1,721,026 research outputs found
Editorial: Natural substances: A new weapon against antibiotic-resistant bacteria in the clinical and veterinary field
Get PDFSpecial Issue: State-of-Art of Microbial Concerns in Food Safety
Get PDFThe microbiological quality of food remains an essential factor for industrial production and for consumers, as foodborne illnesses are still a widespread health and economic problem [...
Preparation and antibacterial activity of hybrid materials containing quaternary ammonium salt prepared via sol-gel process
No full textAbstractOrganic-inorganic hybrid coatings containing quaternary ammonium salts (QAS) bonded to the organic-inorganic network were prepared from tetraethoxysilane and triethoxysilane terminated poly(ethylene glycol)-block-poly(ethylene) using a sol-gel process. They were applied as a thin layer (0.6-1 μm) to PE films and the antibacterial activity of the coated films was tested against both Gram-negative (Escherichia coli ATCC 25922) and Gram-positive (Staphylococcus aureus ATCC 6538) bacteria. Measurements at different contact times showed a rapid decrease of the viable count for both the tested strains. In particular, after 48 h of contact, a decrease of 96.4% and 99.1% of E. coli and S. aureus, respectively, was observed. The permanence of the antibacterial activity of the coated films was demonstrated through repeated washings and prolonged immersion in physiological saline solutions at 37 °C. Indeed, due to the removal of QAS moieties by the nucleophilic attack of water, the antibacterial activity after 24 h was strongly reduced when measured on samples submitted to several washings. However, a quite good antibacterial activity was observed even on the same samples after 96 h, probably due to a spontaneous partial restoring of the QAS on the surface. Very good transparency, quite good adhesion and high wettability are further features of these hybrid coatings
Synergistic Inhibition of Methicillin-Resistant Staphylococcus aureus (MRSA) by Melaleuca alternifolia Chell (Tea Tree) and Eucalyptus globulus Labill. Essential Oils in Association with Oxacillin
Get PDFThe presence of antibiotic-resistant bacteria has become a major therapeutic priority. This trend indicates the need for alternative agents to antibiotics, such as natural compounds of plant origin. By assessing membrane permeability, we investigated the antimicrobial activity of Melaleuca alternifolia and Eucalyptus globulus essential oils (EOs) against three strains of methicillin-resistant Staphylococcus aureus (MRSA). Using the checkerboard method, the efficacy of single EOs, in association with each other or in combination with oxacillin, was quantified by calculating the fractional inhibitory concentrations (FIC Index). All EOs showed a reduction in bacterial load, an alteration of membrane permeability which leads to an increase in its function, resulting in the release of nucleic acids and proteins. The treatment with EO–oxacillin combinations and associated EO–EO resulted in a synergistic effect in most of the tests performed. EO–EO association showed a high activity in the alteration of the membrane, increasing the permeability to about 80% in all the MRSA strains treated. In conclusion, the combination of EOs and antibiotics represents a valid therapeutic support against MRSA bacteria, allowing for a decrease in the antibiotic concentration needed for therapeutic use
Evaluation of Bacterial Biofilm Removal Properties of MEDSTER 2000 Cold Sterilant on Different Materials
No full textWe studied the antibacterial and anti-biofilm properties of MEDSTER 2000, a pH neutral biodegradable mixed acidic peroxide disinfectant belonging to the class IIb medical device which has been designed for decontamination and cold sterilization of hospital instruments. The broth microdilution method was used to define the antibacterial activity against planktonic form of both classified bacteria and antibiotic resistant strains of clinical source, whereas effectiveness toward their biofilm was determined on mature biofilm, grown both on plastic and stainless steel surfaces. The results showed that for the planktonic form the antibacterial activity of MEDSTER 2000 was already observed after 10 min at the lowest concentration (0.1%), and this effect was not exposure-and/or concentration-dependent. After the same time of exposure at the concentration of 2% the disinfectant was able to completely eradicate all tested bacteria grown in sessile form on both surfaces, with a greater than 6 log CFU/cm2 reduction in viable cells. This result is supported by the microscope observation by crystal violet and live/dead assays. For the high antibacterial and anti-biofilm ability emerged, MEDSTER 2000 could represent a new and more effective approach for semicritical devices that need a high-level disinfection and could not sustain the process of heat sterilization
