Intro to Bacterial UTIs - Diebel Flashcards Preview

CRRAB II Week 4 - WLB > Intro to Bacterial UTIs - Diebel > Flashcards

Flashcards in Intro to Bacterial UTIs - Diebel Deck (34):

What are the five major defenses of the Urinary Tract?

  1. Flushing action of urine flow (sloughing epithelial cells)
  2. Mucosa → secrete IgA (adaptive immunity)
  3. Urine chemistry
    1. Acidity
    2. Lysozymes (lyse peptidoglycan & cell walls)
    3. Lactoferrin (iron stealing → slows growth of bacteria)
  4. Surface proteins 
  5. Normal flora (outcompete pathogenic species)


What are the major microbial and immunological threats to the urinary system?

  • Normal biota → OPPORTUNISTIC bugs
    • often from GI tract
  • Catheter insertion
    • hospital acquired
  • Glomerulonephritis
    • Strep pyogenes from skin/throat


What are the five most common causative agents in UTIs?

  • Escherichia coli
  • Staphylococcus saprophyticus
  • Enterococcus species
  • Klebsiella pneumoniae
  • Proteus mirabilis


~95% of UTI cases are caused by what type of bacteria?

normal biota of the GI tract


What is the prevalence of community acquired Acute Urinary Tract Infections?

6-8 million cases of community acquired UTIs in the US per year


What is the overal incidence of Urinary Tract Infections in young women?

0.5-0.7 episodes per year

("reocurring" in 25%-30%)


What are the two biggest risk factors for UTI?

  • Recent sexual intercourse
  • Catheterization


What abnormalities can presdispose children to UTIs?

anatomical or functional abnormalities of the urinary tract


What abnormalities can presdispose men to UTIs?

  • Underlying urinary tract abnormality
    • enlarged prostate → obstruction
      • can also lead to prostatitis & epidydimitis


What is E.coli colonization dependent on in UTIs?

  • specific adhesions on the ends of long fimbriae (recognized by TLR4)
    • P fimbriae
    • Type 1 fimbriae
  • motility


What is the normal mechanism of "transmission" of E.coli in UTIs?

  • Not typically from person to person
  • More often from organ to organ!
    • women: anus → urethra
      • up to 10x-50x more likely


What are nosocomial infections due to E.coli, K. pneumoniae, carbapenem-resistant Enterobacteriaceae (CRE), or vancomycin-resistant enterococci (VRE) associated with?

Urinary catheters


What three things are helpful to prevent UTIs?

  • Regular urination
  • Good hygiene
  • Drink cranberry juice
    • potentially blocks bacterial attachment to the epithelium
  • Vaccines in clinical trial.


What two laboratory findings are diagnostic in Uncomplicated UTIs?

  • Pyuria = 10+ neutrophils per high-power field of unspun, voided midstream urine
  • Bacteriuria = >105 colony-forming units (cfu) per mL of urine obtained from clean-voided midstream urine


In complicated UTIs, colony counts (colony-forming units) can be much _______ for diagnosis?



What does selective media contain?

  • Compounds that selectively inhibit growth of some microbes, but not others.


What does differential media contain?

  • An indicator (usually a dye)
    • detects particular chemical reactions occurring during growth


What quick and easy test can you use to differentiate between Staph or Strep?

Catalase Test

  • Catalase (+) = Staph
  • Catalase (–) = Strep


How do you test for catalase activity?

  • Put small drop of bacteria into hydrogen peroxide
    • if catalase present → rapid release of oxygen bubbles
      • catalase converts H2Ointo H2O + O2
    • if catalase absent → weak/lack of buble production


What test can you use to differentiate between Staph aureus vs. Staph saprophyticus?

  • Coagulase test
    • Staph aureus = coag +
    • Staph saprophyticus = coag –


How do you test for coagulase activity?

  • Add bacteria to plasma 
    • clot forms if bound coagulase or "clumping factor" is on the bacterial cell wall
    • reacts directly with fibrinogen causing cells to clump


If both bacteria are coagulase negative, how can you differentiate between Staph epidermidis or Staph saprophyticus?

  • Novobiocin (drug) Sensitivity
    • Staph epidermidies = sensitive
      • ring indicates inhibition of growth
    • Staph saprophyticus = resistant
      • no ring/disturbance in bacterial growth


When should you avoid treating with Nitrofurantoin?

  • Suspected pyelonephritis
    • due to poor upper urinary tract penetration


When should you use TMP-SMX to treat a UTI?

  • If local prevalence of E.coli resistence to TMP-SMX is less than or equal to 20%
  • If has not been used to treat a UTI in the last 3 months


What are the recommended alternative treatments for UTI?

  • Fluoroquinolones = Ciprofloxacin/Norfloxacin
  • Amoxicillin/Clavulanate


When is it appropriate to treat a UTI with Fluoroquinolones?

(Hint: 4 reasons)

  • With severe symptoms
  • Allergy to 1st line treatments
  • TMP-SMX used in the last 3 months for UTI
  • Infection acquired in locality with greater than 20% resistance to TMP-SMX


When is Amoxicillin/clavulanate a first line treatment for UTI?

UTI due to Staph saprophyticus


What UTI antibiotic treatment should NOT be used empirically?



What type of infection usually presents with vaginal itching, and discharge described as white, cottage cheese-like discharge starting soon after course of oral antibiotics?

Yeast infection => due to Candida


What type of infection causes yellow, frothy discharge?



What color does beta-hemolysing bacteria turn blood agar?

Gold → complete hemolysis/digestion of RBC

(e.g. Staph aureus)


What color does alpha-hemolysing bacteria turn blood agar?

Green or brown → partical lysing of RBC

(e.g. Strep pneumoniae/viridans)


What color does gamma-hemolysing bacteria turn blood agar?

Pink → non-hemolytic

(e.g. Staph saprophyticus, Enterococcus)


What is MacConkey agar used for?

selectively isolate Gram-negative and enteric (normally found in the intestinal tract) bacilli and differentiate them based on lactose fermentation

  • contains bile salts → inhibits Gram (+)
  • Using neutral red pH indicator:
    • utilize lactose => makes acid/lowers pH => pink colonies
      • e.g. E.coli, Klebsiella
    • Non-Lactose fermenting => makes ammonia/raises pH => white or colorless colonies
      • e.g. Proteus species