Gram staining
"Parachlamydia acanthamoebae" has variable Gram staining characteristics and is mesophilic. Trophozoites of "Acanthamoeba" hosting these strains were isolated from asymptomatic women in Germany and also in an outbreak of humidifier fever (‘Hall’s coccus’) in Vermont USA. Four patients from Nova Scotia whose sera recognized Hall’s coccus did not show serological cross-reaction with antigens from the Chlamydiaceae.