Abstract
Enterohaemorrhagic Escherichia coli (E. coli) O157:H7 is one of the most virulent causative agents of foodborne disease. Use of antibiotics for the treatment against E. coli O157:H7 infection leads to hemolytic uremic syndrome. The present study evaluated the potential of ethanolic leaf extract of a medicinal plant, Rhodomyrtus tomentosa in enhancing the killing activity of human neutrophils against E. coli O157:H7. In addition, the effects of the extract on membrane permeability of the organisms were studied. In the killing assay, percentage survival of the bacterial cells after being exposed to human neutrophils in the presence of various concentrations of the extract were determined. At 45 min, percentage survival of E. coli O157:H7 and E. coli ATCC 25922 after treated with neutrophils in the presence of the extract at 125–250 µg/mL was 58.48%–50.28% and 69.13%–35.35%, respectively. Furthermore, upon treatment with R. tomentosa at 250 µg/mL uptake of crystal violet by E. coli O157:H7 and E. coli ATCC 25922 was increased to 40.07% and 36.16%, respectively. Therefore, it is suggested that the extract exhibited dual effects as immunostimulant and membrane permeabilizing agent perhaps resulted in enhancing the killing activity of neutrophils against the organisms.
Highlights
Enterohaemorrhagic Escherichia coli O157:H7 is a Gram-negative human pathogen that causes bloody diarrhea as well leads to severe abdominal cramps in the infected patients
R. tomentosa was evaluated for its ability in increasing killing activity of human neutrophils against
The percentage survival of E. coli after exposed to neutrophils in the presence of the extract is given in Figure 1A and B
Summary
Enterohaemorrhagic Escherichia coli O157:H7 is a Gram-negative human pathogen that causes bloody diarrhea as well leads to severe abdominal cramps in the infected patients. It has been well demonstrated that the bacterial cell membrane is considered as a defensive barrier known to protect the pathogenic bacteria from environmental stress, and, plant extracts possessing an ability to alter bacterial membrane integrity is another strategy to make the pathogen more susceptible to the killing activity of host immune cells or antimicrobials (plant derived drugs) [9,10]. In view of this point, plants exhibiting immunostimulatory effects or have an ability to alter membrane integrity could be exploited to eliminate E. coli O157:H7 infections. Effects of the extract on membrane integrity of the pathogen were evaluated
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