N.46 – Culture media and diluents – Selection of Growth Media in Cleanrooms, RABS, Isolator


Microbiology according USP 38 – The United States Pharmacopeial – Document (1116) Aseptic Processing Environments -Page 1201, 1196.

-Culture media and diluents

The type of medium, liquid or solid, used for sampling or plating microorganisms depends on the procedures and equipment used. Any medium used should be evaluated for suitability for the intended purpose. The most commonly used all purpose solid microbiological growth medium is soybean casein digest agar. As previously noted, the medium can be supplemented with chemicals that counteract the effect of various antimicrobials.

-Selection of growth media

A general microbiological growth medium such as soybean casein digest medium is suitable for environmental monitoring in most cases because it supports the growth of a wide range of bacteria, yeast and molds. The medium can be supplemented with additives to overcome or to minimize the effects of sanitizing agents or of antibiotics.


Manufacturers should consider the specific detection  of yeast and molds.  If necessary, general mycological media such Sabouraud’s, modified Sabouraud’s, or inhibitory mold agar can be used.  In general, monitoring for strict anaerobes is not performed, because these  organisms are unlikely to survive in ambient air. However, micro-aerophilic organisms may be observed in aseptic processing. Should anoxic conditions exist  or if investigation warrant (e.g., identification of these organisms in sterility testing results), facilities or Sterility tests, monitoring for micro-aerophiles  and organisms that growth under low oxygen conditions may be warranted- The ability of any media used in environmental monitoring, including those selected to recover specific types of organisms, must be evaluated for their ability to support growth, as indicated.


USP 38 – The United States Pharmacopeial – Document (1116) Aseptic Processing Environments -Page 1201,1196