Bacteria under Microscope

Enterococcus faecalis
Enterococcus faecalis microscopy, gram-positive cocci
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Centers for Disease Control and Prevention
Public Health Image Library (PHIL)
Bacteria under Microscope
 

Gram-stain:

Gram-positive cocci
 

Microscopic appearance:

Ovoid diplococci and cocci in clusters (in liquid media they grow in chains - formerly classified as streptococci (part of the Group D))
 

Clinical significance:
  • Enterococcus faecalisis a Gram-positive, commensal bacterium inhabiting the gastrointestinal tracts of humans and other mammals.
  • E. faecalis can cause life-threatening infections in humans, especially in the nosocomial (hospital) environment.
  • Urinary tract infections (UTI)
  • Bacteremia
  • Endocarditis
  • Meningitis
  • E. faecalis is resistant to many commonly used antimicrobial agents.
  • VRE (Vancomycin-Resistant Enterococcus)
    Text: Wikipedia
 

Colony morphology:

  
   
A B C
Enterococcus faecalis identification
A Non-hemolytic (gamma-hemolytic) colonies of Enterococcus faecalis on sheep blood agar. Cultivation 24 hours, aerobic atmosphere, 37°C.  
B Enterococcus faecalis on Bile Esculin Agar (BEA). Members of the genus Enterococcus are capable of growing in the presence of 4% bile and hydrolyzing esculin to glucose and esculetin. Esculetin combines with ferric ions to produce a black complex visible as black zones around colonies. Cultivation 24 hours in an aerobic atmosphere, 37°C.  
C Colonies of Enterococcus faecalis. Cultivated on Columbia agar with 5% defibrinated sheep blood, 24 hours in an aerobic atmosphere, 37°C. Grayish colonies without hemolysis (gamma-hemolysis). E.faecalis typically exhibits gamma-hemolysis on sheep's blood agar, but some strains are alfa-hemolytic or even beta-hemolytic (a plasmid-encoded hemolysin, called the cytolysin).  
 
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