Examination of the order of incubation for the recovery of bacteria and fungi from pharmaceutical-grade cleanrooms.

A study was undertaken to compare microbial recoveries from pharmaceutical-grade cleanrooms using two different incubation regimes and a general-purpose agar (Tryptone Soy Agar). One temperature regime (A) incubated plates first at 30 degrees C to 35 degrees C, followed by 20 degrees C to 25 degrees C; the second temperature regime (B) began the incubation with plates at 20 degrees C to 25 degrees C, followed by 30 degrees C to 35 degrees C. The experimental outcomes demonstrated that there was no significant difference with the total microbial count when measured using a t-test (0.05 significance level; 95% confidence interval). However, with the recovery of fungi, the second incubation regime (B), which began with the lower 20 degrees C to 25 degrees C temperature, produced higher incidents and numbers of fungi. While this finding might provide the basis for adopting one incubation regime over another, a review of the types of cleanrooms recovering fungi suggests that fungal incidents are low, and they are more often confined to specific areas. Thus, as an alternative, incubation regimes could be varied to suit different cleanroom environments or a selective mycological agar adopted for specific areas.