UTIs

Question 1

Major defenses of urinary tract:

Answer 1

1. Chemistry of urine- pH, lysosyme, lactoferrin
2. Flushing action of voiding- sloughing epithelial cells
3. IgA against mucosal bacteria
4. Surface protein characteristics of UG tract (differ from GI tract)

Question 2

Major threats to UG system

Answer 2

1. GI tract- most organisms from here
2. Hematogenous spread from other organisms
3. Abnormal urethra/system: i.e. blockage, congenital abnormality; causing decreased flow

Question 3

Most common organisms of bacterial UTIs:

Answer 3

1. UPEC (80%)
2. Staph saprophyticus (especially in sexually active younger women) (10%)
3. Klebsiella, Citrobacter, and proteus mirabilis

Question 4

Most common cause of nosocomial infection?

Answer 4

Catheter-related infections

Question 5

Most common associations with pyelonephritis and papillary necrosis?

Answer 5

S-Sickle cell anemia
O- obstructive pyelonephritis
D- diabetes mellitus
A- analgesia abuse

Question 6

What type of scarring is involved in chronic pyelonephritis? How is this diagnostic?

Answer 6

Uneven scarring (equal scarring would not be present in this but other syndromes such as chronic glomerulonephritis)

Question 7

What are the serotypes of UPEC?

Answer 7

O- polysaccharide sugars in the outer membrane
K- capsule
H- repeating H segments in flagella

Question 8

Major virulence of UPEC?

Answer 8

1. Varies with serotype (O,K, H)
2. adherence- P fimbriae, Type 1 fimbriae
3. genes associated with resistance to serum bactericidal activity
4. increased K antigen production
5. toxins/other

Question 9

How do P fimbriae work?

Answer 9

Bind epithelial cell receptors with P blood antigen (globoseries)
Trigger LPS to increase TLR4 signaling

Question 10

How do Type 1 fimbriae work?

Answer 10

bind mannose containing host epithelial receptors (uroplakin I and II)
since it is competitive binding, this is inhibited in presence of mannose

Question 11

Treatment for carbapenem resistant strains?

Answer 11

polymixin B

Question 12

Treatment for vanco resistant strains?

Answer 12

linezolid

Question 13

Dx requirements for uncomplicated UTI?

Answer 13

Pyuria (>=10 neutrophils per high power field)

Bacteruria (>10^5 CFU/mL via midstream catch)

Question 14

Staph vs strep test?

Answer 14

catalase- determine if break H2O2 into H2O and O2

Staph is catalase positive

Question 15

Differentiating between staph species test?

Answer 15

Coagulase- does it clump?

Aureus is coagulase positive, others are negative

Question 16

Saprophyticus vs epidermidis test?

Answer 16

Novobiocin- test for resistance (would inhibit bacterial gyrase)
Saprophyticus is resistant, epidermidis is sensitive

Question 17

E.coli IMViC results:

Answer 17

indole positive and methyl-red positive

Question 18

Citrobacter IMViC results:

Answer 18

variable indole
MR and citrate positive
Negative VP

Question 19

Klebsiella IMViC results:

Answer 19

variable MR
Positive: VP and citrate
negative indole

Question 20

Proteus Mirabolis IMVic results

Answer 20

negative: indole
Positive: MR, citrate
variable VP

Question 21

Level of regional resistance that TMP-SMX can be used at?

Answer 21

<20% and no previous UTI treatment with TMP-SMX in last three months

Question 22

Nitrofurantoin MOA

Answer 22

inhibit bacterical acetyl-CoA to interfere with carbohydrate metabolism
excreted renally- contraindicated in renal dz

Question 23

Is nitrofurantoin safe during pregnancy?

Answer 23

Yes- BUT not during the last 4 weeks (it will cross the placenta and get into breast milk)

Question 24

TMP-SMX MOA:

Answer 24

blocks folic acid pathway

Question 25

Quinolone MOA:

Answer 25

inhibit topoisomerase II and IV to promote bacterial DNA cleavage
cannot take with antacids-will chelate drug