Which organism is identified as sensitive to bacitracin?

Streptococcus pyogenes, also known as Group A Streptococcus, is the organism known to be sensitive to bacitracin. In laboratory settings, bacitracin is used as a selective agent to differentiate Streptococcus pyogenes from other streptococci species.

When a culture of bacteria is inoculated on a blood agar plate containing bacitracin, only Streptococcus pyogenes will exhibit a zone of inhibition around the bacitracin disk. This characteristic is due to the specific properties of its cell wall and the mechanism by which bacitracin disrupts bacterial cell wall synthesis.

In contrast, other organisms such as Streptococcus pneumoniae (which is primarily known for causing pneumonia and meningitis), Streptococcus agalactiae (Group B Streptococcus), and Staphylococcus aureus (which is a common cause of skin and soft tissue infections) do not show sensitivity to bacitracin in the same way. They either grow in the presence of bacitracin or exhibit varying levels of resistance. This selective sensitivity is a critical component in microbiological diagnostics to accurately identify streptococcal infections.