T. zimbabwensis can infect mammals and possibly humans; this nonencapsulated species was detected in reptiles of Africa.

T. pseudospiralis infects birds and mammals, and has demonstrated infection in humans; it is a nonencapsulated species.

The nonencapsulated group infect saurians, crocodilians and other nonavian archosaurs (T. papuae, T. zimbabwensis) and birds (T. pseudospiralis).

It is also defined as a purulent nonencapsulated parenchymal infection of brain which is characterized by nonspecific features on CT (ill-defined low density area with peripheral enhancement) and cannot reliably be distinguished from neoplasms.

There has been a report that an 80kDa outer membrane protein on M. catarrhalis is immunogenic and common to all nonencapsulated strands of M. catarrhalis, which suggests that it may be used as an antigen for immunization.