Urinary Tract Infections Flashcards
(38 cards)
What are important questions to ask in infection medicine?
- What are risk factors for acquiring this infection?
- What are the organisms responsible?
- What is the pathogenesis?
- Where is the infection – local vs systemic?
- What is source and is there a seed (started in one place and gone to another?)?
Describe urinary tract anatomy
-Upper urinary tract (kidney, ureter)- pyelonephritis
-Lower urinary tract (sphincter, urethra, bladder)- cystitis
=Is it complicated?
Who gets uncomplicated UTIs?
- Normal urinary tract
- Normal immune system
What are the risk factors for uncomplicated UTIs?
-Females
-Those with previous UTI
-Sexual activity
-Vaginal infection
-Diabetes
-Obesity
-Genetic susceptibility
-Older age
=Oestrogen deficiency (atrophic vaginitis, depletes vaginal mucosa which host protective organism lactobacilli)
=Cognitive impairment
*Broadly similar risk factors between cystitis and pyelonephritis
Who gets complicated UTIs?
Patients how have factors that compromise urinary tract system or immune system
What are the risk factors for complicated UTIs?
-Urinary obstruction, e.g. prolapse, prostatic enlargement
-Urinary retention caused by neurological disease
-Immunosuppression
-Renal failure
-Renal transplantation
-Pregnancy
-Presence of foreign bodies
eg indwelling catheters (CAUTI*) or other drainage devices
*CAUTI are MOST common cause of secondary bloodstream infections
What organisms cause UTIs (uncomplicated/complicated)?
- E Coli= 75%/ 65%
- Klebsiella pneumoniae (gram negative and resistant)= 6%/8%
- S. saprophyticus= young sexually active women= 6%/2%
- Enterococci= 5%/11%
Why does UTIs occur?
- Contamination of urethra
- Colonisation, swim upstream into bladder
- Invade bladder wall (bacteria have pili and adhesions)
- Inflammatory response/ fibrinogen accumulation in catheter
- Neutrophil infiltration
- Immune system subversion, bacterial multiplication
- Biofilm formation
- Epithelial damage by toxins and proteases
- Ascend to kidneys
- Colonisation, host tissue damage= bacteraemia
How does the bacteria invade the bladder wall?
-Type 1 pili
-Multiplication to form intracellular bacterial communities (IBC)
=exfoliate OR form quiescent bacteria reservoirs (QIR)
*To cause pyelonephritis bacteria must express pyelonephritis associated (P) pili
What are the bacterial virulence factors?
-Adherence =Pili =Adhesins -Toxin production =eg haemolysins -Immune evasion =eg capsule -Iron acquisition (nutrient) -Other =Flagella (swim upstream)
What are the host’s antibacterial defences?
-Urine:
=Extremes of osmolality, low pH and high urea concentration inhibit bacterial growth
-Urine flow and micturition
-Urinary tract mucosa (bactericidal activity, cytokines)
-Urinary inhibitors of bacterial adherence:
=Tamm-Horsfall protein
-Inflammatory response
Where can the infection be in a male patient?
- Urethritis
- Prostatitis
- Epididymo-orchitis
- Cystitis (bladder)
- Pyelonephritis
Where is the source of infections?
- Uropathogen from gut
- Intracellular bacterial communities/quiescent intracellular reservoirs (recurrent UTIs)
- Haematogenous – rare
What are the seeds of infection?
- Bacteraemia common in pyelonephritis
- Perinephric abscesses
- Can rarely lead to remote deep seated infection
What is the clinical presentation of Pyelonephritis?
- Loin pain/flank tenderness
- Fever/rigors
- Sepsis
What is the clinical presentation of Cystitis?
-Dysuria, frequency, urgency, suprapubic tenderness
How does clinical presentation vary with age?
- In infants (<2yrs) – vomiting/fever
- In elderly - less localised symptoms – confusion/falls
What other questions may be asked on clinical presentation?
-Where is dysuria? =Throughout- urethritis =End- issue in external vaginal area =Dermatological- lichen planus, Bechet syndrome =Foreign body= stent or stone -Menstrual history -Sexual history
How do you diagnose UTIs?
- Dipstick
- Urine culture
- Urinary biomarker
Describe dipsticks
-ONLY TO BE USED IN PATIENTS <65
=asymptomatic bacteria
=Bacteria harmlessly live there, reside and colonise so positive test
-Useful ONLY in presence of clinical UTI symptoms – presence of nitrites (metabolite of bacteria) indicate a UTI is a possible. As low as 75% sensitivity.
=25% may have UTI and have nitrates negative of dipstick
Describe urine culture
-Types of sample
=Mid stream urine (prevent peri-urethral contamination)
=Clean catch urine
=Catheter sample urine CSU – from port not bag (urine sits in bag)
=Other- urostomy/cystoscopy/pad
-Most laboratories will only detect ≥104 – 105 CFU/mL
-Generally significant if >105 CFU/mL
Bacteriuria
Bacteria in urine
Significant bacteriuria
Indicates that the number of bacteria in the voided urine exceeds the number expected from contamination from the anterior urethra
Asymptomatic bacteriuria
Significant bacteriuria in a patient without symptoms
only ever treated in pregnant women
