Microbio 6: UTI Flashcards
UTI definitions?
WCC in urine >10^5 - 1 predominant organism in mixed growth
WCC in urine >10^4 - if just 1 organism (no mixed growth)
WCC in urine >10^3 - if E.coli or Staph. Saprophyticus
What is a Lower UTI?
Infection of the bladder (aka cystitis) usually caused by bacteria from the GIT
What is a Upper UTI? AKA?
Infection of the upper part of the urinary tract —the ureters and kidneys (pyelonephritis)
What is a recurrent UTI?
Usually defined as two or more episodes of UTI in six months
OR three or more episodes in one year.
What is a catheter assocaited UTI?
Symptomatic infection of the bladder or kidneys in a person who is catheterised or who has had a urinary catheter in place within the previous 48 hours
What is bacteriuria?
The presence of bacteria in the urine — may be asymptomatic (only significant / requires mx if pregnant)
How can lower UTIs be categorised?
Uncomplicated UTI— Infection in a structurally and neurologically normal urinary tract + nopredisposing co-morbidities.
Complicated UTI—Infection in a urinary tract with functional or structural abnormalities (includes indwelling catheters and calculi)
RFs: structural or neurological abnormalities of the urinary tract, catheters, virulent/ atypical infecting organisms, poorly controlled diabetes mellitus or immunosuppression.
How can obstruction cause UTIs?
Inhibits urine flow → stasis → infection
How can obstructions that cause UTIs be categorised?
Extrarenal
Intrarenal
Neurogenic malfunction
Vesicoureteral reflux - Residual pool of urine in bladder → ureters → renal scarring in children
Haematogenous spread - S. Aureus bacteraemia / endocarditis → renal abscess
What are some examples of extrarenal obstructions that can lead to UTIs?
Valves, stenosis or bands
Calculi
BPH - tumour compression
What are some examples of intrarenal obstructions that can lead to UTIs?
Nephrocalcinosis
Nephropathy (uric acid, analgesic, hypokalaemic)
Polycystic kidney disease
What are some examples of neurogenic malfunction caused obstructions that can lead to UTIs?
Poliomyelitis
Tabes dorsalis (demyelinating condition caused by advanced syphilis)
Diabetic neuropathy
Spinal cord injuries
What organisms commonly cause UTI in children w/ vesicoureteric reflux?
E. coli and S. saprophyticus
What organisms cause UTIs?
E. coli - MOST COMMON
S. Saprophytics - 2nd MOST COMMON (esp young women)
Proteus mirabilis Pseudomonas Candida Klebsiella aerogenes Enterococcus faecalis Staph epidermis
What organism is likely to cause UTIs in individuals w/ kidney stones (particularly struvite / staghorn calculi)?
Proteus Mirabilis
What organisms are likely to cause UTIs in individuals w/ catheters?
Pseudomonas and Candida
+
Staphylococcus epidermis - coagulase -ve
What organisms are likely to cause UTIs in people with abnormal tracts? what is its virulence factor?
Klebsiella aerogenes - K-antigen
What is the virulence factor of the 2 most common causes of UTIs?
E. Coli - P-fimbrae
S. Saprophyticus - P-fimbrae, this bacteria is coagulase -ve
What are the causes of sterile pyuria (white cells in urine)?
Abx treatment (most common)
Calculi
Catheter
Tumour
TB
STD
Who is more likely to get UTIs and why?
Women are more prone to UTIs than men because they have shorter urethras and so contamination from the rectum is easier to ascend
What would you depending on the different results of urine dipsticks?
Leuc +ve, nit +ve = UTI, start abx
Leuc -ve, nit +ve = Start Abx, further mx guided by MC&S
Leuc +ve, nit -ve = Only start Abx if clinical evidence of UTI
Leuc -ve, nit -ve = UTI unlikley - consider other dx
What are some different results that you can get in MC&S that shows contamination of sample?
Squamous epithelial cells - unable to culture organism due to contaminated smaple
+ mixed growth = contamination of sample
Tests for UTIs
Urine dip + MC&S
Bloods - FBC, U+E, CRP and WCC
Further = Renal USS, IV urography (in complicated UTIs)
List some patient groups in whom culture and sensitivities should be performed?
pregnant, child, pyelonephritis, men, catheter, failed Abx, abnormal tract, renal impairment
Sensitivities: disc diffusion, zones of inhibition
What is mx of UTIs?
3 typical symptoms and no vaginal discharge = empirical treatment 3 days
- If recurrent/ atypical (Abx-resistant)/ > 7 days symptoms/ male = 7-day Abx course
≤ 2 symptoms → urine sample + dipstick
1st Line = Nitrofurantoin or Trimethoprem due to low risk of resistance
Which UTI drugs should be avoided during pregnancy and why?
Trimethoprim contraindication in 1st trimester → folate antagonist
Nitrofurantoin should be avoided in 3rd trimester → neonatal haemolysis
UTI mx if EBSL producing organism?
Outpatient parenteral antimicrobial therapy
Mx of UTI in a person w/ a catheter?
Gentamicin/ Amikacin 140mg), remove catheter (biofilm)
Mx of Pyelonephritis?
Broad spec IV Abx eg: Co-amoxiclav/ Cefuroxime ± Gentamicin
Who is at greater risk of candida infection? mx of this?
Patients with indwelling catheters
Only treat if renal transplant/ urinary tract surgery
Remove catheter (MOST IMPORTANT)
1st line - PO fluconazole,
2nd line - non-liposomal amphotericin B
What is vesicoureteric reflux?
A condition in which urine can reflux into the ureters
It results in a residual pool of infected urine in the bladder after voiding
It can result in scarring of the kidneys
What type of agar is used for urine culture? What do the colours suggest?
Chromogenic agar:
Pink = E. coli
Blue = other coliforms
Light blue = Gram-positives
In which groups of patients is a short course of antibiotics not appropriate?
Women with a history of UTI caused by antibiotic resistant organisms
More than 7 days of symptoms
Men
List some complications of pyelonephritis
Perinephric abscess
Chronic pyelonephritis (scarring, renal impairment)
Septic shock
Acute papillary necrosis
Which part of the kidney is more susceptible to infection?
Renal medulla
Most common cause of UTI in young women?
E. Coli
then comes Staph saprophytics
Why should nitrofurantoin be avoided in late pregnancy?
Neonatal haemolysis
