Microbio 6: UTI Flashcards by D J

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

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What is a Lower UTI?

Infection of the bladder (aka cystitis) usually caused by bacteria from the GIT

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What is a Upper UTI? AKA?

Infection of the upper part of the urinary tract —the ureters and kidneys (pyelonephritis)

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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.

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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

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What is bacteriuria?

The presence of bacteria in the urine — may be asymptomatic (only significant / requires mx if pregnant)

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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.

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How can obstruction cause UTIs?

Inhibits urine flow → stasis → infection

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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

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What are some examples of extrarenal obstructions that can lead to UTIs?

Valves, stenosis or bands

Calculi

BPH - tumour compression

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What are some examples of intrarenal obstructions that can lead to UTIs?

Nephrocalcinosis

Nephropathy (uric acid, analgesic, hypokalaemic)

Polycystic kidney disease

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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

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What organisms commonly cause UTI in children w/ vesicoureteric reflux?

E. coli and S. saprophyticus

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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

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What organism is likely to cause UTIs in individuals w/ kidney stones (particularly struvite / staghorn calculi)?

Proteus Mirabilis

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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

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