Genito-urinary infections I Flashcards
What percentage of women have recurrent UTI episodes?
30%
Where does infection usually ascend?
Infec usually ascends from the external site up the UT continuum
= involve kidneys sometimes
Catherisation is a common route of infection
Why is the female urinogenital tract particularly vulnerable to infection with fecal bacteria?
As the urethra is shorter and nearer to the anus
Also due to the nature of intercourse
What is the main defence in the urinary tract?
Flushing out mechanism of urine
Define UTI
urethritis - urethra cystitis - bladder dysuria - painful urination pyuria - urine that contains pus Pyelonephritis- kidney infection, characterised by fever and back pain
Host and pathogenic factors of UTIs?
Bacterial attributes:
- Capsular antigens
- Haemolysins
- Urease
- Adhesion to uroepithelium
- Introital colonisation
Host factors:
- Renal calculi (host of capsular antigens, urease, haemolysins)
- Ureteric reflux
- Short urethra in women
- Catheterization (intoital colonisation)
How to diagnose UTIs?
Sampling of midstream Urine (with care) cloudy or clear haematuria? (urine might be pink) - culture on agar plates > 2x10(to the power) 5 cells/ml traces of protein, leukocytes >10/ml Raised nitrites (NO3- > NO2-)
Pure or mixed growth?
Gram Stain of isolated bacteria or direct staining from urine sample
What is the main cause of UTIs in a community setting?
E.coli- Gram Negative rod
Proteus mirabilis- Gram negative pleomorphic rod- swarming motility
Staphylococcus saprophyticus- Gram positive coccus
What is the main cause of hospital acquired UTIs?
Candida due to high levels of catheterisation
Cysteine-lactose-electrolyte-deficient (CLED) media features?
MacConkey agar features?
Rich media containing lactose and lacking electrolytes (salt) to repress swarming
Subsequent plating on Macconkey agar if E.coli suspected (although Gram stain informative).
Cysteine promotes growth of some E.coli strains
Lactose gives lactose fermentation info
Macconkey agar
- Pink colonies if lactose fermenter (e.g. E.coli)
- Yellow if non-fermenter
Appearance of bacteria?E
Escherichia coli - Large Yellow colonies, opaque, center slightly deeper yellow
Proteus - Translucent blue colonies
Staphylococcus aureus - Deep yellow colonies, uniform in colour
Staphylococci coagulase-negative (saprophyticus) - Pale yellow colonies
E.coli- UPEC features?
- Gram-negative motile bacillus
- Also causes GI-infections, but UTIs commonly caused by specific strains of E.coli known as UPEC
These differ at the genome level from enteric strains by having up to 1000 extra genes
Possesses potent adhesins for attachment to epithelium
UPEC Pilus adhesins types?
Type I pili:
Binds mannose receptors, common on glycoproteins in uroepithelium
P-fimbriae:
Binds to globobiose
Linked ceramide host lipids
Proteus spp features?
More common in older pts
Most common = proteus mirabilis
Can swarm over catheter surfaces (swarming motility)
Virulence factors?
Urease: urea» ammonia + CO2, raises pH of urine»> can cause precipitation of minerals to form kidney and bladder stones
IgA protease- reduces flushing…
Many pili adhesins
