A small puncture wound on a woman's arm has become swollen, hot to the touch, and intensely painful. There is tissue necrosis, but it is not "gassy," and under the microscope Gram-positive cocci in chains are present. Which of the following microbes is likely to be responsible?

A) Clostridium perfringensB) Pseudomonas aeruginosaC) Streptococcus pyogenesD) Staphylococcus aureusE) Sporothrix schenckii

The correct answer is C) Streptococcus pyogenes

Explanation:

Streptococcus pyogenes are aerotolerant, gram-positive cocci present in chains which come under the genus streptococci. They are important for humans clinically as they are responsible for fatal infections in humans.

It is also called group A streptococcus or flesh-eating bacteria. It is responsible for causing Necrotizing fasciitis which is a skin infection. This infection can occur when the bacteria get into punctured skin and grow there.

After the infection of this bacteria, the first symptoms are warm red skin which converts into red bump which grows further into blister bump that is intensely painful which can become fatal if not properly treated.

So here Streptococcus pyogenes is likely to be responsible.