Urinary tract infections Flashcards
bacterias that cause UTIs:
- escherichia coli → 80%
- staphylococcus saprophyticus → 2nd leading cause → sexually active women
- klebsiella pneumoniae → 3rd leading cause
- proteus mirabilis
what specific characteristic does proteus mirabilis have
- produces ammonia → gives the urine a pungent or irritating smell
- associated with struvite stone formation
if you have a patient with a pungent urine and struvite stone formation, which bacteria do you suspect caused her UTI?
proteus mirabilis
most common cause of UTIs
UPEC
what’s the most important characteristic of UPEC that helps it to create infections
P fimbria (pyelonephritis associated pilli) bind to the urogenital epithelium → cystitis, pyelonephritis
why do cystitis happen?
infections can ascend from the urethra to the bladder
predisposing factors to develop cystitis
structural or functional abnormalities on the urinary tract → they prevent the bladder emptying and/or result in urinary stasis (prostatic hyperplasia, congenital malformations that cause vesicoureteral reflux, urinary bladder diverticulum)
sex (women) → urethra is shorter and anal and genital regions are in close proximity
pregnancy → hormonal changes may cause urinary stasis and vesicoureteral reflux
DM2, immunosuppression, kidney surgery
lower UTI =
cystitis (infection of the bladder), commonly accompanied by urethritis, can be associated with prostatitis in men
upper UTI =
infection of the kidneys and the ureter (pyelonephritis)
a UTI is considered complicated in which cases
men, pregnancy, postmenopause, children with atypical pediatric UTI, anatomical or functional abnormalities
healthcare associated UTI ?
most commonly catheter-associated UTI
clinical features of lower UTIs
irritative lower urinary tract symptoms (LUTS) → increased urinary frequency, urinary urgency, dysuria
hematuria
suprapubic tenderness
clinical features of upper UTIs
symptoms of lower UTI
fever
flank pain, costovertebral angle tenderness
fatigue/malaise; nausea and vomiting
how can you diagnose a UTI
urinalysis
urine cultures
best initial test to detect a UTI
urinalysis
how do you take a urinalysis sample
clean-catch midstream sample OR straight catheterization of the bladder
what are the posible findings of a urinalysis
- pyuria (WBCs in urine) → ≥ 5 WBC/HPF
- bacteriuria → positive urinary nitrites (bacteria like e.coli convert nitrates into nitrites)
- leukocytes may indicate pyelonephritis
- alkaline urine (PH > 8) → urease-producing organisms like proteus, klebsiella or staph saprophyticus
if you have a urinalysis with alkaline urine (PH > 8), what pathogens do you suspect caused your UTI
urease-producing organisms like proteus, klebsiella or staph saprophyticus
positive urinary nitrites in a urinalysis may indicate …
an UTI caused by e.coli (convert nitrates into nitrites)
when do you take an urine culture
use for suspicion for complicated UTI or uncomplicated cystitis with history of recurrent UTIs or ≥ 65
when do you consider positive urine culture
significant bacteriuria (≥ 10^5 CFU/mL) OR any organism in a specimen obtained by suprapubic aspiration
typical colony findings for:
- e. coli
- klebsiella pneumonia
- serratia marcescens
- proteus mirabillis
- pseudomonas aeruginosa
e. coli → intensely pink on MacConkey agar
klebsiella pneumonia → viscous colonies
serratia marcescens → often in red apperance
proteus mirabillis → swarming motility pattern
pseudomonas aeruginosa → blue-green pigment
antibiotic treatment for uncomplicated lower UTIs
Nitrofurantoin
+
Trimethoprim/sulfamethoxazole (TMP/SMX) OR Fosfomycin
**fosfomycin has the advantage of being a single dose medication
antibiotic treatment for complicated lower UTIs →
fluoroquinolones !
