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):
1

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)

2

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

3

What are the five most common causative agents in UTIs?

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

4

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

normal biota of the GI tract

5

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

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

6

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

0.5-0.7 episodes per year

("reocurring" in 25%-30%)

7

What are the two biggest risk factors for UTI?

  • Recent sexual intercourse
  • Catheterization

8

What abnormalities can presdispose children to UTIs?

anatomical or functional abnormalities of the urinary tract

9

What abnormalities can presdispose men to UTIs?

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

10

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

11

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

12

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

Urinary catheters

13

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.

14

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

15

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

LOWER

16

What does selective media contain?

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

17

What does differential media contain?

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

18

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

Catalase Test

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

19

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

20

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

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

21

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

22

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

23

When should you avoid treating with Nitrofurantoin?

  • Suspected pyelonephritis
    • due to poor upper urinary tract penetration

24

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

25

What are the recommended alternative treatments for UTI?

  • Fluoroquinolones = Ciprofloxacin/Norfloxacin
  • Amoxicillin/Clavulanate

26

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

27

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

UTI due to Staph saprophyticus

28

What UTI antibiotic treatment should NOT be used empirically?

Amoxicillin/clavulanate

29

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

30

What type of infection causes yellow, frothy discharge?

trichomoniasis

31

What color does beta-hemolysing bacteria turn blood agar?

Gold → complete hemolysis/digestion of RBC

(e.g. Staph aureus)

32

What color does alpha-hemolysing bacteria turn blood agar?

Green or brown → partical lysing of RBC

(e.g. Strep pneumoniae/viridans)

33

What color does gamma-hemolysing bacteria turn blood agar?

Pink → non-hemolytic

(e.g. Staph saprophyticus, Enterococcus)

34

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