Antibacterial Effect of Essential Oils (Clove Oil, Castor Oil and Ginger Oil) Against Human Pathogenic Bacteria

Essential oils are volatile, natural, complex compounds which are produced as secondary metabolites by plants for their protection against various microorganisms as well as pests. A wide range of plants have been explored for their essential oils in the past few decades. The study was conducted to determine the antibacterial activity of essential oils against human pathogenic bacteria which were gram positive (Staphylococcus aureus and Streptococcus pyogenes) as well as gram negative (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Shigella sonnei). Five ml of three different oils, i.e. clove oil, castor oil, and ginger oil, were taken in a test tube so that each oil had four different concentrations. Four concentrations of (0, 25, 50 and 75) μL of oils were mixed with 1000, 975, 950 and 925 μL of DMSO respectively to make it a volume of 1ml. It was observed that clove oil was effective against the entire gram positive as well as gram negative bacteria that were used. The inhibition zone was greatest in the case of clove oil at 75 μL against P. aeruginosa (23 mm) and the smallest zone of inhibition was shown by castor oil against K. pneumoniae (12 mm). Other oils were sensitive as well as resistant to the bacteria. Hence, it is found that different oils have shown inhibitory activity towards different pathogens to a variable extent. However, clove oil was inhibitory to all the bacteria in all concentrations. Int. J. Appl. Sci. Biotechnol. Vol 9(4): 250-255

Effect of Plasmonic Gold Nanoprisms on Biofilm Formation and Heat Shock Proteins Expression in Human Pathogenic Bacteria

Gold nanoparticles have gained interest in biomedical sciences in the areas of nano-diagnostics, bio-labeling, drug delivery, and bacterial infection. In this study, we examined, for the first time, the antibacterial and antibiofilm properties of plasmonic gold nanoprisms against human pathogenic bacteria using MIC and crystal violet. In addition, the expression level of GroEL/GroES heat shock proteins was also investigated by western blot. Gold nanoparticles were characterized by TEM and EDX, which showed equilateral triangular prisms with an average edge length of 150 nm. Antibacterial activity testing showed a great effect of AuNPs against pathogenic bacteria with MICs values ranging from 50 μg/mL to 100 μg/mL. Nanoparticles demonstrated strong biofilm inhibition action with a percentage of inhibition ranging from 40.44 to 82.43%. Western blot analysis revealed that GroEL was an AuNPs-inducible protein with an increase of up to 66.04%, but GroES was down-regulated with a reduction of up to 46.81%. Accordingly, plasmonic gold nanoprisms, could be a good candidate for antibiotics substitution in order to treat bacterial infections.

Co-Existence of Free-Living Amoebae and Potential Human Pathogenic Bacteria Isolated from Rural Household Water Storage Containers

This study investigated the co-existence of potential human pathogenic bacteria and free-living amoebae in samples collected from stored water in rural households in South Africa using borehole water as a primary water source. Over a period of 5 months, a total of 398 stored water and 392 biofilm samples were collected and assessed. Free-living amoebae were identified microscopically in 92.0% of the water samples and 89.8% of the biofilm samples. A further molecular identification using 18S rRNA sequencing identified Vermamoeba vermiformis, Entamoeba spp., Stenamoeba spp., Flamella spp., and Acanthamoeba spp. including Acanthamoeba genotype T4, which is known to be potentially harmful to humans. Targeted potential pathogenic bacteria were isolated from the water samples using standard culture methods and identified using 16S rRNA sequencing. Mycobacterium spp., Pseudomonas spp., Enterobacter spp., and other emerging opportunistic pathogens such as Stenotrophomonas maltophilia were identified. The results showed the importance of further studies to assess the health risk of free-living amoebae and potential human pathogenic bacteria to people living in rural communities who have no other option than to store water in their homes due to water shortages.

Dual Transcriptomic Analysis Reveals Metabolic Changes Associated with Differential Persistence of Human Pathogenic Bacteria in Leaves of Arabidopsis and Lettuce

Understanding the molecular determinants underlying the interaction between the leaf and human pathogenic bacteria is key to provide the foundation to develop science-based strategies to prevent or decrease the pathogen contamination of leafy greens. In this study, we conducted a dual RNA-sequencing analysis to simultaneously define changes in the transcriptomic profiles of the plant and the bacterium when they come in contact. We used an economically relevant vegetable crop, lettuce (Lactuca sativa L. cultivar Salinas), and a model plant, Arabidopsis thaliana Col-0, as well as two pathogenic bacterial strains that cause disease outbreaks associated with fresh produce, Escherichia coli O157: H7 and Salmonella enterica serovar Typhimurium 14028 s (STm 14028 s). We observed commonalities and specificities in the modulation of biological processes between Arabidopsis and lettuce and between O157: H7 and STm 14028 s during early stages of the interaction. We detected a larger alteration of gene expression at the whole transcriptome level in lettuce and Arabidopsis at 24 hours post inoculation with STm 14028 s compared to that with O157: H7. In addition, bacterial transcriptomic adjustments were substantially larger in Arabidopsis than in lettuce. Bacterial transcriptome was affected at a larger extent in the first 4 hours compared to the subsequent 20 hours after inoculation. Overall, we gained valuable knowledge about the responses and counter-responses of both bacterial pathogen and plant host when these bacteria are residing in the leaf intercellular space. These findings and the public genomic resources generated in this study are valuable for additional data mining.

