Effects of antibacterial mineral leachates on the cellular ultrastructure, morphology, and membrane integrity of Escherichia coliand methicillin-resistant Staphylococcus aureus

Otto, Cunningham, Hansen, Haydel

Description

We have previously identified two mineral mixtures, CB07 and BY07, and their respective aqueous leachates that exhibit in vitro antibacterial activity against a broad spectrum of pathogens. The present study assesses cellular ultrastructure and membrane integrity of methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli after exposure to CB07 and BY07 aqueous leachates. Methods We used scanning and transmission electron microscopy to evaluate E. coli and MRSA ultrastructure and morphology following exposure to antibacterial leachates. Additionally, we employed Bac light LIVE/DEAD staining and flow cytometry to investigate the cellular membrane as a possible target for antibacterial activity. Results Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) imaging of E. coli and MRSA revealed intact cells following exposure to antibacterial mineral leachates. TEM images of MRSA showed disruption of the cytoplasmic contents, distorted cell shape, irregular membranes, and distorted septa of dividing cells. TEM images of E. coli exposed to leachates exhibited different patterns of cytoplasmic condensation with respect to the controls and no apparent change in cell envelope structure. Although bactericidal activity of the leachates occurs more rapidly in E. coli than in MRSA, LIVE/DEAD staining demonstrated that the membrane of E. coli remains intact, while the MRSA membrane is permeabilized following exposure to the leachates. Conclusions These data suggest that the leachate antibacterial mechanism of action differs for Gram-positive and Gram-negative organisms. Upon antibacterial mineral leachate exposure, structural integrity is retained, however, compromised membrane integrity accounts for bactericidal activity in Gram-positive, but not in Gram-negative cells.

Informations

• Publié par: biomed
• Publié le: 01 janvier 2010
• Nombre de lectures: 1
• Langue: English
• Poids de l'ouvrage: 5 Mo

Extrait

Ottoet al.Annals of Clinical Microbiology and Antimicrobials2010,9:26 http://www.annclinmicrob.com/content/9/1/26

R E S E A R C HOpen Access Effects of antibacterial mineral leachates on the cellular ultrastructure, morphology, and membrane integrity ofEscherichia coliand methicillinresistantStaphylococcus aureus 1,2 1,22 1,2* Caitlin C Otto, Tanya M Cunningham, Michael R Hansen , Shelley E Haydel

Abstract Background:We have previously identified two mineral mixtures, CB07 and BY07, and their respective aqueous leachates that exhibitin vitroantibacterial activity against a broad spectrum of pathogens. The present study assesses cellular ultrastructure and membrane integrity of methicillinresistantStaphylococcus aureus(MRSA) and Escherichia coliafter exposure to CB07 and BY07 aqueous leachates. Methods:We used scanning and transmission electron microscopy to evaluateE. coliand MRSA ultrastructure and morphology following exposure to antibacterial leachates. Additionally, we employedBaclight LIVE/DEAD staining and flow cytometry to investigate the cellular membrane as a possible target for antibacterial activity. Results:Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) imaging ofE. coliand MRSA revealed intact cells following exposure to antibacterial mineral leachates. TEM images of MRSA showed disruption of the cytoplasmic contents, distorted cell shape, irregular membranes, and distorted septa of dividing cells. TEM images ofE. coliexposed to leachates exhibited different patterns of cytoplasmic condensation with respect to the controls and no apparent change in cell envelope structure. Although bactericidal activity of the leachates occurs more rapidly inE. colithan in MRSA, LIVE/DEAD staining demonstrated that the membrane ofE. coliremains intact, while the MRSA membrane is permeabilized following exposure to the leachates. Conclusions:These data suggest that the leachate antibacterial mechanism of action differs for Grampositive and Gramnegative organisms. Upon antibacterial mineral leachate exposure, structural integrity is retained, however, compromised membrane integrity accounts for bactericidal activity in Grampositive, but not in Gramnegative cells.

Background th With the advent of antibiotics in the early 20century, morbidity and mortality from bacterial infections were dramatically reduced in the industrialized world. In recent decades, these advances have been tempered by the rapid, widespread emergence of microorganisms that are resistant to multiple, commonly used antibiotics [1]. As our arsenal of effective antibiotics is diminishing, the pursuit of novel therapeutic agents is becoming progres sively more urgent.

* Correspondence: [e-mail] 1 School of Life Sciences, Arizona State University, Tempe, AZ, USA Full list of author information is available at the end of the article

Minerals have been utilized in traditional medicine for centuries as topical treatments for cutaneous wounds, digestive treatments for gastrointestinal ailments, nutri tional supplements, and for removal of toxins from the body [24]. Traditionally, the mechanism of mineral based healing activities has been attributed to physical properties, such as the expansive surface area and resulting highly adsorptive properties of clays present in the mixtures [2]. Recently, various mineral products marketed for their health benefits have been investigated for their potential antimicrobial properties [58]. However, only a small number of clay products have been shown to be

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