Comparison of Antibacterial Efficacy of Triple Antibiotic-Loaded Hydrogel Versus Modified Triple Antibiotic-Loaded Hydrogel as Intracanal Medicament Against Enterococcus faecalis: An In vitro Study

OBJECTIVE

Triple antibiotic paste (TAP) is known to have an essential role in the success of endodontic treatment by eliminating pathogens from the root canal system. Unfortunately, it causes discolouration and cytotoxicity at high concentrations. The objective of this research was to assess and compare the antimicrobial effectiveness of various concentrations (1 mg, 5 mg, 10 mg) of TAP, TAP hydrogel (TAPH), M-TAP, and M-TAP hydrogel (MTAPH) against Enterococcus faecalis.

METHODS

The agar well diffusion method was used to assess the antibiotic sensitivity of the following intracanal medicaments: TAP (ciprofloxacin, metronidazole, and minocycline) mixed in a ratio of 1: 1: 1; TAPH, M-TAP (ciprofloxacin, metronidazole, and amoxicillin), M-TAPH and plain hydrogel. Each tested medicament was individually evaluated for its antimicrobial activity against Enterococcus faecalis. Structural and topographical characterisation were analysed using a Scanning Electron Microscope (SEM) and interpreted using ImageJ software. A microdilution broth test was performed to examine the minimum inhibitory concentration and minimum bactericidal concentration (MBC) of M-TAP and TAP.

RESULTS

Except for the plain hydrogel, M-TAP and hydrogel and TAP and hydrogel showed significantly varied inhibitory zones at different concentrations. M-TAPH showed the highest mean zone of inhibition of 21.6, 33.33 and 38.0 mm at a concentration of 1, 5, and 10 mg/mL when compared to TAPH, which showed a mean zone of inhibition of 3.3 mm,12.3 mm, 21.3 mm at the respective concentrations. The MIC study shows that more than 75% of Enterococcus faecalis growth was inhibited by M-TAP at a concentration of 5 μg/mL, whereas TAP showed inhibition at a concentration of 35 μg/mL. MBC results indicate that almost 99.9% of the bacterial population was killed at a concentration of 100 μg/mL (10-1) for TAP and 10 μg/mL (10-2) for M-TAP.

CONCLUSION

The antibacterial efficacy of M-TAP was significantly higher than TAP. Application of M-TAP at lower doses is advised to overcome the disadvantages seen with TAP.

Antibacterial activity in egg samples from small-spotted catshark Scyliorhinus canicula and nursehound Scyliorhinus stellaris: A preliminary investigation

The study aims to identify antibacterial properties in unfertilized eggs of Scyliorhinus canicula and Scyliorhinus stellaris. Despite challenging marine conditions, these eggs retain their integrity for extended periods and remain unaffected by pathogens. The antibacterial activity was measured using minimum inhibitory and minimum bactericidal concentration analysis. The eggs of S. stellaris exhibited a slight inhibitory effect against Staphylococcus aureus and Listeria monocytogenes, whereas both species' eggs showed no activity against gram-negative microorganisms.

Comparison of the Antibacterial Activity of Selected Deep Eutectic Solvents (DESs) and Deep Eutectic Solvents Comprising Organic Acids (OA-DESs) Toward Gram-Positive and Gram-Negative Species

Deep eutectic solvents (DESs) have been intensively investigated in recent years for their antibacterial properties, with DESs that comprise organic acids (OA-DESs) showing promising antibacterial action. However a majority of the reports focused only on a limited number strains and techniques, which is not enough to determine the antibacterial potential of a substance. To bridge this gap, the antibacterial activity of classical DESs and OA-DESs is assessed on twelve Gram-negative and Gram-positive bacteria strains, with some of them exhibiting specific resistance toward antibiotics. The investigated formulations of OA-DESs comprise glycolic, malic, malonic, and oxalic acids as representatives of this group. Using a range of microbiological assays as well as physicochemical characterization methods, a major difference of the effectiveness between the two groups is demonstrated, with OA-DESs exhibiting, as expected, greater antibacterial effectiveness than classical DESs. Most interestingly, slight differences in the minimum inhibitory and bactericidal concentration values as well as time-kill kinetics profiles are observed between Gram-positive and Gram-negative strains. Transmission electron microscopy analysis reveals the effect of the treatment of the bacteria with the representatives of both groups of DESs, which allows us to better understand the possible mechanism-of-action of these novel materials.

N-Pyrazinylhydroxybenzamides as biologically active compounds: a hit-expansion study and antimicrobial evaluation

Background: The development of novel antimicrobial drugs is an essential part of combatting the uprising of antimicrobial resistance. Proper hit-to-lead development is crucially needed. Methods & results: We present a hit-expansion study of N-pyrazinyl- and N-pyridyl-hydroxybenzamides with a comprehensive determination of structure-activity relationships. The antimicrobial screening revealed high selectivity to staphylococci along with antimycobacterial activity with the best value of 6.25 μg/ml against Mycobacterium tuberculosis H37Rv. We proved an inhibition of proteosynthesis and a membrane depolarization of methicillin-resistant Staphylococcus aureus. Conclusion: Our results are a good starting point for further development of new antimicrobial compounds, where the next step would be tuning the potential between relatively nonspecific membrane depolarization effect and specific inhibition of proteosynthesis.

Zinc Oxide-Based Nanoformulation Zinkicide Mitigates the Xylem-Limited Pathogen Xylella fastidiosa in Tobacco and Southern Highbush Blueberry

The xylem-limited pathogen Xylella fastidiosa causes severe economic losses worldwide, and no effective antimicrobial disease management options are available. The goal of this study was to evaluate the efficacy of a novel ZnO-based nanoparticle formulation, Zinkicide TMN110 (ZnK), against X. fastidiosa in vitro and in planta. In vitro, minimum bactericidal concentration (MBC) of ZnK analyzed in Pierce's Disease 2 medium was estimated at approximately 60 ppm. Time-kill kinetics assay showed a 100% reduction of culturable X. fastidiosa in less than 1 h after ZnK treatment. Microfluidic chambers assays showed that ZnK also inhibits X. fastidiosa cell aggregation and growth under flow conditions. Phytotoxicity assessments in the greenhouse demonstrated that ZnK can be applied as a soil drench in 50 ml at 500 ppm/plant/week up to four times to tobacco and blueberry without causing visible damage. ZnK was also evaluated for disease control in the greenhouse using tobacco infected with X. fastidiosa subsp. fastidiosa strain TemeculaL. ZnK soil drench weekly applications at concentrations of 500 followed by 1,000 ppm (500/1,000) and 500/500/1,000 ppm (in 50 ml each), reduced X. fastidiosa populations by >2 to 3 log₁₀ units and disease severity by approximately 57 and 76%, respectively, compared with the untreated control. Similarly, when blueberry plants infected with X. fastidiosa subsp. multiplex strain AlmaEm3 were soil drenched with ZnK at concentrations 1,000/1,000 ppm and 1,000/1,000/500 ppm (in 200 ml each), the bacterial population was reduced by approximately 1 to 2 log₁₀ units, and disease severity decreased by approximately 39 and 43%, respectively. Overall, this study shows antibacterial activity of ZnK against X. fastidiosa and its effectiveness in plants to reduce disease symptoms under controlled conditions.

Nanoparticle surface stabilizing agents influence antibacterial action

The antibacterial properties of nanoparticles are of particular interest because of their potential to serve as an alternative therapy to combat antimicrobial resistance. Metal nanoparticles such as silver and copper nanoparticles have been investigated for their antibacterial properties. Silver and copper nanoparticles were synthesized with the surface stabilizing agents cetyltrimethylammonium bromide (CTAB, to confer a positive surface charge) and polyvinyl pyrrolidone (PVP, to confer a neutral surface charge). Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and viable plate count assays were used to determine effective doses of silver and copper nanoparticles treatment against Escherichia coli, Staphylococcus aureus and Sphingobacterium multivorum. Results show that CTAB stabilized silver and copper nanoparticles were more effective antibacterial agents than PVP stabilized metal nanoparticles, with MIC values in a range of 0.003 μM to 0.25 μM for CTAB stabilized metal nanoparticles and 0.25 μM to 2 μM for PVP stabilized metal nanoparticles. The recorded MIC and MBC values of the surface stabilized metal nanoparticles show that they can serve as effective antibacterial agents at low doses.

