600-ns pulsed electric fields affect inactivation and antibiotic susceptibilities of Escherichia coli and Lactobacillus acidophilus

Abstract

Cell suspensions of Escherichia coli and Lactobacillus acidophilus were exposed to 600-ns pulsed electric fields (nsPEFs) at varying amplitudes or High-23.5 kV cm −1 ) and pulse numbers (0 (sham), 1, 5, 10, 100 or 1000) at a 1 hertz (Hz) repetition rate. The induced temperature rise generated at these exposure parameters, hereafter termed thermal gradient, was measured and applied independently to cell suspensions in order to differentiate inactivation triggered by electric field (E-field) from heating. Treated cell suspensions were plated and cellular inactivation was quantified by colony counts after a 24-hour (h) incubation period. Additionally, cells from both exposure conditions were incubated with various antibiotic-soaked discs to determine if nsPEF exposure would induce changes in antibiotic susceptibility. Results indicate that, for both species, the total delivered energy (amplitude, pulse number and pulse duration) determined the magnitude of cell inactivation. Specifically, for 18.5 and 23.5 kV cm −1 exposures, L. acidophilus was more sensitive to the inactivation effects of nsPEF than E. coli, however, for the 13.5 kV cm −1 exposures E. coli was more sensitive, suggesting that L. acidophilus may need to meet an E-field threshold before significant inactivation can occur. Results also indicate that antibiotic susceptibility was enhanced by multiple nsPEF exposures, as observed by increased zones of growth inhibition. Moreover, for both species, a temperature increase of ≤ 20 °C (89% of exposures) was not sufficient to significantly alter cell inactivation, whereas none of the thermal equivalent exposures were sufficient to change antibiotic susceptibility categories.

Prevalence, antimicrobial resistance, and genotyping of Shiga toxin-producing Escherichia coli in foods of cattle origin, diarrheic cattle, and diarrheic humans in Egypt

“…Human infection with these pathogens may result in clinical illness ranging from self-limiting diarrhoea to life-threatening hemolytic uremic syndrome (HUS) [2]. Cattle are attributed to most zoonotic human STEC cases worldwide [1][2][3]. These animals are the main reservoir of O157 STEC and some important non-O157 STEC such as O26, O111, O113, and O103 [1][2][3][4].…”

Resistance and Adaptation of Bacteria to Non-Antibiotic Antibacterial Agents: Physical Stressors, Nanoparticles, and Bacteriophages

“…In such a case, one usually tunes PEF parameters so that creating holes is reversible [ 49 ]. The amplitude, pulse number, and pulse duration form are the factors that determine inactivation, especially for species such as E. coli and Lactobacillus acidophilus [ 51 ]. The mechanism of electroporation is still not well understood [ 52 ], but the parameters at which this phenomenon occurs are known.…”

“…For E. coli BL21 this value is 3.65 ± 0.09 kV/cm [ 53 ]. The most exciting fact is that antibiotic susceptibility is enhanced by the application of PEF, as concluded by the increased zones of growth inhibition [ 51 ]. Currently, PEF is also evaluated as a new method for cancer treatment [ 54 ].…”

Biomedical Science to Tackle the COVID-19 Pandemic: Current Status and Future Perspectives

“…mRNA-1273 consists of an mRNA pharmacological substance that is manufactured in LNPs composed of the patented ionizable lipid, SM-102, and 3 commercially available lipids, cholesterol, 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and 1,2-dimyristoyl-rac-glycero-3-methoxypolyethyleneglycol-2000 (DMG-PEG2000). Moderna’s mRNA vaccine against COVID-19 has entered Phase III trials in July 2020, raising the hope to have vaccine doses ready by early 2021 [ 287 ].…”