Question:medium
A child presents with sepsis. The bacteria isolated showed beta hemolysis on blood agar, resistance to bacitracin, and a positive CAMP test. The most likely organism is:
A child presents with sepsis. The bacteria isolated showed beta hemolysis on blood agar, resistance to bacitracin, and a positive CAMP test. The most likely organism is:
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Beta hemolytic, bacitracin resistant, CAMP positive equals Group B Streptococcus.
Updated On: Jun 24, 2026
- Streptococcus agalactiae (Group B Streptococcus)
- Streptococcus pyogenes (Group A Streptococcus)
- Streptococcus pneumoniae
- Enterococcus faecalis
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The Correct Option is A
Solution and Explanation
A septic infant with this culture pattern is a Group B streptococcal case. The reconstructed traits, beta hemolysis, bacitracin resistance, and a positive CAMP reaction, line up only with $Streptococcus$ $agalactiae$.
Hemolysis: Clear beta hemolysis tells us we are dealing with a pyogenic Streptococcus, leaving Group A and Group B in play.
Bacitracin: The cheap bedside differentiator. Group A is killed by bacitracin, Group B is not. A resistant isolate is Group B.
CAMP test: Group B Streptococcus secretes the CAMP factor, which synergizes with the staphylococcal beta lysin to widen hemolysis into an arrowhead. A positive CAMP test seals the identification as Group B.
Clinical setting: Group B Streptococcus is the classic agent of neonatal early onset sepsis and meningitis, so a septic infant is exactly the expected host.
Eliminating the rest: S. pyogenes is bacitracin sensitive and CAMP negative. S. pneumoniae gives green alpha hemolysis and is optochin sensitive. Enterococcus grows in bile and 6.5 percent salt but is not CAMP positive. None fits the full profile.
\[\boxed{\text{Streptococcus agalactiae (Group B Streptococcus)}}\]
Hemolysis: Clear beta hemolysis tells us we are dealing with a pyogenic Streptococcus, leaving Group A and Group B in play.
Bacitracin: The cheap bedside differentiator. Group A is killed by bacitracin, Group B is not. A resistant isolate is Group B.
CAMP test: Group B Streptococcus secretes the CAMP factor, which synergizes with the staphylococcal beta lysin to widen hemolysis into an arrowhead. A positive CAMP test seals the identification as Group B.
Clinical setting: Group B Streptococcus is the classic agent of neonatal early onset sepsis and meningitis, so a septic infant is exactly the expected host.
Eliminating the rest: S. pyogenes is bacitracin sensitive and CAMP negative. S. pneumoniae gives green alpha hemolysis and is optochin sensitive. Enterococcus grows in bile and 6.5 percent salt but is not CAMP positive. None fits the full profile.
\[\boxed{\text{Streptococcus agalactiae (Group B Streptococcus)}}\]
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