2011 - 2012
Harmonization of methods for cultivation of high pathogenic bacteria in BSL-3 laboratories
The aim of this project was to harmonize methods for cultivation of the bacterial category A agents Bacillus anthracis, Yersinia pestis, Francisella tularensis and Burkholderia spp. In 2011 an inventory was performed in order to identify the different solid culture media frequently used at the agencies for cultivation of the bacterial agents. In addition, a search of published peer reviewed literature describing solid culture media for the five agents was performed. Taken together, the result from the inventory and literature search constituted the basis for the design of a side by side test where different types of solid culture media were evaluated for growth of the four bacterial agents.
Results from the side by side test showed small differences in the time required for bacterial growth. However a variety of morphologies of bacterial colonies could be observed for one bacterial strain cultured on different media. This may significantly affect the ability to determine a culture as positive or negative for a specific agent. Moreover differences in both colony morphology and time for observed growth were apparent for the same bacterial strain grown on media prepared with the same recipe but prepared at different laboratories.
We recommend the Horse blood and Tul -agar as “FBD Choice Medium” for cultivation of the studied bacteria from clinical samples. However the recommendation is limited to relatively clean samples with low level of contamination due to lack of selectivity necessary for cultivation from mixed/contaminated samples. There is still a need for further collaboration between agencies to harmonize methods for enrichment and selectivity for cultivation of bacterial agents from complex matrixes as food, environmental and degraded clinical samples.