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Block 6 - Renal > Micro > Flashcards

Flashcards in Micro Deck (34):

What is the incidence of UTI in kids?

infants <3 months boys more common due to anatomic abnormalities
preschool girls more due to hygiene problems


Why does the incidence of UTIs in men increase over the age of 65?

BPH, urinary retention, incontinence, institutionalization


What kinds of microbes are involved in long term vs. short term CAUTI?

long term - polymicrobial
short term - monomicrobial


What are host defenses against UTIs?

vaginal pH <4.5
pH and high urea of urine
free unobstructed flow of urine
Tamm-Horsfall proteins from renal tubular cells capture bacteria with Type I fimbrae


What is the main mechanism of UTIs in children?

vesicoureteral reflux


What are red flags that can suggest an underlying anatomic abnormality in kids with UTIs?

recurrent inf
palpable kidney or poor urinary stream
unusual organisms
bacteremia or clinical sepsis
failure to respond within 48 hours
older boy
known dilation or abnormality of urinary tract on sonogram


Why do women get UTIs much more commonly than men?

shorter urethra
less distance from urethra to anus or vagina


What is the biggest risk factor for UTI in young women?

sex - transient urethral edema and obstruction of urinary flow
normal flora impacted by spermicides and recent antimicrobial exposure


What are risk factors for UTIs in older women?

post menopause - hormonal mucosal changes
urinary incontinence, antibiotic exposure, history of previous UTI
also still sex


How does pregnancy impact the risk for UTIs?

urinary retention and stasis due to enlarging uterus
ureteral compression (R>L)
loss of ureteral and bladder tone causes stasis
vecisoureteral reflex


Which bacteria cause UTIs in pregnant women in order from most common to least?

E. Coli
Group B strep


What is the normal response of UTIs in pregnancy to treatment with antibiotics and what are some complications?

Should resolve w/i 48-72 hrs
intrarenal abscess
perinephric abscess
resistance to antibiotics
alveolar injury can cause ARDS and edema


How do catheters cause UTIs?

if more than 30 days, bacteriuria is universal
disrupt epithelial mucosa and expose binding sites
biofilms form from exopolysaccharides
recognized by bacterial adhesins


What are adhesins associated with uropathogenic strains of E coli?

p fimbrae involved in invading kidney
type I fimbrae - mannose sensitive, more often in lower tract inf than upper UTI


What are toxins associated with uropathogenic strains of E coli?

hemolysin - injury to neutrophils and uroepithelial cells, children with UTIs and adults with upper UTIs
CNF1 - causes cytoskeleton rearrangement in host cells and apoptosis in bladder cells
Secreted autotransporters (Tsh, Sat, Pic) - serine protease activity


How do siderophores play a role in uropathogenic E coli?

allow bacteria to acquire host iron


What are uncomplicated UTIs?

women without anatomic abnormalities
usually monomicrobial
usually enteric GNRs, occasionally CAN staph or enterococci


What are complicated UTIs?

any male patient
female patient with other risk factors - obstruction, instrumentation, pregnancy
mono or poly microbial


What pathogens are associated with UTIs in children?

neonates have group B strep
if proteus, s aureus, or CAN staph found - consider anatomic abnormalities or immunodeficiency


What does the differential diagnosis of UTIs include?

vaginitis, urethritis (esp due to STDs like chlamydia), structural urethral abnormalities, PID, nephrolithiasis, appendicitis, prostatitis


What kinds of symptoms do children with UTIs present with?

nonspecific signs like fever, fussiness, diarrhea, constipation, vomiting, poor feeding, enuresis, prolonged neonatal jaundice
no rash


What does a dipstick urinalysis detect?

specific gravity, pH, leukocyte esterase, blood, nitrite, bilirubin, urobilinogen, protein, glucose


What does the microscopic exam of urinalysis detect?

Red cells, white cells, casts, crystals


What do cell casts in a UTI suggest?

kidney involvement


How does the nitrite test in urinalysis work?

nitrate in diet converted to nitrite by most bacteria
must be in bladder 4 hrs to happen - can get false negative


How does pyuria detection work in urinalysis?

generally leukocytes >5 WBC/hpf in true UTI
sterile pyuria can be in urine contamination, chronic interstitial nephritis, kidney stones, uroepithelial tumors, interstitial cystitis, rarely renal tuberculosis or inf like chlamydia


What agars are used in urine cultures?

sheep blood - nonselective
MacConkey - isolates gram- and differentiates lactose fermenting from non fermenting
CNA - isolates gram+


What CFU is suggestive of infection rather than contamination?

at least 10^5
some symptomatic women with pyuria will have inf with lower colony counts (still at least 10^2)
lower colony counts may represent true inf in those already being treated and men


If a patient with a catheter is symptomatic, what colony counts define a UTI?

>10^5 regardless of urinalysis results
>10^3 with evidence of pyuria


How are urine specimens collected in children?

no clean catch
catheterization or suprapubic aspiration


In children, what urine culture results indicate UTI?

symptoms PLUS pyuria or bacteriuria PLUS >10^4 bacteria


How are imaging tests used in UTIs?

not indicated for cystitis
considered in early eval of pyelonephritis
Ultrasound or CT can see abscess, urolithiasis, anatomic complications


What population should always receive imaging?

afebrile infants with UTI - renal and bladder ultrasonography
VCUG based on ultrasound results, if recurrent febrile UTIs, or hydronephrosis and scarring


What are the generic principles of treating UTIs?

treat asymptomatic only in pregnant - reduces risk of symptomatic - or about to undergo urologic procedures
if pyelonephritis - antibiotic should have systemic distribution, not concentrate in urine (no nitrofurantoin)
no ampicillin alone for E coli