Urinary tract infections Flashcards
What is another name for urinary tract infections?
Acute cystitis
How many women are affected by UTIs in their lifetime?
50%
What causes UTIs?
Bacteria
Fungi
What is pyelonephritis?
Infection of the kidneys
Following its spread from the bladder to the kidneys
What is urosepsis?
Spread of the urinary tract infection to the blood
Do UTIs happen more often in one gender?
Yes
Women are affected more often
Due to the anatomy of their bladders
What percentage of nosocomial infections are UTIs?
40%
What is the most common cause of UTIs?
Catherization
Why are UTIs important?
High prevalence
High economic burden
High human impact
Antibiotic resistance
Management is suboptimal
How many people are affected by UTIs worldwide?
150 million people
How do UTIs have large human impacts?
Adds one extra bed day to hospital patients
What percentage of E.coli are resistant to first-line antibiotics?
50%
Common UTI pathogens
Gram negative bacilli like E. coli, Klebisella, P. aeruginosa
Gram positive cocci like S.aureus, enterococcus
Candida
Uncommon UTI pathogens
Mycobacterium
Chlamydia trachomatis
What is the most common pathogen causing UTI?
E. coli
Which behaviours encourage bacteria to get into the bladder?
Sex
Horseback riding
Poor hygiene
What are common symptoms of cystitis?
Dysuria
Frequency
Pain
Blood in urine
WBC in urine
What are common symptoms in pyelonephritis?
Pain
Fever
Tachycardia
Nausea
What are common symptoms in urosepsis?
Increased heart rate
Low blood pressure
Rapid breathing
Shivering
What are common diagnostic tools for UTIs?
Dipstick analysis
Routine culture
Urinary microscopy
What does dipstick analysis test for?
Leukocyte esterase
Nitrite
What does routine culture test for?
Bacterial growth above 10^5 cfu ml-1
What does urinary microscopy test for?
White blood cells in the urine, observed under microscopy
What is the sensitivity of disptick?
46-66% in leukocyte esterase
6-18% in nitrite
What is the sensitivity of urinary microscopy?
61-70%
What are the disadvantages of dipstick analysis?
Misses infections
Only tests for leukocyte esterase, indicating the presence of leukocytes in the urine, and nitrites, indicative of gram negative bacteria
What does the nitrite on dipstick tests rely on?
The bacteria must be able to reduce nitrate
Only gram negative bacteria are able to do this
What are the advantages of dipstick analysis?
Quick
Cheap
What is the disadvantage of routine cultures to diagnose UTIs?
Guidelines show diagnostic cutoff at 100 000 colony-forming units of bacteria per ml of urine
UTIs may be present at lower numbers
Also discarded if more than one bacteria grow
What percentage of UTIs are recurrent?
25%
What are the three types of UTIs?
Acute
Recurrent acute
Chronic
What are the characteristics of chronic UTIs?
Lower urinary tract symptoms
Overactive bladders
Usually test negative for UTI
Pyuria
What is the treatment of chronic UTIs?
Requires long-term antibiotic treatments with various side-effects
What is LUTS?
Subacute UTI infections that don’t reach the diagnostic cutoff for UTIs
What is the relationship between UTIs and urinary incontinence?
There is a theory that UTIs are related to urinary incontinence, a condition that affects 1.5-22% of the population
What is the significance of the relationship between UTIs and urinary incontinence?
If a small proportion of patients has a bacteria-treatable-aetiology, their care could be transformed
What antibiotics are E. coli resistant to?
Third generation cephalosporins
Fluoroquinolones
What treatments are UTI sufferers relying on?
Carbapenems
Describe the urothelium
Highly specialised tissue
Highly stratified morphology
Slow turnover - 200 days to shed completely
What is the name of the cells making up the apical layer of the urothelium?
The umbrella cells
Which mechanism is used to turnover the urothelium?
Conveyer-belt-like mechanism
Describe how the urothelium turns itself over
The progenitor cells on the basal side of the urothelium makes new epithelial cells which replace the cells on the apical membrane
In a conveyer-belt-like mechanism
How do bacteria use the urothelium to evade immune attack?
Attach and invade the urothelium by going inside umbrella cells
The umbrella cells die following invasion, leaving gaps in the urothelium
Bacteria enter through these gaps to form pods or long-term reservoirs
How do bacteria form colonies?
Pods
Long-term reservoirs
What shape are bacteria in reservoirs?
Spherical
What happen to bacteria when they escape their reservoirs?
Change from spherical to normal rod-shape
Regain motility
Form longer filaments
List the hypotheses trying to explain the reason behind recurrent infections present in UTIs
Vaginal commensal dysbiosis
Genetic risks
Covert pathogens
Describe bacterial pods
Inside cells, bacteria divide to form huge colonies called pods
Bacteria change from rod-shaped to spherical to accommodate for the tight packing
Pushing of the epithelium leads to the formation of pods that explode to cause recurrent infection
What are the benefits of pods for bacteria?
Allows them to evade immunity and antibiotics
How do pods cause recurrent infection?
Pushing of the epithelium leads to the formation of pods that explode to cause recurrent infection
Example of an innate immune response by the urothelium to infection
Shedding of the umbrella cells
How can shedding of the urothelium cause issues
Allows small numbers of bacteria to invade into the deeper layers of the urothelium
Forms reservoirs that evade host degenses
They form intracellular pods by infecting and multiplying inside cells
Can bacterial pods form in immature cells?
No
How does filamentation act as an immune evading mechanism?
Tic tac shaped E. coli form longer filaments
These stick to the bladder, which allows bacteria to resist high tensile forces from the urine flow
Also, leukocytes cannot detect these filaments, so they allow the bacteria to evade immunity
Describe future research areas in UTI
Use other uropathogens
Models based on humans
Increase the understanding of the mechanisms behind UTI recurrences
Understand the role of commensal bacteria
Better antibiotic treatment
Explain the concept of covert pathogens
UTIs can be driven by short-lived but powerful urinary tract exposures to vaginal bacteria that are themselves not uropathogenic in the classic sense
= G. vaginalis
