Carmen M S Ambrosio1, Carmen J Contreras-Castillo1, Eduardo M Da Gloria2. 1. Department of Agri-Food Industry, Food and Nutrition, "Luiz de Queiroz" College of Agriculture, University of São Paulo, São Paulo, SP, Brazil. 2. Department of Biological Science, Luiz de Queiroz" College of Agriculture, University of São Paulo, São Paulo, SP, Brazil.
Abstract
AIM: This study investigated the in vitro mechanism of action of a commercial citrus EO, Brazilian orange terpenes (BOT), on an enterotoxigenic Escherichia coli (ETEC) isolated from pig gut and on Lactobacillus rhamnosus. METHODS AND RESULTS: Firstly, bacteria were exposed sequentially to BOT every 3 h (three times) at sub-MICs and results showed that sequential exposure to BOT provoked a higher reduction of bacteria viability than a single exposure and the reduction of ETEC viability was higher compared to that of L. rhamnosus. Then, evaluation of the BOT effects on the cell membrane permeability and integrity, indicated that BOT increased the membrane permeability and caused disruptive effects on the integrity of bacterial cells as reflected by an increase of the relative electric conductivity and the release of essential cell constituents. Interestingly, BOT effects were more pronounced on the ETEC than on L. rhamnosus. This was ratified by scanning electron microscopy (SEM), which showed more noticeable morphological damages and disturbances on ETEC cells than L. rhamnosus cells. Limonene was detected as the major compound in BOT by polar/non-polar GC-MS (78.65% / 79.38%). CONCLUSIONS: Results revealed that the probable mechanism underlying the selective antibacterial action of the citrus EO, BOT, can be described as altering more remarkable the permeability and integrity of the cytoplasmic membrane as well as the external structure of an ETEC than L rhamnosus. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides information about the mechanism of antibacterial action displayed by a citrus EO, a by-product of the citrus processing industry, as a natural alternative to antibiotics used in pig production sector to combat pathogens as ETECs. This article is protected by copyright. All rights reserved.
AIM: This study investigated the in vitro mechanism of action of a commercial citrus EO, Brazilian orange terpenes (BOT), on an enterotoxigenic Escherichia coli (ETEC) isolated from pig gut and on Lactobacillus rhamnosus. METHODS AND RESULTS: Firstly, bacteria were exposed sequentially to BOT every 3 h (three times) at sub-MICs and results showed that sequential exposure to BOT provoked a higher reduction of bacteria viability than a single exposure and the reduction of ETEC viability was higher compared to that of L. rhamnosus. Then, evaluation of the BOT effects on the cell membrane permeability and integrity, indicated that BOT increased the membrane permeability and caused disruptive effects on the integrity of bacterial cells as reflected by an increase of the relative electric conductivity and the release of essential cell constituents. Interestingly, BOT effects were more pronounced on the ETEC than on L. rhamnosus. This was ratified by scanning electron microscopy (SEM), which showed more noticeable morphological damages and disturbances on ETEC cells than L. rhamnosus cells. Limonene was detected as the major compound in BOT by polar/non-polar GC-MS (78.65% / 79.38%). CONCLUSIONS: Results revealed that the probable mechanism underlying the selective antibacterial action of the citrus EO, BOT, can be described as altering more remarkable the permeability and integrity of the cytoplasmic membrane as well as the external structure of an ETEC than L rhamnosus. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides information about the mechanism of antibacterial action displayed by a citrus EO, a by-product of the citrus processing industry, as a natural alternative to antibiotics used in pig production sector to combat pathogens as ETECs. This article is protected by copyright. All rights reserved.
Authors: Carmen M S Ambrosio; Gloria L Diaz-Arenas; Leidy P A Agudelo; Elena Stashenko; Carmen J Contreras-Castillo; Eduardo M da Gloria Journal: Molecules Date: 2021-05-13 Impact factor: 4.411