Enterococcus

Question 1

What was Enterococcus assumed to be before it was seen as an individual genus? How was this separation done?

Answer 1

Streptococcus - in 1984, due to sequencing of the 16S rRNA gene

Question 2

How do Enterococci look under the microscope?

Answer 2

• Gram-positive
• occurs in pairs or short chains
• non-capsulated
• non-motile (no flagella)

Question 3

How does Enterococci respond to catalase tests? What is their Lancefield group antigen?

Answer 3

catalase negative
Lancefield Group D antigen

Question 4

What type of respiration do Enterococci undergo?

Answer 4

facultative anaerobe

Question 5

What are the 5 most widely used culture media for Enterococcus growth?

Answer 5

1. blood agar - non-hemolytic (γ)*
2. 40% bile esculin - produces dark colonies
3. MacConkey agar - ferment lactose, producing small dark-red, magenta colonies
4. Mannitol salt agar - high salt concentration*
5. Kenner-fecal agar - selective for Enterococcus*

Question 6

Even though they are non-spore forming bacteria, Enterococci are still…..

Answer 6

hardy
- can survive in hypotonic/hypertonic and acidic/alkaline conditions
- can withstand detergents, oxidative stress, desiccation, and heavy metals
- resistant to multiple antimicrobials (member of ESKAPE)

Question 7

In what 4 areas of the body is Enterococcus considered commensal?

Answer 7

1. colon/bile tract
2. oral cavity
3. urethra
4. vulva/vagina

Question 8

Where is Enterococcus considered the leading part of the microbiota? What does this entail?

Answer 8

gut and fecal microbiota - millions are excreted with feces daily into the environment, infecting soil, water, and food/feed

Question 9

What are 5 body structures used as virulence factors of Enterococcus?

Answer 9

1. collagen binding proteins
2. endocarditis specific antigens (pili)
3. surface proteins
4. enterococcal polysaccharide - cell wall acts as capsule
5. aggregation substance

Question 10

What is the purpose of the aggregation substance on the cell membrane of Enterococci? Why is it so dangerous?

Answer 10

binds to host cells or is used for bacteria-to-bacteria conjugation

trafficker or AMR genes by transferring them horizontally, allowing for acquired broad-spectrum antimicrobial resistance

Question 11

What 2 enzymes are considered virulence factors of Enterococcus?

Answer 11

1. gelatinase - digests gelatin, elastin, collagen, hemoglobin, and other bioactive peptides
2. hyaluronidase - destroys blood vessels and mucopolysaccharides of the connective tissue/cartilage for bacterial spread into deeper tissue

Question 12

What is the main toxin that Enterococci use as virulence factors? What 2 things does it do?

Answer 12

cytolysin/hemolysin (AKA bacteriocin)

1. kills RBCs and WBCs by forming a pore
2. killed Gram-negative bacterial competitors to defend its territory that contribute to niche control

Question 13

What unique secreted substance is Enterococci able to produce? What do they do?

Answer 13

sex pheromone

stimulates expression of aggregation substances that result in conjugation and acquiring and accumulation of plasmids

Question 14

What are 5 common diseases caused by Enterococcus based on species? What species causes 65-95% of the diseases?

Answer 14

1. septicemia in poultry
2. mastitis in cows
3. endocarditis in cattle and lambs
4. urinary tract infection in pets
5. chronic liver disease in humans

E. faecalis

Question 15

What 2 species of Enterococcus typically cause disease in poultry?

Answer 15

1. E. faecalis - affects birds of all ages, especially severe in embryos and young chicks; colonizes the intestines
2. E. cecorum - major cause of skeletal disease in adult broiler chicken, causing osteomyelitis, femoral head necrosis, spondylitis (back and neck pain due to inflammation of veterbral joints), and arthritis

Question 16

What zoonotic infection is Enterococcus a leading cause of in humans? What 3 specific conditions do they cause?

Answer 16

nosocomial infection (Staphylococcus and Pseudomonas too)

1. endocarditis
2. endodontic infection
3. urinary infection

Question 17

What 2 species of Enterococcus commonly cause infection in humans? What do they cause? What are some other less common species that can cause infections?

Answer 17

1. E. faecalis - nosocomial Enterococci infections
2. E. faecium - vanomycin and ampicillin resistance

E. durans, E. avium, E. gallinarum, E. casseliflavus

Question 18

How do Enterococci enter and exit the body?

Answer 18

enter orally - ingestion

exit via feces from the gut or through urine/milk from other body parts

Question 19

Since Enterococci are excreted in high concentrations in feces, what is it typically used as an indicator for?

Answer 19

• fecal contamination and hygienic quality of food, milk, and meat
• water and environmental contamination/pollution by fecal materials (sewage)

Question 20

Why is the treatment of Enterococci challenging? How do they compare to Steptococci, in this aspect?

Answer 20

multidrug resistance (ESKAPE)

Enterococci are naturally resistant to commonly used antimicrobial agents like β-lactams

Question 21

How do Enterococci able to spread AMR genes? What 2 species are most commonly MDR?

Answer 21

horizontally transfer plasmid to other bacteria using conjugation

• E. faecium**
• E. faecalis

Question 22

What 2 drugs should be used to treat Enterococci infection?

Answer 22

1. β-lactams: amoxicilin, vancomycin
2. carbapenem

Question 23

In what 4 ways are Enterococci infections controlled and prevented?

Answer 23

1. effective waste treatment of feces/manure and hygiene
2. water sanitation to reduce the incidence
3. ensuring proper cleaning and disinfection of facilities to reduce environmental reservoirs of the bacteria
4. preventing immunosuppressive diseases and conditions, since Enterococci tend to occur secondary to another disease