Edwardsiella, Aeromonas, Plesiomonas & Vibrio Flashcards
Edwardsiella, Aeromonas, Plesiomonas, and Vibrio phylogeny:
What is Edwardsiella tarda? Is it motile? Where is it most commonly found?
facultative anaerobic Gram-negative rod in the Enterobacteriaceae family
yes - peritrichous flagella
terrestrial and aquatic environments
What kind of pathogen is Edwardsiella tarda?
opportunistic pathogen (Edwardsiellosis) of fish with zoonotic potential via foodborne and waterborne infection
What attachment and secretion virulent factors are present in Edwardsiella tarda?
ATTACHMENT: flagella, LPS, fimbriae
SECRETION: hemolysin, proteinase, T3SS, T6SS
How is Edwardsiella able to evade host immune system and form biofilm?
IMMUNE EVASION: serum resistance, capsule
BIOFILM: quorum sensing - releases signal molecules to attract others to increase the bacterial population
What are the causative agents of Edwarsiellosis in flounder, channel catfish/tilapia, and eel?
FLOUNDER: E. tarda, E. piscicida
CHANNEL CATFISH/TILAPIA: E. ictaluri
EEL: E. anguillarum
What are 3 symptoms of Edwardsiellosis in fish?
- granuloma in multiple organs
- ascites
- skin ulceration
What is the causative agent of Edwarsiellosis in humans? What are 2 symptoms?
E. tarda
- gastroenteritis —> diarrhea
- bacteremia/septicemia
What can Edwardsiella tarda cause in cows? How does it present? How is it differentiated from other bacteria causing similar signs?
typhlocolitis
- greenish fluid in abdominal cavity and fecal material
- deposition of fibrin in abdominal cavity
- ruptures of cecum and colon
- necrosis in cecum
+ growth on MacConkey agar
- growth on deoxycholate citrate agar
- growth on Yersinia selective agar
E. tarda rarely causes typhlocolitis in cows. What may have caused this infection?
- water supply contamination
- stress leading to immunocompromisation: post-partum, post-weaning, travel, living environment
How does Edwardiella tarda grow on blood agar, MacConkey agar, brilliant green agar, and XLD agar?
BLOOD: hemolytic
MACCONKEY: pale, colorless
BG: no growth (made for Salmonella)
XLD: reddish/black center
How does Edwardsiella tarda respond to oxidase and catalase tests? What serological tests can be used for diagnosis?
oxidase -, catalase +
agglutination, ELISA
How is Edwardsiella tarda infection treated/controlled in fish and humans?
FISH
- antibiotic therapy: oxytetracycline
- control with quarantine and water quality
HUMANS
- natural, spontaneous cure
- antibiotic theraphy
- debridement
What is Plesiomonas shigelloides? What makes it a unique member of Enterobacteriaceae?
Gram-negative, facultative anaerobic rod motile by polar and lateral flagella
only oxidase-positive member
Where is Plesiomonas shigelloides found in the environment? What kind of pathogen is it?
fresh water limited to tropical and subtropical regions
opportunistic pathogen of fish and reptiles with zoonotic potential
How does the arrangement of Plesiomonas shigelloides flagella alter depending on what media it is growing in?
LIQUID = polar
SOLID = lateral
What are the 2 sources of infection of Plesiomonas shigelloides in humans? What are 2 symptoms?
- ingestion of contaminated water or seafood
- contact with infected animals
~ gastroenteritis - watery diarrhea
~ bacteremia/septicemia
What 4 virulence factors affect Plesiomonas shigelloides pathogenicity?
- enterotoxins (diarrhea)
- LPS
- hemolysin
- iron acquisition system
A 7 y/o male gray wolf was found dead at a zoo after an exhibition. He presents with a swollen abdomen, hemorrhagic congestion and ascites, decolorization of the liver, air bubbles in the stomach, and splenomegaly.
Histology found rod-shaped bacteria in the liver parenchyma and hemorrhagic ascites.
Plesiomonas shigelloides infection is rare in zoon animals, what can contribute to it causing the death of this wolf?
- septicemia is possible, which leads to the systemic effects
- wolf has a history of storing food before it ate, which can lead to contamination
- exhibition = stress = immunocompromised
From what specimen can Plesiomonas shigelloides be isolated? How does it grow on blood agar, MacConkey agar, and Hektoen enteric agar?
wound or stool culture
BLOOD: hemolytic or non-hemolytic
MACCONKEY: colorless, non-lactose fermenter
HEKTOEN: green colonies, no use of carbohydrates
How does Plesiomonas respond to catalase, oxidase, and indole tests?
catalase +
oxidase +**
indole +
Why aren’t Plesiomonas shigelloides infections typically treated with antibiotics?
- treatment usually not required
- β-lactamase producers: cephalosporins, carbapenems, fluoroquinolones, trimethoprim-sulfamethoxazole
What is Aeromonas? In what 2 places is it typically found?
Gram-negative, facultative anaerobic straight rod
- fresh water - fish ponds and tanks
- normal flora of freshwater fish (opportunistic)
What are the 2 groups of Aeromonas?
