Automation of antimicrobial activity screening

AMB Express

Table 2 Time requirements for manual and automated pipetting

Growth condition	Setup and inoculate (min)	Growth analysis (min)	Agar plating (min)
Planktonic growth	Manual: 37	Manual: 0	Manual: 31
Planktonic growth	Automated: 16	Automated: 0	Automated: 6
Biofilm forming	Manual: 37	Manual: 31	Manual: 47
Biofilm forming	Automated: 16	Automated: 15	Automated: 14
24 h biofilm	Manual: 16	Manual: 51	Manual: 47
24 h biofilm	Automated: 6	Automated: 32	Automated: 14

The assays generating the data for Fig. 4 required many (nearly 3000) pipetting operations from initial set up through analysis: three culture conditions, with different media formulations and orders of operations; for each condition, sixteen antimicrobial concentrations were evaluated with four replicates and positive and negative controls; for each individual well, media, antimicrobial and cells were added in varying proportions; the metabolic activity assessment of the biofilms required multiple media exchanges; and aliquots from every well were inoculated onto agar to estimate the MBC. The time requirements (in minutes) for each automated (measured) or manual (estimated) step are tabulated here. Overall, manual pipetting would require 5 h of hands-on time while automated pipetting required only 2 h of machine time. (The actual duration of the experiments was several days for each condition to allow for bacterial growth.)