Streptococcus agalactiae bacteria

Streptococcus agalactiae

Streptococcus agalactiae picture Gram-positive cocci drawing

Streptococcus agalactiae on Columbia agar with 5% sheep blood (Bio-Rad™). Colonies of group B streptococci tend to be larger and often have less pronounced zones of beta-hemolysis than do other beta-hemolytic streptococci; some group B strains are nonhemolytic. The majority of group B streptococci produce a diffusable extracellular protein (CAMP factor) that acts synergistically with staphylococcal beta lysin to lyse erythrocytes.

Streptococcus agalactiae (also known as Group B streptococcus or GBS) is a beta-hemolytic gram-positive streptococcus. S. agalactiae is a species of the normal flora of the female urogenital tract and rectum. Its chief clinical importance is that it can be transferred to a neonate passing through the birth canal and can cause serious group B streptococcal infection. In the western world, S. agalactiae is one of the major causes of bacterial septicemia of the newborn, which can lead to death or long-term sequelae. S. agalactiae can also cause neonatal meningitis, which does not present with the hallmark sign of adult meningitis, a stiff neck; rather, it presents with nonspecific symptoms such as fever, vomiting and irritability and can consequently go undiagnosed until it is too late. Hearing loss can be a long-term sequelae of GBS-meningitis. Somewhat more rarely, S. agalactiae can also cause invasive group B streptococcal disease of the adult in the pregnant, elderly, or immunosuppressed. S. agalactiae is present in up to one-third of women of childbearing age, and one in every thousand live births will be affected by group B streptococcal infection. In the elderly or persons with compromised immune systems septicemia or other serious infections are seen. This occurs also rarely during pregnancy or maternity.

Abbreviated from Wikipedia.

Streptococcus agalactiae basic characteristics

  • GRAM-POSITIVE COCCI
  • NONMOTILE
  • NON-SPORE-FORMING
  • CATALASE: NEGATIVE
  • OXIDASE: NEGATIVE
  • FACULTATIVELY ANAEROBIC

Identification of Streptococcus agalactiae

  • catalase test (negative)
  • CAMP test (positive)
  • PYR test ( negative unlike S.pyogenes )
  • Lancefield's group B antigen presence(latex agglutination)



Antibiotic treatment of Streptococcus pneumoniae infections

Should be always guided by in vitro susceptibility tests!!
Selection of appropriate antibiotics depends on diagnosis!!

IF SUSCEPTIBLE:
  • penicillin

  • ampicillin
  • amoxicillin

  • cephalosporins I, II, III

  • macrolides

  • clindamycin

ALTERNATIVES:
  • vancomycin

Streptococcus agalactiae colonies on agar cultivation media

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Streptococcus agalactiae beta-hemolysis

streptococcus agalactiae streptococcus agalactiae streptococcus agalactiae streptococcus agalactiae streptococcus agalactiae streptococcus agalactiae streptococcus agalactiae

Streptococcus agalactiae CAMP test

streptococcus agalactiae streptococcus agalactiae streptococcus agalactiae streptococcus agalactiae

Streptococcus agalactiae Gram stain

streptococcus agalactiae

Useful Links

WIKIPEDIA
CENTERS FOR DISEASE CONTROL AND PREVENTION (CDC)
E-MEDICINE