Growth promotion viability study of prepared tubed media – FTG and TSB – for sterility testing that has been subjected to harsh environmental conditions

Objectives To determine if prepared tubed media, which has been subjected to harsh conditions of temperature change, is still able to support microbial growth. This data can be used to make a rational decision on whether a manufacturer’s certificate of analysis (C of A) is sufficient to permit its use for sterility testing of parenterals following shipment in a potenially non-controlled environment.

Methods To simulate extreme conditions of temperature exposure on samples of commercially prepared tubed media, fluid thioglycollate (FTG) or trypticase soybean broth (TSB), were stored at freezer temperature -16^oC or heated to 80^oC for 90 hr. Controls were FTG stored at 4^oC and TSB 22^oC, i.e. normal storage conditions. Each sample was allowed to come to RT and inoculated with a mixture of microbes and incubated under “normal” conditions: RT (~22^oC) for TSB and ~32^oC for FTG.

Results Under our simulated temperature conditions TSB did not set solid on freezing. Both FTG and TSB had become quite dark on being heated to 80^oC for 90 hr. Notwithstanding these differences, the onset and type of growth was indistinguishable between normal, cooled or heated versions for each type of media.

Conclusions These preliminary data suggest that concerns over the temperature stability and viability of growth promotion media, FTG and TSB, from commercial vendors and shipped under somewhat unknown conditions are not warranted. It would seem that manufacturer’s C of A with a simple identity/viability check on receipt should be acceptable without compromising patient care in these days of concern over medical costs.