Efficacy and Synergistic Potential of Cinnamon (Cinnamomum zeylanicum) and Clove (Syzygium aromaticum L. Merr. & Perry) Essential Oils to Control Food-Borne Pathogens in Fresh-Cut Fruits
Get PDFThe presence of microbial pathogens in ready-to-eat produce represents a serious health problem. The antibacterial activity of cinnamon (Cinnamomum zeylanicum) and clove (Syzygium aromaticum L. Merr. & Perry) essential oils (EOs) was determined toward food-borne pathogens by agar disk diffusion and minimum inhibitory concentration (MIC) assays. The growth kinetics of all strains, both in a buffer suspension assay and “on food” in artificially contaminated samples, were also investigated. The two EOs demonstrated a good antibacterial effect both alone and in combination (EO/EO). The use of EO/EO led to a synergistic antibacterial effect, also confirmed by the growth kinetics studies, where the EOs were active after 10 h of incubation (p < 0.0001) at significantly lower concentrations than those when alone. In the “on food” studies performed on artificially contaminated fruit samples stored at 4 °C for 8 days, the greatest killing activity was observed at the end of the trial (8 days) with a reduction of up to 7 log CFU/g compared to the control. These results confirm the good antibacterial activity of the EOs, which were more effective when used in combination. Data from the "on food" studies suggest cinnamon and clove essential oils, traditionally used in the food industry, as a possible natural alternative to chemical additives.
Keywords: cinnamon and clove essential oils; synergistic activity; food-borne pathogens; fresh-cut fruit; bio-preservatio
Melaleuca alternifolia Cheel (Tea Tree) and Eucalyptus globulus Labill. Essential Oils’ Effectiveness Against an Acanthamoeba polyphaga Strain Responsible for Human Keratitis
Get PDFAmong free-living amoebae (FLA), Acanthamoeba polyphaga is an important causal
agent of Acanthamoeba keratitis (AK), a severe and potentially sight-threatening condition. The present study evaluated the “in vitro” efficiency of Melaleuca alternifolia Cheel (tea tree) (tea tree oil—TTO) and Eucalyptus globulus Labill. (Eucalyptus essential oil—EEO) essential oils against an Acanthamoeba strain isolated from human keratitis. The Minimum Inhibitory Concentration (MIC) of the EOs and the Fractional Inhibitory Concentration (FIC) Index were used to evaluate the decrease in viable cells of Acanthamoeba over time and at different concentrations of EOs, used alone or in association. A relevant amoebicidal effect emerged during the first hours of exposure for both compounds, and TTO was the most effective.
The TTO/EEO association clearly indicated a synergistic effect in all tests, and at 2 days
post-treatment, no viable A. polyphaga cells were observed at all tested concentrations. In conclusion, the potential therapeutic use of EOs represents a promising therapeutic strategy for the treatment of AK
Effects of Melaleuca alternifolia Chell (Tea Tree) and Eucalyptus globulus Labill. Essential Oils on Antibiotic-Resistant Bacterial Biofilms
Get PDFIn the present investigation, the anti-biofilm potential of two essential oils (EOs), Melaleuca alternifolia Chell (Tea-Tree) (TTO) and Eucalyptus globulus Labill. (EEO) was characterized and tested “in vitro” against both mature biofilms and biofilms in the process of formation, produced by strains belonging to three main categories of antibiotic resistant bacteria (ARB): Vancomycin-resistant enterococci (VRE), methicillin-resistant Staphylococcus aureus (MRSA) and broad-spectrum β-lactamase-producing Escherichia coli (ESBL). The study was carried out in 96-well microtiter-plates using EOs alone, in association with each other and in combination with antibiotics against both single and multi-species biofilm. The study demonstrated the ability of TTO and EEO to counteract the ARB strains in sessile form, with promising results in particular against the biofilm in formation. Mature biofilm by ESBL E. coli was the most sensitive in the results from the quantification study of viable cells performed in multi-species biofilms. Lastly, in all tests, carried out using TTO/EEO associations and EOs/antibiotic combinations, the synergistic effect which emerged from the FIC-index has been confirmed, and both the reduction of biofilm in formation, and the removal of mature structure was obtained at very low concentrations, with values from 4 to >512-fold lower than the minimum inhibitory concentration (MIC) of the single compounds
