16.3 Microbiology- Urinary tract infections Flashcards
What is the most common aetiological agent causing UTIs?
E. coli
Community acquired: 80%
Hospital acquired: 40%
What is an aetiological agent that more commonly causes UTIs in males?
Proteus species
Where does Staph. saprophyticus live?
Skin, genital tract and peritoneum
What especially causes UTIs in hospital? What %?
Other GNRs (Klebsiella, Enterobacter, Serratia, Pseudomonas), G+ bacteria (Enterococcus, other Staph)
48% of hospital acquired UTIs
What happens in CMV UTIs?
Urine is potentially contaminated and could transmit the infection
How do most UTIs spread?
Ascending, up urethra, cause cystitis (sometime pyelonephritis)
Which bacteria can access the urinary tract via the blood? (3)
Staph. aureus (renal abscesses)
Salmonella Typhi (systemic, first sign often bronchitis)
TB
What is an innate immunity (epithelial) in the urinary tract?
Transitional epithelium resists colonisation by most bacteria
(epithelium is also relatively resistant)
What is a common source of UTI aetiological agents?
Microbiota that live in urethra and peritoneum
Why are UTIs more common in females? (2)
Short urethra, and urethra opens in the peritoneum
What could a young boy with a UTI indicate?
Abnormal urinary tract (so don’t just prescribe antibiotics)
What is vesicoureteric reflux? How can we diagnose this?
When bladder contracts and urine is pushed up into urethra (and even into kidneys)
Contrast up urethra into bladder
How do microbial factors such as adhesions (2 types) contribute to colonsiation?
What organism expresses these?
Type 1 pili: allow adherance to baldder
PAP (polynephritis associated pili): allow bacteria to adhere to transitional epithelium
Both expressed by E.coli
What has a polysaccharide capsule (contributing to colonosation)?
E.coli, Klebs (we don’t know how)
What forms a biofilm? What is this (and another example elsewhere)?
E.coli
It is a community of bacteria within a matrix (e.g. streptococcus producing acid within mouth from sugar)
What can haemolysin do?
Breaks down RBCs, can contribute to kidney damage (E.coli)
What are siderophores? What produces them?
Acquire iron (to grow better). Some E.coli produce
What produces urease? What does this do?
Proteus (males esp.) produces urease, promoting stone formation via change in urine pH
What are 3 virulence determinants of E.coli? Where do they have an effect?
PAP (kidneys)
Flagella (ureters)
Type I pili (bladder)
What is a filament forming bacteria (that contributes to virulence)?
E.coli
What is the most common (suspected UTI) sample? Why?
Mid-stream urine (prevent confusion from normal urethral microbiota and avoid prosthetic secretions)
What do we do if a UTI is suspected in a baby? What does this tell us?
Can collect sample from bag (not sterile), so only a negative culture is useful (this would exclude UTI)
How do we collect urine for sampling from a catheter?
Collect from catheter itself, NOT bag
When do we see eggs in the urine? What may be a symptom?
Shishtosoma, may see blood in urine
