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CRRAB 2 > 2: ID - Bacterial UTI > Flashcards

2: ID - Bacterial UTI Flashcards

1
Q

What type of bacteria cause most UTIs? What % of the time is it this type?

A

Normal enteric flora, 95%. Note: these are not the species that cause GI disease.

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2
Q

What is ABU?

A

Asymptomatic bacteriuria. UTI minus symptoms.

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3
Q

First line antimicrobials for uncomplicated UTI for men vs women

A

Men: Fluoroquinolone or TMP-SMXWomen: Nitrofurantoin or TMP-SMX

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4
Q

Therapy for complicated UTIs

A

Individualized, based on culture results

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5
Q

Natural barriers to harmful pathogens in urinary tract (4)

A

acidity of urine, act of urination -> desquamation, mucosal lining, urethral sphincter

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6
Q

What percent of UTIs occur by bacteria ascending the urethra? How do the rest occur?

A

90%. Rest are hematogenous.

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7
Q

What makes a UTI complicated?

A

underlying factors -> predisposed to ascending bacterial infection e.g. catheter, anatomic abnl, obstruction of urine flow, poor bladder emptying.

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8
Q

How do antibiotic and spermicide use make UTI more likely?

A

Change vaginal flora allowing for overgrowth of E. coli.

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9
Q

Pathogen most common for acute uncomplicated UTI. What percent of the time? How does it accomplish this?

A

E. coli 75%. Special attachment factors for transitional epithelium

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10
Q

____ is the #2 cause of uncomplicated UTI and accounts for ___%, more frequent in ________.

A

Staphylococcus saprophyticus, 5-15%, younger women

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11
Q

5-10% of uncomplicated UTIs caused by what other enteric organisms?

A

Klebsiella, Proteus, Enterococcus, Citrobacter.

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12
Q

Most common cause of complicated UTI

A

E. coli

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13
Q

Other causes of complicated UTI

A

Aerobic and facultative anaerobic gram neg rods inc: Klebsiella, Proteus, Citrobacter, Acinetobacter, Morganella, and Pseudomonas. Gram Pos: enterococci and staph aureus. Yeasts. (prob don’t need to know all these, just that there are many).

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14
Q

E. coli virulence factors contributing to UTI

A

Surviving low pH + surface adhesions. P fimbriae: hair-like protein interacting w renal epithelial cells, important in pyelonephritis and subsequent bloodstream invasion. Type 1 pilus (fimbria): all e. coli possess, not all express, mediate binding to uroplakins on bladder uroepithelial cells.

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15
Q

How does Sulfamethoxazole work?

A

Inhibits PABA to DHF via dihydropteroate synthetase

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16
Q

How does Trimethoprim work?

A

Inhibits conversion of DHF to THF via dihydrofolate reductase

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17
Q

How do the fluoroquinolones work?

A

Bind topo II/DNA gyrase –> tension -> double strand breaks

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18
Q

How does nitrofurantoin work?

A

Bacterial nitrofuran reductase reduces the drug -> damage or inactivate ribosomal proteins

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19
Q

How does urine chemistry block colonization? (3)

A

Acidity, lysozyme (breaks down peptidoglycan), lactoferrin (binds iron to prevent microorganisms from scavenging it)

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20
Q

How do the epithelial cells of the urinary tract prevent colonization?

A

Surface proteins differ from those of GI tract - prevents most enteric from gaining a foothold

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21
Q

What adaptive immune response defends the urinary tract?

A

Secretory IgA (requires previous exposure)

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22
Q

How does normal flora of the urinary tract prevent pathological colonization?

A

Physical barrier

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23
Q

What are the 3 major threats to the urinary system?

A

Microorganisms moving from GI to urinary tract, catheters, immune system malfunction -> glomerulonephritis

24
Q

Cause of urine cloudiness in UTI (2)

A

Bacteria and WBCs

25
Q

Back pain with UTI symptoms suggests

A

Progression of infection to kidneys

26
Q

Cause of orange-tinged urine

A

Pyridium or blood

27
Q

Overall incidence of UTI in young women

A

0.5-0.7 episodes/year, recurring in 25-30%

28
Q

Most common cause of nosocomial UTI

A

Catheter related (40%)

29
Q

UTI in children suggests

A

Anatomic or functional abnormality

30
Q

What is the role of TLR4 in UTIs?

A

E coli’s LPS comes into contact w tissue TLR4 -> inflammation and tissue damage

31
Q

What do mice studies tell us about TLR4

A

Knockouts do not get symptoms of UTI. It is the inflammation triggered at TLR4 that causes damage.

32
Q

How many times more likely are UTIs in women than men

A

10-50x

33
Q

What does drinking cranberry juice help?

A

Blocks bacterial attachment to the epithelium

34
Q

Lab findings for uncomplicated UTI (2)

A

Pyuria: 10+ neutrophils/ high power fieldBacteriuria >10^5 CFU/ mL urine

35
Q

How may colony counts differ in complicated UTIs?

A

Can be much lower

36
Q

What laboratory analyses are possible for diagnosis of UTI microorganism?

A

Antibody assays, microscopic exam, growth-dependent microbiology

37
Q

What is selective media?

A

Contains compounds that selectively inhibit growth of some microbes but not others

38
Q

What is differential media?

A

Contains an indicator (dye) that reacts to a particular chem rxn during growth

39
Q

Two types of culture media

A

Chemically defined (defined medium) or undefined (complex medium)

40
Q

2 common microorganism culture tests

A

Catalase test, cytochrome oxidase test

41
Q

How does the catalase test work?

A

Put a couple drops of hydrogen peroxide on bacteria. Bubbles = catalase pos, nothing = neg

42
Q

Staph, enterococcus, and strep catalase status

A

Staph: catalase pos Strep: catalase neg, Entero: catalase neg

43
Q

What test can differentiate staph aureus from saprophyticus?

A

Coagulase: pos with aureus, neg with other staph (saprophyticus and epidermidis

44
Q

How does the coagulase test work?

A

Bacteria + fibrinogen = clumping? Pos: solid gelatin mass in test tube, neg test stays liquid.

45
Q

What test can differentiate between epidermidis and saprophyticus?

A

Novobiocin sensitivity test

46
Q

Novobiocin sensitivity/ resistance of epidermidis and saprophyticus

A

Epidermidis: sensitive. Saprophyticus: resistant

47
Q

What does novobiocin do?

A

Inhibits DNA gyrase in susceptible micoorganisms

48
Q

After taking antibiotics for a UTI, women are particularly susceptible to ____

A

Yeast, esp candida. This is an endogenous overgrowth.

49
Q

What microscopic finding is suggestive of yeast?

A

Hyphae

50
Q

Gram positive gamma hemolytic microorg

A

Saprophyticus or enterococcus (sapro statistically more likely)

51
Q

How does vaginal pH generally change with infection?

A

Decreased (acidic)

52
Q

What is gamma-hemolysis

A

Lack of hemolysis

53
Q

Staph aureus type of hemolysis and color on media

A

beta-hemolytic, yellow when grown on media

54
Q

Classify e. coli with regards to gram, oxidase, indole, and fermentation

A

Gram neg, oxidase pos, indole pos, lactose fermentation

55
Q

What is MacConkey agar?

A

Selective (against gram +) and differential (lactose ferm) media. Red-pink colonies are lactose fermenters while non-ferms are colorless

56
Q

What does the indole test test?

A

Ability of the organism to convert tryptophan into the indole. E. coli are indole positive.

CRRAB 2 (12 decks)

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