A systematic review of antibacterial activity of polyphenolic extract from date palm (Phoenix dactylifera L.) kernel

Background: Emergence of antibiotic-resistant bacteria makes exploration of natural antibacterial products imperative. Like other fruit processing industry by-products, date kernels, a waste from date processing industry is rich in its extractable polyphenols. The rich polyphenolic content suggests that date kernel extracts (DKE) can be a cost-effective source of antimicrobial agents, however, their antibacterial activity is poorly understood. Hence, a systematic review of available literature to establish DKE's antibacterial activity is warranted. Methods: A systematic PRISMA approach was employed, and relevant studies were identified using defined keywords from Google Scholar, Scopus, PubMed, and Web of Science databases. The search results were screened based on predefined eligibility criteria and data extraction, organization, pooling, and descriptive statistical analyses of original research records conducted. Results: A total of 888 published records were retrieved from databases. Preliminary screening by applying specific eligibility criteria reduced records to 96 which after full text screening further decreased to 14 records. Escherichia coli and Staphylococcus aureus were the most studied organisms. Results indicate moderate to highly active effect shown by the less polar solvent based DKE's against Gram-positive and by the aqueous based DKE's against Gram-negative bacteria. The review confirms antibacterial activity of DKE against both Gram-positive and -negative bacteria. Heterogeneity in reported polyphenolic content and antibacterial activity are due to differences in cultivars, extraction methods, test methods, model organisms, etc. Use of standardized protocols for isolation, characterization, testing of DKE's active polyphenols to elucidate its antibacterial activity is recommended to establish the clinical efficacy of natural antibacterial compounds from DKE. Conclusion: This review outlines the current knowledge regarding antibacterial activity of polyphenolic DKE, identifying gaps in information and provides key recommendations for future research directions.

Efficacy of Five Disinfectant Products Commonly Used in Pig Herds against a Panel of Bacteria Sensitive and Resistant to Selected Antimicrobials

The growing threat of antimicrobial resistance worldwide has led to an increasing concern in the human, veterinary, and environmental fields, highlighting the need for strategies to effectively control bacterial contamination. Correct biosecurity practices, including the appropriate use of disinfectants, play a crucial role in controlling bacterial contamination. This study aimed to verify whether the recommended concentrations defined according to the Defra General Orders concentration (GO, published by the UK Department for Environment, Food and Rural Affairs' disinfectant-approval scheme) of five commercial disinfectant preparations (peroxygen-based, phenol-based, two halogen-releasing agents, and glutaraldehyde/quaternary ammonium compound-based; disinfectants A to E, respectively) were sufficient to inhibit growth and inactivate selected bacterial strains, including some that carry known phenotypic patterns of multidrug resistance. The effectiveness of each disinfectant was expressed as the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values, determined by the broth-microdilution method. The results indicate that the type of disinfectant and its concentration influence the inhibitory and bactericidal efficacy. The glutaraldehyde/quaternary ammonium compound-based (disinfectant D) and chlorocresol-based products (disinfectant B) were the most effective, and the GO concentration was bactericidal in all the strains tested. The efficacy of the other compounds varied, depending on the bacterial species tested. The GO concentrations were at least able to inhibit the bacterial growth in all the products and bacterial strains tested. A greater tolerance to the compounds was observed in the strains of E. coli with multidrug-resistance profiles compared to the strains that were sensitive to the same antimicrobials.

Evolution of Chlorhexidine Susceptibility and of the EfrEF Operon among Enterococcus faecalis from Diverse Environments, Clones, and Time Spans

Chlorhexidine (CHX) is widely used to control the spread of pathogens (e.g., human/animal clinical settings, ambulatory care, food industry). Enterococcus faecalis, a major nosocomial pathogen, is broadly distributed in diverse hosts and environments facilitating its exposure to CHX over the years. Nevertheless, CHX activity against E. faecalis is understudied. Our goal was to assess CHX activity and the variability of ChlR-EfrEF proteins (associated with CHX tolerance) among 673 field isolates and 1,784 E. faecalis genomes from the PATRIC database from different sources, time spans, clonal lineages, and antibiotic-resistance profiles. The CHX MIC (MICCHX) and minimum bactericidal concentration (MBCCHX) against E. faecalis presented normal distributions (0.5 to 64 mg/L). However, more CHX-tolerant isolates were detected in the food chain and recent human infections, suggesting an adaptability of E. faecalis populations in settings where CHX is heavily used. Heterogeneity in ChlR-EfrEF sequences was identified, with isolates harboring incomplete ChlR-EfrEF proteins, particularly the EfrE identified in the ST40 clonal lineage, showing low MICCHX (≤1mg/L). Distinct ST40-E. faecalis subpopulations carrying truncated and nontruncated EfrE were detected, with the former being predominant in human isolates. This study provides a new insight about CHX susceptibility and ChlR-EfrEF variability within diverse E. faecalis populations. The MICCHX/MBCCHX of more tolerant E. faecalis (MICCHX = 8 mg/L; MBCCHX = 64 mg/L) remain lower than in-use concentrations of CHX (≥500 mg/L). However, increased CHX use, combined with concentration gradients occurring in diverse environments, potentially selecting multidrug-resistant strains with different CHX susceptibilities, signals the importance of monitoring the trends of E. faecalis CHX tolerance within a One Health approach. IMPORTANCE Chlorhexidine (CHX) is a disinfectant and antiseptic used since the 1950s and included in the World Health Organization's list of essential medicines. It has been widely applied in hospitals, the community, the food industry, animal husbandry and pets. CHX tolerance in Enterococcus faecalis, a ubiquitous bacterium and one of the leading causes of human hospital-acquired infections, remains underexplored. Our study provides novel and comprehensive insights about CHX susceptibility within the E. faecalis population structure context, revealing more CHX-tolerant subpopulations from the food chain and recent human infections. We further show a detailed analysis of the genetic diversity of the efrEF operon (previously associated with E. faecalis CHX tolerance) and its correlation with CHX phenotypes. The recent strains with a higher tolerance to CHX and the multiple sources where bacteria are exposed to this biocide alert us to the need for the continuous monitoring of E. faecalis adaptation toward CHX tolerance within a One Health approach.

Antimicrobial Activity of β-Sitosterol Isolated from Kalanchoe tomentosa Leaves Against Staphylococcus aureus and Klebsiella pneumonia

<b>Background and Objective:</b> <i>Kalanchoe tomentosa</i> is identified and their different characteristics regarding the antibacterial and antioxidant properties have a vast effect. Fresh <i>K. tomentosa</i> leaves obtained from Bandung, Indonesia was extracted using n-hexane followed by serial dichloromethane maceration. <b>Materials and Methods:</b> N-hexane and ethyl acetate were used to separate the dichloromethane extract using vacuum liquid chromatography and the isolated compounds were recrystallized with n-hexane. <b>Results:</b> About 37 mg of dichloromethane extract was obtained from the extraction process. Recrystallized compound isolates were identified as stigmast-5-en-3-ol or β-sitosterol. Both dichloromethane extract and β-sitosterol isolated compounds showed strong bacteriostatic activity against <i>S. aureus</i> with MIC = 15.63 and 7.81 μg mL<sup></sup><sup>1</sup> and<i> K. pneumonia</i> with MIC = 7.81 and 31.25 μg mL<sup></sup><sup>1</sup>, respectively. However, only dichloromethane extract exhibited a bactericidal effect (7.81 μg mL<sup></sup><sup>1</sup>). <b>Conclusion:</b> The pure β-sitosterol compound was isolated from<i> K. tomentosa</i> dichloromethane extract. Both the dichloromethane extract and the isolated β-sitosterol compound had antibacterial effects against <i>S. aureus</i> and <i>K. pneumonia.</i&gt.

