Aims
The goal was to study the effects of sub‐minimum inhibitory concentrations (sub‐MICs) of amoxicillin (AMX) on various physiological responses and virulence determinants in a commensal strain of ...Escherichia coli.
Materials and Results
The commensal strain was passaged under various sub‐MICs of AMX and its effect on bacterial growth, motility, biofilm formation, expression of outer membrane proteins (OMPs) and cell adhesion was analysed. Bacterial growth was diminished at 1/2 and 1/4 MICs of AMX with significant reduction in growth rate. Using crystal violet (CV) assays and quantification of surface polysaccharides we observed strong biofilm formation, together with reduced swimming motility in E. coli at 1/2 MIC of AMX. Differential OMP expression upon AMX sub‐MIC exposure coincided with enhanced cell adhesion to HT‐29 cells in vitro. The results demonstrated that sub‐MICs of AMX can stimulate unpredictable changes in commensal bacterial strains which can be a potent source for the propagation of antibiotic resistance.
Conclusions
The study reports that AMX at 1/2 MIC significantly compromised bacterial growth and swimming motility, alongside inducing biofilm formation. This was also accompanied by upregulation of a single OMP which subsequently increased cell adhesion capabilities in E. coli at 1/2 MIC, thereby enhancing its colonization and survival abilities within the gut microsphere.
Significance and Impact of the Study
For the first time, the effects of AMX sub‐MICs on a commensal E. coli strain were described. The results corroborate on how antibiotics can act as stimulatory molecules and determine the pathogenicity of commensal bacteria in vivo that can disseminate resistance to other intestinal pathogens or microbes.
This study intends to develop novel two antimicrobial phenolic chitosan Schiff bases (I) and (II) via coupling of chitosan with Indole-3-carboxaldehyde and 4-dimethylaminobenzaldehyde, respectively, ...for boosting the antimicrobial activity of native chitosan. The alterations in the chemical structure and morphology of the Schiff bases were verified using FT-IR, electronic spectrum analysis, and SEM, whereas the thermal properties were investigated by TGA and DSC instruments. The results obtained from the potentiometric analysis referred that the degrees of substitution were 1.15 and 12.05% for Schiff bases (I) and (II), respectively. The antimicrobial activities of Schiff base (I) were significantly augmented more than Schiff base (II) and chitosan. Minimum inhibitory concentration (MIC) of Schiff base (I) was perceived at 50 µg/ml against tested microorganisms except for B. cereus and C. albicans. The highest concentration of Schiff base (I) could inhibit the growth of Gram-positive up to 99%. However, Schiff base (II) recorded the maximum inhibition rate versus Gram-positive approximately 82%. The cytotoxicity of the developed materials was estimated by MTT assay that substantiated their safety to fibroblast cells. The findings emphasized that the developed Schiff bases might be implemented as antimicrobial contenders to pure chitosan for treatments of wound infections.
Essential oils are concentrated natural extracts derived from plants, which were proved to be good sources of bioactive compounds with antioxidative and antimicrobial properties. This study followed ...the effect of some commonly used essential oils in micellar and aqueous extract on some of the most common pathogenic bacteria. Frankincense, myrtle, thyme, lemon, oregano and lavender essential oils were tested against
,
,
,
and
. Both micellar and aqueous extracts were used for determination of their minimal inhibitory (MIC) and bactericidal concentrations (MBC). The most active oils were oregano, thyme, lemon and lavender, while the least active were frankincense and myrtle. Oregano oil presented up to 64 times lower MICs/MBCs than ethylic alcohol, if considered as standard, on all bacteria. Most susceptible bacteria were the Gram-positive cocci, including methicillin resistant
, while the most resistant was
. With some exceptions, the best activity was achieved by micelles suspension of essential oils, with MICs and MBCs ranging from 0.1% to > 50% v/v. Only oregano and lavender aqueous extracts presented bactericidal activity and only on
(MIC = 6.3%). Thyme, lemon and oregano oils present significantly lower overall average MICs for their micellar form than for their aqueous extracts. The present results may suggest some formulas of colloid or micelle suspensions of whole essential oils such as oregano, thyme or lemon oil, that may help in antimicrobial fight. Aqueous extracts of oregano or thyme oil with good antibacterial activity could also be used in selected cases.
