UTIs Flashcards
What is leukocyte esterase test?
a marker for increased neutrophils using the urine dipstick.
PMN >10 is a + test
What is the nitrite test?
It is a marker for most bacteria that cause UTI on the urine dipstick.
Most UTI bacteria cleave nitrates to nitrites
What are the two types of infections that fall under the blanket term “UTI”?
- Cystitis- infection of the bladder
- Pyelonephritis- infection of the kidney
UTI do NOT includes infections of urethra, prostate gland, testes or epididymis.
Describe how the epidemiology of UTI changes with age.
Infants boys due to contamination of the urethra with rectal flora (poor wiping technique)
Adults: Women > men due to proximity of urinary tract to vaginal tract, rectum, and the short urethra.
Elderly: Women > men, but there is an increase in older men due to prostate problems
Describe the recurrence rates of UTIs.
Women - recurrence of 25%
Men- recurrence 50% (less likely to get them, but if they do, they will continue to come back)
Describe the pathogenesis of UTI.
Bacteria in stool –> colonization of urethra, introitus–> bladder colonization—> REFLUX/OBSTRUCTION—> ascending infection
What are the 3 main natural defense mechanisms the body has against UTIs?
- lactobacillus of the perineal flora keep vagina pH t allow colonization
- pH, osmolarity and urea in the urine inhibit bacteria (if the urine is free flowing)
- Tamm-Horsfall proteins from renal tubular cells bind and capture mannose epitopes of bacteria with type 1 fimbrae
What are the risk factors for children to get UTI?
- anatomical abnormality
2. vesicouteral reflux (VSR) which sends urine from bladder back up through the ureter and to kidneys
What are the three anatomical reasons why women are more likely to get UTI than men?
- short distance anus –> urethra
- short distance vagina–> urethra
- short urethral tract–> less distance for the bacteria to go to get to the bladder
What is the most common risk factor for UTI in young women? Why?
sexual intercourse is the most common risk factor (honeymoon cystitis) because
- it leads to transient urethral edema and obstruction of urine flow
- spermicide and antimicrobials affect normal vaginal flora
What are the 5 most most common risk factors for UTI in older women?
- hormonally associated change in the mucousa (estrogen is protective) after menopause
- incontinence
- antibiotic use
- history of prior UTI
- sex
Why does pregnancy increase the risk of developing a UTI?
- physical/hormonal changes
- loss of ureteral and bladder muscle tone leading to functional obstruction of urine flow
- Uterine bulk can compress the right ureter leading to hydroureter and hydronephrosis
- VUR
What are the risk factors for men developing UTI?
- BPH with age can decrease or obstruct urinary outflow
- incontinence (diabetic nephropathy, vascular disease)
- institutional settings
What are the typical infecting organisms for UTI caused by catheter (CAUTI)?
enteric flora, skin flora, environmental organisms
What are the virulence factors associated with UPEC (uropathogenic E. coli)?
- Flagella
- adhesins
- Toxins
- siderophores
What are the 2 types of adhesins UPEC possess?
Which is more likely to cause cystitis?
Which is more likely to cause pyelonephritis?
Adhesins are pili or fimbrae that allow adhesion to epithelial cells of the colon, vagina, and uroepithelium.
- P fimbrae- invade kidney (p = pyelonephritis)
- Type I fimbrae- mannose sensitive and adhere to mannose receptor sites on Tamm Horsfall proteins. These are more likely to cause lower tract infections
What are the 3 main toxins associated with UPEC?
- Hemolysin- cytotoxic injury to PMNs and uroepithelial cells [children with UTI, adult upper UTI]
- Cytotoxic necrotizing factor 1 (CNF1) - cytoskeletal rearrangement of cells and apoptosis of bladder cells
- Secreted autotransporter proteins (Tsh, Sat, Pic) with serine protease activity
What is the function of siderophores of UPEC?
acquire iron for the bacteria
What is an uncomplicated UTI?
Is it more commonly cystitis or pyelonephritis?
What are the offending organisms?
It affects women without anatomical abnormalities or catheters.
It can be cystic or pyelonephrotic.
The offending organism is usually monomicrobial and is:
1. E coli
2. klebsiella
3. proteus
4. Staph saprophyticus -CONS is occassional
What makes a UTI “complicated”?
- male patients
- females with other risk factors (pregnant, instrumentation, obstruction)
It can be mono or polymicrobial depending on the underlying issue
What is the most common infecting organ for a child UTI?
neonates, anatomic abnormalities
Enteric flora.
Neonates- GB strep (from mother)
Anatomic abnormalities, primary immunodeficiency
- proteus mirabilis
- staphylococcus aureus
- CONS
A patient comes to see you and has fever chills, malaise, sepsis, flank pain, dysuria.
Lab tests show leukocytosis, pyuria, bactiuria, +/- bacteremia. There are occasional WBC casts.
What is the likely diagnosis and location?
Pyelonephritis- upper tract (kidneys, ureter)
A patient presents with dysuria, frequency and suprapubic pain.
Lab findings show pyuria and bacteriuria.
What is the likely diagnosis and location?
Cystitis in the bladder
A patient comes for a routine physical. They dont have any symptoms, but lab results show bacteriuria and pyuria.
What is the likely cause and location?
Asymptomatic bacteriuria in the lower urinary tract
