Antimicrobial Susceptibility of Escherichia coli Strains Isolated from Alouatta spp. Feces to Essential Oils

Antibacterial and Antibiofilm Effects of Different Samples of Five Commercially Available Essential Oils

Essential oils (EOs) have gained economic importance due to their biological activities, and increasing amounts are demanded everywhere. However, substantial differences between the same essential oil samples from different suppliers are reported-concerning their chemical composition and bioactivities-due to numerous companies involved in EOs production and the continuous development of online sales. The present study investigates the antibacterial and antibiofilm activities of two to four samples of five commercially available essential oils (Oregano, Eucalyptus, Rosemary, Clove, and Peppermint oils) produced by autochthonous companies. The manufacturers provided all EOs' chemical compositions determined through GC-MS. The EOs' bioactivities were investigated in vitro against Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). The antibacterial and antibiofilm effects (ABE% and, respectively, ABfE%) were evaluated spectrophotometrically at 562 and 570 nm using microplate cultivation techniques. The essential oils' calculated parameters were compared with those of three standard broad-spectrum antibiotics: Amoxicillin/Clavulanic acid, Gentamycin, and Streptomycin. The results showed that at the first dilution (D1 = 25 mg/mL), all EOs exhibited antibacterial and antibiofilm activity against all Gram-positive and Gram-negative bacteria tested, and MIC value > 25 mg/mL. Generally, both effects progressively decreased from D1 to D3. Only EOs with a considerable content of highly active metabolites revealed insignificant differences. E. coli showed the lowest susceptibility to all commercially available essential oils-15 EO samples had undetected antibacterial and antibiofilm effects at D2 and D3. Peppermint and Clove oils recorded the most significant differences regarding chemical composition and antibacterial/antibiofilm activities. All registered differences could be due to different places for harvesting the raw plant material, various technological processes through which these essential oils were obtained, the preservation conditions, and complex interactions between constituents.

An Optimization of Oregano, Thyme, and Lemongrass Essential Oil Blend to Simultaneous Inactivation of Relevant Foodborne Pathogens by Simplex–Centroid Mixture Design

(1) Background: This study aimed to use the simplex–centroid mixture design methodology coupled with a microdilution assay to predict optimal essential oil (EO) formulations against three potential foodborne pathogens simultaneously through the desirability (D) function. (2) Methods: Oregano (ORE; Origanum vulgare), thyme (THY; Thymus vulgaris), and lemongrass (LG; Cymbopogon citratus) and their blends were evaluated concerning minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for Salmonella enterica serotype Enteritidis, Escherichia coli and Staphylococcus aureus. (3) Results: THY combined with ORE or LG were the most promising EO formulations in inhibiting and killing each bacterium separately. Regarding the simultaneous effect, the optimal proportion for maximum inhibition was composed of 75% ORE, 15% THY, and 10% LG, while for maximum inactivation was 50% ORE, 40% THY, and 10% LG. (4) Conclusion: The multiresponse optimization allowed identifying an EO blend to simultaneously control three potential foodborne pathogens. This first report could be a helpful natural and green alternative for the industry to produce safer food products and mitigate public health risks.

Lemongrass Growth, Essential Oil, and Active Substances as Affected by Water Deficit

Environmental stress has a major influence on the growth and quality of medicinal plants. More than half of the agricultural land worldwide suffers from a lack of water. In this study, we estimated the effect of different irrigation intervals on growth, yield, and essential oil content as well as their effect on the main compounds of the essential oil of lemongrass, Cymbopogon citratus. The major objective was to test how much irrigation consumption can be lowered without a significant impact on yield and quality properties. Water deficit led to significant decreases in growth characteristics including the number of tillers as well as fresh and dry herb yield. In addition, the relative leaf greenness decreased under water deficit, especially in plants irrigated every 20 days. In contrast, proline content increased with increasing water deficit, especially in plants irrigated every 15 and 20 days. Essential oil percentage also increased under a water deficit condition, and the highest essential oil percentage was observed in plants irrigated every 15 and 20 days. However, the yield of essential oil per plant significantly decreased due to decreasing the herb yield. GC-MS analysis identified 31 compounds, mainly geranial and neral. Geranial and neral percentage decreased under a water deficit of 10-day irrigation intervals but increased with increasing the water deficit severity at irrigation intervals of 15 and 20 days. These results suggest that the lemongrass plant was sensitive to drought. Nevertheless, the quality represented by essential oil percentage and the main active substances improved with prolonging the irrigation intervals. This study recommends increasing irrigation intervals to 10 days to maintain small decreases in the yield with higher quality. In addition, it is recommended to conduct more studies to improve the growth of lemongrass under water shortage conditions.

