Optimisation of storage conditions for maintaining culturability of penicillin-susceptible and penicillin-resistant isolates of Streptococcus pneumoniae in transport medium

Abstract

Methods employed by the World Health Organization (WHO) are used during this study to determine the optimum storage conditions for maintaining the culturability of Streptococcus pneumoniae in skimmed milk, tryptone, glucose and glycerin (STGG) transport medium. A comparison of S. pneumoniae strains sensitive and resistant to penicillin showed no significant difference in their survival ability in STGG medium. Furthermore, it is confirmed that storage at –70°C remains most effective for maintaining viability by culture of S. pneumoniae. Storage at –20°C would only be acceptable in the short-term, while storage at +4°C is not recommended. Of note, this study has shown STGG medium at room temperature to be an efficient growth medium for pneumococci in the short-term. This work will help to establish robust sampling protocols when performing community studies to ensure culturability of comparison between community and laboratory pneumococci survival.