Urinary tract infections Flashcards
What is the Significance of UTIs?
•Represent 5-17% of all canine admissions
Are UTIs common in cats and horses?
- Inflammation of the lower urinary tract is very common in cats but infection uncommon (<1% of admissions). Get clear difference between inflammation and infection.
- Not as common in horses and farm animals (though the principals are the same)
What are the Barriers to Infection in the Urinary Tract?
Things which are present to inhibit bacterial growth:
- Flushing effect of urine
- Resident normal flora in the lower urogenital tract. Compete against pathogenic organisms.
- Urine is also a hostile environment for bacteria (either very acidic or alkali and contains and toxic compounds)
- Hostile environment (urine pH, concentration, constituents)
- Physical barriers – bladder sphincter, one way flow through ureters into bladder. Prevent urine coming back up into bladder.
- If bacteria does get past all the above the Epithelial cell layer and tissue behind them have their own immune reponse
- Mucosal immune system
The kidneys and the bladder in the normal animal are?
- The Kidneys and Bladder in a normal animal are a sterile environment
- Should have no bacteria in there at all
What are Routes of Infection into the urinary tract?
- Haematogenous spread from blood stream into the Kidneys (e.g septicaemia leading to bacteria lodging in glomerulus)
- Not very common
- Risk increased if there is trauma or obstruction (RTA, or obstruction increased risk of this thing happening)
Discuss more common routes of infection into the urinary tract?
- More common: Retrograde infection (tracks up from the external genitalia into bladder then higher up into kidneys)
- Most UTIs occur via this route
Are upper or lower UTIs more common?
- Lower UTIs (urethra and bladder) are the most common
- Upper UTIs (involving the kidney and ureters) are rarer but more serious
What are the Predispositions to Infections?
- Females> males (due to length of urethra as much shorter in females so shorted distance for bacteria to track up into the bladder)
- Dogs> cats (?)
- Physical defect causing incontinence (e.g ectopic ureters, spey incontinance) – prevention of complete emptying, one part of barrier not working
- Catherisation!!!!! (major iatrogenic cause great surface for bacteria to colonise)
- Immunocompromise (hyperadrenocorticism, systemic disease)
What Bacteria are Involved in UTI infections?
- Are usually ones that are normal gut or skin flora as outlet from GI tract is near outlet from urogenital tract
- All bar Streptococcus commonly exhibit antimicrobial resistance
What bacteria are involved in different species UTIs?
- Same range of bacteria seen in large animals as in small plus:
- Corynebacterium spp, Actinobacillus spp and Arcanobacter spp (contaminates from the environment small animals are not so exposed to)
What is more common in Cattle/sheep/pigs?
- Cattle/sheep/pigs pyleonephritis (UTI) is more common, often secondary to metritis/retained placenta
- Pyleonephritis = infection of kideny
Horses often get UTIs secondary to other problems (eg trauma, anatomical defects)
What do horses and rabbits also suffer from?
Horses (and rabbits) get “sabulous cystitis”
Both secrete a high concentration of calcium carbonate in urine.
Leads to accumulation of calcium carbonate crystals in bladder often concurrent with bacterial infection.
Discuss the bacteria involved in UTIs?
Not all strains of these bacteria are pathogenic in the urinary tract. Difference between being able to cause infection and not relate to how they can adapt and change their resistance:
- R plasmids (antimicrobial resistance)
- E.coli
- Adhesion factors (fimbriae)
- K (capsular) and O (envelope) antigens
•Proteus, Staphylococcus, Klebsiella
-Urease a protein which converts urea-> ammonia (means they can use the ammonia as as an energy source) Ammonia also goes on to acidify the urine.
•You may also have mixed infections with whole diff range of AB resistance.
What are the Clinical Signs of Lower UTI?
- May be none
- Straining to urinate/difficulty urinating/painful urination/urinating in strange places/increased frequency of urination (pollakiuria, anuria etc)
- Urine scalding (particularly horses)
- Blood in the Urine/Discoloured/smelly urine (pyuria/haematuria)
- Bladder may be painful to palpate/thickened
- Abdominal pain (large animals may kick at their abdomens to express pain)
What are the Clinical Signs of Upper UTI?
- May be none
- May be increased temperature (or not if it has been going on for a while and it is chronic)
- Abdominal pain (kidney pain)
- Kidneys may be enlarged and painful
- If there is renal compromise may exhibit PU/PD or signs of renal failure, tends to be when damage had been going on for a while
- Pyelonephritis (infection of the kidney)
- May be anorexia/innapetance
- May be weight loss, drop in milk production (particularly large animals)
- Sudden death (pigs) do PM and find horrible kidneys
What is Bacteriuria on a sediment exam?
Bacteriuria
Presence of bacteria indicates infection (contamination) use x100 oil lens to see
What is the gold standard for definitive diagnosis of UTI?
Urine Culture
- Definitive diagnosis
- Prior to treatment (in an ideal world pragmatically rarely happens as culture will take a few days and unlikely to send home without Abs)
- Storage and transport of sample (Check what lab requires)
–Sterile container without additives
–Commercially available kits
–Refrigeration up to 6hrs
•Gets cultured on Blood or MacConkey’s agar
Discuss the future of anti-microbial identification?
- Some labs now moving to Maldi-Tof (spectrometry) ID of bacteria. Machine chops bacteria into little pieces apply charge across stream it across a detector and each set of amino acids builds a profile when you add them all up across each isolate each isolate has a distinct profile. Database has huge profiles saved.
- In some cases this can be done direct from the urine sample without pre-culture
- Faster, but relies on database of spectra for strain ID.
Discuss Iatrogenic UTI’s?
- Patients with indwelling urinary catheters commonly develop urinary tract infections (20-40%)
- You have breached one of the physical barriers to infection
- Hospitalised patients are often immunocompromised/ have other factors that predispose them to UTIs (spinal injury and incontinence)
- Try to minimise catheterisation (only when necessary!)
