Chronic fatigue syndrome
Mycoplasma fermentans is a very small bacterium in the class Mollicutes. Like other mycoplasmas "M. fermentans" is characterized by the absence of a peptidoglycan cell wall and resulting resistance to many antibacterial agents. It is a possible human pathogen with roles suggested in many illness such as respiratory, genital, and rheumatoid diseases among others. Investigations have focused on a possible link to it being a cofactor in HIV infection as well as fibromyalgia, Gulf War syndrome and Chronic fatigue syndrome, however the belief that "M. fermentans" is pathogenic in such conditions has largely been disregarded after the failure of several large scale studies to find a link. Due to its incredibly small size it is difficult to determine the full extent of its role in human diseases, while "M. fermentans" has been implicated in a myriad of diseases, research at the current point has not conclusively proven its pathogenicity in humans outside of opportunistic infections.