Research Article

Development of a Novel Test for Simultaneous Bacterial Identification and Antibiotic Susceptibility

Figure 2

Determination of the limit of detection following incubation at 37° Celsius. GBS (a), Enterococcus (b), and N. gonorrhoeae (c) were prepared at 0.5 McFarland in Fastidious Broth and diluted out serially. For GBS, samples were incubated for either 0.5, 1, 2, 4, 6 or 24 hours at 37° Celsius (a). For E. faecalis, samples were incubated overnight at 37° Celsius. Tubes were noted to be turbid down to 100 bacteria per mL, and this sample and the following two dilutions, 10−1 and 10−2 bacteria per mL, were prepared further by diluting in PBS out to 1 : 1,000. For N. gonorrhoeae, samples were prepared at a 0.5 McFarland in Fastidious Broth and then incubated overnight at 37° Celsius (c). Following these incubation time-points for each study, 10 μL of each sample was transferred to microtiter wells containing 90 μL PBS and allowed to stand for 20 minutes at room temperature. Any bound organism was detected by HRP-conjugated antibody against the specific pathogen. As with Figure 1, three distinct strains of GBS were tested, as were two strains of Enterococcus and N. gonorrhoeae each. Results shown are of GBS clinical isolate 01.12.76 (a), Enterococcus ATCC strain 29212 (b), and N. gonorrhoeae strain 19424 (c), each performed in triplicate and representative of three individual experiments. Again, bacterial concentrations were confirmed by CFUs following plating on agar for 24–48 hours.
(a)
(b)
(c)