In Vitro Antimicrobial Potential of CAPE and Caffeamide Derivatives against Oral Microbes

Caffeic acid phenethyl ester (CAPE) is a natural component isolated from propolis and used in traditional medicine. We aimed to investigate the antimicrobial properties and action mechanism of CAPE and caffeamide derivatives (26G and 36M) against oral disease microbes. We resolved the minimum inhibitory and bactericidal concentrations of 26G and 36M and their stability at different temperatures and pH. We also evaluated their effect on biofilm formation and antibiotic resistance gene expression in methicillin-resistant Staphylococcus aureus (MRSA). Our results revealed that 26G and 36M showed the best anticancer and antimicrobial activities, respectively, compared with the other four caffeamide derivatives. Both 26G and 36M showed heat-dependent decreases in antimicrobial activity. The 36M derivative was stable irrespective of pH, whereas 26G was not stable under high pH conditions. Biofilm formation and antibiotic resistance-related gene expression were consistent with their respective phenotypes. This study provides evidence for the potential application of CAPE and caffeamide derivatives in dental medicine to cure or prevent oral diseases.

Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) for Twelve Antimicrobials (Biocides and Antibiotics) in Eight Strains of Listeria monocytogenes

When selecting effective doses of antimicrobials, be they biocides or antibiotics, it is essential to know the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of these substances. The present research determined the MICs and MBCs for three biocides, sodium hypochlorite (SH), benzalkonium chloride (BC), and peracetic acid (PAA), and nine antibiotics in eight strains of Listeria monocytogenes of varying serotypes. Marked intra-species differences were observed in the resistance of L. monocytogenes to the biocides and antibiotics. The MICs (ppm) for the biocides ranged between 1750 and 4500 for SH, 0.25 and 20.00 for BC, and 1050 and 1700 for PAA. Their MBCs (ppm) ranged from 2250 to 4500 for SH, 0.50 to 20.00 for BC, and 1150 to 1800 for PAA. The MICs (ppm) for antibiotics lay between 1 and 15 for ampicillin, 8 and 150 for cephalothin, 20 and 170 for cefoxitin, 0.05 and 0.20 for erythromycin, 4 and 50 for chloramphenicol, 3 and 100 for gentamicin, 2 and 15 for tetracycline, 2 and 80 for vancomycin, and 160 and 430 for fosfomycin. The corresponding MBCs (ppm) were from 5 to 20 for ampicillin, 9 to 160 for cephalothin, 70 to 200 for cefoxitin, 4 to 5 for erythromycin, 9 to 70 for chloramphenicol, 5 to 100 for gentamicin, 3 to 30 for tetracycline, 3 to 90 for vancomycin, and 160 to 450 for fosfomycin. Notably, erythromycin showed considerable efficacy, demonstrated by the low values for both MIC and MBC. Based on EUCAST and the CLSI criteria, all strains were susceptible to erythromycin. All strains were resistant to cephalothin, cefoxitin, gentamicin, and fosfomycin. Further values for resistance were 87.50% for ampicillin and vancomycin, 75.00% for tetracycline, and 62.50% for chloramphenicol. The high prevalence of antibiotic resistance is a matter for concern. A positive correlation was found between MIC and MBC values for most of the biocides and antibiotics. The higher the hydrophobicity of the cell surface, the higher the susceptibility to biocides, suggesting that surface characteristics of bacterial cells influence resistance to these compounds.

Antibacterial Effect of Colloidal Suspensions Varying in Silver Nanoparticles and Ions Concentrations

A lot of effort has been dedicated recently to provide a better insight into the mechanism of the antibacterial activity of silver nanoparticles (AgNPs) colloidal suspensions and their released silver ionic counterparts. However, there is no consistency regarding whether the antibacterial effect displayed at cellular level originates from the AgNPs or their ionic constitutes. To address this issue, three colloidal suspensions exhibiting different ratios of AgNPs/silver ions were synthesized by a wet chemistry method in conjunction with tangential flow filtration, and were characterized and evaluated for their antimicrobial properties against two gram-negative, Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa), and two gram-positive, Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis), bacterial strains. The produced samples contained 25% AgNPs and 75% Ag ions (AgNP_25), 50% AgNPs and 50% Ag ions (AgNP_50), and 100% AgNPs (AgNP_100). The sample AgNP_100 demonstrated the lowest minimum inhibitory concentration values ranging from 4.6 to 15.6 ppm for all four bacterial strains, while all three samples indicated minimum bactericidal concentration (MBC) values ranging from 16.6 ppm to 62.5 ppm against all strains. An increase in silver ions content results in higher bactericidal activity. All three samples were found to lead to a significant morphological damage by disruption of the bacterial cell membranes as analyzed by means of scanning electron microscopy (SEM). The growth kinetics demonstrated that all three samples were able to reduce the bacterial population at a concentration of 3.1 ppm. SEM and growth kinetic data underline that S. epidermidis is the most sensitive among all strains against the investigated samples. Our results showed that all three AgNPs colloidal suspensions exhibited strong antibacterial properties and, thus, they can be applied in medical devices and antimicrobial control systems.

In vitro activity of essential oils against microbial isolates from otitis externa cases in dogs

Despite the number of studies focused on the potential use of essential oils (EOs) as an alternative to conventional treatments of canine external otitis, there is controversy about their antimicrobial activity which could be explained by differences in technical or biological aspects. This study focuses on the antimicrobial activity of three single EO compounds (thymol, cinnamaldehyde and carvacrol) and two EOs (clove and oregano) against clinical isolates recovered from canine otitis externa cases (14 bacterial isolates belonging to five different genera and six Malassezia pachydermatis isolates). All compounds showed activity and cinnamaldehyde exhibited the highest bactericidal and fungicidal activity. The susceptibility was lower among bacterial isolates than fungal isolates, being this difference more evident for Gram-positive bacteria. No relationship between antibiotic multi-resistant profile and susceptibility to compounds was observed. To sum up, our results provide appropriate information about appropriate concentrations of promising candidates for the topic treatment of canine otitis.

In Vitro Activity and Clinical Outcomes of Clofazimine for Nontuberculous Mycobacteria Pulmonary Disease

Limited data are available regarding the in vitro activity of clofazimine against nontuberculous mycobacteria (NTM) or on outcomes of clofazimine-containing regimens in NTM-pulmonary disease (PD). Therefore, we evaluated the in vitro activity of clofazimine and the clinical outcomes of clofazimine-containing regimens. We evaluated clofazimine in vitro activity for 303 NTM isolates from NTM-PD patients. Fifty-seven clarithromycin-resistant and 35 amikacin-resistant isolates were also analyzed. Culture conversion after a 12-month treatment regimen containing clofazimine was evaluated in 58 NTM-PD patients, including 20 patients with drug-resistant isolates. Most of the 303 isolates (238/303) had minimum inhibitory concentrations (MICs) ≤ 0.25 µg/mL for clofazimine (57/63 Mycobacterium avium, 53/57 M. intracellulare, 49/52 M. kansasii, 22/64 M. abscessus, and 57/67 M. massiliense). For the 57 clarithromycin-resistant and 35 amikacin-resistant isolates, most had MICs ≤ 0.25 µg/mL (47/57 and 32/35, respectively). Among the 38 NTM-PD patients without resistance to clarithromycin or amikacin, 47% achieved culture conversion (8/27 M. abscessus, 9/9 M. massiliense, 0/1 M. avium, and 1/1 M. intracellulare). The conversion rate was higher in the MIC ≤ 0.25 µg/mL group than in the MIC = 0.5 µg/mL group (13/18 vs. 5/20, p = 0.004), and an MIC ≤ 0.25 µg/mL remained a significant factor in multivariable analysis. Culture conversion was achieved in 20% of 20 patients with clarithromycin- or amikacin-resistant isolates. However, a clofazimine MIC ≤ 0.25 µg/mL was not significant for culture conversion in the 58 NTM-PD patients, regardless of the drug resistance pattern. Clofazimine was effective in vitro against NTM species. Some patients on clofazimine-containing regimens achieved culture conversion.

