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Fig. 5 | BMC Research Notes

Fig. 5

From: Validation of an automated colony counting system for group A Streptococcus

Fig. 5

Efficacy of automated counting system over growth cycles. a An exemplar growth curve showing the average concentration of bacteria over the different phases of the growth curve for GAS strain M33 plated on THY-TTC and HBA. At each point the standard error of the means are overlapping. b Comparison of the average bias from Bland–Altman analysis at each time point of growth curves performed for four strains in triplicate. The analysis compares each replicate of each dilution with samples from the same culture plated on HBA plates and THY-TTC plates. The bias is based on the formula [100 × (THY-TTC plates–HBA plates)/average of the two counts] and is averaged for each of the 8 h of growth. As none of the biases fall outside the 10 % cut-off this indicates that plating on THY-TTC is not detrimental at any particular phase of the growth cycle. A series of three dilutions was plated for the four strains for each time point, of which 652 counts fell between 10 and 200 colonies (2 h: 90; 3 h: 104; 4 h: 111; 5 h: 103; 6 h 108; 7 h: 86; 8 h: 50). c The percentage biases and standard deviations

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