Streptococcus agalactiae, Enterococcus genus

Question 1

General Features and habitat of S. Agalactiae

Answer 1

Gram + (long chain cocci)

Habitat- human vagina (20-30% asymptomatic carriers) and GI tract

Question 2

Biochemical Properties of S. Agalactiae

Answer 2

Polysaccharide capsule
Hydrolyze Hippurate
Bacitracin Resistant (used to differentiate between Group A and B)
Catalase -

Question 3

Pathogenesis of S. Agalactiae

Answer 3

Newborns are infected at birth (50-75% acquire rate)

Question 4

Clinical Features of S. Agalactiae

Answer 4

Early onset disease- within 6 days of birth:
- Meningitis in neonates (#1 cause in neonates)
- Sepsis in neonates
- Pneumonia in neonates
Late onset disease- within 4 months:
Meningitis, bacteremia, osteoarthritis
In non-pregnant adults: (mainly > 60 years old)
Skin and bone infections, bacteremia, urosepsis, pneumonia

Question 5

Diagnosis of S. Agalactiae

Answer 5

beta-Hemolysis on Blood agar
CAMP positive (used to distinguish S. agalactiae from all other Streptococci)

Enhanced hemolytic activity when plated with S. aureus, seen as arrow-shaped
or butterfly-shaped pattern

Question 6

Treatment of S. Agalactiae

Answer 6

Penicillin or Ampicillin (intrapartum prophylactic - given to mother)

Question 7

Prevention of S. Agalactiae

Answer 7

Culture at 35-37 weeks of pregnancy- check if colonized (intrapartum prophylaxis)

Question 8

General Features and habitat of Enterococci Genus

Enterococcus faecalis, Enterococcus faecium

Answer 8

Gram +
Short chains or pairs
Habitat- normal intestinal flora, urethra and female genital tract

Question 9

Biochemical Properties of Enterococci Genus

Answer 9

Very resistant- both can survive up 6.5% NaCl (and high temperature)
Both are resistant to bile
Esculin hydrolysis (positive)
PYR + (to distinguish between certain Streptococci)
Catalase -

Question 10

Pathogenesis of Enterococci Genus

Answer 10

Nosocomial infection- 2nd most frequent Gram+ (after S. aureus)

• Easily growing (non-fastidious)- also causes to develop resistance rapidly
• Highly resistant (salt, bile)
• Biofilm formation

Question 11

Clinical Features of Enterococci Genus

Answer 11

Urinary Tract Infection (UTI)- catheter associated
Endocarditis and sepsis- cannula associated
Biliary tract (“Tree”) infection

Can also cause- peritonitis, abdominal abscess and meningitis (if spread in blood)

Question 12

Diagnosis of Enterococci Genus

Answer 12

Might be alpha, beta or gamma hemolysis- greyish, glittering, round-shaped colonies
Bile Esculin agar- hydrolysis esculin, forming black / dark-brown color (esculetin)

Question 13

Treatment of Enterococci Genus

Answer 13

Vancomycin Resistant Enterococci (VRE)- especially E. faecium Susceptibility test (e.g. disk diffusion) is essential
Linezolid- mainly used against VRE
Tigecycline

Question 14

Prevention of Enterococci Genus

Answer 14

Prophylactic use of Penicillin and Gentamycin in patients with damaged heart valves prior to intestinal or urinary tract manipulations