Emergence of drug resistance has created unmet medical need for the development of new classes of antibiotics. Discovery of new antibacterial agents with new mode of action remains a high priority ...universally. 4(3H)-quinazolinone, a fused nitrogen heterocyclic compound has emerged as a biologically privileged structure, possessing a wide range of biological properties viz. anticancer, antibacterial, antitubercular, antifungal, anti-HIV, anticonvulsant, anti-inflammatory and analgesic activities. Promising antibacterial properties of quinazolinones have enthused the medicinal chemists to explore and develop this fused heterocyclic system for new antibacterial agents. Utilization of quinazolinone core for the design and synthesis of new antibacterial agents has recently gained momentum. This review aims to provide an overview of the structures and antibacterial activity of various 4(3H)-quinazolinone derivatives covering various aspects of in vitro and in vivo pharmacological activities and structure activity relationships (SARs).
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•Overview of the structures and antibacterial activity of various 4(3H)-Quinazolinone derivatives.•Discusses various aspects of in vitro and in vivo pharmacological activities and Structure Activity Relationships (SARs).•Recent reports on antibacterial activity of quinazolinone derivatives.
To assess the association between minimum inhibitory concentration (MIC) and clinical outcomes in a fungal keratitis clinical trial.
Experimental study using data from a randomized comparative trial.
...Of the 323 patients enrolled in the trial, we were able to obtain MIC values from 221 patients with monocular fungal keratitis.
The Mycotic Ulcer Treatment Trial I was a randomized, double-masked clinical trial comparing clinical outcomes of monotherapy with topical natamycin versus voriconazole for the treatment of fungal keratitis. Speciation and determination of MIC to natamycin and voriconazole were performed according to Clinical and Laboratory Standards Institute guidelines. The relationship between MIC and clinical outcome was assessed.
The primary outcome was 3-month best spectacle-corrected visual acuity. Secondary outcomes included 3-month infiltrate or scar size; corneal perforation and/or therapeutic penetrating keratoplasty; and time to re-epithelialization.
A 2-fold increase in MIC was associated with a larger 3-month infiltrate or scar size (0.21 mm; 95% confidence interval CI, 0.10-0.31; P < 0.001) and increased odds of perforation (odds ratio, 1.32; 95% CI, 1.04-1.69; P = 0.02). No correlation was found between MIC and 3-month visual acuity. For natamycin-treated cases, an association was found between higher natamycin MIC with larger 3-month infiltrate or scar size (0.29 mm; 95% CI, 0.15-0.43; P < 0.001) and increased perforations (odds ratio, 2.41; 95% CI, 1.46-3.97; P < 0.001). Among voriconazole-treated cases, the voriconazole MIC did not correlate with any of the measured outcomes in the study.
Decreased susceptibility to natamycin was associated with increased infiltrate or scar size and increased odds of perforation. There was no association between susceptibility to voriconazole and outcome.
is an important ecosystem entity of the Malaysian mangrove forest. Since the species grows in a harsh environment, any organism that is isolated from this species would be of huge interest due to its ...potential in having novel bioactive compounds. In the present work, we isolated, identified and characterized, a total of 78 fungal isolates harboring inside the leaf tissues of
. Molecular identification using the nuclear ribosomal DNA internal transcribe spacer (ITS) sequences returned with high similarity matches to known sequences in the GenBank. Maximum likelihood analysis revealed the phylogenetic relationship of all isolates from this study. Most of the dominating fungal endophytes were from the genera
, followed by
and
. Six isolates representing the genera
, and
, were further screened for their antagonism activities. Dual culture test assay revealed their inhibition percentages against the phytopathogenic fungus
between 45-66%, and 0.8-23% when using non-volatile test assay. Of the six isolates, only
and
sp. showed antibacterial activities against the pathogenic bacteria,
, and
, with the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) ranging from 0.5 to 2 mg/mL. The DPPH radical scavenging assay recorded a high level of antioxidant activity in
sp., 3-fold above that of
.
