Comparison of different culture media and storage temperatures for the long-term preservation of Streptococcus pneumoniae in the tropics

• Published in: Bulletin of the World Health Organization Vol. 79; no. 1; pp. 43 - 47
• Main Authors: SIBERRY, George, BRAHMADATHAN, K. N, PANDIAN, Rajeswar, LALITHA, M. K, STEINHOFF, Mark C, JOHN, T. Jacob
• Format: Journal Article
• Language: English
• Published: Genève Organisation mondiale de la santé 2001; World Health Organization
• Subjects: Antibiotics; Bacteriological methods and techniques used in bacteriology; Bacteriology; Biological and medical sciences; Cell Culture Techniques - methods; Cost-Benefit Analysis; Cryopreservation - methods; Culture Media; Developing countries; Epidemiology; Fundamental and applied biological sciences. Psychology; Glycerol; Humans; India; Laboratories; LDCs; Microbiology; Physiology; Pneumococcal infections; Pneumococcal vaccine; Preservation, Biological - economics; Preservation, Biological - methods; Prevention; Sand & gravel; Sheep; Specimen Handling - economics; Specimen Handling - methods; Storage; Streptococcus infections; Streptococcus pneumoniae; Surveillance; Temperature; Tropical Climate; India; Culture medium; Freeze drying; Temperature; Cold; Desiccation; Tropical zone; Environmental factor; Method; Long term; Streptococcus pneumoniae; Streptococcaceae; Storage; Cryopreservation; Bacteria; Micrococcales; Sample conservation; Comparative study
• ISSN: 0042-9686; 1564-0604

The preservation of Streptococcus pneumoniae by standard freezing methods for subsequent tests--such as serotyping and antibiotic susceptibility--is not possible or is difficult in many developing countries because of the high cost of equipment, inadequate equipment maintenance, and irregular power supply. We evaluated alternative low-cost methods, by comparing different culture media and storage temperatures. Clinical isolates of five capsular types (1, 5, 7, 19, and 23) of S. pneumoniae were preserved in rabbit blood, sheep blood, skimmed milk, or glycerol-chocolate broth, and stored at -20 degrees C or -70 degrees C. The cultures were also preserved by lyophilization or sand desiccation, followed by storage at room temperature and 4 degrees C. The viability of the preserved cultures was determined by making serial colony counts on day 0 and after 1 week, 4 weeks, 4 months and 16 months. The viability of cultures preserved by sand desiccation and storage at 4 degrees C was also determined every 6 months for up to 68 months. Irrespective of the media used, cultures maintained at -20 degrees C became nonviable by the fourth month, while those maintained at -70 degrees C were still viable at 16 months. Cultures preserved by lyophilization or sand desiccation lost their viability by the fourth month when maintained at local room temperature (30-42 degrees C), but remained viable when stored at 4 degrees C for up to 68 months. Our results confirm that freezing at -70 degrees C, or lyophilization and storage at 4 degrees C are the ideal methods for the preservation of S. pneumoniae. In laboratories where lyophilization is not feasible, sand desiccation and storage at 4 degrees C offers an alternative low-cost method for the long-term preservation of S. pneumoniae.