An erroneous interpretation of ‘lethality’ could result (Davidson and Parish, 1989). There have been many publications using this method to study the antimicrobial activity of medicinal plants, spices, and their essential oils including Shelef et al. (1984), Meena et al. (1986), Syed et al. (1986a, 1986b), Ismaiel and Pierson (1990), Kanemaru and Miyamoto (1990), Rajashekhara et al. (1990), Kim et al. (1995a, 1995b), Sivropoulou et al. (1995, 1996), Chaibi et al. (1997), Wilson et al. (1997), Smith-Palmer et al. (1998), Ultee et al. (1998), Jeong Jun et al. (1999), Pol and Smid (1999), Kokoska and Rada (2001), Skandamis et al. (2001), Ultee and Smid (2001), and Mejlholm and Dalgaard (2002).

In addition to turbidimetric analyses, there is the inhibition curve, also known as the ‘killing curve’ in clinical research. This test simply involves inoculation of a microorganism into a medium, addition of an antimicrobial, followed by incubation and periodic sampling to determine growth of survival. It is a more accurate analysis than the turbidimetric assay because of the wide detection range. Some of the resulting curves are easy to interpret, other are not.