Urinary tract infections Flashcards
Epidemiology of UTI
Most common in females (50% in lifetime)- shorter urethra
Also common in the elderly- starts to affect both genders equally
Shown in infants (<3 months)- more males
Consequences of UTI [5]
Kidney damage- more frequently in younger children
Antibiotic resistance
Urosepsis
C.dif infections
Pre-term birth
Risk factors for UTI
- Lower [7]
- Upper [3]
Lower:
Being female
Diabetes- bacteria thrive in glucose inside urine
Catherisation
Prostatic enlargement
Vesico-enteric fistula (between bladder and bowel)
Sexual intercourse
Poor bladder emptying
Upper:
Having a lower UTI
Vesicoureteral reflux
Obstruction- i.e kidney stone
Uncomplicated lower UTI
Infection with no anatomical or neurological abnormalities of the urinary tract.
Includes:
- Cystitis: bladder inflammation
- Urethritis
- Prostatitis
- Epididymo-orchitis: inflammation of epididmysis and/or testicle
Pathogenesis of UTI
- Periurethral are is contaminated with uropathogen from the gut.
- The pathogens colon the urethra and migrate to the bladder.
- Pili and adhesins on the pathogen (E.Coli) allows colonisation of the bladder and invasion of umbrella cells.
- Neutrophils infiltrate to remove bacteria extracellular but bacteria multiply and some evade immune system.
- Surviving bacteria multiply and form biofilm. They release toxins and proteases to damage host cell.
- Damage of host cells release nutrients to promote bacterial survival.
- Bacteria colonise the kidneys and release toxins to damage tissue cells.
- Pathogen may cross the tubular-epithelial barrier in the kidneys and cause bacteremia.
Adherence of E.Coli
Uropathogenic E.coli (UPEC) expresses Type 1 pili.
- Allows colonisation, invasion and persistence
P-pilli on E.coli also confer tropism to the kidney- infection specificity to the kidney.
Invasion of E.coli
Type 1 pilus on E.coli binds to host cell- induces actin rearrangement
- Causes the host cell to uptake the E.coli
Toll like receptor-4 recognise LPS from UPEC and activates exocytosis of E.coli
- This is evaded by E.coli as they multiply in the cytoplasms to form intracellular bacterial communities (IBC)
E.coli can invade more host cells and form an intracellular reservoir
Factors secreted by UPEC to acquire nutrients form host cells.
Hemolysin A
- releases iron and other nutrients
Siderophores- scavenges iron
Blocking apoptotic pathways of host cells.
Filamentous morphology- difficult for neutrophils to kill
Evasion of E.coli
Toll like receptor-4 recognise LPS from UPEC and activates exocytosis of E.coli
- This is evaded by E.coli as they multiply in the cytoplasms to form intracellular bacterial communities (IBC)
E.coli can invade more host cells and form an intracellular reservoir
Cystitis
- Definiton
- Clinical signs and symptoms
Inflammation of the bladder, usually due to infection.
Symptoms and signs:
- Dysuria
- High urinary frequency in low volumes.
- Cloudy and offensive smelling urine
- Localised super-pubic pain
- NO FEVER OR SYSTEMIC SYMPTOMS.
Pyelonephritis
- Definiton
- Clinical signs and symptoms
Inflammation of the kidneys usually due to infection.
Signs and symptoms:
- Fever (>38)
- Flank/Loin pain and tenderness
- Vomitting and nausea
- Rigors
- Tachycardia
- Hypotensive
- Tacynpea
- Other symptoms associated with cystitis (dysuria, urinary frequency, cloudy and offensive smelling urine).
Urine dipstick test
Clinical diagnosis for UTI
- Test done at point of care
When to use- when symptoms are vague
What to look for:
- Nitrites
- Leucocytes
Negative for either = no UTI
Positive nitrites with suggestive symptoms for cytitis= treat for cystitis
Midstream urine
Method of obtaining urine for culture in UTI.
- Minimises urethral contamination
Lab is sent for culture if:
- Pregnant
- Child
- Man
- Pyelonephritis recurrence
- Failed treatment
- Abnormal UT
- Renal impairment
Methods of preventing UTI
Correcting underlying host causes
Behavioral changes:
- High fluid intake
- Void after sex
- Double voiding
Catheter associated UTIs
Catheters are commonly inserted
- Can develop UTI as bacteria attach to catheter
Bacteremia common with catheters (21% E.coli infection with UC inserted)
