Mechanical damage to Gram-negative bacteria by surface plating with the Drigalski-spatula technique

Int J Food Microbiol. 2011 Mar 15;146(1):105-7. doi: 10.1016/j.ijfoodmicro.2011.02.005. Epub 2011 Mar 2.


Colony counting by spreading bacterial suspensions on plating media by various techniques is of general concern. Comparative studies between hand plating (Drigalski-spatula technique) for different time intervals and spiral plating resulted in significant differences in colony counts. Lower counts of Gram-negative bacteria were obtained by using hand plating for more than 10s, compared with short time hand plating (5s) or spiral plating. Colony counting of Gram-positive bacteria showed no differences between both techniques. Further characterisation of Escherichia coli cells spread with the Drigalski-spatula technique by electron microscopy revealed a large number of damaged cells compared to control samples. The data clearly shows that the mechanical forces during hand plating are sufficient to damage E. coli cells.

Publication types

  • Comparative Study

MeSH terms

  • Bacteriological Techniques / methods*
  • Colony Count, Microbial
  • Gram-Negative Bacteria / growth & development
  • Gram-Negative Bacteria / ultrastructure*
  • Microscopy, Electron