Inoculum effect

Steels, H., James, S.A., Roberts, I.N., and Stratford, M. 2000. Sorbic acid resistance The inoculum effect. Yeast 16 1173-1183. 

In a number of cases, microbial resistance is mediated by the production of bacterial enzymes that attack the antibiotic molecule, changing its structure to an inactive form. This can lead to a so-called inoculum effect, in which a susceptible antibiotic is apparently less potent when larger numbers of bacteria are present in the medium than when fewer cells are employed. The more bacteria that are present, the more antibiotic-destroying enzyme that is present, and the more antibiotic that is required to overcome this to achieve the desired response. An antibiotic that is not enzyme modified is comparatively free of inoculum effects. 

Table 11.2 Effect of inoculum size on the minimum inhibitory concentration (MIC) of three antiseptics against Staphylococcus aureus... 

Effect of preservative concentration, temperature and size of inoculum... 

Inoculum pressure/tillage/previous crop effects on fungal infection and mycotoxin loads... 

Stewart, H. E. (1990). Effect of plant age and inoculum concentration on expression of major gene resistance to Phytophthora infestans in detached potato leaflets , Mycological Research, 94, 823-826. 

Ward, P.F.V. and N.S. Huskisson. 1969. The metabolism of fluoroacetate by plants. Biochem. Jour. 113 9P. Wong, D.H., W.E. Kirkpatrick, D.R. King, and J.E. Kinnear. 1992a. Defluorination of sodium monofluoroacetate (1080) by microorganisms isolated from western Australian soils. Soil Biol. Biochem. 24 833-838. Wong, D.H., W.E. Kirkpatrick, D.R. King, and J.E. Kinnear. 1992b. Environmental factors and microbial inoculum size, and their effect on biodefluorination of sodium monofluoroacetate (1080). Soil Biol. Biochem. 9 838-843. 

Field soil solarization was effective in dramatically reducing or completely eliminating the infection of Pythium spp. in carrot (Daucus carota L.) and strawberry roots (Becker and Wrona 1995 Pinkerton et al. 2002), as well as reduced inoculum levels of P. aphanidermatum in watermelon and potato down to 25-30 cm soil depth (Mansoori and Jaliani 1996 Triki et al. 2001). Summer soil solarization in greenhouse reduced Pythium root rot even in the temperate climate of Denmark (Christensen and Thinggaard 1999). 

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