Essential-Oil-Loaded Nanoemulsion Lipidic-Phase Optimization and Modeling by Response Surface Methodology (RSM): Enhancement of Their Antimicrobial Potential and Bioavailability in Nanoscale Food Delivery System

Nanoencapsulation is an attractive technique used for incorporating essential oils in foods. Thus, our main goal was to formulate a novel nanoemulsion (NE) with nanoscale droplet size and lowest interfacial tension in the oil–water interface, contributing positively to the stability and the enhancement of essential oil potential. Thereby, response surface methodology (RSM), with mixture design was used to optimize the composition of the NE lipid phase. The essential oil combinations were encapsulated through high-pressure homogenization (HPH) with the binary emulsifier system (Tween 80: Gum Arabic). Then, the electrophoretic and physical properties were evaluated. We also conducted a follow-up stability and antimicrobial study that examined the stabilization mechanism of optimal NE. Thereafter, the effect of nanoencapsulation on the essential oil composition was assessed. The RSM results were best fitted into polynomial models with regression coefficient values of more than 0.95. The optimal NE showed a nanometer-sized droplet (270 nm) and lower interfacial tension (~11 mN/m), favoring negative ζ-potential (−15 mV), showing good stability under different conditions—it synergistically enhances the antimicrobial potential. GC-MS analysis showed that the use of HPH affected the active compounds, consistent with the differences in linalool and 2-Caren-10-al content. Hence, the novel nanometric delivery system contributes to food industry fortification.

Essential Oils: An Impending Substitute of Synthetic Antimicrobial Agents to Overcome Antimicrobial Resistance

Antimicrobial resistance (AMR) is an emerging problem in the world that has a significant impact on our society. AMR made conventional drugs futile against microorganisms and diseases untreatable. Plant-derived medicines are considered to be safe alternatives as compared to synthetic drugs. Active ingredients and the mixtures of these natural medicines have been used for centuries, due to their easy availability, low cost, and negligible side effects. Essential oils (EOs) are the secondary metabolites that are produced by aromatic plants to protect them from microorganisms. However, these EOs and their constituents have shown good fighting potential against drug-resistant pathogens. These oils have been proved extremely effective antimicrobial agents in comparison to antibiotics. Also, the combination of synthetic drugs with EOs or their components improve their efficacy. So, EOs can be established as an alternative to synthetic antimicrobial agents to eradicate tough form of infectious microorganisms. EO's can interact with multiple target sites, like the destruction of cytoplasm membrane or inhibition of protein synthesis and efflux pump, etc. The purpose of this review is to provide information about the antimicrobial activity of EOs attained from different plants, their combination with synthetic antimicrobials. In addition, mechanism of antimicrobial activity of several EOs and their constituents was reported.

Entrapment of a phage cocktail and cinnamaldehyde on sodium alginate emulsion-based films to fight food contamination by Escherichia coli and Salmonella Enteritidis

Notwithstanding the implementation of good processing practices in food companies and appropriate washing of food products by the consumer, Salmonella and Escherichia coli outbreaks continue to occur. In this study, different combinations of bacteriophages (phages) and cinnamaldehyde (CNMA) were incorporated on sodium alginate emulsion-based films to impart them with antimicrobial activity towards S. Enteritidis and E. coli. Films were prepared by casting and they were characterized in terms of CNMA and/or phages loading, thickness, moisture content, water vapor permeability (WVP), swelling index (SW), chemical interactions by FTIR, surface morphology by SEM and antimicrobial performance. Results showed that phages incorporation was not compromised by CNMA as evidenced by their viability inside the films. Increasing CNMA concentration yielded formulations less heterogeneous and a higher amount of CNMA loaded. Films characterization revealed that, in general, phages incorporation did not introduce significant changes on films parameters while the presence of CNMA increased the roughness, thickness and swelling ability of films. Sodium alginate films incorporated with EC4 and φ135 phages displayed antimicrobial activity against E. coli and S. Enteritidis, respectively, while CNMA empowered the films with activity against both species. Combination of both phages with the higher concentration of CNMA resulted in a synergic antimicrobial effect against E. coli and a facilitative effect against Salmonella. Overall, incorporation of EC4 and φ135 phages together with CNMA on alginate emulsion-based films holds great potential to be further applied in food packaging to prevent food contamination.

Molecular characterization of Escherichia coli isolated from cheese and biocontrol of Shiga toxigenic E. coli with essential oils

The current research was carried out to study the incidence of Escherichia coli (E. coli) in Egyptian cheese (Kariesh and Ras) and molecular characterization of certain E. coli virulence genes (stx1, stx2, eaeA, hlyA and fimH) using multiplex PCR technique. Biocontrol of E. coli with essential oils (clove and thyme oil) was also studied. A total of 150 random samples of Kariesh and Ras cheese (75 each) were collected from various areas in Governorate of Menoufia. According to our results, the frequency of E. coli isolated from Kariesh and Ras cheese was 16% and 5.3%, respectively. Serological identification classified the E. coli strains into two groups, enterohemorrhagic E. coli (EHEC) serogroup (O26: H11, O91: H21, O111: H2 and O103: H2). While the enterotoxigenic E. coli (ETEC) serogroup were detected as O125: H21 which is the most prevalent strain. O171: H2, O86 and O119: H6 belonging to enteropathogenic E. coli (EPEC). The most prevalent gene detected in E. coli strains was stx1 (87.5%) followed by stx2 (86%), fimH (75%), hlyA (50%) and eaeA (25%) genes. Concerning the antimicrobial activity with essential oils, thyme oil (1%) is considered as the bactericidal effect against E. coli (ATCC35150) with improved the sensory evaluation than clove oil (1%). In conclusion, Kariesh and Ras cheese are extremely tainted with pathogenic E. coli strains, which represent a strong hazard on the human health.

