Microbiology Flashcards
Define a lower UTI
Infection confined to the bladder (cystitis)
Define cystitis
Inflammation of the bladder not always due to infection
Define upper UTI
Infection involving ureters/kidneys (pyelonephritis)
Describe the physiological bacteria in the urinary tract
Normally the lower end of the urethra is colonised by bacteria - coliform and enterococci but the rest is sterile
What is a complicated UTI?
Systemic sepsis
Structural abnormality
Stones
Define bacteriuria
Presence of bacteria in the urine - not always infectious (elderly and catheterised patients)
State the risk factors for UTI
Women>Men (short wide urethra, proximity of urethra to anus, sexual activity, pregnancy)
Catheterisation (colonised bacteria can easily enter bladder)
Abnormalities of the urinary tract
Name the two key routes of infection
Ascending - from bowel to perineal skin to lower urethra to urinary tract
Blood stream - seeded into kidneys from blood leading to multiple small abscesses and bacteria in the urine
What are the most common organisms in a UTI?
Coliforms - e.coli, klebsiella, enterobacter, proteus
What is proteus associated with?
Calculi - foul smelling due to urease breaking down to ammonia increasing pH and causes salt precipitation
Name the other organisms apart from coliform that cause UTIs
Enterococcus faecilus and faecium
Staphylococcus saphrophyticus (young child bearing age)
Staph aureus
Pseudomonas
What are pseudomonas associated with?
Catheters and instrumentation - resistant to most antibiotics except ciprofloxacin
How does ciprofloxacin work? What is the risk of using it?
Inhibits DNA gyrate to prevent supercoiling - not used in children/pregnant women risk of c.diff
What are the symptoms of a UTI?
Dysuria Frequency of urination Nocturia Haematuria Fever Loin pain Rigors
State the different methods of collecting urine for sample
Mid-stream specimen of urine
Clean catch (nurse catches sample)
Bag urine (used in babies but can be contaminated with bowel flora)
Supra-pubic aspirate (babies and young kids)
Catheter specimen of urine (aspirate from catheter)
What is the best container for the urine to go to the lab in?
Boron container (red top) contains boric acid which stops bacteria multiplying
What does a dipstick often show in a patient with a UTI?
Leukocyte esterase (WBC)
Nitrites (bacteria converts nitrates to nitrites)
Protein
Blood
State the test used in urgent cases
Microscopy will only show WBC, red cells and bacteria
On culture what volume of organism indicates infection
<10^3 organisms/ml - not significant
10^4 organisms/ml - doubtful
>10^5 organisms/ml - significant
How is an uncomplicated LUTI in women treated?
Nitrofurantoin/trimethoprim 3 days
How is an uncatheterised LUIT in men treated?
Nitrofurantoin/trimethoprim 7 days
In primary care how is complicated UTI/pyelonephritis treated?
Co-amoxiclav (co-trimoxazole if allergic)
In secondary care how is complicated UTI/pyelonephritis treated?
Amoxicillin and gentamicin
Step down to oral co-trimoxazole
Describe gentamicin
Given IV it has a narrow therapeutic index 7mg/kg for 3 days only - avoid in pregnancy
