MICRO: UTIs Flashcards
1
Q
risk factors for UTIs
A
- female (due to proximity of anus to vagina and shorter urethra so easy access to bladder)
- urinary tract obstruction
- vesicoureteral reflux (VUR)
- pregnancy
- diabetes mellitus due to glycosuria and neuropathy
- catheterisation
2
Q
3 main types of UTIs
A
- urethritis
- cystitis
- pyelonephritis
3
Q
who can have asymptomatic bacteriuria? do we need to treat this?
A
- pregnant women
- young children
- IDC
- elderly
- diabetics
- don’t really need to treat unless pregnant
4
Q
atypical UTI Sx in elderly ppl
A
- restlessness
- hallucination
- withdrawal
- agitation
- confusion
- nausea
5
Q
atypical UTI Sx in infants
A
- fever
- crying during urination
- cloudy, foul smelling or bloody urine
- irritability
- vomiting
- refusing to eat
6
Q
two types of recurrent UTIs
A
- relapse: another infection by the SAME organism (hide in epithelium and then regrow if immunocompromised/not on antibiotics anymore)
- re-infection: another infection from a DIFFERENT organism
7
Q
predisposing factors for recurrent UTIs - pre and post menopause
A
- pre-menopause: regular sex, spermicides, early onset UTI (<15 yrs)
- post-menopause: cystocele (prolapsed bladder), post-void residual volume, incontinence, Hx of pre-menopausal UTI, previous gynaecological surgery, (chronic prostatitis in males)
8
Q
Ix for UTI
A
- urine sample (dipstick or MCS): mid-stream (can get contaminated in young children so use a sterile bag attached to urethra), suprapubic aspiration, catheterised urine sample
- blood tests if febrile/sick: WCC, CRP, blood culture if upper UTI
- imaging (sometimes in children): renal/bladder ultrasound, voiding cystourethrogram (VCUG)
9
Q
4 main things to look for in urine dipstick
A
- leukocytes and blood: infection, damage, cancer etc
- nitrite: indicates gram -ve bacteria (convert nitrates > nitrites) = use broad-spectrum antibiotic
- pH: high pH can indicate proteus infection due to urease (urea > ammonia)
10
Q
2 main mechanisms of UTI pathophys
A
- most common: colonise urethra e.g. sexual intercourse, catheterisation, faeces then ascend to bladder
- haematogenous
11
Q
main bacteria causing UTIs
A
- most commonly normal bowel/perineal flora
- gram -ve: E. coli (UPEC), P. mirabilis
- gram +ve: staph saprophyticus (young, sexually active), S. epidermis, enterococcus
- rare: virus/parasites
12
Q
virulence factors on uropathogenic E. coli (UPEC)
A
- fimbriae: adherence to bladder wall
- capsular polysaccharide: inhibits phagocytosis and ascend to cause pyelonephritis
- haemolysin: damages blood cells and cell membrane > renal injury
13
Q
virulence factors on proteus bacteria
A
- urease enzyme (urea > ammonia) = makes urine more basic so it can survive
- can cause pyelonephritis and kidney stones (calculi)
14
Q
host defences against UTI
A
- low pH and chemicals in urine
- flushing action
- vesicoureteral valve - prevents reflux
- length of urethra: provides distance between bladder
- vaginal flora - prevents colonisation of lactobacilli
- bladder has protective mucus layer + can initiate inflammatory response
15
Q
lower UTI Sx
A
- dysuria: burning sensation
- urgency to urinate when you don’t actually need to
- frequency
- suprapubic pain
- fever absent or low-grade
- cloudy/smelly urine
- pyuria
16
Q
upper UTI Sx (pyelonephritis)
A
- fever, chills, shivering
- back/flank pain
- nausea/vomiting
- dysuria
- frequency
- haematuria, pyuria, bacteriuria
17
Q
urine culture process
A
- measure colony-forming units (CFU): how many colonies started from one individual cell (per mL of urine)
- > 10^5 CFU = UTI (doesn’t apply to suprapubic nephrostomy tube - would be much lower)
18
Q
measures to reduce risk of false results/contamination of urine sample
A
- do before starting antibiotics
- culture within 1-2h because new bacteria can grow = false results
- store at 4˚ for <18-24h before culture
- must properly collect mid-stream sample
19
Q
2 main media used for urine culture
A
- macconkey: selective and differential - identifies enteric gram -ve bacteria e.g. E. coli
- blood agar: rich media - allows gram +ve to grow and shows haemolysis
20
Q
what does UTI Tx depend on?
A
- location of infection: more urgent to treat pyelonephritis
- status: age, pregnancy
- severity of presentation
- likely pathogen + antimicrobial resistance
21
Q
how to treat UTI
A
- if uncomplicated (cystitis/urethritis): oral antibiotic for 3-5 days
- complicated (pyelonephritis): IV antibiotics for 10-14 days
- follow-up culture after Tx
22
Q
how to prevent UTIs
A
- drink lots of water (flushing)
- wipe from front to back
- urinate after sex
- avoid spermicide for sex
- postmenopausal: topical oestrogen and probiotics help normalise vaginal pH to support lactobacilli growth
