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BioMed Research International
Volume 2014 (2014), Article ID 142168, 7 pages
http://dx.doi.org/10.1155/2014/142168
Research Article

Microbubble-Mediated Ultrasound Enhances the Lethal Effect of Gentamicin on Planktonic Escherichia coli

Department of Orthopaedic Surgery, Second Affiliated Hospital, School of Medicine, Zhejiang University, No. 88 Jiefang Road, Hangzhou 310009, China

Received 22 January 2014; Revised 23 April 2014; Accepted 27 April 2014; Published 15 May 2014

Academic Editor: Konstantinos Anagnostakos

Copyright © 2014 Han-Xiao Zhu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Previous research has found that low-intensity ultrasound enhanced the lethal effect of gentamicin on planktonic E. coli. We aimed to further investigate whether microbubble-mediated low-intensity ultrasound could further enhance the antimicrobial efficacy of gentamicin. The planktonic E. coli (ATCC 25922) was distributed to four different interventions: control ( ), microbubble only ( ), ultrasound only ( ), and microbubble-mediated ultrasound ( ). Ultrasound was applied with 100 mW/cm2 (average intensity) and 46.5 KHz, which presented no bactericidal activity. After 12 h, plate counting was used to estimate the number of bacteria, and bacterial micromorphology was observed with transmission electron microscope. The results showed that the viable counts of E. coli in were decreased by 1.01 to 1.42 log10 CFU/mL compared with ( ). The minimal inhibitory concentration (MIC) of gentamicin against E. coli was 1 μg/mL in the and groups, lower than that in the and groups (2 μg/mL). Transmission electron microscopy (TEM) images exhibited more destruction and higher thickness of bacterial cell membranes in the than those in other groups. The reason might be the increased permeability of cell membranes for gentamicin caused by acoustic cavitation.