Microbiology and Urinary tract Flashcards
How are UTIs classified?
Route of acquisition in the body
Site of infection
Route of transmission ( community acquired vs nosocomial)
What are the routes of acquisiton of bacteria in UTI?
Ascending from urethra to bladder (in cystitis) or kidney (in pyelonephritis)
Haematogenous from blood to kidney (in pyelonephritis/renal abscess)
What is renal abscess?
Pocket of pus formed in the kidney due to bacteria migration via ascending route from the urethra
What is a nosocomial infection?
Infection transmitted while in hospital. UTI is the most nosocomial infection
What is an upper UTI?
Pyelonephritis caused by ascending spread of bacteria from urethra to kidney
What is a lower UTI?
Cystitis or urethritis. Cystitis is caused by ascending spread of bacteria from the urethra to the bladder.
Cystitis
Inflammation of the bladder
What is the epidemiology of UTI?
Greatest prevalence in elderly population, and in men enlarged prostate with reduced urinary flow increases risk.
Generally women due to anatomical sex differences. Peaks at pre-school age due to poor hygiene routines. and the elderly population
Why are females at a higher risk for UTI?
Shorter urethra closer to perineum
What is the bacterial cause of UTI?
Uropathogenic E.Coli
Mycobacterium tuberculosis
What is Uropathogenic UTI?
Contains extra genetic material compared to commensal E.coli on pathogenicity-associated islands, coding for bacterial pathogenesis
What are the virulence factors of Uropathogenic E.Coli?
Type 1 fimbriae for attachment to mannose residues on host cells for upper UTI, associated with cystitis causing strains.
Type P fimbriae to adhere to urinary tract cells
K antigen prevents phagocytosis
What is the viral cause of UTI?
Adenovirus
BK and JC virus
What is the BK and JC virus
Associated with infection and graft failure in kidney transplant.
What is the parasitic cause of UTI?
Schistosoma hematobomium which resides in the bladder and causes inflammation, leading to cystitis
How does adenovirus cause UTI?
Typically causes gastroenteritis but can lead to haemorrhagic cystitis (blood in urine)
What increases risk of infection post-micrutition?
Urine remaining in
What are the host defences against UTI?
Retrograde urine flow
Urine chemistry
Secreted factors
Mucosal defences
What are the anti-microbial properties of urine chemistry?
Hypertonicity: causes water loss from microbe plasma membrane and leads to plasmolysis
Low pH
High urea concentration
What is the antibody defence in UTI?
IgA
What are the secretory factors against UTI?
IgA
Lactoferrin: milk derived protein which has high affinity for iron, a key element for organism growth.
What are the mucosal defences against UTI?
Very few receptors in urinary tract for targeting by micro-organisms
Mucopolysaccharides such as glucoseoaminoglyca forming protective layer
Secretion of Tamms-Horsfall anti-adhesive protein for bacteria fimbraie
What are the risk factors for UTI?
Female sex, catheterisation, Urinary tract surgery, pregnancy
Anatomical or congenital abnormality.