. We demonstrate for the first time, two members belonging to the endophytic fungal community in the tropical mangrove species that have potential use as antagonists and antibacterial agents for future biotechnological applications.
is a major foodborne pathogen which causes widespread contamination and infection worldwide.
Typhimurium is one of the leading serovars responsible for human and animal salmonellosis, globally. The ...increasing rate of antibiotic resistance in
Typhimurium poses a significant global concern, and an improved understanding of the distribution of antibiotic resistance patterns in
Typhimurium is essential for choosing the suitable antibiotic for the treatment of infections. To evaluate the roles of animal and human in antibiotic resistance dissemination, this study aims to categorize 11,447
. Typhimurium strains obtained across the food-chain, including food animals, retail meats and humans for 21 years in the United States by analyzing minimum inhibitory concentrations (MICs) values for 27 antibiotics. Random Forest Algorithm and Hierarchical Clustering statistics were used to group the strains according to their minimum inhibitory concentration values. Classification and Regression Tree analysis was used to identify the best classifier for human- and animal-populations' isolates. We found the persistent population or multi-drug resistant strains of
. Typhimurium across the four time periods (1996∼2000, 2001∼2005, 2006∼2010, 2011∼2016). Importantly, we also detected that there was more diversity in the MIC patterns among
. Typhimurium strains isolated between 2011 and 2016, which suggests significant emergence of diversified multi-drug resistant strains. The most frequently observed (43%) antibiotic resistance patterns found in
. Typhimurium were tetra-resistant pattern ASSuT (ampicillin, streptomycin, sulfonamides, and tetracycline) and the penta-resistant pattern ACSSuT (ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline). Animals (mainly swine and bovine) are the major source for these two frequently found antibiotic resistance patterns. The occurrence of antibiotic resistant strains from humans and chicken is alarming. Strains were mostly susceptible to fluoroquinolones. Together, this study helped in understanding the expansion of dynamics of antibiotic resistance of
. Typhimurium and recommended fluoroquinolones as a possible treatment options against
. Typhimurium infection.
Antimicrobial resistance seriously threatened human health, and new antimicrobial agents are desperately needed. As one of the largest classes of plant secondary metabolite, flavonoids can be widely ...found in various parts of the plant, and their antibacterial activities have been increasingly paid attention to. Based on the physicochemical parameters and antibacterial activities of sixty-six flavonoids reported, two regression equations between their ACD/LogP or LogD
and their minimum inhibitory concentrations (MICs) to gram-positive bacteria were established with the correlation coefficients above 0.93, and then were verified by another sixty-eight flavonoids reported. From these two equations, the MICs of most flavonoids against gram-positive bacteria could be roughly calculated from their ACD/LogP or LogD
, and the minimum MIC was predicted as approximately 10.2 or 4.8 μM, more likely falls into the range from 2.6 to 10.2 μM, or from 1.2 to 4.8 μM. Simultaneously, both tendentiously concave regression curves indicated that the lipophilicity is a key factor for flavonoids against gram-positive bacteria. Combined with the literature analyses, the results also suggested that the cell membrane is the main site of flavonoids acting on gram-positive bacteria, and which likely involves the damage of phospholipid bilayers, the inhibition of the respiratory chain or the ATP synthesis, or some others.