Responsive Quaternized PDMAEMA Copolymers with Antimicrobial Action

In this work, the antimicrobial action of partially quaternized poly(2-(dimethylamino)ethyl methacrylate) (PQDMAEMA) copolymers using different alkyl halides is presented. The poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) homopolymer was synthesized by group transfer polymerization, followed by the modification of its tertiary amine groups, using bromoethane, iodoethane, bromohexane and bromoethanol, to introduce permanent cationic, quaternary ammonium salt moieties, randomly distributed along the polymer chains. In all cases, the degree of quaternization was low, at ~10 mol%, as verified by proton nuclear magnetic resonance spectroscopy to preserve the thermo-responsive character of the PDMAEMA precursor polymer. The biocidal activity of the lightly quaternized PQDMAEMA copolymers against Escherichia coli and Staphylococcus aureus was evaluated by calculating the minimum inhibitory concentration (MIC) as well as the minimum bactericidal concentration (MBC) of the polymers and by comparing them to the respective values of the precursor non-quaternized PDMAEMA homopolymer. The antibacterial mechanism of action in the solution was studied by zeta potential measurements, scanning electron microscopy and protein leakage tests signifying the disruption of the outer membrane of the bacterial cells to release their periplasmic proteins.

In Vitro Profiling of Antitubercular Compounds by Rapid, Efficient, and Nondestructive Assays Using Autoluminescent Mycobacterium tuberculosis

Anti-infective drug discovery is greatly facilitated by the availability of in vitro assays that are more proficient at predicting the preclinical success of screening hits. Tuberculosis (TB) drug discovery is hindered by the relatively slow growth rate of Mycobacterium tuberculosis and the use of whole-cell-based in vitro assays that are inherently time-consuming, and for these reasons, rapid, noninvasive bioluminescence-based assays have been widely used in anti-TB drug discovery and development. In this study, in vitro assays that employ autoluminescent M. tuberculosis were optimized to determine MIC, minimum bactericidal concentration (MBC), time-kill curves, activity against macrophage internalized M. tuberculosis (90% effective concentration [EC₉₀]), and postantibiotic effect (PAE) to provide rapid and dynamic biological information. Standardization of the luminescence-based MIC, MBC, time-kill, EC_90, and PAE assays was accomplished by comparing results of established TB drugs and two ClpC1-targeting TB leads, ecumicin and rufomycin, to those obtained from conventional assays and/or to previous studies. Cumulatively, the use of the various streamlined luminescence-based in vitro assays has reduced the time for comprehensive in vitro profiling (MIC, MBC, time-kill, EC_90, and PAE) by 2 months. The luminescence-based in vitro MBC and EC₉₀ assays yield time and concentration-dependent kill information that can be used for pharmacokinetic-pharmacodynamic (PK-PD) modeling. The MBC and EC₉₀ time-kill graphs revealed a significantly more rapid bactericidal activity for ecumicin than rufomycin. The PAEs of both ecumicin and rufomycin were comparable to that of the first-line TB drug rifampin. The optimization of several nondestructive, luminescence-based TB assays facilitates the in vitro profiling of TB drug leads in an efficient manner.

Residue Dynamics of Streptomycin in Citrus Delivered by Foliar Spray and Trunk Injection and Effect on 'Candidatus Liberibacter asiaticus' Titer

Streptomycin (STR) has been used to control citrus huanglongbing (HLB) caused by 'Candidatus Liberibacter asiaticus' (CLas) via foliar spray. Here, we studied the residue dynamics of STR and its effect on CLas titers in planta applied by foliar spray and trunk injection of 3-year-old citrus trees that were naturally infected by CLas in the field. After foliar spray, STR levels in leaves peaked at 2 to 7 days postapplication (dpa) and gradually declined thereafter. The STR spray did not significantly affect CLas titers in leaves of treated plants as determined by quantitative PCR. After trunk injection, peak levels of STR were observed 7 to 14 dpa in the leaf and root tissues, and near-peak levels were sustained for another 14 days before significantly declining. At 12 months after injection, moderate to low or undetectable levels of STR were observed in the leaf, root, and fruit, depending on the doses of STR injected, with a residue level of 0.28 µg/g in harvested fruit at the highest injection concentration of 2.0 µg/tree. CLas titers in leaves were significantly reduced by trunk injection of STR at 1.0 or 2.0 g/tree, starting from 7 dpa and throughout the experimental period. The reduction of CLas titers was positively correlated with STR residue levels in leaves. The in planta minimum effective concentration of STR needed to suppress the CLas titer to an undetectable level (cycle threshold ≥36.0) was 1.92 µg/g fresh weight. Determination of the in planta minimum effective concentration of STR against CLas and its spatiotemporal residue levels in planta provides the guidance to use STR for HLB management.

Antibacterial Activity of Co(III) Complexes with Diamine Chelate Ligands against a Broad Spectrum of Bacteria with a DNA Interaction Mechanism

Cobalt coordination complexes are very attractive compounds for their therapeutic uses as antiviral, antibacterial, antifungal, antiparasitic, or antitumor agents. Two Co(III) complexes with diamine chelate ligands ([CoCl₂(dap)₂]Cl (1) and [CoCl₂(en)₂]Cl (2)) (where dap = 1,3-diaminopropane, en = ethylenediamine) were synthesized and characterized by elemental analysis, an ATR technique, and a scan method and sequentially tested against Gram-positive and Gram-negative bacteria. The minimum inhibitory concentration results revealed that anaerobic and microaerophilic bacteria were found to be the most sensitive; the serial passages assay presented insignificant increases in bacterial resistance to both compounds after 20 passages. The synergy assay showed a significant reduction in the MIC values of nalidixic acid when combined with Compounds (1) or (2). The assessment of cell damage by the complexes was performed using scanning electron microscopy, transmission electron microscopy, and confocal microscopy, which indicated cell membrane permeability, deformation, and altered cell morphology. DNA interaction studies of the Co(III) complexes with plasmid pBR322 using spectrophotometric titration methods revealed that the interaction between Complex (1) or (2) and DNA suggested an electrostatic and intercalative mode of binding, respectively. Furthermore, the DNA cleavage ability of compounds by agarose gel electrophoresis showed nuclease activity for both complexes. The results suggest that the effect of the tested compounds against bacteria can be complex.

Antimicrobial Activity of Fermented Vegetable Byproduct Extracts for Food Applications

To prevent foodborne diseases and extend shelf-life, antimicrobial agents may be used in food to inhibit the growth of undesired microorganisms. In addition to the prevention of foodborne diseases, another huge concern of our time is the recovery of agri-food byproducts. In compliance with these challenges, the aim of this work was to more deeply investigate the antimicrobial activity of extracts derived from fermented tomato, melon, and carrot byproducts, previously studied. All the fermented extracts had antimicrobial activity both in vitro and in foodstuff, showing even higher activity than commercial preservatives, tested for comparison against spoilage microorganisms and foodborne pathogens such as Salmonella spp., L. monocytogenes, and B. cereus. These promising results highlight an unstudied aspect for the production of innovative natural preservatives, exploitable to improve the safety and shelf-life of various categories of foodstuff.

