Which among the following is known as 'Eaton agent' which causes respiratory infection?

M. pneumoniae pneumonia is also referred to as Eaton agent pneumonia (the organism having first been isolated in the early 1940s by Monroe Eaton), primary atypical pneumonia, and "walking" pneumonia. A mild tracheobronchitis with fever, cough, headache, and malaise is the most common syndrome associated with acute M pneumoniae infection. The pneumonia is typically less severe than other bacterial pneumonias. It has been described as "walking" pneumonia because most cases do not require hospitalization. Ref: Hardy R.D. (2012). Chapter 175. Infections Due to Mycoplasmas. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.