Currently, I am not active but I must mention let downs by a few R&D labs in the United States during my microbiology career. Watch the composition of each sample that follows your report on the earlier one. Some operators, especially the smaller business houses- looking for University lab evaluations- neglect to report "minor" alterations in the samples sent. Often, they omit a solvent or buffer or even add an ingredient- without even a twinkle in their eye- so long as an MIC/MBC number is available. Good for product development but not for the reputation of the reporting lab!.