Selective Inactivation of Pseudomonas aeruginosa and Staphylococcus epidermidis with Pulsed Electric Fields and Antibiotics

Application of pulsed electric field (PEF) as a strategy to enhance aminoglycosides efficacy against Gram-negative bacteria

In this study, two aminoglycosides (AGs), Kanamycin and Gentamicin, with similar modes of action and molecular weights, were combined with PEF treatment to enhance the inactivation of E. coli cells. Various PEF strengths were applied to assess the combined effect. To compare the inactivation efficacy of different AGs, bacterial growth measurements in suspension were performed at 3 and 10 h intervals over a 10-h period after PEF treatment. Interestingly, it was found that the additive effect of PEF treatment on E. coli growth inhibition was significantly greater with Kanamycin (IC50) than with Gentamicin (IC50). Further analysis revealed that the combined treatment with Kanamycin (IC50) was most effective within a timeframe of around 3 h. Our findings suggest that PEF treatment can significantly enhance the efficacy of AGs against Gram-negative bacteria; however, the extent of the additive effect varies depending on the specific antibiotic and the intensity of the applied PEF treatment.

Inactivation of antibiotic-resistant bacteria Escherichia coli by electroporation

Introduction

In modern times, bacterial infections have become a growing problem in the medical community due to the emergence of antibiotic-resistant bacteria. In fact, the overuse and improper disposal of antibiotics have led to bacterial resistance and the presence of such bacteria in wastewater. Therefore, it is critical to develop effective strategies for dealing with antibiotic-resistant bacteria in wastewater. Electroporation has been found to be one of the most promising complementary techniques for bacterial inactivation because it is effective against a wide range of bacteria, is non-chemical and is highly optimizable. Many studies have demonstrated electroporation-assisted inactivation of bacteria, but rarely have clinical antibiotics or bacteria resistant to these antibiotics been used in the study. Therefore, the motivation for our study was to use a treatment regimen that combines antibiotics and electroporation to inactivate antibiotic-resistant bacteria.

Methods

We separately combined two antibiotics (tetracycline and chloramphenicol) to which the bacteria are resistant (with a different resistance mode) and electric pulses. We used three different concentrations of antibiotics (40, 80 and 150 µg/ml for tetracycline and 100, 500 and 2000 µg/ml for chloramphenicol, respectively) and four different electric field strengths (5, 10, 15 and 20 kV/cm) for electroporation.

Results and discussion

Our results show that electroporation effectively enhances the effect of antibiotics and inactivates antibiotic-resistant bacteria. The inactivation rate for tetracycline or chloramphenicol was found to be different and to increase with the strength of the pulsed electric field and/or the concentration of the antibiotic. In addition, we show that electroporation has a longer lasting effect (up to 24 hours), making bacteria vulnerable for a considerable time. The present work provides new insights into the use of electroporation to inactivate antibiotic-resistant bacteria in the aquatic environment.

[ARTICLE WITHDRAWN] Preventive and Therapeutic Effect of Lanthanide Coordination Polymers on Severe Burn Infection by Inhibiting Staphylococcus epidermidis Infection

THIS ARTICLE WAS WITHDRAWN BY THE PUBLISHER IN SEPTEMBER 2022

Regenerative Approaches for Chronic Wounds

Chronic skin wounds are commonly found in older individuals who have impaired circulation due to diabetes or are immobilized due to physical disability. Chronic wounds pose a severe burden to the health-care system and are likely to become increasingly prevalent in aging populations. Various treatment approaches exist to help the healing process, although the healed tissue does not generally recapitulate intact skin but rather forms a scar that has inferior mechanical properties and that lacks appendages such as hair or sweat glands. This article describes new experimental avenues for attempting to improve the regenerative response of skin using biophysical techniques as well as biochemical methods, in some cases by trying to harness the potential of stem cells, either endogenous to the host or provided exogenously, to regenerate the skin. These approaches primarily address the local wound environment and should likely be combined with other modalities to address regional and systemic disease, as well as social determinants of health. Expected final online publication date for the Annual Review of Biomedical Engineering, Volume 24 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Bacteriological Investigation and Drug Resistance Analysis of Chronic Refractory Wound Secretions: A Clinical Study

BACKGROUND

Chronic refractory wounds were common and the treatments were complicated for burn and plastic surgeons. This study was to investigate the bacterial distribution characteristics and bacterial drug resistance of chronic refractory wound secretions.

METHODS

The authors retrospectively analyzed 425 patients with chronic refractory wound infection. The results of bacterial culture of wound secretions and drug sensitivity test were retrospectively analyzed. Further, the location area of the wound was divided into 4 regions, and the difference of the bacterial culture results between different regions was analyzed.

RESULTS

The wound secretions were cultured into 401 bacterial strains, including 206 gram-positive bacteria strains, accounting for 51.4%, with the highest detection rate of Staphylococcus aureus at 26.2% (105/401). There were 195 gram-negative bacteria strains, accounting for 48.6%, with the highest detection rate of Pseudomonas aeruginosa at 14.2% (57/401). There were 6 fungal strains. The proportion of gram-negative bacteria in the III region of the wound zone was significantly greater than that in the other 3 regions.

CONCLUSIONS

The detection rate of gram-positive bacteria and gram-negative bacteria of chronic refractory wound secretions is not much different. However, in the area close to the perineum (III region), gram-negative bacteria is significantly higher, which has a certain reference value for the use of antibiotics in clinical practice.Level of evidence: Level 4.