Evaluation of the Phenolic Content, Antioxidant and Antimicrobial Activities of Oil and Non-Oil Extracts of Citrus sinensis (L.) Osbeck Seeds

The seeds of Citrus sinensis (L.) Osbeck (sweet orange) are waste products usually discarded. They may however contain phytochemicals that have potent bioactivities. In this study, the phenolic content, and antioxidant and antimicrobial activities of oil and non-oil (solid) extracts of C. sinensis seeds were evaluated using standard protocols. The seed oil contained significantly (P>0.05) higher contents of total phenol and total flavonoid when compared to the solid extract. However, the non-oil extract contained significantly (P<0.05) higher tannin contents than the seed oil. Ferric reducing antioxidant potential was not significantly different between both extracts. The antimicrobial activities of both extracts revealed that the seed oil possesses better antibacterial activities compared to the non-oil extract. The antifungal test revealed that the seed oil significantly inhibited the growth of Candida albicans (20 mm zone of inhibition at a concentration of 200 μg/mL), however, it did not inhibit the growth of Aspergillus niger and Penicillum sp. The minimum inhibitory concentration values against the bacterial and fungal strains were similar for both extracts in the range of 50∼100 μg/mL. Minimum bactericidal concentration and minimum fungicidal concentration values ranged from 100∼200 μg/mL for both extracts. The results in this study indicate that C. sinensis seed oil and non-oil extracts possess antioxidant, and antibacterial and antifungal properties that may be differentially exploited in the development of antimicrobial agents.

The Role of Silver Nanoparticles in a Treatment Approach for Multidrug-Resistant Salmonella Species Isolates

PURPOSE

The main objective of this study is to investigate the antibacterial activity of silver nanoparticles (AgNPs) against multidrug-resistant Salmonella isolates recovered from diarrheic  sheep and goats.

METHODS

This study used chemical reduction synthesis of AgNPs to evaluate their antimicrobial effects by estimation of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for each isolate using the microplate dilution method and tetrazolium salt reduction test to detect the viability percentage. In vivo treatment efficacy was assessed in mice by determining the viable count of Salmonella Enteritidis recovered from feces and by hematologic, biochemical and histopathologic examinations to confirm that use of AgNPs has no toxic or pathologic effects and to evaluate its ability in tissue regeneration following treatment.

RESULTS

All recovered strains were identified as MDR with a prevalence of 4% and 3.6% in sheep and goats, respectively. The results of TEM, DLS, Zeta potential, and FTIR revealed typical characteristics of the synthesized AgNPs. Silver nanoparticles showed antibacterial activity against all recovered strains with MIC of ≤0.02-0.313 μg/mL (mean average 0.085±0.126 μg/mL) and MBC of 0.078-1.250 μg/mL (average 0.508±0.315 μg/mL). In vivo efficacy of AgNPs was observed by a reduction in the number of viable S. Enteritidis recovered from feces in an S. Enteritidis infected mouse model, with complete shedding stopping between treatment days 4 and 6. Hematologic, serum biochemical, and histopathologic analyses proved the ability of AgNPs to suppress inflammatory reaction caused by S. Enteritidis infection.

CONCLUSION

The study proved the effective ability of AgNPs to fight MDR Salmonella spp. in vitro and in vivo without adverse effects.

Frog Skin-Derived Peptides Against Corynebacterium jeikeium: Correlation between Antibacterial and Cytotoxic Activities

Corynebacterium jeikeium is a commensal bacterium that colonizes human skin, and it is part of the normal bacterial flora. In non-risk subjects, it can be the cause of bad body smell due to the generation of volatile odorous metabolites, especially in the wet parts of the body that this bacterium often colonizes (i.e., groin and axillary regions). Importantly, in the last few decades, there have been increasing cases of serious infections provoked by this bacterium, especially in immunocompromised or hospitalized patients who have undergone installation of prostheses or catheters. The ease in developing resistance to commonly-used antibiotics (i.e., glycopeptides) has made the search for new antimicrobial compounds of clinical importance. Here, for the first time, we characterize the antimicrobial activity of some selected frog skin-derived antimicrobial peptides (AMPs) against C. jeikeium by determining their minimum inhibitory and bactericidal concentrations (MIC and MBC) by a microdilution method. The results highlight esculentin-1b(1-18) [Esc(1-18)] and esculentin-1a(1-21) [Esc(1-21)] as the most active AMPs with MIC and MBC of 4-8 and 0.125-0.25 µM, respectively, along with a non-toxic profile after a short- and long-term (40 min and 24 h) treatment of mammalian cells. Overall, these findings indicate the high potentiality of Esc(1-18) and Esc(1-21) as (i) alternative antimicrobials against C. jeikeium infections and/or as (ii) additives in cosmetic products (creams, deodorants) to reduce the production of bad body odor.

Antibacterial activity of graphene oxide nanosheet against multidrug resistant superbugs isolated from infected patients

Graphene oxide (GO) is a derivative of graphene nanosheet which is the most promising material of the decade in biomedical research. In particular, it has been known as an antimicrobial nanomaterial with good biocompatibility. In this study, we have synthesized and characterize GO and checked its antimicrobial property against different Gram-negative and Gram-positive multidrug drug resistant (MDR) hospital superbugs grown in solid agar-based nutrient plates with and without human serum through the utilization of agar well diffusion method, live/dead fluorescent staining and genotoxicity analysis. No significant changes in antibacterial activity were found in these two different conditions. We also compare the bactericidal capability of GO with some commonly administered antibiotics and in all cases the degree of inhibition is found to be higher. The data presented here are novel and show that GO is an effective bactericidal agent against different superbugs and can be used as a future antibacterial agent.

Susceptibility of Contact Lens-Related Pseudomonas aeruginosa Keratitis Isolates to Multipurpose Disinfecting Solutions, Disinfectants, and Antibiotics

Purpose

This study analyzed the susceptibilities of 17 contact lens (CL)-related keratitis isolates of Pseudomonas aeruginosa from Australia to antibiotics, multipurpose contact lens disinfecting solutions (MPDS), and disinfectants through minimum inhibitory (MIC) and minimum bactericidal concentrations.

Methods

Antibiotics included ciprofloxacin, levofloxacin, gentamicin, tobramycin, piperacillin, imipenem, ceftazidime, and polymyxin B. The MPDS OPTI-FREE PureMoist, Complete RevitaLens OcuTec, Biotrue, and Renu Advanced Formula and the constituent disinfectants; alexidine dihydrochloride, polyquaternium-1, polyaminopropyl biguanide, and myristamidopropyl dimethylamine (Aldox) were analyzed. The combined susceptibility of disinfectants based on the MPDS formulation was assessed through fractional inhibitory concentration.

Results

All isolates were susceptible to levofloxacin and gentamicin, 2/17 were resistant to ciprofloxacin; 1/17 was resistant to tobramycin, piperacillin, and polymyxin; and 3/17 were resistant to ceftazidime whereas 12/17 were resistant to imipenem. Of the four MPDSs, for Renu Advanced Formula 8/17 strains have an MIC ≤ 11.36 for OPTI-FREE PureMoist 14/17 strains have an MIC ≤ 11.36% for Complete RevitaLens 9/17 strains have an MIC ≤ 11.36, and for Biotrue 5/17 strains have MIC = 11.36. All strains were killed by 100% MPDS. At the concentrations used in the MPDSs, individual disinfectants were not active. From three tested isolates, no synergy was found in dual combinations of disinfectants. However, synergy was found for triple combination of disinfectants for three tested strains.

Conclusions

Australian CL-related isolates of P aeruginosa were susceptible to most antibiotics. There was variability in susceptibility to different MPDS. Individual disinfectant excipients had limited activity. The combination of the disinfectants showed synergy, antagonism, and no interaction.

Translational Relevance

This study will help to choose better preventive and treatment measures for microbial keratitis.

