Enteric Bacterial Infections 2: More Enterobacteriaceae: Yersinia and the ICU Bugs Flashcards
What are the cellular characteristics of Yersinia enterocolitica and pseudotuberculosis?
Gram (-) oval rods, Lactose (-), Urease (+), Motile at 25C, nonmotile at 37C
What is a useful cellular characteristic of Y enterocolitica and pseudotuberculosis that will allow for identification?
Motility at 25C and nonmotility at 37C
What is the general mechanism of infection of the Yersinia enterocolitica and pseudotuberculosis?
Infection thru M cells and can either infect the epithelium from the basal side or use macros as Trojan horses
What are the Virulence factors for Y. spp?
- Pili and Inv adhesin - M cell binding
- CNF - dermonecrotic toxin
- Yop - T3SS injects proteins into macros resulting in no phag. and no inflamm response
What enhanced dietary intake would result in a greater likelihood of Yersinia infection? Why?
Enhanced by iron overload because Y. does not produce siderophores
What reaction typically occurs following a Yersinia infection?
Reactive arthritis (“Can’t see, can’t pee, can’t climb a tree”) - Conjuctivitis, Urethritis, Arthritis;
What is similar b/w Y. enterocolitica and Shigella enterocolitis?
Invasion of intestinal wall and risk of reactive arthritis
What is a Pavlovian sign of Yersinia infection?
False appendicitis
What is the process of culture of Yersinia spp?
Following cold enrichment, bugs grow on Cefsulodin-irgasan-novobiocin (CIN) agar
How are Y. enterocolitica and pseudotuberculosis differentiated in lab?
P differentiated from e by fermentation of sorbitol and ornithine decarboxylase activity
What is the general Tx for Yersinia enterocolitis? Bacteremia? Prevention?
- Enterocolitis - Replace fluids and electrolytes
- Bacteremia - trimethoprim-sulfamethoxazole or ciprofloxacin
- Prevention - clean/cooked food, handwashing
In what scenario is Klebsiella pnemoniae typically seen?
Can be a primary pathogen, but typically seen in patients with predisposing conditions (Age, chronic respiratory disease, diabetes, alcoholism)
Virulence factors for K. pneumoniae?
- Polysacc. capsule - antiphagocytic
- Adhesins
- Siderophores
Pavlovian Syx of K. pneumoniae?
Currant jelly sputum
What is a major concern of Klebsiella in the future?
Carbapenem-resistant K. pneumoniae spreading world wide
What is the typical patient infected with Klebsiella?
Homeless alcoholic
What is the virulence factor for Enterobacter?
Exotoxin (cytolysin)
What is the typical scenario of a Serratia marcescens infection?
IV drug user
Give a basic overview of bug ID for Klebsiella/Enterovacter/Serratia
- Culture and gram stain (Gram - rod)
- K. pneumoniae - polysaccharide capsule - mucoid appearance on agar
- S. marcescens - red pigmented colonies
What is the typical Tx strategy for K/E/S?
- Culture and AB resistance testing
- Aminoglycoside and cephalosporin
What is a red flag in enterobacter Tx?
Do not treat Enterobacter with cephalosporin
What is an important strategy in the management of K/E/S?
Prompt removal/relocation of catheters, maintenance of respiratory therapy devices, minimize stay length, scrub down ICU
Describe the cellular characteristics of Proteus/Providencia/Morganella
- Gram (-) rods
- Produce phenylalanine Deaminase
- Lactose (-)
- Urease (+)
- All normal flora gone bad
What typical infections do Proteus/Providencia/Morganella cause?
UTIs
What does the urease production of Proteus/Providencia/Morganella lead to?
Raise pH of urine in bladder and leads to struvite (Ammonium Magnesium Phosphate stones)
What is the difference in presentation/occurence of UTIs in those with E. coli vs the Proteus/Providencia/Morganella group?
The PPM group UTIs typically occur as opportunisitic and cause struvite stones
What in a patient’s history would make you suspect an PPM infection?
UTI, Hx of recent beta-lactam AB Tx
What is the typical Tx strategy for Proteus/Providencia/Morganella? What if Indole (+) species?
- AB sensitivity test!
- Most sensitive to Aminoglycosides, Trimethoprim/Sulfamethoxazole
- Indole (+) - use cephalosporins
