surfaces on the surface of the crystalline carbon characterized
by macroporosity. Samples PB2 and PB3 showed
enhanced pore sizes that facilitated adsorption of large
molecules. Metronidazole is adsorbed by the micro- and
mesopores, while Escherichia coli O157:H7 is adsorbed by
the macropores.
The number of bacteria adsorbed as a function of time
was explored using the combined time–kill curve against
Escherichia coli O157:H7 (Figure 5). The number of bacterial
cells exponentially increased with the amount in the initial
inoculum for the control. The time–kill curve for metronidazole
against Escherichia coli was almost a replica of the
curve for growth control [1,15]. Confluent bacterial growth
was observed using metronidazole alone when compared
to metronidazole combined with AC or PB3 (Figure 6). AC
alone in the pharmacodynamic model produced a 1 log
killing of the bacteria and this was increased with a combination
of AC with metronidazole. When AC (AC, PB1, and
PB3) was used alone, significant regrowth occurred above
the lower limit of accuracy (LLA) of bacterial counting.
Significant regrowth (increase in the number of bacteria
to quantifiable levels following a 3-log killing) did
not occur. In the case of metronidazole–AC combination,