Urinary Tract Infections Flashcards
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
Symptomatic bacteriuria
UTI
Culture results SUPPORT clinical diagnosis only
What technologies have been developed for rapid detection?
-Flexicult – for primary care – culture at the bedside in 24 h
-Rapid detection using molecular markers
=Presence of bacteria
=Presence of inflammation (active in urinary tract?= biomarkers like IL6)
=Presence of antimicrobial resistance genes
-Challenge of phenotypic vs genotypic resistance
*all antimicrobial Rx to be prescribed with diagnostic
What antibiotics are used for lower UTIs/ cystitis?
- Trimethoprim (200mg every 12 hours)
- Nitrofurantoin (100mg every 12 hours) if risk factors for trimethoprim resistance and eGFR>30
How are antibiotics used for cystitis?
Antibiotics are for amelioration and shortening of symptom duration in cystitis (self-limiting infection)
-RCT – trim decreased symptom duration by 4 days.
-What subgroup of patients could be managed without Antibiotics?
=Ibuprofen trial adverse events.
=25% culture negative
==Same symptom burden as culture positive
==Ibuprofen more effective as a treatment in culture negative group
What are the problems with antimicrobial use?
- Increases risk of recurrent UTI
- Increases antimicrobial resistance
How do we choose antibiotics?
-Do they need antibiotics?
-Dependent on clinical syndrome (where?)
=Nitrofurantoin for cystitis ONLY
-What is resistance risk?
=E.coli
==60-70% amox resistance
==30% trim resistance
-Oral vs intravenous
=are there signs of SIRS (systemic inflammatory response) or sepsis?
=some MDR organisms only have IV choices available
How are upper UTIs managed?
-Blood cultures
-Urine culture
-Gentamycin (bactericidal)
=Add amoxicillin (enterococcus)
=Add vancomycin
Review in 48 hrs
How are catheter associated UTIs managed?
-Do not use dipstick
-Blood culture and urine culture, change catheter
-Temp above 38, no evidence of focal infection elsewhere, rigor, suprapubic or flank pain, haematuria, delirium
=Gentamycin
How are UTIs managed in men?
-Is prostate involved (where?)
=Requires longer treatment and specific Abx to penetrate prostate
How are UTIs managed in pregnant women?
-Avoid contra-indicated antibiotics
-Treatment of asymptomatic bacteriuria
=Historically thought to decrease risk of development of pyelonephritis which can lead to pre-term labour
How are UTIs managed in children?
All children with confirmed UTI need investigation and consideration of vesico-ureteric reflux (causes renal scarring so transplants)
What is the advice for recurrent UTI?
- Fluid intake 2-2.5L per day (osmolarity)
- Encourage water, diluting juice, decaf drinks, avoid fizzy drinks
- Reduce alcohol – diuretic effect may cause dehydration
- Intercourse advice - lubrication, pre and post coital voiding, personal hygiene, positioning to reduce friction
- STI screening
- Hygiene – wipe front to back
- Avoid perfumed products and soap for intimate hygiene
- Treat constipation (obstruct flow of urine)
- Consider weight reduction
- Smoking cessation
Why do people get recurrent UTIs?
- High grade vesico-ureteric reflux
- Voiding dysfunction
- Periureteral E Coli colonisation
- E coli adhesions, bacterial reservoirs
- Frequent sexual intercourse, spermicides
- Familial tendency, uroepithelial cell susceptibility (secretor status), vaginal mucus properties
- Candidate genes
What drug helps prevent UTIs?
Methenamine= makes urine very hostile to bacteria
- High dose vitamin C for acidity
- Post-coital antibiotics
- Oestrogen replacement (topical vaginal)
