse (same strain, Tx failure)
Recurrence or reinfection (new strain, susceptibility of the animal)
> collect samples over several months from the same animal
PDF factors for cats and dogs developing UTIs?
- bitches more common
- older cats more common
- mostly bacterial (fungal rare, viral implicated as causal factor for FLUTD, incidence Unknown)
- parasitism possible 3rd world, not UK
Define UTI
Adherence, multiplication and persistence of an infectious agent in the urogenital system
Define microburia
- presence of microbes in the urine
Define bacteruria
- presence of bacteria in the urine
> 10^5 organisms/ml = infection
>10^3 suggestive on infection but depends on collection technique
Define funguria
- presence of funghi in the urine
Define pyuria
- ^ noWBCs in the urine >5/hpf
> cystocentesis >3-5 significant
> catheter/free catch >5-10 significant - NB: WBCs do not mean infection necessarily, just inflammation
How does the nomenclature of trueperella / corynebacterium differ??
- trueperella pyogenes causes abscesses in farm animals
- corynebacterim renale causes pyelonephritis
Hx and PE Findings with UTIs?
- may or may not be associated with clinical dz
> predominant site (upper v lower)
> presence of preddisposign factors (calculi, DM, neooplasia)
> UPPER - renal/lumbar pain, haematuria, septicaemia
> LOWER - pollakuria, stranguria, dysuria, innapropriate urination
How can UTIs be Dx?
> gold standard - quantitative culture of urine > not diagnostic but indicative - urinalysis and sediment - gross appearance and smell
Best method of sample collection for urine? Other ways?
> aseptically ideal - cystocentesis best - catheterisation good if done carefully - free catch not ideal > no Abx for a week before sampling
What other samples besides urine can be collected?
Urolithiasis for culture
How should pathological urine samples be transported ?
- sealed sterile containers
- fridge
- boric acid sometimes used as bacteriostatic (may not be appropriate)
- Royal Mail regulations
- costs
Tx of UTIs?
> Abx mainstay
- empirical initially, but ideally based on culture sensitivity
- first occourence, pending culture results only!
Ideal ABx choice for s UTI
- bacteriocidal
- based on C + S
- excreted in urine
- easy to administer
- cheap
- good penetration to other tissues (eg. prostate) if required
- cascade
- not newer/broad spec products
Outline empirical Abx Tx of a UTI
- short course (5-7 d) most likely to hit E. Coli and Staph > best appropriate - ampicillin - potentiated amoxicillin - cefalexin - TMS (side effects) > use top end of dose range > if signs recur must do sensitivity
What is a therapeutic culture?
- using bacteriology to monitor tx
- if UTI high morbidity or mortality (prostatitis, pyelonephritis, immunosuppression)
- antibx is toxic (gentamicin, amikacin)
- if signs not improving after 3-5d
- before discontinuing Abx after serious infection
What is surveillance culture?
> provide info after Abx discontinued
- ensure Tx successful
- if signs recur
- Concerns about underlying causes (FLUTD, incontinence, recessed vulva)
Why may Tx of UTIs fail?
- infection not the cause
- inadequate delivery (client or animal effective drug or delivery)
- Abx resistance (intrinsic eg. Penicilinase producing bacteria, acquired)
- undiagnosed or untx PDF -> superinfection (don’t Tx catheterised animals until Catheter removed!)
What do you suspect if poor clinical response is seen
> culture
- no bacterial growth?
- same bacteria susceptible to current Abx?
- same bacteria resistant to current ABx
- new speceies
Most common source of UTIs?
Feacal flora most common, may be skin flora