Electroporation as an Efficacy Potentiator for Antibiotics With Different Target Sites

Antibiotic resistance is a global health threat, and there is ample motivation for development of novel antibacterial approaches combining multiple strategies. Electroporation is among the promising complementary techniques – highly optimizable, effective against a broad range of bacteria, and largely impervious to development of resistance. To date, most studies investigating electroporation as an efficacy potentiator for antibacterials used substances permissible in food industry, and only few used clinical antibiotics, as acceptable applications are largely limited to treatment of wastewaters inherently contaminated with such antibiotics. Moreover, most studies have focused mainly on maximal achievable effect, and less on underlying mechanisms. Here, we compare Escherichia coli inactivation potentiation rates for three antibiotics with different modes of action: ampicillin (inhibits cell wall synthesis), ciprofloxacin (inhibits DNA replication), and tetracycline (inhibits protein synthesis). We used concentrations for each antibiotic from 0 to 30× its minimum inhibitory concentration, a single 1-ms electric pulse with amplitude from 0 to 20 kV/cm, and post-pulse pre-dilution incubation either absent (≲1 min) or lasting 60 min, 160 min, or 24 h. Our data show that with incubation, potentiation is significant for all three antibiotics, increases consistently with pulse amplitude, and generally also with antibiotic concentration and incubation time. With incubation, potentiation for ampicillin was rather consistently (although with weak statistical significance) superior to both ciprofloxacin and tetracycline: ampicillin was superior to both in 42 of 48 data points, including 7 with significance with respect to both, while at 60- and 160-min incubation, it was superior in 31 of 32 data points, including 6 with significance with respect to both. This suggests that electroporation potentiates wall-targeting antibiotics more than those with intracellular targets, providing motivation for in-depth studies of the relationship between the mode of action of an antibiotic and its potentiation by electroporation. Identification of substances permissible in foods and targeting the cell wall of both Gram-negative and Gram-positive bacteria might provide candidate antibacterials for broad and strong potentiation by electroporation applicable also for food preservation.

High-Voltage, Pulsed Electric Fields Eliminate Pseudomonas aeruginosa Stable Infection in a Mouse Burn Model

Objective: The incidence of severe infectious complications after burn injury increases mortality by 40%. However, traditional approaches for managing burn infections are not always effective. High-voltage, pulsed electric field (PEF) treatment shortly after a burn injury has demonstrated an antimicrobial effect in vivo; however, the working parameters and long-term effects of PEF treatment have not yet been investigated. Approach: Nine sets of PEF parameters were investigated to optimize the applied voltage, pulse duration, and frequency or pulse repetition for disinfection of Pseudomonas aeruginosa infection in a stable mouse burn wound model. The bacterial load after PEF administration was monitored for 3 days through bioluminescence imaging. Histological assessments and inflammation response analyses were performed at 1 and 24 h after the therapy. Results: Among all tested PEF parameters, the best disinfection efficacy of P. aeruginosa infection was achieved with a combination of 500 V, 100 μs, and 200 pulses delivered at 3 Hz through two plate electrodes positioned 1 mm apart for up to 3 days after the injury. Histological examinations revealed fewer inflammatory signs in PEF-treated wounds compared with untreated infected burns. Moreover, the expression levels of multiple inflammatory-related cytokines (interleukin [IL]-1α/β, IL-6, IL-10, leukemia inhibitory factor [LIF], and tumor necrosis factor-alpha [TNF-α]), chemokines (macrophage inflammatory protein [MIP]-1α/β and monocyte chemoattractant protein-1 [MCP-1]), and inflammation-related factors (vascular endothelial growth factor [VEGF], macrophage colony-stimulating factor [M-CSF], and granulocyte-macrophage colony-stimulating factor [G-CSF]) were significantly decreased in the infected burn wound after PEF treatment. Innovation: We showed that PEF treatment on infected wounds reduces the P. aeruginosa load and modulates inflammatory responses. Conclusion: The data presented in this study suggest that PEF treatment is a potent candidate for antimicrobial therapy for P. aeruginosa burn infections.

Nanosecond electric pulses rapidly enhance the inactivation of Gram-negative bacteria using Gram-positive antibiotics

Physically disrupting microorganism membranes to enable antibiotics to overcome resistance mechanisms that inhibit or excrete antibiotics has great potential for reducing antibiotic doses and rendering resistance mechanisms inert. We demonstrate the synergistic inactivation of a Gram-positive (Staphylococcus aureus) and two Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria by combining 222 30 kV/cm electric pulses (EPs) or 500 20 kV/cm EPs with 300-ns EP duration with various antibiotics with different mechanisms of action is demonstrated. Doses of antibiotics that produced no inactivation in 10 min of exposure in solution with bacteria induced several log reductions under the influence of nanosecond EPs. Combining 2 μg/L or 20 μg/mL of rifampicin with the 30 kV/cm EPs enhanced Staphylococcus aureus inactivation compared with EPs alone, while only a few of the other combinations demonstrated improvement. Combining 2 μg/L or 20 μg/mL of mupirocin or rifampicin with either EP train enhanced E. coli inactivation compared with EPs alone. Combining 2 μg/L or 20 μg/mL of erythromycin or vancomycin with the 30 kV/cm EPs enhanced E. coli inactivation compared with EPs alone. These results indicate that EPs can make Gram-positive antibiotics efficient for inactivating Gram-negative bacteria with future studies required to optimize EP parameters for other antibiotics and Gram-negative bacteria.