- motile and mesophilic (moderate temp) = A. hydrophila = human pathogen
- non-motile and psychrophilic (low temp) = A. salmonicidia = fish pathogen
What virulence factors do Aeromonas use for attachment and secretion?
ATTACHMENT: type I and IV pili, flagella
SECRETION: exoenzymes, hemolysins, enterotoxins, T3SS, T6SS
How is Aeromonas able to form biofilms and resist the host immune system?
BIOFILMS: quorum sensing (cell-to-cell communication)
IMMUNE EVASION: capsule, slime layer
How does Aeromonas hydrophila infection affect freshwater fish and humans?
FISH: hemorrhagic septicemia and skin lesions
HUMANS: diarrhea, septicemia
- contaminated typically through contaminated water/seafood or open wound exposure to water
What are 2 common symptoms of Aeromonas salmonicida infection in fish?
- furunculosis in salmonids
- ulcer disease in goldfish
How does Aeromonas hydrophila and salmonicida grow differently on plated media?
A. hydrophila - hemolysis +, catalase +, oxidase +, growth at 37C for 24 hrs, large colonies, mobility +
A. salmonicida - hemolysis +, catalase +, oxidase +, growth at 25C for 48 hrs, small colonies, mobility -
What antibiotics are Aeromonas resistant to? What treatment is recommended?
penicillin, ampicillin, carbenicillin, ticarcillin due to β-lactamase production
- 3rd gen cephalosporins
- carbapenems
- tetracyclines
- aminoglycosides
- fluoroquinolones
- trimethoprim-sulfamethoxazole
What is Vibrio? What environment does it prefer?
Gram-negative, facultative anaerobic, curved rod motile by polar flagella
HALOPHILIC - present in brackish and seawater
What kind of pathogen is Vibrio? What are the causative agents of disease in humans, chickens, and eels?
opportunistic pathogen of fish and reptiles
HUMANS: V. cholerae, V. parahemolyticus
CHICKENS: V. metschnikovii
EELS: V. anguillarum
What is Vibrio cholerae the causative agent of? What allows it to cause symptoms? How is it treated?
cholera in humans
cholera toxin —> watery diarrhea —> dehydration —> death
oral rehydration therapy
What is Vibrio parahaemolyticus the causative agent of? What 5 virulence factors does it contain?
food poisoning in humans (typically from seafood)
- thermostable direct hemolysin (TDH)
- LPS
- T3SS/T6SS
- flagella
- adhesin (MAM7)
What is unique about Vibrio parahaemolyticus growth on blood agar?
does not grow on the usual blood agar containing sheep blood - must grow on Wagatsuma agar containing human/rabbit blood where it is hemolytic
What agar is best recommended for isolating and identifying Vibrio parahemolyticus? What else is used?
TCBS agar - greenish colonies
Mannitol salt agar - yellow colonies
How does Vibrio parahemolyticus respond to oxidase and catalase tests?
oxidase +
catalase +
What is Vibrio metschnikovii the causative agent of? What are its 2 main virulence factors?
cholera-like disease in chickens and other birds
- hemolysin
- verotoxin
How does Vibrio metschnikovii grow on blood agar and MacConkey agar? How does it respond to oxidase and catalase tests?
BLOOD: hemolytic - smooth, transparent colonies
MACCONKEY: grows poorly
oxidase -*
catalase +
In what animals does Vibrio anguillarum typically cause infection? What are 2 clinical signs?
saltwater eels and other fish
- skin necrosis
- hemorrhagic septicemia
What 4 virulence factors are important in Vibrio anguillarum?
- iron uptake system
- hemolysins
- metalloproteases
- flagella, pili, LPS
What specimen can be taken for Vibrio anguillarum isolation? How does it grow on blood agar? What is the agar of choice for its growth?
water samples, swab, infected tissue
+ 1% NaCl - hemolytic
TCBS agar - yellow colonies
In what 4 ways is Vibrio anguillarum infection typically treated/controlled?
- antibiotics - cephalosporins, gentamycin, nalidixic acid
- phage therapy
- probiotics
- vaccination
Edwardsiella, Plesiomonas, Aeromonas, Vibrio summary:
Plesiomonas shigelloides is intrinsically resistant to what class of antibiotics?
a. penicillins
b. cephalosporins
c. aminoglycosides
d. fluoroquinolones
A
An 11 y/o FS Border Collie developed severe soft tissue infection after swimming in saltwater. What organism if more commonly associated with the skin lesion?
a. Plesiomonas shigelloides
b. Aeromonas hydrophila
c. Vibrio vulnificus
d. Edwardsiella tarda
C
Which oxidase-positive and indole-positive organism is more commonly associated with freshwater injuries?
a. Aeromonas hydrophila
b. Vibrio parahaemolytica
c. Edwardsiella tarda
d. Escherichia coli
A
What is the most likely cause of death of tilapia, mallard ducks, and snowy egrets using the same pond?
Edwarsdiella tarda
