Urinary Tract Infections Flashcards
Briefly describe the pathophysiology of urinary tract infections & name the likely causative microorganisms that can cause such infections.
1) Ascending route
- Colonic/fecal flora colonise periurethral area or urethra & ascend to bladder & kidney
- Higher risk in females > males due to shorter urethra, use of spermicides & diaphragms as contraceptives
- Usually by gram-negative GIT bacteria e.g. E. coli, Klebsiella, Proteus & Enterobacteriaceae
2) Descending route (rarer)
- Organism is likely found at distant primary site (e.g. heart valve [endocarditis], bone [osteomyelitis] -> bloodstream [bacteremia] -> urinary tract)
- Usually by gram-positive non-GIT microorganisms e.g. S. aureus & M. tuberculosis
What are the normal host defence mechanisms that are important in the prevention of UTI?
1) Increased micturition w/ increased diuresis, so as to empty bacteria in bladder as urine
2) Antibacterial properties of urine & prostatic secretion
3) Anti-adherence mechanisms of bladder preventing bacterial attachment to bladder
4) Inflammatory response with polymononuclear leukocytes (PMN) which phagocytose bacteria to prevent/control spread
What are some factors determining the development of UTI?
1) Competency of natural host defence mechanism
- Increased micturition & increased diuresis
- Antibacterial properties of urine & prostatic secretions
- Anti-adherence mechanisms of bladder
- Presence of polymononuclear (PMN) leukocytes
2) Size of inoculums
- Increased risk w/ urinary retention / obstruction
3) Virulence / pathogenicity of microorganisms
- e.g. bacteria w/ pili (E. coli) is resistant to washout or removal by anti-adherence mechanisms of bladder
What are some host risk factors that increase the risk of developing UTI?
1) Females > males (shorter urethra)
2) Sexual intercourse & use of diaphragms / spermicides (increase colonisation at vaginal area & change in vaginal flora)
3) Structural abnormalities in urinary tract
- Prostatic hypertrophy
- Kidney stones
- Urethral strictures (narrowing of urethra)
- Vesicourectal reflex (backflow of urine from bladder to kidney due to valve malfunction)
4) Neurological dysfunction (e.g. stroke, diabetes, spinal cord injuries -> urinary retention)
5) Anticholinergics (results in urinary retention)
6) Catheterisation & other mechanical instrumentation
7) Diabetes (risk of neuropathy & high sugar content in urine promotes bacterial growth)
8) Pregnancy
9) Genetic association (esp. mothers & sisters)
10) Previous UTI
What are some non-pharmacological counselling points that are recommended to minimise the risk of UTI?
1) Drink lots of fluid (6-8 glasses a day) to flush bacteria (watch for fluid restrictions)
2) Urinate frequently & go when you first feel the urge
3) Urinate shortly after sexual intercourse
For females specifically:
4) Wear cotton underwear & loose-fitting clothes to keep periurethra area dry
5) Wipe from front to back esp. after bowel movement
6) Modify birth control methods if having trouble w/ UTIs
Briefly discuss how UTIs are classified.
1) Complicated UTIs
- Associated w/ conditions that increase potential for serious outcomes & risk of therapy failure
- i.e. UTIs in men, children & pregnant women or recurrent UTIs
- Urinalysis & urine culture are indicated
2) Uncomplicated UTIs
- Usually in healthy pre-menopausal, non-pregnant women of child-bearing potential w/ no Hx suggestive of abnormal urinary tract
- Urinalysis & urine culture not routinely indicated unless pyelonephritis
- Note that this is an overly simplistic classification!
What are some factors that indicate that a UTI is likely to be a complicated one?
1) Males
2) Functional & structural abnormalities of urinary tract
3) Genitourinary instrumentation
4) Diabetes mellitus / immunocompromised hosts
5) Neurogenic bladder / renal insufficiency
What are some clinical symptoms presented in a patient who has a likely lower UTI?
- Dysuria, urinary urgency / frequency, nocturia
- Suprapubic heaviness or pain
- Gross hematuria
What are some clinical symptoms presented in a patient who has a likely upper UTI?
- Fever, rigour, chills & headache
- N/V & general GI symptoms
- Malaise
- Flank / abdominal pain
- Costovertebral tenderness (positive renal punch)
- Altered mental status, drowsiness & low alertness (esp. elderly pt.)
- Change in eating habits
Besides examining for signs of UTI via vital signs, laboratory test results & radiological imaging, what other objective results can be used for the diagnosis of UTIs?
1) UFEME
- Pyuria if WBC > 10 per mm3; signifies presence of inflammation that may / may not be due to infection -> Absence of pyuria = unlikely UTI
- Hematuria if RBC > 5/HPF
- Gram staining results
- Presence of WBC casts indicates upper UTI (casts = mass of cells/proteins formed in renal tubules)
- High number of squamous epithelial cells suggests high levels of contamination
2) Nitrite test (e.g. of chemical urinalysis)
- Positive indicates presence of gram-negative bacteria
- Only GN bacteria can reduce nitrate to nitrite
- False-negatives can be attributed to inability to detect Gram-positives or P. aeruginosa (able to reduce nitrite into NO), low urinary pH or frequent voiding / dilution of urine
3) Leukocyte esterase (LE) test (e.g. of chemical urinalysis)
- Positive indicates leukocyte activities
- Correlates w/ significant pyuria (WBC > 10 per mm3)
When is it necessary for pre-treatment cultures for a patient diagnosed with a likely UTI?