EFFECTIVENESS OF MENIRAN (PHYLLANTHUS NIRURI LINN) AS ANTIBACTERIAL FOR RESISTANCE ANTIBIOTICS PREVENTION OF ENTEROTOXIN ESCHERICHIA COLI

ABSTRACT               Escherichia coli (E. coli) can be isolated from the environment both inside and outside the hospes body. There were 89 serotypes in which 21% showed resistance to various antibiotics, such as E. coli enterotoxin. Alternative efforts were needed as a substitute for antibiotics, one of them through the use of medicinal plants, such as meniran (Phyllanthus niruri Linn).  Meniran plant is an immunomodulator that serves to repair the immune system of the body. The research was done through several stages: isolation and identification of  E. coli enterotoxin from several broiler farms in East Java using the polymerase chain reaction (PCR) method, E. coli resistance test against some antibiotics, making meniran extract and activation test against E. coli enterotoxin The study was divided into five treatments: T0+ (group of chickens were infected by E. coli enterotoxin), T0- (control group, not infected), T1 (infected by E. coli enterotoksin + 20% meniran extract), T2 (infected by E. coli enterotoksin + 25% extract meniran), T3 (infected by E. coli enterotoxin + 30% extract meniran). Data were analyzed by ANOVA (Analysis of Variance). The results were showed that all of  E. coli DNA isolates which tested by the PCR method was showed positive reactions at 600 bp. In the next stage, that E. coli enterotoxin are resistance to some antibiotics, such as Amoxicillin, Amphicillin, Erythromycin, Cephalosporins, Tetracycline, Cloxacillin and Gentamicin. Furthermore, 30% Phyllanthus niruri linn extract  effective as an antibacterial for the prevention of antibiotic resistance from E. coli enterotoxin. 

Molecular characterization of Escherichia coli recovered from traditional milk products in Kashan, Iran

AIM

Shiga toxigenic Escherichia coli (STEC) strains as emerging groups of foodborne pathogens are responsible for most foodborne illnesses. The aim of this study was to determine the antibiotic resistance pattern in STEC isolated from traditional milk products and their molecular characterization.

MATERIALS AND METHODS

A total of 116 samples were randomly purchased from local markets in Kashan, Iran, and evaluated for the occurrence of STEC by culturing and molecular methods. The antibiotic resistance of obtained isolates was determined by Kirby Bauer method. Furthermore, isolates were assayed for the presence of Shiga toxins (stx1 and stx2) and intimin gene (eae).

RESULTS

The incidence of E. coli in 60 ice cream, 30 yoghurt, and 26 cheese samples was 8.33%, 10%, and 11.54%, respectively. The findings showed that 11 out of 11 (100%) E. coli had both stx1 and stx2 while eae gene was not found in E. coli isolated of traditional milk products. For E. coli strains carrying stx1 and stx2, highest antibiotic sensitive levels were related to trimethoprim/sulfamethoxazole, norfloxacin, chloramphenicol, and ciprofloxacin, respectively.

CONCLUSION

The results showed relationship between the presence of virulence factors and antimicrobial resistance. These results can be used for further studies on STEC as an emerging foodborne pathogen.

Inactivation of Norovirus by Lemongrass Essential Oil Using a Norovirus Surrogate System

This study investigated the effect of lemongrass essential oil (LGEO) on the infectivity and viral replication of norovirus. Murine norovirus 1 (MNV-1), a surrogate of human norovirus, was preincubated with LGEO and then used to infect RAW 264.7 cells in a plaque reduction assay. LGEO exhibited a significant reduction in MNV-1 plaque formation in both time- and dose-dependent manners. The quantification of viral genome by quantitative real-time PCR showed similar results in line with those of the plaque reduction assay. It was revealed that citral, a single compound in LGEO, showed dramatic reduction in MNV-1 infectivity (-73.09% when using a treatment of 0.02%, v/v). The inhibitory activity of LGEO on viral replication was further investigated in HG23 cells that harbored a human norovirus replicon. LGEO treatment significantly reduced viral replication in HG23 cells, which suggests that LGEO may have dual inhibitory activities that inactivate viral coat proteins required for viral infection and suppress norovirus genome replication in host cells. In animal experiments, oral administration of murine norovirus preincubated with LGEO significantly suppressed virus infectivity in vivo. Collectively, these results suggest that LGEO, in particular the LGEO component citral, inactivates the norovirus and its subsequent replication in host cells. Thus, LGEO shows promise as a method of inhibiting norovirus within the food industry.