Enterococci

Question 1

1) classification

Answer 1

Family: enterococcaceae

• formally classified as group D steptococci
• 29 species
• leading cause of nosocomial infection
• most clinically important:
  E.faecalis (80-90%) of all enterococcal infection

E.faecium (5- 10%)

Part of normal gut flora
They do not cause infection
Only if they change normal habitat; such as vagina, urinary tract etc.

Question 2

2) morphology

Answer 2

• gram positive

- singly, pairs or chains

Question 3

3) growth characteristics

Answer 3

• facultative anaerobes
• 10 to 45oC
• non fastidious
• ferment carbohydrate
• typically non-hemolytic (can be alpha or beta)
• in contrast to other gram (+) catalase (-) cocci:

Grow in 6.5 NaCl
Grow in 40% Bile salts
Hydrolyse esculin
In pH- 9.6 (alkaline pH similar to V.cholera)

Question 4

4) antigenic structure

Answer 4

Have Lancefield group D antigen:

Glycerol teichoic acid antigen in their cell wall

Question 5

6) disease

Answer 5

UTI 
Endocarditis 
Bacteremia 
Wound infections 
Abscesses 

Ur WEBA

Question 6

7) microbiological diagnosis

Answer 6

> culture

Blood agar plate:
- very small or pinpoint colonies, that are usually nonhemolytic, and occasionally alpha or beta hemolytic

> specific tests

• Catalase: negative
• PYR: positive
  Pyrrolidonyl Aminopeptidase

In 6.5% NaCl broth
At pH 9.6
Between 15 to 45oC
In the presence of bile and hydrolyse esculin

Question 7

8) treatment and prevention

Answer 7

• resistance to aminoglycoside and vancomycin
  > transmitted by plasmids
• combine antibiotic therapy (synergy): an aminoglycoside (gentamicin or streptomycin) and a cell wall active antibiotic:
  >ampicillin + aminoglycoside
  >vancomycin + aminoglycoside
  > linezolid (in case of vancomycin resistance)

Antimicrobial susceptible tests
> disk diffusion susceptibility testing should be done routinely on isolated from significant infections