1) Pregnant women
2) Recurrent UTIs (relapse w/in 2 weeks or frequent)
3) Pyelonephritis
4) CA-UTI
5) UTI in men
What is the most likely microorganism causing uncomplicated UTI?
Are there other possible microorganisms that can cause uncomplicated UTI?
Most likely (> 85%): Escherichia coli Others include Staphylococcus saprophyticus (5-15%), Enterococcus faecalis, Klebsiella pneumonia & Proteus spp.
What is the most likely microorganism causing complicated UTI?
Are there other possible microorganisms that can cause complicated UTI?
Most likely (> 50%): Escherichia coli Others include Enterococci, more resistant strains Enterobactericeae (Klebsiella spp., Proteus spp. & Enterobacter spp.) & Pseudomonas aeruginosa (healthcare-associated).
What are possible risk factors that may result in complicated UTI caused by P. aeruginosa?
- Hospitalisation in the last 90 days
- Current hospitalisation >= 2 days
- Residence in nursing home
- Antimicrobial use in the last 90 days (consider ESBL resistance)
- Home infusion therapy
- Chronic dialysis
What is a likely contaminant that may be found in urine culture?
Yeast (candida)
If the urine culture results show that the infection is likely caused by Staphylococcus aureus, can we diagnose the current infection as an UTI?
No! Consider other primary sites of infection as S. aureus is commonly a result of bacteremia.
It is generally recommended to treat patients displaying asymptomatic bacteriuria with a course of antibiotics. True or false?
False!
Only pregnant women & patients undergoing invasive urologic procedures with mucosal trauma a day later are treated with Abx despite being asymptomatic.
Why is it recommended to treat pregnant women with asymptomatic bacteriuria?
Reduce development of pyelonephritis, risk of preterm (< 37 weeks) labour & low birth weight infants.
Why is it recommended to treat patients undergoing invasive urologic procedures with mucosal trauma a day later with a course of antibiotics?
Prophylaxis to prevent post-operative bacteremia & sepsis.
To obtain urine culture first, then start Abx based on AST & culture results 12-24 h (1-2 doses) before the procedure.
List all recommended first-line empiric Abx for the treatment of uncomplicated cystitis in women.
1) PO Nitrofurantoin 50mg QDS x 5 days
2) PO Cotrimoxazole 960mg BD x 3 days
List all recommended first-line empiric Abx for the treatment of cystitis in pregnant women.
1) PO Cefuroxime 250mg BD x 7 days
2) PO Cephalexin 500mg BD x 7 days
3) PO Amoxicillin-clavulanate 625mg BD x 7 days
What are some possible first-line empiric Abx for the treatment of uncomplicated cystitis in women with sulfa allergy?
1) PO Nitrofurantoin 50mg QDS x 5 days
2) PO Cefuroxime 250mg BD x 5 days
3) PO Cephalexin 500mg BD x 5 days
4) PO Amoxicillin-clavulanate 625mg BD x 5 days
List all recommended first-line empiric Abx for the treatment of complicated cystitis in women.
1) PO Cotrimoxazole 960mg BD x 7 days
2) PO Nitrofurantoin 50mg QDS x 7-14 days
3) PO Fosfomycin 3g EOD x 3 doses
List all possible empiric Abx for the treatment of community-acquired mild/moderate pyelonephritis in women.
First-line: 1) PO Ciprofloxacin 500mg BD x 7 days 2) PO Levofloxacin 750mg OD x 5 days Alternatives: 3) PO Cotrimoxazole 960mg BD x 14 days 4) PO Cephalexin 500mg BD x 10-14 days 5) PO Amoxicillin-clavulanate 625mg TDS x 10-14 days
List all recommended empiric Abx for the treatment of community-acquired severe pyelonephritis in women who require hospitalisation.
1) IV Ciprofloxacin 400mg BD
2) IV Cefazolin 1g q8h
3) IV Amoxicillin-clavulanate 1.2g q8h
4) Additional IV/IM Gentamicin 5 mg/kg to cover ESBL-producing E. coli / Klebsiella
List all recommended first-line empiric Abx for the treatment of community-acquired UTI in men w/o concern for prostatitis.
Tx similar to complicated cystitis in women
1) PO Cotrimoxazole 960mg BD x 7 days
2) PO Fosfomycin 3g EOD x 3 doses
List all recommended first-line empiric Abx for the treatment of community-acquired UTI in men with concern for prostatitis.
1) PO Ciprofloxacin 500mg BD x 10-14 days
2) PO Cotrimoxazole 960mg BD x 10-14 days
* Duration of Tx = 6 weeks if prostatitis is confirmed
If prostatitis is ruled out subsequently, possible to streamline ciprofloxacin to beta-lactams:
3) PO Cephalexin 500mg BD
4) PO Cefuroxime 250mg BD
5) PO Amoxicillin-clavulanate 625mg BD
Define ‘nosocomial UTI’.