This study aimed to investigate the antioxidant and antibacterial activities (AOA and ABA) of broccoli sprout extract (BSE) nanoliposomes co-encapsulated into basil seeds gum (BSG). The ...characteristics of the BSE-loaded nanoliposomes and nano-capsules were firstly determined. Their functional (antioxidant and antibacterial) properties were tested in vitro, and their anti-Listeria effect (at 0.4 and 0.8% w/w) on ricotta cheese was evaluated. The produced nanoliposomes and nano-capsules were spherical in shape and did not tend to accumulate. The mean particle size, polydispersity index (PDI) and encapsulation efficiency (EE) were observed about 39.60 and 69.00 nm, 0.279 and 0.496, 85.73 and 88.46% for nano-capsules and nanoliposomes, respectively. The zeta potential (ζ) values were observed at −65.73 and −71.16 mV and therefore the nanoparticles had good stability and uniform particle size distribution. Encapsulation had no significant effect on total phenol and flavonoids content of the BSE. The amounts of these active compounds were in the range of 25.12–26.97 mg GAE/g dw and 6.84–6.95 mg QE/g dw, respectively. The free and encapsulated BSE displaying good AOA in the DPPH, ABTS and FRAP assays. Results of the ABA measured by inhibition zone diameter and the minimum inhibitory concentration (MIC) demonstrated that the free BSE had antibacterial action against the tested Gram-positive and Gram-negative bacteria, and the nano-encapsulation process led to improved ABA of this extract. The organic acids in BES indicated the presence of high levels of citric, malic and oxalic acids at 613, 98 and, 45 (mg/g dw), respectively. The BSE-loaded nanoparticles showed remarkable anti-Listeria activity in ricotta cheese, which their activity increased with increasing their concentration. In conclusion, BSE-loaded nanoliposomes and nano-capsules have potential interest to be used as natural antioxidants and preservatives for food applications.
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•Co-encapsulation of nano-liposomes BSE into basil seed gum BSG was successfully achieved.•The co-encapsulated nano-liposomes had good stability and size distribution.•The liposomes were able to maintain the functional properties of the core.•Co-encapsulation of BSE as nano-liposomes showed anti-Listeria properties in Ricotta cheese.
Antimicrobial resistance represents a serious threat to human health across the globe. The cost of bringing a new antibiotic from discovery to market is high and return on investment is low. ...Furthermore, the development of new antibiotics has slowed dramatically since the 1950s' golden age of discovery. Plants produce a variety of bioactive secondary metabolites that could be used to fuel the future discovery pipeline. While many studies have focused on specific aspects of plants and plant natural products with antibacterial properties, a comprehensive review of the antibacterial potential of plants has never before been attempted.
This systematic review aims to evaluate reports on plants with significant antibacterial activities.
Following the PRISMA model, we searched three electronic databases: Web of Science, PubMed and SciFinder by using specific keywords: "plant," "antibacterial," "inhibitory concentration."
We identified a total of 6,083 articles published between 1946 and 2019 and then reviewed 66% of these (4,024) focusing on articles published between 2012 and 2019. A rigorous selection process was implemented using clear inclusion and exclusion criteria, yielding data on 958 plant species derived from 483 scientific articles. Antibacterial activity is found in 51 of 79 vascular plant orders throughout the phylogenetic tree. Most are reported within eudicots, with the bulk of species being asterids. Antibacterial activity is not prominent in monocotyledons. Phylogenetic distribution strongly supports the concept of chemical evolution across plant clades, especially in more derived eudicot families. The Lamiaceae, Fabaceae and Asteraceae were the most represented plant families, while
,
and
were the most studied species. South Africa was the most represented site of plant collection. Crude extraction in methanol was the most represented type of extraction and leaves were the main plant tissue investigated. Finally,
was the most targeted pathogenic bacteria in these studies. We closely examine 70 prominent medicinal plant species from the 15 families most studied in the literature.
This review depicts the current state of knowledge regarding antibacterials from plants and provides powerful recommendations for future research directions.
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