Tarja Kaijalainen et al.
Journal of clinical microbiology, 42(1), 412-414 (2004-01-13)
In STGG (skim milk, tryptone, glucose, glycerol) medium at -80 degrees C, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis isolates survived for at least 3 years, and the same species have survived in nasopharyngeal swabs for at least 1.5 years.