Onset of UTI > 48h post-admission
Define ‘healthcare-associated UTI’.
UTI occurring in patients who have been hospitalised or underwent invasive urological procedures in the last 6 months or has indwelling urine catheter.
List all recommended first-line empiric Abx for the treatment of nosocomial / healthcare-associated pyelonephritis.
Broad-spectrum beta-lactams used for empiric Tx.
Consider the possibility of P. aeruginosa & other resistant bacterias present.
1) IV Cefepime 2g q12h +- IV Amikacin 15mg/kg/day x 7-14 days
2) IV Imipenem 500mg q6h x 7-14 days
3) IV Meropenem 1g q8h x 7-14 days
For less sick patients:
1) PO Ciprofloxacin 500mg BD x 7-14 days
2) PO Levofloxacin 750mg OD x 7-14 days
- Shorter duration if no longer febrile in 3 days
Define ‘catheter-associated UTI’.
Presence of symptoms or signs compatible with UTI w/ no other identifiable source of infection along with 10^3 cfu/mL of >= 1 bacterial species in a single catheter urine specimen in patients with indwelling urethral/suprapubic or intermittent catheterization (inserted for >= 48h), or in midstream voided urine specimen from patients whose catheter has been removed w/in previous 48h.
What are some factors that increase the risk of developing CA-UTI?
1) Duration of catheterisation (most impt; 3-5% chance of isolating bacteria per day)
2) Colonisation of drainage bag, catheter & periurethral segment
3) Diabetes mellitus
4) Female
5) Renal function impairment
6) Poor quality of catheter care, including insertion
If an indwelling catheter has been in place for _____ & still indicated, catheter should be replaced to hasten resolution of symptoms & reduce risk of subsequent CA-UTI bacteriuria & CA-UTI.
> 2 weeks at the onset of CA-UTI
List all recommended first-line empiric Abx for the treatment of symptomatic CA-UTI.
1) IV Cefepime 2g q12h +- IV Amikacin 15mg/kg/day
2) IV Imipenem 500mg q6h
3) IV Meropenem 1g q8h
* 7 days Tx if afebrile in 3 days; otherwise 10-14 days Tx
For less sick patients:
1) PO/IV Levofloxacin 750mg OD x 5 days
2) PO Cotrimoxazole 960mg BD x 3 days (for women <= 65 y/o w/ CA-UTI w/o upper urinary tract symptoms after indwelling catheter has been removed)
List all recommended first-line empiric Abx for the treatment of pyelonephritis in pregnant women.
1) PO Cefuroxime 250mg BD x 14 days
2) PO Cephalexin 500mg BD x 14 days
3) PO Amoxicillin-clavulanate 625mg BD x 14 days
What are some non-pharmacological recommendations for the prevention of CA-UTI?
1) Avoid unnecessary catheter use (trial of catheter to see if pt. can urinate w/o help of catheter)
2) Use for minimal duration
3) Long-term indwelling catheters changed before blockage is likely to occur
4) Use of closed system (less fiddling of catheter & urine bag)
5) Ensure aseptic insertion technique
6) Topical/Prophylatic antiseptic & antibiotics not recommended
7) Chronic suppressive antibiotics not recommended
What are some considerations when treating UTI in pregnant women?
1) Avoid fluoroquinolones
2) Avoid cotrimoxazole in first (neural tube defects in infants) & third (kernicterus) trimesters
3) Avoid nitrofurantoin at term (38-42 weeks)
4) Caution w/ aminoglycosides
5) Beta-lactams are first-line Abx
6) Duration of Tx = 7 days for asymptomatic bacteriuria & cystitis; 14 days for pyelonephritis
What are some general patient counselling points for Abx?
- This is an antibiotic to treat your _____ infection.
- Take _ tablets/capsules _ times a day / about _ hours apart. Take ___ food. Do not take together with ___, space _ hours apart.
- Side effects may include…
- Complete the whole _ day course unless signs of allergy (like rash, itch, swollen eyes) or serious side effects occur.
- If allergy or any intolerable effects occur, stop taking and see your doctor immediately.
- You should feel better in 2-3 days, if not, please see your doctor.
- Do remember to complete the course even if you feel better.
What are some adjunctive therapies for the management of UTI?
1) Pain & fever - paracetamol & NSAIDs
2) Vomiting - rehydration
3) Urinary symptoms - Phenazopyridine (Urogesic) 100-200mg TDS
What are the therapeutic goals & monitoring parameters in the treatment of UTI?
1) Resolution of signs & symptoms
- Improvement/resolution in 24-72h after effective Abx initiation
- If fail to respond clinically w/in 2-3 days or have persistent positive blood cultures, consider further investigation to exclude bacterial resistance, possible obstruction, renal abscess or other disease processes.
2) Bacteriological clearance
- Repeat culture not required for pt. who responded
- Culture to document clearance of infection in pregnant women.
3) Absence of ADR & allergies
