Lactic Acid Bacteria and Staphylococcus epidermidis
Lactic Acid Bacteria and Staphylococcus epidermidis
Introduction. Lactic acid bacteria (LAB) and bifidobacteria are able to produce antimicrobial compounds to inhibit opportunistic-wounding skin pathogen. The antimicrobial compounds produced are organic acids, putative bacteriocin, hydrogen peroxide, and diacetyl. Staphylococcus epidermidis is well-known as an opportunistic wounding skin pathogen in wound infections related to implanted medical devices.
Objective. To screen 87 strains of LAB and 3 strains of bifidobacteria for antimicrobial activity against Staphylococcus epidermidis. Additionally, this study sought to determine and quantify types of antimicrobial compounds produced by LAB.
Materials and Methods. Inhibitory activity of LAB and bifidobacteria on S. epidermidis was assessed with the spectrophotometric method using a 96-well microplate reader. Characterization of cell-free supernatant (CFS) was done using analytical methods. Lactobacillus fermentum (collected by the Bioprocess Department at the Universiti Sains Malaysia [BD]) 1912d, Lactobacillus casei BD 1415b, Lactobacillus fermentum BD 8313a, Pediococcus pentosaceus BD 1913b, and Weissella cibaria (collected by the Food Technology Department at the Universiti Sains Malaysia [FTDC]) 8643 with high percentage of inhibition (P < 0.05), ranging from 73.7% to 88.2%, as compared to the control, were selected for subsequent analyses. Upon neutralization, the antimicrobial activity showed a drastic drop (P < 0.05) in the percentage of inhibition. Concentrations of the inhibitive metabolites were produced in varying amounts and were strain dependent.
Results. Results demonstrated that lactic acid in all strains was produced in a more predominant amount than acetic acid. Protein concentration production ranged from 0.081–0.215 mg/mL. L. fermentum BD 1912d yielded as much as 0.014 mg/mL hydrogen peroxide, which was significantly higher than other strains studied. Diacetyl was produced in a higher concentration by Weissella cibaria FTDC 8643 at 2.884 ng/mL; the lowest concentration of 0.465 ng/mL was produced by Ped. pentosaceus BD 1913b.
Conclusion. Antimicrobial metabolites from CFS of lactic acid bacteria were effective in repressing the growth of opportunistic wounding dermal pathogen Staphylococcus epidermidis.
Staphylococcus epidermidis is a commensal organism having a benign relationship with the host on human skin. However, S. epidermidis is also an opportunistic pathogen and is ranked first in nosocomial and implant-based infections such as peripheral or central intravenous catheters, prosthetic heart valves, and prosthetic joints. Infections of S. epidermidis can occur at the device insertion site or in wounds. Due to their abundance, there is a high probability of device contaminations during insertion through the introduction of bacteria from the skin of the patient or from health care personnel. At least 22% of surgical site infections and cardiac device infections are caused by S. epidermidis. The occurrence of infection by this opportunistic wounding dermal pathogen has been attributed to the ability of S. epidermidis to adhere to biomaterial and to wound sites, causing the wound healing process to slowdown. Although S. epidermidis infections rarely develop into life-threatening diseases, their ubiquity and resisitance to treatment has led to an increased burden for the public health system, costing $2 billion annually in the United States. Similar to S. aureus, S. epidermidis also exhibits its virulence through biofilm formation, intercellular aggregation, protective exopolymers, toxins, and exoenzymes. The formation of biofilm has complicated various antibiotic treatments (methicillin, rifamycin, gentamycin, and erythromycin) at infection sites.S. epidermidis contains abundant surface proteins, bifunctional adhesion and autolysin, and the biofilm associated protein (Bap), all of which are likely to contribute to the hydrophobicity of the cell surface and promote the adhesion to abiotic surfaces such as catheters. A fibrinogen-binding protein of S. epidermidis is necessary and sufficient to promote S. epidermidis adhesion to fibrinogen in vitro and promotes central intravenous catheter-associated infection in vivo. Due to increasing resistance of the pathogen against antibiotics, the use of lactic acid bacteria (LAB) and bifidobacteria to inhibit pathogens is seen as a natural and nontoxic alternative.
Lactic acid bacteria and bifidobacteria are Gram-positive bacteria which have been associated with various health effects ranging from digestive health to metabolic diseases and, recently, dermal health as well. Most of these health benefits are related to the ability of LAB and bifidobacteria to produce a broad range of bioactive metabolites and acids in situ. Some antimicrobial metabolites exerted by LAB that are crucial for skin health include lactic and acetic acids, bacteriocin, hydrogen peroxide, diacetyl, and carbon dioxide. However, bifidobacteria do not produce hydrogen peroxide or bacteriocins.
Organic acids (lactic and acetic acids) are the main inhibitors among the antimicrobial compounds produced via fermentation. The acidic nature provides a suitable environment to prevent and inhibit the growth of many pathogenic and spoilage microorganisms. Lactic acid inhibits the pathogens through the penetration of the undissociated form across the membrane which interferes with the metabolic functions of the pathogen. The decrease in the intracellular pH causes dissipation of the membrane and leads to membrane disruption.
Bacteriocins exhibit antimicrobial activity towards closely related Gram-positive bacteria. As reviewed by Savadogo et al, bacteriocins generally consist of antimicrobial peptides that exhibit hydrophobic or amphiphilic properties to target bacterial membrane. They form pores on the membrane of the Gram-positive pathogen which increase membrane permeability and cause rapid cell death. On the other hand, hydrogen peroxide performs its inhibitory effect by oxidizing lipids in the membrane layer which increases membrane permeability, leading to denaturing of basic molecular structures of cellular proteins and subsequently causes cell destruction.
