∞ generated and posted on 2017.03.19 ∞
∞ updated on 2022.06.05 ∞
Multiplicity of infection (MOI) is the ratio of adsorbed phages to phage-adsorbable bacteria, both as found within a specific volume.
Please cite as:
Stephen T. Abedon
Multiplicity of Infection Calculator.
moi.phage.org
Click here for calculator or see immediately below for further explanation and discussion.
| There are a number of issues associated with the definition of multiplicity of infection that, in my opinion, have a hampering effect on certain aspects of phage research. The biggest problem appears to be confusion as to the actual definition of multiplicity of infection along with how one should calculate multiplicity of infection in its various guises. The calculator below allows not only the calculation of 'actual' multiplicity of infection – or MOIactual, i.e., the historically accurate definition – but also allows comparison with the truly problematic 'input' multiplicity of infection (MOIinput), that is, what can be described as a 'multiplicity of addition'. For the sake of illustration, in the calculator below, try setting n for phages to 7 (= 1e7/ml = 1 × 107/ml), n for bacteria to 4 (= 1e4/ml = 1 × 104/ml), and time (t) to 120 (= 120 minutes or two hours). Press the button at the bottom to calculate and you should see that while the input "MOI" is 1000, the actual MOI is only 3. Then try setting n for phages to 8 (= 1e8/ml = 1 × 108/ml) and see what happens. (You will see that though the ratio of MOIactual to MOIinput ramains constant, MOIactual jumps from a relatively meager 3 to a substantially robust 30. As an aside, I and others have been advocating for some time now for the achievement of phage titers for phage therapy of at least 108/ml in the vicinity of target bacteria, whether reached based on dosing alone or instead as a consequence of in situ phage population growth. The above example illustrates why. For more on phage therapy, see phage-therapy.org.) -------------------------------------- For more discussion, see: Abedon, S. T. (2016). Phage Therapy Dosing: The Problem(s) with Multiplicity of Infection (MOI). Bacteriophage 6:e1220348. Abedon, S.T. (2022). Further Considerations on How to Improve Phage Therapy Experimentation, Practice, and Reporting: pharmacodynamic perspectives. Phage 3:98-111. -------------------------------------- Note that I've calculated MOIinput in two ways, and each these calculations are presented only when t > 0. These are (i) assuming that phage concentrations remain constant versus (ii) phage concentrations being allowed to decline as a consequence of phage adsorption to bacteria. In the latter case, numbers of adsorbable bacteria are not assumed to decline, just virions. Since phage populations can grow in situ, actual MOIs (as MOAs) eventially may be found somewhere between these two approximations, or indeed ultimately could be greater. MOA, by the way, stands for multiplicity of adsorption, which I feel is a more accurate way of thinking about MOIactual. For more on infection versus adsorbable, see . -------------------------------------- For discussion of multiplicity-related terms, see multiplicity.phage.org. For discussion of phage adsorption theory, see adsorption.phage.org. See also Inundative Phage Density Calculator Lastly, don't forget to be consistent with your units. Mixing minutes with hours, milliliters with liters, or absolute numbers with concentrations simply will not do! And if you need a refresher on scientific notation, there is always Wikipedia… In any case, I am assuming that you at least are using milliters as volume units. |