UTIs Flashcards
Bacteriuria
Presence of bacteria in the urine
- not necessarily infectious
- can be asymptomatic
What are 7 mechanisms that normally maintain sterility of the urine?
- Adequate urine volume
- Free-flow from kidneys through urinary meatus
- Complete bladder emptying
- Normal acidity of urine
- Peristaltic activity of ureters
- Increased intra-vesicular pressure preventing reflux
- In males, antibacterial effect of zinc in prostatic fluid
What is the difference between an uncomplicated and a complicated UTI?
Uncomplicated UTIs: that occurs in a normal urinary tract.
Complicated UTIs: that occurs in a urinary tract with anatomical and/or physiological abnormalities.
What constitutes and upper vs a lower UTI?
Upper (pyelonephritis)
Lower (cystitis and urethritis)
What is an acute UTI?
one that develops with the sudden onset of severe symptoms
What is a chronic UTI?
when the symptoms persist over time (symptoms that don’t disappear within 24 to 48 hours after treatment begins; a urinary tract infection that lasts longer than two weeks).
What is a recurrent UTI?
when there are repetitive episodes (relapses or reinfections)
considered recurrent when at least two or more infections have occurred in a six-month period and/or three or more infections in a 12-month period
What is a relapse?
a recurrence of the bacteriuria with the same infecting micro-organism that was present before therapy was started. This is due to persistence of the organism in the urinary tract.
What is a reinfection?
a recurrence of the bacteriuria with a micro-organism different from the original infecting bacterium (new infection). Reinfection may also occur with the same micro-organism two weeks after treatment. Even though this can be mistaken as a relapse, due to the two-week gap between the first and second infection, this is considered a reinfection.
What is cystitis?
UTI assumed to be confined to the bladder
What are 3 main symptoms of cystitis?
Dysuria
Urinary frequency
Urinary urgency
What important differential diagnosis needs to be made for patients presenting with cystitis?
additional testing for STIs may be warranted
- like Chlamydia trachomatis and Neisseria gonorrhoeae
What is pyelonephritis?
More invasive upper UTI where inflammation of the kidney and renal pelvis is assumed to be present if patients have pain or tenderness involving the flank, together with other clinical or laboratory evidence of UTI
What are common symptoms of pyelonephritis?
Flank pain, flu like symptoms, headaches..
What is prostatitis?
inflammation / infection of the prostate gland
– may present as acute or chronic
What is an intrarenal abscess / perinephric abscess?
- collection of pus in the kidney or inthe soft tissue surrounding the kidney
What is the typical cause (not agent) of a UTI?
The patients own intestinal flora traveling up the urethra to the urinary tract
the majority of UTI’s are caused by..
the Enterobacteriaceae
- most infections are monomicrobial
What is the most commonly isolated pathogen in all UTIs?
E. coli
What do uropathogenic E. coli have that make them specially adapted to infect?
P. fimbriae
How do P fimbriae attach?
-P fimbria bind to the P blood group Ag present on uro-epithelial cells of 99% of the population
What 2 factors aid in resistance to complement dependent bactericidal effect of serum
Colicin V and hemolysins
What antigen is associated with upper tract infections?
K antigen
what are type 1 fimbriae involved in?
interbacterial binding and biofilm formation
What are the 3 classical uropathogens?
Proteus, Morganella, Providencia
What features are common to all the classical uropathogens?
production of urease
motility
fimbria for attachment
What is the result of urease action
- turns urea into ammonia which increases urine pH
- increased pH leads to crystal and struvite stone formation
- These block urine flow and provide a place for bacteria to establish biofilms
- there they can be protected from host defences and antibiotics
What % of UTIs are caused by Staphylococcus saprophyticus? coag neg or pos?
Coagulase negative
1-5% of UTIs
What test can be performed to determine if it is an infection with S. saprophyticus?
Resistance test to novobiocin
- S. saprophyticus is resistant while other staph like epidermidis are susceptible
What is the principle of the dipstick test?
detects presence of leukocytes and nitrites in the urine
- detection of both is what makes the test clinically relevant
What is the sensitivity/specificity of leukocyte and nitrite testing?
Detection of nitrites is reasonably sensitive for gram-negative bacteria but highly specific
Detection of leukocytes is sensitive but not specific
What concentration of bacteria in the urine is considered as true bacteriuria ? When is this value altered?
> 105 bacteria / ml. (108 / litre)
- lower numbers may be significant in children and in catheter collected specimens
What kinds of media/agar plates can be used to culture urine samples?
- SBA : because urine is sterile
- MacConkey because 99% of UTI’s are caused by gram negative bacteria. 90% are caused by the enterobacteriaceae so MacConkey will split this amount in half
- Chromagenic agar: can tell you what is growing based on the colour of the colonies due to certain metabolites being produced
What 4 methods of collection are used to obtain urine samples
- Midstream urine sample
- Collection bags (children)
- Indwelling catheters
- Suprapubic aspiration
What 4 factors influence the empiric management plan of UTIs?
- based on most probable pathogens
- lower vs upper tract infection
- local rates of resistance
- acute infection vs relapse / re-infection
What are the 3 first line drugs to treat uncomplicated cystitis ?
- Nitrofurantoin
- Fosfomycin
- TMP/SMX
Why is TMP/SMX being used less frequently?
because there are high (>20%) rates of resistance
What are 2 second line drugs for the treatment of uncomplicated cystitis
Doxycycline and Ciprofloxacin
What are the 2 drugs used to treat pyelonephritis?
- Ciprofloxacin
2. ß-lactam + aminoglycoside
