CD4 and ventilator-associated pneumonia: On the contrary, the bacterial specie M. massiliensis is associated with the absence of VAP occurrence which is on high interest due to the ability of M. massiliensis to produce valerate, butyrate, and pentanoate, decreasing the production of IL-6 in vitro, having HDAC inhibitory function and modulating both CD4 and CD8 T cells functions (62, –, 64).