3.7.4. Urinary Tract Infections

Question 1

Describe complicated UTI’s

Answer 1

1. serious infections
2. often catheter related in hospital settings
3. associated with metabolic disorders, secondary to anatomic or functional abnormalities that impair UT drainage or involve pathogens
4. Often involve kidney stones
5. Symptoms often non-specific

Question 2

Describe uncomplicated UTI’s

Answer 2

1. Sexual intercourse contributes to increased risk (as well as diaphragms and spermicides)
2. Women at increased risk
3. 10% of children acquire

Question 3

Factors that can compromise a sterile urinary tract

Answer 3

1. Bladder volume depletion
2. sexual intercourse
3. obstruction
4. instrumentation/catheterization
5. metabolic/ immunological state

Question 4

Describe manifestations of cystitis

Answer 4

Cystitis is the introduction of pathogens via the bowel, vaginal flora, or catheter that involves:

1. dysuria
2. frequent urination
3. Supropubic pain
4. rule out STI if sexually active

Question 5

Describe manifestations of pyelonephritis

Answer 5

Involves pathogen ascension from the bladder or hematogenous spread. Symptoms:

1. flank pain
2. fever
3. nausea, vomiting, chills
4. increased C reactive protein
5. bacteremia (30% of cases)

Question 6

describe uropathic E. Coli

Answer 6

1. Enterobacteriaceae family
2. normal intestinal flora
3. facultatively anaerobic
4. gram negative rods
5. oxidase negative

Question 7

virulence factors of E. coli

Answer 7

1. type I fimbriae. These contribute to bladder colonization and exfoliation
2. P pili. These adhere to digalactoside receptors which are important for kidney colonization
3. Hemolysin. These damage cell membranes
4. CNF toxin. These affect actin cytoskeleton by inhibiting rho GTPases

Question 8

Describe staph saprophyticus

Answer 8

1. gram positive cocci

2. adapted to urinary tract

Question 9

describe proteus mirabilis

Answer 9

1. contribute to biofilm formation
2. belong to eneterobacteriaceae family
3. swarming motility on agar
4. produces urease which causes salt precipitation (relate to kidney stones)
5. predilection for upper urinary tract
6. Gram negative facultative anaerobe

Question 10

lab criteria for positive urine culture of staph. saprophyticus

Answer 10

1. gram positive cocci in clusters
2. culture on blood agar
3. Hemolytic: aureas
4. non-hemolytic: other staph
5. catalase positive
6. coagulase negative: staph. epidermidis, staph. sapro.
7. Novobiocin susceptibility: resistant = S. sapro.

Question 11

urine culture uncomplicated UTA bacterial count

Answer 11

> 10E5 bacteria/ml single species

Question 12

urine culture complicated UTA bacterial count

Answer 12

10E2-10E4 bacteria/ml

Question 13

Effective oral therapy for most UTI

Answer 13

Trimethoprim. This inhibits bacterial dihydrofolate reductase which leads to bacterial stasis. (enterococci can incorporate dihydrofolate and tetrahydrofolate from urine increasing MIC by 60-357 fold)

Question 14

What are common treatments for UTI?

Answer 14

1. antibiotics (cephalosporin, timethroprim sulfate). Antibiotic resistance is common
2. Phenazopyridine (pyridium) to relieve pain

Question 15

risk factors for uncomplicated UTI

Answer 15

female (esp. sexually active), elderly, pregnant

Question 16

risk factors for complicated UTI

Answer 16

metabolic disorders, kidney stones, catheter use

Question 17

bacterial pathogen most often cause of uncomplicated UTI

Answer 17

E coli. can also be any of enterobacteriaceae family or staph. saprophyticus.

Question 18

two types of colonization pili produced by UPEC (uropathogenic E. Coli)

Answer 18

1. type 1: cause exfoliation of bladder cells to increase adherence. Important for bladder colonization
2. P pili: adhere to digalactoside-receptors (P blood group). important for colonization of the kidney

Question 19

common causes of complicated and catheter-related UTI

Answer 19

1. biofilms on indwelling medical devices

2. invasive procedures

Question 20

compare/contrast S. aureus, S. epidermidis, and S. saprophyticus for reservoir/key lab tests

Answer 20

S. aureus: coagulase positive
S. epidermidis/ S. saprophyticus: coagulase negative
S. saprophyticus: novobiocin resistant

Question 21

lab characteristics of P. aeruginosa

Answer 21

gram negative rods, non-lactose fermenter on MacConkey agar, pyoverdin (green fluorescent spore) producer, oxidase positive

Question 22

Why is P. aeruginosa such a successful nosocomial (hospital acquired) pathogen?

Answer 22

ubiquitous nature, resistance to detergent, resistant to antibiotics, forms biofilm, multiple colonization factors

Question 23

What role does urease produced by P. mirabilis play in UTI?

Answer 23

causes precipitation of salts in solution and may contribute to formation of kidney stones and complicated UTI

Question 24

How might lateral flagella (causes swarming in vitro) enable P. mirabilis to establish pyelonephritis?

Answer 24

They allow for swarming motility which allows for movement of organism up the urinary system

Question 25

Discuss Enterococcus faecalis and E. faecium with regard to antibiotic resistance

Answer 25

Faecalis is susceptible to amoxicillin and nitrofurantoin. It has developed some resistance to these but is sensitive to linezolid.

Question 26

How are UTI diagnosed in the laboratory? What is the importance of a “clean catch midstream” urine specimen?

Answer 26

Diagnosed by quantity in a specimen. Clean catch allows for clearance of perineum and for sampling the partially empty bladder, presumably a more accurate measurement.