Bactericidal effect of underwater shock waves on Escherichia coli ATCC 10536 suspensions

An electrohydraulic shock wave generator was used to study the bactericidal action of shock waves on Escherichia coli ATCC 10536 suspensions in 0.9% (w/v) NaCl solution (initial cell population: 8.2 log10 CFU/ml). The influence of treatment temperature, shock wave energy, number of applied shock waves, the acoustic cavitation produced by the shock wave, and the spark gap-generated light (UV and visible) were analyzed using E. coli cultures in the exponential phase. Part of the experiment was repeated in the stationary phase. Results indicate that light, number of shock waves, cavitation and interactions between them, influence bactericidal activity (P<0.05). The best viability reduction of 4.06 log10 CFU/ml was achieved at 350 shock waves, administered during approximately 14.5 min, with bacteria in the stationary phase by enhancing acoustic cavitation inside the vial, and without protecting the samples from the visible and UV radiation produced by the shock wave-generating spark.