Mechanistic insights into response of Staphylococcus aureus to bioelectric effect on polypyrrole/chitosan film

ABSTRACT Bacterial biofilms are resistant to conventional antimicrobial agents. Prior in vitro studies have shown that electrical current (EC) enhances the activities of aminoglycosides, quinolones, and oxytetracycline against Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus epidermidis, Escherichia coli, and Streptococcus gordonii. This phenomenon, known as the bioelectric effect, has been only partially defined. The purpose of this work was to study the in vitro bioelectric effect on the activities of 11 antimicrobial agents representing a variety of different classes against P. aeruginosa, methicillin-resistant Staphylococcus aureus (MRSA), and S. epidermidis. An eight-channel current generator/controller and eight chambers delivering a continuous flow of fresh medium with or without antimicrobial agents and/or EC to biofilm-coated coupons were used. No significant decreases in the numbers of log10 CFU/cm2 were seen after exposure to antimicrobial agents alone, with the exception of a 4.57-log-unit reduction for S. epidermidis and trimethoprim-sulfamethoxazole. We detected a statistically significant bioelectric effect when vancomycin plus 2,000 microamperes EC were used against MRSA biofilms (P = 0.04) and when daptomycin and erythromycin were used in combination with 200 or 2,000 microamperes EC against S. epidermidis biofilms (P = 0.02 and 0.0004, respectively). The results of these experiments indicate that the enhancement of the activity of antimicrobial agents against biofilm organisms by EC is not a generalizable phenomenon across microorganisms and antimicrobial agents.

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Microbial Growth Inhibition by Alternating Electric Fields

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00673-08 ◽

2008 ◽

Vol 52 (10) ◽

pp. 3517-3522 ◽

Cited By ~ 45

Author(s):

Moshe Giladi ◽

Yaara Porat ◽

Alexandra Blatt ◽

Yoram Wasserman ◽

Eilon D. Kirson ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Pseudomonas Aeruginosa ◽

Electric Fields ◽

Microbial Growth ◽

Bacterial Biofilms ◽

Electric Currents ◽

Bioelectric Effect ◽

Planktonic Bacteria ◽

Alternating Electric Fields ◽

Microbial Growth Inhibition

ABSTRACT Weak electric currents generated using conductive electrodes have been shown to increase the efficacy of antibiotics against bacterial biofilms, a phenomenon termed “the bioelectric effect.” The purposes of the present study were (i) to find out whether insulated electrodes that generate electric fields without “ohmic” electric currents, and thus are not associated with the formation of metal ions and free radicals, can inhibit the growth of planktonic bacteria and (ii) to define the parameters that are most effective against bacterial growth. The results obtained indicate that electric fields generated using insulated electrodes can inhibit the growth of planktonic Staphylococcus aureus and Pseudomonas aeruginosa and that the effect is amplitude and frequency dependent, with a maximum at 10 MHz. The combined effect of the electric field and chloramphenicol was found to be additive. Several possible mechanisms underlying the observed effect, as well as its potential clinical uses, are discussed.

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Cytochemical Studies of Cell Wall Biosynthesis in Staphylococcus Aureus

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100094905 ◽

1972 ◽

Vol 30 ◽

pp. 328-329

Author(s):

Masaatsu Koike ◽

Koichi Nakashima ◽

Kyoko Iida

Keyword(s):

Staphylococcus Aureus ◽

Periodate Oxidation ◽

Early Time ◽

The Other ◽

Penicillin G ◽

Cell Wall Biosynthesis ◽

Septal Wall ◽

Peptidoglycan Biosynthesis ◽

Gram Positive Bacteria ◽

Cross Linkage

Penicillin exerts the activity to inhibit the peptide cross linkage between each polysaccharide backbone at the final stage of wall-peptidoglycan biosynthesis of bacteria. Morphologically, alterations of the septal wall and mesosome in gram-positive bacteria, which were occurred in early time after treatment with penicillin, have been observed. In this experiment, these alterations were cytochemically investigated by means of silver-methenamine staining after periodate oxidation, which is applied for detection of localization of wall mucopolysaccharide.Staphylococcus aureus strain 209P treated with 100 u/ml of penicillin G was divided into two aliquotes. One was fixed by Kellenberger-Ryter's OSO4 fixative at 30, 60 and 120 min after addition of the antibiotic, dehydrated through alcohol series, and embedded in Epon 812 (Specimen A). The other was fixed by 21 glutaraldehyde, dehydrated through glycolmethacrylate series and embedded in glycolmethacrylate mixture, according to Bernhard's method (Specimen B).

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Gold labeling of teichoic acid on adjacent surfaces of staphylococcus aureus

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100160443 ◽

1990 ◽

Vol 48 (3) ◽

pp. 578-579

Author(s):

Margaret Hukee

Keyword(s):

Staphylococcus Aureus ◽

Teichoic Acid ◽

Protein Labeling ◽

Minimal Amount ◽

Section Thickness ◽

Double Labeling ◽

Parallel Surfaces ◽

Supporting Membrane

Gold labeling of two antigens (double labeling) is often done on two section surfaces separated by section thickness. Whether labeling is done on both sides of the same section or on two parallel surfaces separated by section thickness (PSSST), comparable results are dependent on an equal number of epitopes being exposed at each surface. We propose a method to study protein labeling within the same field of proteins, by examining two directly adjacent surfaces that were split during sectioning. The number of labeling sites on adjacent surfaces (AS) were compared to sites on PSSST surfaces in individual bacteria.Since each bacteria needed to be recognizable in all three section surfaces, one-hole grids were used for labeling. One-hole grids require a supporting membrane and excessive handling during labeling often ruptures the membrane. To minimize handling, a labeling chamber was designed that is inexpensive, disposable, minimizes contamination, and uses a minimal amount of solution.

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