Minimum Bactericidal Concentration Techniques in Mycobacterium tuberculosis: A Systematic Review

Minimum bactericidal concentration (MBC) assay is an accepted parameter for evaluating new antimicrobial agents, and it is frequently used as a research tool to provide a prediction of bacterial eradication. To the best of our knowledge, there is no standardization among researchers regarding the technique used to detect a drug's MBC in Mycobacterium tuberculosis. Thus, the aim of this systematic review is to discuss the available literature in determining a drug's MBC in M. tuberculosis, to find the most commonly used technique and standardize the process. A broad and rigorous literature search of three electronic databases (PubMed, Web of Knowledge, and LILACS) was performed according to the PRISMA statement. We considered studies that were published from January 1, 1990 to February 19, 2019. Google Scholar was also searched to increase the number of publications. We searched for articles using the MeSH terms "microbiological techniques," "Mycobacterium," "antibacterial agents." In addition, free terms were used in the search. The search yielded 6,674 publications. After filter application, 5,348 publications remained. Of these, we evaluated the full text of 187 publications. By applying the inclusion criteria, 69 studies were included in the present systematic review. In the literature analyzed, a great variety in the techniques used to determine a drug's MBC in M. tuberculosis was observed. The most common variability is related to the culture media used, culture incubation time, and the percentage of bacterial death for the drug to be considered as bactericidal. The most commonly used technique for drug's MBC determination was carried out using the drug's minimum inhibitory concentration (MIC) assay. Aliquots from prior MIC values were subcultured in Middlebrook agar and incubated for 4 weeks at 35°C for determining the colony forming unit (CFU) with relevance to detect 99.9% bacilli killed or reduction in 3 log₁₀ viable bacilli.

Bacteriostatic and Bactericidal Activity of Deer Musk on Multidrug Resistance Bacteria

BACKGROUND AND OBJECTIVE

Infecting agents (e.g., bacteria, fungi, virus and parasite) have comprised high levels of multidrug resistance (MDR) with increased morbidity and mortality; so the main aim of this study was to investigate and demonstrate the antimicrobial activity of deer musk on multidrug-resistance bacteria and to proof that musk had a bacteriostatic and bactericidal effects against MDR bacteria.

MATERIALS AND METHODS

Deer musk evaluated 11 multi-drug resistance (MDR) species were selected, namely, Staphylococcus capitis, Staphylococcus aureus, Klebsiella pneumonia, Escherichia coli, Acinetobacter baumanni, Pseudomonas aeruginosa, Proteus mirabilis, Serratia marcescens, Streptococcus agalactiae, Streptococcus pyogenes and Enterococcus faecalis the MDR strain were tested by means of disk diffusion, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) by the time-kill method recommendation by CLSI. In addition, the antimicrobial susceptibility of 8 commonly used antimicrobials was examined on the same MDR bacterial strains.

RESULTS

The minimum inhibitory concentration MIC and MBC values were <2% (v/v) against all MDR strains except Pseudomonas aeruginosa, but the deer musk has bacteriostatic and bactericidal activity against Pseudomonas aeruginosa at >2% (v/v), in addition changes was observed in the morphological form of the bacterial colonies in of most of MDR bacteria such as Staphylococcus aureus, Streptococcus agalactiae, Pseudomonas aeruginosa and Klebsiella baumanni and indicating that the musk had an effect on bacterial cellular membranes.

CONCLUSION

The findings of this study indicated that deer musk has a bacteriostatic and bactericidal effects on the growth of all tested MDR bacteria.

Formulation, characterization, and in vitro testing of azelaic acid ethosome-based cream against Propionibacterium acnes for the treatment of acne

Azelaic acid is an antiacne drug by inhibiting thioredoxin reductase enzyme of Propionibacterium acnes (P. acnes) that affects the inhibition of bacterial DNA synthesis which occurs in the cytoplasm. Azelaic acid must penetrate through the stratum corneum to the sebaceous tissue and into cytoplasm by passing through thick peptidoglycan of P. acnes. Thus, it is necessary to increase the penetration of azelaic acid that formulated based ethosome. This study using thin-layer hydration method forms an ethosomal suspension with variations of concentration ethanol (30%, 35%, and 40%). Antibacterial activity was conducted using broth dilution method to determine minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The antibacterial activity of azelaic acid ethosome cream based was compared with the marketed cream (Zelface^® cream). Azelaic acid ethosome with 35% ethanol has given best result with entrapment efficiency of 94.48% ± 0.14%. Antibacterial activity to P. acnes showed that azelaic acid ethosome-based cream was given better activity than marketed cream (Zelface^® cream). The value of MIC and MBC of azelaic acid ethosome-based cream was 250 μg/ml while the marketed cream (Zelface^® cream) was shown MIC of 250 μg/ml and MBC of 500 μg/ml. This study proved that the azelaic acid ethosome-based cream has better antibacterial activity.

Antibacterial activity of fig leaf (Ficus carica Linn.) extract against Enterococcus faecalis and its cytotoxicity effects on fibroblast cells

Background:

Enterococcus faecalis is one of the bacteria that commonly found in root canal and pulp infection after root canal treatment. Sodium hypochlorite is the most widely used root canal irrigation, but it has toxic properties if exposed to periradicular tissues. It is necessary to develop an alternative for root canal irrigation. Fig leaf (Ficus carica Linn.) extract contains active substances such as flavonoid, tannin, and terpenoid which have been known for their antibacterial potency.

Aim:

This study aimed to determine the minimum bactericidal concentration (MBC) of fig leaf (F. carica Linn.) extract against E. faecalis and its cytotoxicity on fibroblast cells in vitro.

Materials and Methods:

A serial dilution method was used to determine the MBC of fig leaf extract on E. faecalis which grown on nutrient agar media. Inoculation was carried out at concentrations that suspected minimum inhibitory concentration (MIC), MBC, concentration between MIC and MBC, and control groups on different nutrient agar. MIC and MBC of fig leaf extract against E. faecalis were known by counting the growth of bacteria colonies on nutrient agar media in CFU/ml. The cytotoxicity of MIC and MBC of the extract acquired were tested using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and the results were read using an ELISA reader. Data of E. faecalis colonies were analyzed using Kruskal–Wallis and Mann–Whitney test.

Results:

The result showed a significant difference among the groups (p<0.05). fig leaf extract at a concentration of 50% showed no bacterial growth, and cell viability at this concentration was 77.7%.

Conclusion:

Fig leaf extract has antibacterial effect on E. faecalis with MBC at 50% and not cytotoxic to fibroblast cells.

Propionibacterium acnes Has Low Susceptibility to Chlorhexidine Digluconate

BACKGROUND

The skin bacterium Propionibacterium acnes has been reported to be responsible for surgical site infections (SSIs). Skin disinfection before surgery therefore is of the utmost importance in the prevention of SSIs caused by skin bacteria.

METHODS

We assessed the susceptibility of clinical isolates of two skin bacteria, P. acnes and Staphylococcus epidermidis, to disinfectants.

RESULTS

The range of chlorhexidine digluconate (CHG) minimum inhibitory concentrations (MICs) for P. acnes isolates was 0.25-1 mcg/mL. Furthermore, the minimum bactericidal concentrations (MBCs) for a range of disinfectants were determined to evaluate their rapid bactericidal activity. The MBC range of CHG against the P. acnes isolates was 4,096->32,768 mcg/mL (MBC₈₀ 16,384 mcg/mL) after one minute of exposure and 1,024-32,768 mcg/mL (MBC₈₀ 8,192 mcg/mL) after five minutes, indicating that some strains required a CHG MBC higher than the commercial concentration of 2% (20,000 mcg/mL). In contrast, the MBCs of glutaraldehyde, sodium hypochlorite, povidone-iodine, ethanol, benzalkonium chloride, and olanexidine gluconate were all sufficiently lower than their commercial concentrations. In S. epidermidis, the MBC range of CHG was 128-1,024 mcg/mL at one minute of exposure and 4-8 mcg/mL at five minutes.

