Transport and storage conditions for cultural recovery of Chlamydia pneumoniae

Abstract

Chlamydia pneumoniae is characterized by rapidly decreasing viability outside the host cell, and efficient preservation of its infectivity is a prerequisite for subsequent cell culture recovery. Extracellular survival of three C. pneumoniae stock strains and three wild-type strains subjected to simulated conditions of transport was therefore examined in order to establish recommendations for transport and storage of clinical specimens. The presence of fetal calf serum in transport media as well as refrigeration distinctly improved chlamydial retrieval during prolonged transport. Loss of infectivity was kept to a minimum in Eagle's minimal essential medium or sucrose-phosphate-glutamine medium. Storage at 22°C permitted a stock strain recovery of 81% after 12 h. When refrigeration to 4°C was provided, recovery rates of 74% could be achieved after 48 h. Though the strains were from different geographic regions, requirements for good survival were comparable and should therefore apply worldwide. The results indicate that the laboratory strains are not extremely labile. However, comparative examination of the wild-type strains showed less stability: primary isolates were not satisfactorily retrievable beyond 4 h at 22°C or beyond 24 h at 4°C. Further extension of storage times resulted in rapidly decreasing recovery, indicating a requirement to freeze samples at -75°C to preserve viability. Adherence to the shorter storage periods suggested by the data obtained with primary isolates is recommended to ensure successful transport until more extensive testing with clinical materials is available.