UTIs Flashcards
adult UTI
dysuria, frequency, and urgency with >100 organisms/mL urine culture.
pediatric UTI
tenderness in lower abdomen with inadequate urine flow and >50000 IUs/mL urine culture. frequency inversely proportional to age.
e. coli bacteriology
straight gram negative rod. facultative anaerobe. lactose fermenter. H2S negative, urease negative. may be mobile or nonmobile. normal GI flora.
e. coli pathogenesis
75% of UTIs are caused by e. coli. uropathogenic strains of E. coli carry virulence factor type 1 or P fimbriae, which mediates attachment to uroepithelial cells. diabetes is a risk factor. periurethral region is colonized, organism reaches bladder during sex. can proceed to kidney if untreated. leading cause of nosocomial bacteremia
UTI diagnosis
take urine samples. dipsticks and microscopy. semiquantitative culture
semiquantitative culture
transport urine quickly to lab. use loop to take known volume of sample. streak on agar plate. calculate CFU/mL corresponding to resulting colony number. check cultured organism for lactose fermentation, indole reaction, and antibiotic susceptibility.
e. coli treatment
cystitis: treat with trimethoprim-sulfamethoxazole or fluoroquinolone.
polynephritis or sepsis: fluoroquinolone, cephalosporin 3rd gen, test for antibiotic resistance
klebsiella/enterobacter/serratia group bacteriology
less pathogenic than e. coli. gram negative rods. opportunistic nosocomial infections. men, neonates, elderly at highest risk. ppl with history of urinary tract procedures/catheterization. antibiotic resistance is a major problem for whole group
k. pneumoniae pathogenesis
can be a primary pathogen, but usually with a predisposing condition like age, chronic respiratory disease, diabetes, alcoholism. large polysaccharide capsule defends against phagocytosis/complement. adhesins adhere to gut cells, siderophores chelate iron. causes lobar pneumonia with necrosis, abscesses, and hemorrhage. thick bloody sputum (currant jelly).
enterobacter pathogenesis
infections usually nosocomial. bacteremia, lower respiratory tract infections, skin and soft tissue infections, UTIs, endocarditis, etc. opportunistic. possesses exotoxin (cytolysin). antibiotic resistant!
s. marcenscens pathogenesis
opportunistic. bloodstream, lower resp tract, skin, Urinary tract. serratia can cause endocarditis and osteomyelitis in IV drug users.
kleb/entero/serratia diagnosis
begin with culture and gram stain. do urine culture if UTI. k. pneumoniae capsule gives mucoid appearance on agar. s. marcescens forms red colonies. more specific lab tests available
kleb/entero/serratia treatment
begin with aminoglycoside and cephalosporin. do not treat enterobacter with cephalosporin (resistance appears quickly).
proteus/providencia/morganella group bacteriology
enterobacteriaceae. gram neg rods. produce phenylalanine deaminase and urease, not lactose fermenters. some proteus swarm and make H2S. usually opportunistic. increasing resistance to extended-spectrum beta lacatamase.
proteus/providencia/morganella group pathogenesis
primarily cause UTIs. fimbriae attach to urinary tract epithelium. urease production raises pH of urine in bladder and leads to struvite stones. stones cause abrasion/inflammation and harbor more bacteria. untreated UTI obstruction leads to septicemia. proteus can cause pneumonia or wound infection. providencia may cause gastroenteritis. morganella is rarest.
