Dear Ali. You can use Time–kill experiments with mixed and pure cultures
http://jac.oxfordjournals.org/content/early/2010/11/08/jac.dkq394.full
Other authors use two-compartment pharmacodynamic model
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0003846
http://www.wjgnet.com/2220-3176/pdf/v2/i3/28.pdf
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3038999/
With best regards
Well, i think, if you know the bacterial community structure (e.g., bacterial species present in that mixed bacterial population), then you should be able to see the effect of a antibiotic on such mixed population quite simply.
The real question is; what is the purpose of your experiments? Is well known that the antibacterial agents are affective against Gram positive and/or Gram negative, against aerobic and anaerobic strains. First of all, I think, is necessary to know the bacterial species that compose your population in order to utilise the most effective antibiotics against these species. Than is sufficient to culture your suspension in presence of chiosed antibiotic and evaluate the growth of survived bacteria in culture media and identify it or them. This is the standard method utilise in clinical microbiology on human specimens of blood, urine, etc. The real problem, according to me, is the choise of the right antibiotic. You can use one or two diffent anibiotics utilising their additive or synergistic effect.
Hi Ali, under what environmental conditions is this to be done and how does this affect the "health" of the two strains, the extent to which they remain homogenous (mixed) and interactions of these and other factors on the actual antibiotic effect?
Ali, irrespective of the method(s) you decide to you to use, I think you should check the effect of your test agent on the individual organisms first, then check also the interaction between the organisms in your mixture in the absence of the antimicrobial agent to see if there is any antagonism between them before you can assess the effect of the antimicrobial agent on the mixed culture.
Hello Ali, the effect of an antibiotic on bacteria is best measured by the use of the pure culture.Thus, it is advisable to check the effect of the antibiotic first on the pure culture of each of the bacteria in the mixed population to know how the different bacteria in the mixed population react with the agent before checking the overall effect of the agent on the mixed population.
Hi Ali, I think before go to check antibiotic sensitivity, so many other issues have to resolve like...what type of bacterial culture u have, their interaction effect with each other, effect of antibiotic on their corresponding pure culture, normally every one should go on pure culture for antibiotic sensitivity.......
I think you must know the species and genera of mixed bacteria and the effective antibiotic for each. You must try more than antibiotic in your test and you must take in consideration that some of these bacteria my be antagonistic to others in mixed cultures.
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