ANTIBACTERIAL ACTIVITY OF ROBUSTA COFFEE (Coffea robusta L.) PEEL EXTRACT AGAINST HUMAN PATHOGENIC BACTERIA

Now in these days infectious diseases seriously affect human health and sometimes these infections might become the cause of human mortality. Most of these infectious diseases are caused by bacteria, viruses, and fungi. Although large numbers of antibiotics are available increasing drug resistance in these microorganisms became a serious matter of concern in the scientific community. There is an urgent need for research on alternate natural products that can manage these pathogenic microorganisms without inducing any resistance. The purpose of this study was to determine the antibacterial activity of Robusta coffee (Coffea robusta L.) fruit peel extract against 5 human pathogenic bacteria i.e. Bacillus subtilis ATCC 6633, Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and Salmonella thypi NCTC 786. The sample was extracted using the maceration method with methanol as the solvent. The antibacterial activity of fruit peel extract was determined by using the agar diffusion method while the presence of active ingredients was determined by the using TLC-Bioautography assay performed using the mobile phase of n-hexane: ethyl acetate (1 : 3). The results of the study revealed significant antibacterial activity of coffee peel extract against E. coli and B. subtilis with an inhibition zone of 10.15 mm and 10.96 mm, respectively. Furthermore, results of the TLC-Bioautography revealed that the compounds at Rf 0.76 inhibit the growth of E. coli and the compounds at Rf 0.27 inhibit the growth of B. subtilis bacteria. These active spots were suspected to be flavonoid and phenolic compounds, respectively but further confirmation detail study is required in the future.

Semi- and fully synthetic carbohydrate vaccines against pathogenic bacteria: recent developments

The importance of vaccine-induced protection was repeatedly demonstrated over the last three decades and emphasized during the recent COVID-19 pandemic as the safest and most effective way of preventing infectious diseases. Vaccines have controlled, and in some cases, eradicated global viral and bacterial infections with high efficiency and at a relatively low cost. Carbohydrates form the capsular sugar coat that surrounds the outer surface of human pathogenic bacteria. Specific surface-exposed bacterial carbohydrates serve as potent vaccine targets that broadened our toolbox against bacterial infections. Since first approved for commercial use, antibacterial carbohydrate-based vaccines mostly rely on inherently complex and heterogenous naturally derived polysaccharides, challenging to obtain in a pure, safe, and cost-effective manner. The introduction of synthetic fragments identical with bacterial capsular polysaccharides provided well-defined and homogenous structures that resolved many challenges of purified polysaccharides. The success of semisynthetic glycoconjugate vaccines against bacterial infections, now in different phases of clinical trials, opened up new possibilities and encouraged further development towards fully synthetic antibacterial vaccine solutions. In this mini-review, we describe the recent achievements in semi- and fully synthetic carbohydrate vaccines against a range of human pathogenic bacteria, focusing on preclinical and clinical studies.

Conjugation Dynamics of Self-Transmissible and Mobilisable Plasmids into E. coli O157:H7 on Arabidopsis thaliana Rosettes

Many antibiotic resistance genes present in human pathogenic bacteria are believed to originate from environmental bacteria. Conjugation of antibiotic resistance conferring plasmids is considered to be one of the major reasons for the increasing prevalence of antibiotic resistances. A hotspot for plasmid-based horizontal gene transfer is the phyllosphere, i.e., the surfaces of aboveground plant parts. Bacteria in the phyllosphere might serve as intermediate hosts with transfer capability to human pathogenic bacteria. In this study, the exchange of mobilisable and self-transmissible plasmids via conjugation was evaluated. The conjugation from the laboratory strain Escherichia coli S17-1, the model phyllosphere coloniser Pantoea eucalypti 299R, and the model pathogen E. coli O157:H7 to the recipient strain E. coli O157:H7::MRE103 (EcO157:H7red) in the phyllosphere of Arabidopsis thaliana was determined. The results suggest that short-term occurrence of a competent donor is sufficient to fix plasmids in a recipient population of E. coli O157:H7red. The spread of self-transmissible plasmids was limited after initial steep increases of transconjugants that contributed up to 10% of the total recipient population. The here-presented data of plasmid transfer will be important for future modelling approaches to estimate environmental spread of antibiotic resistance in agricultural production environments.