UTI Microbiology

Question 1

E. coli characteristics

Answer 1

Gram - bacilli, catalase +, oxidase -, reduces nitrates to nitrites. Indole +. Colonies appear green metallic on EMB agar. Ferments lactose.

Question 2

E. coli virulence factors

Answer 2

Surface adhesions, P. fimbrae, Type 1 pilus, LPS

Question 3

E. coli lab findings

Answer 3

Nitrites in urine, urease -

Question 4

Surface adhesions

Answer 4

Facilitate binding to epithelial cells (colonization)

Question 5

P fimbriae

Answer 5

Interacts with receptor on renal epithelial cells, important for pyelonephritis

Question 6

Type 1 pilus

Answer 6

Binds uroplakins on luminal surface of bladder uroepithelial cells, important for cystitis (not always expressed)

Question 7

S. saprophyticus characteristics

Answer 7

Gram + cocci, catalase +, coagulase -, novobiocin resistant

Question 8

Klebsiella pneumoniae characteristics

Answer 8

G- bacilli, lactose fermenting, facultative anaerobe. Colonies viscous w/large mucoid capsule

Question 9

Klebsiella pneumoniae virulence factors

Answer 9

pili, capsule

Question 10

Klebsiella pneumoniae lab findings

Answer 10

Urease + (associated with struvite crystals)

Question 11

Proteus mirabilis characteristics

Answer 11

G- bacilli, facultative anaerobe

Question 12

Proteus mirabilis virulence factors

Answer 12

pili, adhesions, capsule, flagella

Question 13

Proteus mirabilis lab findings

Answer 13

Urease + (associated with struvite crystals)

Question 14

Enterococcus characteristics

Answer 14

G+ bacilli, catalase -

Question 15

Enterococcus lab findings

Answer 15

Urease -

Question 16

Gold standard for UTI diagnosis

Answer 16

Urine culture.

Question 17

Most common bacteria in uncomplicated UTI’s (top several)

Answer 17

1. E. coli
2. S. saprophyticus (esp. in young females)
3. Klebsiella, proteus, enterococcus, citrobacter etc.

Question 18

Most common bacteria in complicated UTIs

Answer 18

1. E. coli

2. Klebsiella, proteus, citrobacter, acinetobacter, morgonella, pseudomonas etc.

Question 19

Pyuria in uncomplicated UTIs

Answer 19

10+ neutrophils/high power field of unspun, midstream voided urine.

Question 20

Bactiuria in uncomplicated UTIs

Answer 20

> 10^5 colony forming units/mL of urine from clean-voided midstream urine

Question 21

Colony counts in complicated UTIs

Answer 21

Can be much lower and be deceiving

Question 22

Catalase test

Answer 22

+: staphylococcal and micrococcal organisms

-: streptococcal organisms

Question 23

Coagulase test

Answer 23

+: staph auerus

-: staph epidermidis and staph saprophyticus

Question 24

Novobiocin test

Answer 24

Sensitive: epidermidis
Insensitive: Saprophyticus

Question 25

MacConkey Agar

Answer 25

Growth of G- organisms. Pink if able to ferment lactose (E. coli). Translucent if unable to ferment lactose

Question 26

Defenses of the urinary tract (5)

Answer 26

1. Flushing action of urine flow. Encourages shedding of epithelial cells–>lose microorganisms that are attached.
2. IgA secreted into mucosa. Helps control bacteria levels. Involved in adaptive immune response.
3. Urine chemistry. Acidity, lysozyme, lactoferrin.
4. Surface proteins on transitional epithelium different form GI.
5. Normal flora outcompete other pathogens from est. infections

Question 27

Lactoferrin

Answer 27

Steals iron away from cells

Question 28

Lysozyme

Answer 28

Lyses peptidoglycan breaking down cell walls

Question 29

Microbial and immunological threats to urinary system (3)

Answer 29

1. Normal biota (often from GI)
2. Catheter insertion (hospital acquired UTIs often from this. Can be more prone to antibiotic resistant infections).
3. Glomerular nephritis. Inappropriate immune function. Especially from strep. pyogenes (from skin or throat) that can lead to type 2 and 3 hypersensitivities.