Enteric Bacterial Infections 2: More Enterobacteriaceae: Yersinia and the ICU Bugs

Question 1

What are the cellular characteristics of Yersinia enterocolitica and pseudotuberculosis?

Answer 1

Gram (-) oval rods, Lactose (-), Urease (+), Motile at 25C, nonmotile at 37C

Question 2

What is a useful cellular characteristic of Y enterocolitica and pseudotuberculosis that will allow for identification?

Answer 2

Motility at 25C and nonmotility at 37C

Question 3

What is the general mechanism of infection of the Yersinia enterocolitica and pseudotuberculosis?

Answer 3

Infection thru M cells and can either infect the epithelium from the basal side or use macros as Trojan horses

Question 4

What are the Virulence factors for Y. spp?

Answer 4

• Pili and Inv adhesin - M cell binding
• CNF - dermonecrotic toxin
• Yop - T3SS injects proteins into macros resulting in no phag. and no inflamm response

Question 5

What enhanced dietary intake would result in a greater likelihood of Yersinia infection? Why?

Answer 5

Enhanced by iron overload because Y. does not produce siderophores

Question 6

What reaction typically occurs following a Yersinia infection?

Answer 6

Reactive arthritis (“Can’t see, can’t pee, can’t climb a tree”) - Conjuctivitis, Urethritis, Arthritis;

Question 7

What is similar b/w Y. enterocolitica and Shigella enterocolitis?

Answer 7

Invasion of intestinal wall and risk of reactive arthritis

Question 8

What is a Pavlovian sign of Yersinia infection?

Answer 8

False appendicitis

Question 9

What is the process of culture of Yersinia spp?

Answer 9

Following cold enrichment, bugs grow on Cefsulodin-irgasan-novobiocin (CIN) agar

Question 10

How are Y. enterocolitica and pseudotuberculosis differentiated in lab?

Answer 10

P differentiated from e by fermentation of sorbitol and ornithine decarboxylase activity

Question 11

What is the general Tx for Yersinia enterocolitis? Bacteremia? Prevention?

Answer 11

• Enterocolitis - Replace fluids and electrolytes
• Bacteremia - trimethoprim-sulfamethoxazole or ciprofloxacin
• Prevention - clean/cooked food, handwashing

Question 12

In what scenario is Klebsiella pnemoniae typically seen?

Answer 12

Can be a primary pathogen, but typically seen in patients with predisposing conditions (Age, chronic respiratory disease, diabetes, alcoholism)

Question 13

Virulence factors for K. pneumoniae?

Answer 13

• Polysacc. capsule - antiphagocytic
• Adhesins
• Siderophores

Question 14

Pavlovian Syx of K. pneumoniae?

Answer 14

Currant jelly sputum

Question 15

What is a major concern of Klebsiella in the future?

Answer 15

Carbapenem-resistant K. pneumoniae spreading world wide

Question 16

What is the typical patient infected with Klebsiella?

Answer 16

Homeless alcoholic

Question 17

What is the virulence factor for Enterobacter?

Answer 17

Exotoxin (cytolysin)

Question 18

What is the typical scenario of a Serratia marcescens infection?

Answer 18

IV drug user

Question 19

Give a basic overview of bug ID for Klebsiella/Enterovacter/Serratia

Answer 19

• Culture and gram stain (Gram - rod)
• K. pneumoniae - polysaccharide capsule - mucoid appearance on agar
• S. marcescens - red pigmented colonies

Question 20

What is the typical Tx strategy for K/E/S?

Answer 20

1. Culture and AB resistance testing
2. Aminoglycoside and cephalosporin

Question 21

What is a red flag in enterobacter Tx?

Answer 21

Do not treat Enterobacter with cephalosporin

Question 22

What is an important strategy in the management of K/E/S?

Answer 22

Prompt removal/relocation of catheters, maintenance of respiratory therapy devices, minimize stay length, scrub down ICU

Question 23

Describe the cellular characteristics of Proteus/Providencia/Morganella

Answer 23

• Gram (-) rods
• Produce phenylalanine Deaminase
• Lactose (-)
• Urease (+)
• All normal flora gone bad

Question 24

What typical infections do Proteus/Providencia/Morganella cause?

Answer 24

UTIs

Question 25

What does the urease production of Proteus/Providencia/Morganella lead to?

Answer 25

Raise pH of urine in bladder and leads to struvite (Ammonium Magnesium Phosphate stones)

Question 26

What is the difference in presentation/occurence of UTIs in those with E. coli vs the Proteus/Providencia/Morganella group?

Answer 26

The PPM group UTIs typically occur as opportunisitic and cause struvite stones

Question 27

What in a patient’s history would make you suspect an PPM infection?

Answer 27

UTI, Hx of recent beta-lactam AB Tx

Question 28

What is the typical Tx strategy for Proteus/Providencia/Morganella? What if Indole (+) species?

Answer 28

• AB sensitivity test!
• Most sensitive to Aminoglycosides, Trimethoprim/Sulfamethoxazole
• Indole (+) - use cephalosporins