CONCLUSIONS

Different skin bacteria have different susceptibilities to disinfectants. To prevent SSIs, the selected disinfectant agent and the disinfection time should have bactericidal activity toward all the bacteria that pose a risk of infection.

Diastereomeric bactericidal effect of Ru(phenanthroline)2 dipyridophenazine

Metal susceptibility assays and spot plating were used to investigate the antimicrobial activity of enantiopure [Ru(phen)₂ dppz]²⁺ (phen =1,10-phenanthroline and dppz = dipyrido[3,2-a:2´,3´-c]phenazine) and [μ-bidppz(phen)₄ Ru₂ ]⁴⁺ (bidppz =11,11´-bis(dipyrido[3,2-a:2´,3´-c]phenazinyl)), on Gram-negative Escherichia coli and Gram-positive Bacillus subtilis as bacterial models. The minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) were determined for both complexes: while [μ-bidppz(phen)₄ Ru₂ ]⁴⁺ only showed a bactericidal effect at the highest concentrations tested, the antimicrobial activity of [Ru(phen)₂ dppz]²⁺ against B. subtilis was comparable to that of tetracyline. In addition, the Δ-enantiomer of [Ru(phen)₂ dppz]²⁺ showed a 2-fold higher bacteriostatic and bactericidal effect compared to the Λ-enantiomer. This was in accordance with the enantiomers relative binding affinity for DNA, thus strongly indicating DNA binding as the mode of action.

In vitro Antimicrobial Activity of Chlorquinaldol against Microorganisms Responsible for Skin and Soft Tissue Infections: Comparative Evaluation with Gentamicin and Fusidic Acid

Skin and soft tissue infections (SSTIs) are a major therapeutic challenge for clinicians. The emergence of pathogens with decreased susceptibility to available therapies has become an emerging problem often associated with treatment failure. Hence, there is an urgent need for novel broad-spectrum antimicrobial agents. The purpose of this study was to assess the feasibility of chlorquinaldol as an alternative approach to currently used topical antibiotics for the treatment of skin and soft tissue infections. The activity of chlorquinaldol was investigated against a collection of bacterial isolates responsible for skin infections, including strains resistant to fusidic acid and gentamicin. After determination of MIC and MBC, time-kill experiments were carried out by counting colonies grown after 0, 3, 6, 9, 24, and 48 h of incubation with concentrations equal to ¼×, ½×, 1×, 2×, and 4× MIC of chlorquinaldol, gentamicin, or fusidic acid. Staphylococci resulted the Gram-positives most sensitive to chlorquinaldol, with MIC-values ranging from 0.016 to 0.5 mg/L. A lower activity was observed against Gram-negative bacteria, with 77% of the isolates being inhibited at concentrations ranging from 128 to 512 mg/L. Generally, in time-kill studies, chlorquinaldol showed a bactericidal activity at the higher concentrations (2×, 4× MIC) after 24-48 h of incubation. In conclusion, chlorquinaldol may represent a valuable alternative to conventional topical antibiotics for the treatment of skin and soft tissue infections.

Experimental and statistical methods to evaluate antibacterial activity of a quaternary pyridinium salt on planktonic, biofilm-forming, and biofilm states

Robust evaluation and comparison of antimicrobial technologies are critical to improving biofilm prevention and treatment. Herein, a multi-pronged experimental framework and statistical models were applied to determine the effects of quaternary pyridinium salt, 4-acetyl-1-hexadecylpyridin-1-ium iodide (QPS-1), on Streptococcus mutans in the planktonic, biofilm-forming and biofilm cell states. Minimum inhibitory and bactericidal concentrations (MIC and MBC, respectively) were determined via common methods with novel application of statistical approaches combining random effects models and interval censored data to estimate uncertainties. The MICs and MBCs for planktonic and biofilm-forming states ranged from 3.12 to 12.5 μg ml^-1, with biofilm values only ≈ 8 times higher. Potent anti-biofilm activity and reactive structural features make QPS-1 a promising antibacterial additive for dental and potentially other biomedical devices. Together, the experimental framework and statistical models provide estimates and uncertainties for effective antimicrobial concentrations in multiple cell states, enabling statistical comparisons and improved characterization of antibacterial agents.

Bactericidal activity of propylene glycol, glycerine, polyethylene glycol 400, and polyethylene glycol 1000 against selected microorganisms

Aim:

The aim of the present study was to evaluate the bactericidal activity of propylene glycol, glycerine, polyethylene glycol 400 (PEG 400), and polyethylene glycol 1000 (PEG 1000) against selected microorganisms in vitro.

Materials and Methods:

Five vehicles, namely propylene glycol, glycerine, PEG 400, PEG 1000, and combination of propylene glycol with PEG 400, were tested for their bactericidal activity. The minimum bactericidal concentration was noted against four standard strains of organisms, i.e. Streptococcus mutans American Type Culture Collection (ATCC) 25175, Streptococcus mutans ATCC 12598, Enterococcus faecalis ATCC 35550, and Escherichia coli ATCC 25922, using broth dilution assay. Successful endodontic therapy depends upon thorough disinfection of root canals. In some refractory cases, routine endodontic therapy is not sufficient, so intracanal medicaments are used for proper disinfection of canals. Intracanal medicaments are dispensed with vehicles which aid in increased diffusion through the dentinal tubules and improve their efficacy. Among the various vehicles used, glycerine is easily available, whereas others like propylene glycol and polyethylene glycol have to be procured from appropriate sources. Also, these vehicles, being viscous, aid in sustained release of the medicaments and improve their handling properties. The most commonly used intracanal medicaments like calcium hydroxide are ineffective on many microorganisms, while most of the other medicaments like MTAD (Mixture of Tetracycline, an Acid, and a Detergent) and Triple Antibiotic Paste (TAP) consist of antibiotics which can lead to development of antibiotic resistance among microorganisms. Thus, in order to use safer and equally effective intracanal medicaments, newer alternatives like chlorhexidine gluconate, ozonized water, etc., are being explored. Similarly, the five vehicles mentioned above are being tested for their antimicrobial activity in this study.

Results:

All vehicles exhibited bactericidal activity at 100% concentration.

Conclusion:

Propylene glycol was effective against three organisms namely S. mutans E. faecalis and E. coli and its bactericidal activity was at 50%, 25% and 50% respectively. PEG 1000 was effective against S. mutans and E. coli at 25%. Hence propylene glycol was effective on more number of organisms of which E. faecalis is a known resistant species. PEG 1000 was bactericidal at a lower concentration but was effective on two organisms only.

Determination of antibacterial activity of green coffee bean extract on periodontogenic bacteria like Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum and Aggregatibacter actinomycetemcomitans: An in vitro study

BACKGROUND

The aim of this study was to evaluate the antibacterial activity of pure green coffee bean extract on periodonto pathogenic bacteria Porphyromonas gingivalis (Pg), Prevotella intermedia (Pi), Fusobacterium nucleatum (Fn) and Aggregatibacter actinomycetemcomitans (Aa).

MATERIALS AND METHODS

Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBC) were used to assess the antibacterial effect of pure green coffee bean extract against periodonto pathogenic bacteria by micro dilution method and culture method, respectively.

RESULTS

MIC values of Pg, Pi and Aa were 0.2 μg/ml whereas Fn showed sensitive at concentration of 3.125 μg/ml. MBC values mirrors the values same as that of MIC.

CONCLUSION

Antimicrobial activity of pure green coffee bean extract against Pg, Pi, Fn and Aa suggests that it could be recommended as an adjunct to mechanical therapy in the management of periodontal disease.