Antibiotic Resistance and Virulence Traits in Vancomycin-Resistant Enterococci (VRE) and Extended-Spectrum β-Lactamase/AmpCproducing(ESBL/AmpC) Enterobacteriaceaefrom Humans and Pets
Get PDFBackground: We investigated the virulence factors, genes, antibiotic resistance patterns,
and genotypes (VRE and ESBL/AmpC) production in Enterococci and Enterobacteriaceae strains
isolated from fecal samples of humans, dogs, and cats. Methods: A total of 100 fecal samples from
50 humans, 25 dogs, and 25 cats were used in the study. MICs of nine antimicrobials were
determined using the broth microdilution method. Polymerase chain reaction was used for the
detection of genes responsible for antibiotic resistance (VRE and ESBL/AmpC) and virulence genes
both in Enterococcus species, such as cytolysin (cylA, cylB, cylM), aggregation substance (agg),
gelatinase (gelE), enterococcal surface protein (esp), cell wall adhesins (efaAfs and efaAfm), and in
Enterobacteriaceae, such as cytolysin (hemolysin) and gelatinase production (afa, cdt, cnf1, hlyA,
iutA, papC, sfa). Results: Enterococcus faecium was the most prevalent species in humans and cats,
whereas Enterococcus faecalis was the species isolated in the remaining samples. A total of 200
Enterobacteriaceae strains were also detected, mainly from humans, and Escherichia coli was the most
frequently isolated species in all types of samples. In the Enterococcus spp, the highest percentages
of resistance for ampicillin, amoxicillin/clavulanate, erythromycin, tetracycline, ciprofloxacin,
teicoplanin, and vancomycin were detected in cat isolates (41.6%, 52.8%, 38.9%, 23.6%, 62.5%, 20.8%,
and 23.6% respectively), and in E. coli, a higher rate of resistance to cefotaxime and ceftazidime
emerged in cat and dog samples, if compared with humans (75.4% and 66.0%, 80.0% and 71.4%, and
32.0% and 27.2%, respectively). Regarding the total number of enterococci, 5% and 3.4% of the
strains were vancomycin and teicoplanin resistant, and the vancomycin resistance (van A) gene has
been detected in all samples by PCR amplification. All the Enterobacteriaceae strains were confirmed
as ESBL producers by PCR and sequencing, and the most frequent ESBL genes in E. coli strains from
humans and pet samples were blaCTX-M-1 and blaCTX-M-15. Conclusions: Our results provide evidence
that one or more virulence factors were present in both genera, underlining again the ability of pet
strains to act as pathogen
Essential Oils: A Natural Weapon against Antibiotic-Resistant Bacteria Responsible for Nosocomial Infections
Get PDFAbstract: The emergence of antibiotic-resistant bacteria has become a major concern worldwide. This
trend indicates the need for alternative agents to antibiotics, such as natural compounds of plant
origin. Using agar disc diffusion and minimum inhibitory concentration (MIC) assays, we investigated
the antimicrobial activity of Citrus aurantium (AEO), Citrus x limon (LEO), Eucalyptus globulus
(EEO), Melaleuca alternifolia (TTO), and Cupressus sempervirens (CEO) essential oils (EOs) against
three representatives of antibiotic-resistant pathogens and respective biofilms: vancomycin-resistant
enterococci (VRE), methicillin-resistant Staphylococcus aureus (MRSA), and extended-spectrum -
lactamase (ESBL)-producing Escherichia coli. Using the checkerboard method, the efficacy of the EOs
alone, in an association with each other, or in combination with the reference antibiotics was quantified
by calculating fractional inhibitory concentrations (FICs). All the EOs displayed antibacterial
activity against all strains to different extents, and TTO was the most effective. The results of the
EO–EO associations and EO–antibiotic combinations clearly showed a synergistic outcome in most
tests. Lastly, the effectiveness of EOs both alone and in association or combination against biofilm
formed by the antibiotic-resistant strains was comparable to, and sometimes better than, that of the
reference antibiotics. In conclusion, the combination of EOs and antibiotics represents a promising
therapeutic strategy against antibiotic-resistant bacteria, even protected inside biofilms, which can
allow decreasing the concentrations of antibiotics used
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