Comparative study between liquid and solid media for the detection of bacterial contamination in intravenous...

For the sterility testing of intravenous solutions, the Pharmacopeia recommend the use of liquid media. However, contamination by a single micro-organism during the test may lead to the inappropriate blocking of the release of the batch. An alternative method using solid media for culturing the membranes used in the filtration was therefore sought. With an artificial contamination with 10-100 colony-forming-units (cfu) of nine different micro-organisms, including those advocated by the Pharmacopeia, the feasibility of two different methods was assessed using two different intravenous solutions manufactured in our hospital. The results show that recoveries of minute amounts of bacteria using solid media and liquid media were similar. In all experiments there was a concordance in both positive and negative results. However, the batches of solutions have to be tested as quickly as possible after their preparation, whatever the method used, to avoid false-negative tests.