UTI Micro- Debiel Flashcards
Why are B-lactam antibiotics not recommended as first line therapy for acute uncomplicated cystitis?
Widespread E. coli resistance rates above 20 percent!
What is the key feature distinguishing cystitis and pyelonephritis?
Pyelonephritis will have a fever
Only members of what bacterial family convert nitrate to nitrite?
Enterobacteriaceae (E. Coli)
What is the gold standard for diagnosing UTI?
Detection of bacteria in urine culture
First line treatments for uncomplicated cystitis?
Nitrofurantoin
Bactrim (Trimethoprim/sulfamehtoxazole)
First line treatment for acute uncomplicated pyelonephritis?
Fluoroquinolones (ciprofloxacin, levofloxacin)
OR
Bactrim or Ceftriaxone
What is the central pathogenesis for catheter associated UTIs?
Formation of BIOFILM (a living layer of uropathogens) on the urinary catheter
What are three phrophylactic strategies for UTI management?
Continuous Antibiotics
Postcoital antibiotics
Patient- initiated therapy
What are the 4 general defenses of the urinary tract?
- Mechanical flushing of urination
- IgA in urinary mucosa
- Urine chemistry = acidity, lysozymes, lactoferrin
- Surface proteins are different from other epitheliums
What are the 3 major threats to the urinary tract system?
Normal Biota (often from GI) Catheters Glomerular Nephritis (strep pyogenes)
Does strep pyogenes from skin infection AND strep throat both cause damage to the kidneys?
YES!
What is the leading cause of both complicated and uncomplicated UTIs?
E. Coli
Second leading cause of UTIs, and common in young sexually active females?
Staph. saprophyticus
Are E. Coli strains that cause UTIs the same strains that cause diarrhea???
NO! THEY ARE NOT! E. coli strains that cause UTIs are NORMAL FLORA of the GI tract
Name two risk factors for UTIs
Sexual intercourse
Catheterization
What are the most common type of nosocomial (hospital-related) infections?
Catheter- related UTIs
Are UTIs common in children? When would you see a UTI in a child?
Not common. If see in child it is usually an anatomic or functional abnormality
UTIs more common in women or men? When would you see a UTI in a man?
more common in women
In men, usually underlying urinary tract abnormality = obstruction from an enlarged prostate
Define selective media
contains compounds that selectively inhibit growth of some microbes but not others
Define differential media
contains an indicator, usually a dye, that detect particular chemical reactions occurring during growth
How do you distinguish staph from strep?
Catalase test!
Staph is catalase +
Strep is catalase -
What does catalase enzyme do?
Converts hydrogen peroxide to water and oxygen
How do you perform a catalase test?
Putting a small inoculum of bacteria into hydrogen peroxide.
With catalase present there is a rapid release of oxygen bubbles
How do you differentiate Staph aureus from Staph saprophyticus?
Coagulase test
Staph Aureus = coagulase +
Staph Sapro = coagulase -
What are you looking for in a coagulase test?
- Bound coagulase (clumping factor) is bound to bacterial wall
- It reacts with fibrinogen and results in precipitation of fibrinogen on staph cells
- This causes cells to clump with bacterial suspension is mixed with plasma
How do you determine Staph epidermidis from Staph saprophyticus?
Both are catalase positive and coagulase negative
Look at sensitivity to novobiocin!
Sapro = resistant Epidermidis = sensitive
MOA of novobiocin?
Inhibits bacterial DNA gyrase in susceptible organisms
Gram + cocci
Catalse +
Coagulase -
Novobiocin RESISTANT
Staph Saprophyticus
When would you use flurorquinolones like ciprofloxacin?
Only use with severe symptoms and allergy to 1st line treatments OR
Bactrim was used in the last 3 months for UTI OR bactrim resistance in area is greater than 20%
What is the specific 1st line treatment for S. saprophyticus but is NOT suppose to be used empirically?
Amoxicillin/clavulanate
Gamma hemolysis bug (no clearing)
Staph saprophyticus
What colonies appear yellow with beta hemolysis when grown on blood agar?
Staph aureus
Describe MacConkey agar
Promotes growth of gram neg (and inhibits gram +)
Determines if they can ferement lactose
If you can ferment lactose colonies will appear pink
If you cannot ferment lactose the colonies will by colorless/translucent
Gram negative bacteria
Oxidase negative
Indole positive
Round pink circular colonies on MacConkey agar (can ferment lactose)
E. Coli
What protein chelates iron away from microorganisms that like to use iron for their ATP-generating reactions?
Lactoferrin
What component of our urinary tract inhibits most microorganisms from colonizing?
Surface proteins on epithelial cells
Why is urine cloudy in a UTI?
presence of WBCs and bacteria
What are the 2 names we use to differentiate categories of E. Coli that cause UTIs vs. diarrhea?
Uropathogenic E. Coli = UPEC
Extraintestinal E. Coli = ExPEC
What type of hemolysis does Staph saprophytic have?
Gamma hemolysis
Post-antibiotic course, itching, burning, vaginal discharge that is white like cottage cheese. WHat is the infection?
Candida Albicans Yeast Infection
What does Trichomonas discharge look like?
Yellow-frothy dischare
What type of hemoysis does staph aureus have?
Beta hemolysis
What kind of agar would you grow Klebsiella on?
What test would you then do to differentiate it from E. Coli?
MacConkey agar Indole testing (Klebsiella is indole negative)
