Micro UTI Flashcards
e coli bacteriology
gram - rod, facultative, lactose fermenter, indole positive, H2S negative, urease negative
MCC uncomplicated UTI
uropathogenic e coli (autoinoculates from GI)
how do e coli become pathogenic
virulence factors on plasmids (normal GI flora otherwise)
what do uropathogenic strains of e coli have?
P fimbriae aka type 1 fimbriae virulence factor
leading cause of nosocomial bacteremia?
e coli
diagnosis of e coli UTI
urinalysis: dipstick (+ nitrates because bacteria are reducing nitrates, + leukocyte esterase because PMNs are present)
microscopy: RBC = hematuria; WBC = pyuria, WBC casts = upper tract infection
e coli treatment
cystitis: trimethoprim-sulfamethoxazole or fluoroquinolone
polynephritis or sepsis: fluoroquinolone, third generation cephalosporin for longer course
e coli prevention
nosocomial: prompt removal/switching of catheters
recurring: cranberry juice (tannins reduce fimbrae binding)
how is a UTI defined?
dysuria, frequency, and urgency with >10^5 organisms/mL by semiquantitative urine culture (use a loop)
> 50,000 for pediatric
list the bacteria that cause UTIs
e coli (MC) klebsiella/enterobacter/serratia proteus, providencia, morganella enterococcus species STIs pseudomonas aeruginosa staph saprophyticus strep B
klebsiella/enterobacter/serratia bacteriology
enterobacteriaceae (less pathogenic than e coli)
- gram -
- normal flora
- men, neonates, elderly highest risk
- Ab resistance a major problem
which bacteria is MC in people with urinary tract procedures/catherization UTI
klebsiella/enterobacter/serratia
e coli MC in previously-healthy
when is klebsiella pneumoniae most likely to cause UTI
usually with predisposing condition like old, chronic respiratory disease, diabetes, alcoholism
klebsiella pneumoniae virulence factor
1- large polysaccharide capsule defends against phagocytosis, complement
2- adhesins adhere to gut cells
3- siderophores chelate iron
MC nosocomial outbreak bacteria
- e coli
2. klebsiella pneumonia
when is enterobacter most likely to cause UTI
nosocomial, ICU bugs
-opportunistic, rarely causes disease in previously healthy
enterobacter virulence factor
exotoxin (cytolysin)
serratia marcenscens most likely to cause infections
opportunistic nosocomial pathogen
-endocarditis and osteomyelitis in IV drug users
klebsiella/enterobacter/serratia diagnosis
culture and gram stain
- k. pneumoniae polysaccharide capsule gives mucoid appearance
- s. marcescens forms red-pigmented colonies
treatment for klebsiella/enterobacter/serratia
begin with sensitivity testing - NO cephalosporin for enterobacter
-usually begin with aminoglycoside then cephalosporin
Proteus/Providencia/Morganella bacteriology
- enterobacteriaceae
- gram -
- produce PHENYALANINE DEAMINASE and UREASE
- NOT lactose fermenters
- produce H2S
- proteus “swarm”
when does Proteus/Providencia/Morganella cause infection
opportunistic nosocomial infections - all normal flora gone bad
Proteus/Providencia/Morganella virulence factors
- fimbriae attachment
- urease production raises pH or urine leading to struvite (ammonium magnesium phosphate) stones which then cause abrasion/inflammation and harbor more bacteria
Proteus/Providencia/Morganella differences
- morganella: rarest and causes lots of other things
- proteus: can also cause pneumonia or wound infection
- providencia: may cause gastroenteritis