Diarylacylhydrazones: Clostridium-selective antibacterials with activity against stationary-phase cells

Current antibiotics for treating Clostridium difficile infections (CDI), that is, metronidazole, vancomycin and more recently fidaxomicin, are mostly effective but treatment failure and disease relapse remain as significant clinical problems. The shortcomings of these agents are attributed to their low selectivity for C. difficile over normal gut microflora and their ineffectiveness against C. difficile spores. This Letter reports that certain diarylacylhydrazones identified during a high-throughput screening/counter-screening campaign show selective activity against two Clostridium species (C. difficile and Clostridium perfringens) over common gut commensals. Representative examples are shown to possess activity similar to vancomycin against clinical C. difficile strains and to kill stationary-phase C. difficile cells, which are responsible for spore production. Structure-activity relationships with additional synthesised analogues suggested a protonophoric mechanism may play a role in the observed activity/selectivity and this was supported by the well-known protonophore carbonyl cyanide m-chlorophenyl hydrazone (CCCP) showing selective anti-Clostridium effects and activity similar to diarylacylhydrazones against stationary-phase C. difficile cells. Two diarylacylhydrazones were shown to be non-toxic towards human FaDu and Hep G2 cells indicating that further studies with the class are warranted towards new drugs for CDI.

Traditional usage, phytochemistry and pharmacology of the South African medicinal plant Boophone disticha (L.f.) Herb. (Amaryllidaceae)

ETHNOPHARMACOLOGICAL RELEVANCE

Boophone disticha is the most common member of the South African Amaryllidaceae used extensively in traditional medicine of the various indigenous population groups, including the Sotho, Xhosa and Zulu as well as the San. This survey was carried out to identify and highlight areas relevant to the traditional usage of Boophone disticha. Pharmacological aspects were examined with the purpose of reconciling these with the traditional usage of the plant. In relation to phytochemical make-up, particular attention was paid on how its alkaloid constitution might corroborate the various biological effects manifested by the plant.

MATERIALS AND METHODS

Information gathering involved the use of four different database platforms, including Google Scholar, ScienceDirect, SciFinder(®) and Scopus. Arrangement and detailing of this information is as reflected in the various sections of the paper.

RESULTS

Sixteen categories were identified under which Boophone disticha finds use in traditional medicine. These were shown to include general usage purposes, such as 'cultural and dietary', 'well-being', 'personal injury', 'divinatory purposes', 'psychoactive properties' and 'veterinary uses'. Furthermore, traditional usage was seen to involve six body systems, including functions pertaining to the circulatory, gastrointestinal, muscular, neurological, respiratory and urinary systems. The four remaining categories relate to use for inflammatory conditions, cancer, malaria and tuberculosis. Overall, three areas were discernible in which Boophone disticha finds most usage, which are (i) ailments pertaining to the CNS, (ii) wounds and infections, and (iii) inflammatory conditions. In addition, several aspects pertaining to the toxic properties of the plant are discussed, including genotoxicity, mutagenicity and neurotoxicity.

CONCLUSION

The widespread ethnic usage of Boophone disticha has justified its standing as a flagship for the Amaryllidaceae and its relevance to South African traditional medicine. Furthermore, its promising pharmacological and phytochemical profiles have stimulated significant interest in the clinical realm, especially in the areas of cancer and motor neuron disease chemotherapy. These collective properties should prove useful in steering the progress of the plant towards a wider audience.

Nanotechnology as a therapeutic tool to combat microbial resistance

Use of nanoparticles is among the most promising strategies to overcome microbial drug resistance. This review article consists of three parts. The first part discusses the epidemiology of microbial drug resistance. The second part describes mechanisms of drug resistance used by microbes. The third part explains how nanoparticles can overcome this resistance, including the following: Nitric oxide-releasing nanoparticles (NO NPs), chitosan-containing nanoparticles (chitosan NPs), and metal-containing nanoparticles all use multiple mechanisms simultaneously to combat microbes, thereby making development of resistance to these nanoparticles unlikely. Packaging multiple antimicrobial agents within the same nanoparticle also makes development of resistance unlikely. Nanoparticles can overcome existing drug resistance mechanisms, including decreased uptake and increased efflux of drug from the microbial cell, biofilm formation, and intracellular bacteria. Finally, nanoparticles can target antimicrobial agents to the site of infection, so that higher doses of drug are given at the infected site, thereby overcoming resistance.

Nanotechnology as a therapeutic tool to combat microbial resistance

Use of nanoparticles is among the most promising strategies to overcome microbial drug resistance. This review article consists of three parts. The first part discusses the epidemiology of microbial drug resistance. The second part describes mechanisms of drug resistance used by microbes. The third part explains how nanoparticles can overcome this resistance, including the following: Nitric oxide-releasing nanoparticles (NO NPs), chitosan-containing nanoparticles (chitosan NPs), and metal-containing nanoparticles all use multiple mechanisms simultaneously to combat microbes, thereby making development of resistance to these nanoparticles unlikely. Packaging multiple antimicrobial agents within the same nanoparticle also makes development of resistance unlikely. Nanoparticles can overcome existing drug resistance mechanisms, including decreased uptake and increased efflux of drug from the microbial cell, biofilm formation, and intracellular bacteria. Finally, nanoparticles can target antimicrobial agents to the site of infection, so that higher doses of drug are given at the infected site, thereby overcoming resistance.

Pharmacological and toxicological insights to the South African Amaryllidaceae

The plant family Amaryllidaceae is of provenance in the South African region which is known to harbor about a third of the global complement of around 1000 species. It has widespread usage in the traditional medicinal practices of the indigenous peoples of the region. As a consequence and given its unique alkaloid principles, its members have provided a viable platform for phytochemical based drug discovery. The medicinal potential of the family has been realized through the commercialization of galanthamine as an Alzheimer's drug due to its potent and selective inhibitory activity against the enzyme acetylcholinesterase. Further promising chemotherapeutic candidates of the family reside with the phenanthridone class of alkaloids such as pancratistatin which exhibit potent and cell line specific antiproliferative properties with significant potential for clinical development. Despite these interesting medicinal attributes, plants of the Amaryllidaceae are known to be poisonous and several of them have been classified as such. This survey taking into consideration Amaryllidaceae plants native to South Africa aims to strike a balance between the medicinal potential of the family on one hand and its adverse and toxic effects on the other.

Evaluation of antimicrobial efficacy of flavonoids of withania somnifera L

In the present study antimicrobial activity of Withania somnifera L. Dunal (Solanaceae) has been evaluated against selected pathogens. Free and bound flavonoids of different parts (root, stem, leaf and fruit) of W. somnifera have been studied for their antimicrobial activity using disc diffusion assay against three Gram negative bacteria (Escherichia coli MTCC 46, Proteus mirabilis MTCC 3310 and Pseudomonas aeruginosa MTCC 1934), one Gram positive bacteria (Staphylococcus aureus MTCC 3160) and three fungi (Candida albicans MTCC 183, Aspergillus flavus MTCC 277 and Aspergillus niger MTCC 282). Minimum inhibitory concentration (MIC) of the extracts was evaluated through micro broth dilution method, while minimum bactericidal/fungicidal concentration was determined by sub culturing the relevant samples. C. albicans was found to be the most susceptible organism followed by S. aureus, P. mirabilis, E. coli and P. aeruginosa. Out of the tested organisms, A flavus and A. niger were observed to be resistant as none of the tested extracts showed activity against them. Total activity (TA) of extracts (ml/g) against each sensitive pathogens was also evaluated. Bound flavonoid extract of root showed best activity against C. albicans (IZ 30, MIC 0.039, MFC 0.039, respectively). However all the microorganisms were found to be sensitive against the extracts tested. Total activity of bound flavonoid extract of root was found to be same for E.coli, P. mirabilis, S. aureus and C. albicans (153.84 ml/g). Results of the present study reveal that extracts of W. somnifera showing great antimicrobial potential against test microorganisms may be exploited for future antimicrobial drugs.