Abstract and Introduction
Abstract
Introduction. Lactic acid bacteria (LAB) and bifidobacteria are able to produce antimicrobial compounds to inhibit opportunistic-wounding skin pathogen. The antimicrobial compounds produced are organic acids, putative bacteriocin, hydrogen peroxide, and diacetyl. Staphylococcus epidermidis is well-known as an opportunistic wounding skin pathogen in wound infections related to implanted medical devices.
Objective. To screen 87 strains of LAB and 3 strains of bifidobacteria for antimicrobial activity against Staphylococcus epidermidis. Additionally, this study sought to determine and quantify types of antimicrobial compounds produced by LAB.
Materials and Methods. Inhibitory activity of LAB and bifidobacteria on S. epidermidis was assessed with the spectrophotometric method using a 96-well microplate reader. Characterization of cell-free supernatant (CFS) was done using analytical methods. Lactobacillus fermentum (collected by the Bioprocess Department at the Universiti Sains Malaysia [BD]) 1912d, Lactobacillus casei BD 1415b, Lactobacillus fermentum BD 8313a, Pediococcus pentosaceus BD 1913b, and Weissella cibaria (collected by the Food Technology Department at the Universiti Sains Malaysia [FTDC]) 8643 with high percentage of inhibition (P < 0.05), ranging from 73.7% to 88.2%, as compared to the control, were selected for subsequent analyses. Upon neutralization, the antimicrobial activity showed a drastic drop (P < 0.05) in the percentage of inhibition. Concentrations of the inhibitive metabolites were produced in varying amounts and were strain dependent.
Results. Results demonstrated that lactic acid in all strains was produced in a more predominant amount than acetic acid. Protein concentration production ranged from 0.081–0.215 mg/mL. L. fermentum BD 1912d yielded as much as 0.014 mg/mL hydrogen peroxide, which was significantly higher than other strains studied. Diacetyl was produced in a higher concentration by Weissella cibaria FTDC 8643 at 2.884 ng/mL; the lowest concentration of 0.465 ng/mL was produced by Ped. pentosaceus BD 1913b.
Conclusion. Antimicrobial metabolites from CFS of lactic acid bacteria were effective in repressing the growth of opportunistic wounding dermal pathogen Staphylococcus epidermidis.
Introduction
Staphylococcus epidermidis is a commensal organism having a benign relationship with the host on human skin. However, S. epidermidis is also an opportunistic pathogen and is ranked first in nosocomial and implant-based infections such as peripheral or central intravenous catheters, prosthetic heart valves, and prosthetic joints. Infections of S. epidermidis can occur at the device insertion site or in wounds. Due to their abundance, there is a high probability of device contaminations during insertion through the introduction of bacteria from the skin of the patient or from health care personnel. At least 22% of surgical site infections and cardiac device infections are caused by S. epidermidis. The occurrence of infection by this opportunistic wounding dermal pathogen has been attributed to the ability of S. epidermidis to adhere to biomaterial and to wound sites, causing the wound healing process to slowdown. Although S. epidermidis infections rarely develop into life-threatening diseases, their ubiquity and resisitance to treatment has led to an increased burden for the public health system, costing $2 billion annually in the United States. Similar to S. aureus, S. epidermidis also exhibits its virulence through biofilm formation, intercellular aggregation, protective exopolymers, toxins, and exoenzymes. The formation of biofilm has complicated various antibiotic treatments (methicillin, rifamycin, gentamycin, and erythromycin) at infection sites.S. epidermidis contains abundant surface proteins, bifunctional adhesion and autolysin, and the biofilm associated protein (Bap), all of which are likely to contribute to the hydrophobicity of the cell surface and promote the adhesion to abiotic surfaces such as catheters. A fibrinogen-binding protein of S. epidermidis is necessary and sufficient to promote S. epidermidis adhesion to fibrinogen in vitro and promotes central intravenous catheter-associated infection in vivo. Due to increasing resistance of the pathogen against antibiotics, the use of lactic acid bacteria (LAB) and bifidobacteria to inhibit pathogens is seen as a natural and nontoxic alternative.
Lactic acid bacteria and bifidobacteria are Gram-positive bacteria which have been associated with various health effects ranging from digestive health to metabolic diseases and, recently, dermal health as well. Most of these health benefits are related to the ability of LAB and bifidobacteria to produce a broad range of bioactive metabolites and acids in situ. Some antimicrobial metabolites exerted by LAB that are crucial for skin health include lactic and acetic acids, bacteriocin, hydrogen peroxide, diacetyl, and carbon dioxide. However, bifidobacteria do not produce hydrogen peroxide or bacteriocins.
Organic acids (lactic and acetic acids) are the main inhibitors among the antimicrobial compounds produced via fermentation. The acidic nature provides a suitable environment to prevent and inhibit the growth of many pathogenic and spoilage microorganisms. Lactic acid inhibits the pathogens through the penetration of the undissociated form across the membrane which interferes with the metabolic functions of the pathogen. The decrease in the intracellular pH causes dissipation of the membrane and leads to membrane disruption.
Bacteriocins exhibit antimicrobial activity towards closely related Gram-positive bacteria. As reviewed by Savadogo et al, bacteriocins generally consist of antimicrobial peptides that exhibit hydrophobic or amphiphilic properties to target bacterial membrane. They form pores on the membrane of the Gram-positive pathogen which increase membrane permeability and cause rapid cell death. On the other hand, hydrogen peroxide performs its inhibitory effect by oxidizing lipids in the membrane layer which increases membrane permeability, leading to denaturing of basic molecular structures of cellular proteins and subsequently causes cell destruction.
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