Naringin inhibits the biofilms of metallo-β-lactamases (MβLs) producing Pseudomonas species isolated from camel meat

Activity and safety evaluation of natural preservatives

Synthetic preservatives are widely used in the food industry to control spoilage and growth of pathogenic microorganisms, inhibit lipid oxidation processes and extend the shelf life of food. However, synthetic preservatives have some side effects that can lead to poisoning, cancer and other degenerative diseases. With the improvement of living standards, people are developing safer natural preservatives to replace synthetic preservatives, including plant derived preservatives (polyphenols, essential oils, flavonoids), animal derived preservatives (lysozyme, antimicrobial peptide, chitosan) and microorganism derived preservatives (nisin, natamycin, ε-polylysine, phage). These natural preservatives exert antibacterial effects by disrupting microbial cell wall/membrane structures, interfering with DNA/RNA replication and transcription, and affecting protein synthesis and metabolism. This review summarizes the natural bioactive compounds (polyphenols, flavonoids and terpenoids, etc.) in these preservatives, their antioxidant and antibacterial activities, and safety evaluation in various products.

The one-humped camel: The animal of future, potential alternative red meat, technological suitability and future perspectives

The 2020 world population data sheet indicates that world population is projected to increase from 7.8 billion in 2020 to 9.9 billion by 2050 (Increase of more than 25%). Due to the expected growth in human population, the demand for meats that could improve health status and provide therapeutic benefits is also projected to rise. The dromedary also known as the Arabian camel, or one-humped camel ( Camelus dromedarius), a pseudo ruminant adapted to arid climates, has physiological, biological and metabolic characteristics which give it a legendary reputation for surviving in the extreme conditions of desert environments considered restrictive for other ruminants. Camel meat is an ethnic food consumed across the arid regions of Middle East, North-East Africa, Australia and China. For these medicinal and nutritional benefits, camel meat can be a great option for sustainable meat worldwide supply. A considerable amount of literature has been published on technological aspects and quality properties of beef, lamb and pork but the information available on the technological aspects of the meat of the one humped camel is very limited. Camels are usually raised in less developed countries and their meat is as nutritionally good as any other traditional meat source. Its quality also depends on the breed, sex, age, breeding conditions and type of muscle consumed. A compilation of existing literature related to new technological advances in packaging, shelf-life and quality of camel meat has not been reviewed to the best of our knowledge. Therefore, this review attempts to explore the nutritional composition, health benefits of camel meat, as well as various technological and processing interventions to improve its quality and consumer acceptance. This review will be helpful for camel sector and highlight the potential for global marketability of camel meat and to generate value added products.

High-throughput combination assay for studying biofilm formation of uropathogenic Escherichia coli

Uropathogenic Escherichia coli, the most common cause for urinary tract infections, forms biofilm enhancing its antibiotic resistance. To assess the effects of compounds on biofilm formation of uropathogenic Escherichia coli UMN026 strain, a high-throughput combination assay using resazurin followed by crystal violet staining was optimized for 384-well microplate. Optimized assay parameters included, for example, resazurin and crystal violet concentrations, and incubation time for readouts. For the assay validation, quality parameters Z' factor, coefficient of variation, signal-to-noise, and signal-to-background were calculated. Microplate uniformity, signal variability, edge well effects, and fold shift were also assessed. Finally, a screening with known antibacterial compounds was conducted to evaluate the assay performance. The best conditions found were achieved by using 12 µg/mL resazurin for 150 min and 0.023% crystal violet. This assay was able to detect compounds displaying antibiofilm activity against UMN026 strain at sub-inhibitory concentrations, in terms of metabolic activity and/or biomass.

Computational and experimental strategies for combating MBL P. aeruginosa (MBLPA) biofilms using phytochemicals: Targeting the quorum sensing network

Pseudomonas aeruginosa is a Gram-negative opportunistic bacterium, ubiquitously found in nature and causative agent in many infections. Due to increased antibiotic resistance, there is a need to develop more robust antibacterial agents from natural sources. In this study, we worked on two metallo-β-lactamase (MBL) producing Pseudomonas aeruginosa strains and targeted the Quorum Sensing mechanism (QS) of these bacteria to combat antibiotic resistance. Our study aimed at using phytochemicals which have been used since centuries in herbal medicine. We used fifteen commercially available phytochemicals and check their effects on biofilm formation, quorum sensing and inter-related mechanisms. Sub-inhibitory concentration of isoliquiritin inhibited biofilm formation 55 % in P8 at day 6 and 48 % in P6 at day 6; quorum sensing 83 % in P6 and 61 % in P8 whereas sub-inhibitory concentration of 6-gingerol suppressed biofilm formation by 48 % in P8 at day 6 and 44 % in P6 at day 6; quorum sensing 69 % in P6 and 48 % in P8, respectively. The results indicated isoliquiritin, epigallocatechin gallate, eugenol, luteolin and chrysin to be the potential candidates in inhibiting QS and related mechanisms. Isoliquiritin which was never been used before against biofilm and QS related studies, showed remarkable results and found to be more efficient in inhibiting QS than 6-gingerol -a known QS inhibitor. For examining the molecular interaction between phytochemicals and QS, In-silico molecular docking was performed between phytoligands and four QS proteins (Las I, Las R, RhlI and Rhl R). In-silico docking analysis revealed that isoliquiritin showed strong bond with amino acids (Trp34, Asp35, Asp35, Tyr105, Arg104, Val138, Thr140) present at the active site of RhlI with binding energy value of -8.4 kcal/mol as compared to that of 6-gingerol with Rhl1 (-7.3 kcal/mol). In conclusion, our study may help in controlling nosocomial infections caused by carbapenem-resistant metallo beta-lactamase P. aeruginosa (MBL-PA) by utilizing these phytochemicals in biofilms disruption and quorum sensing inhibition. Moreover their synergism with antibiotics may help in lowering the MIC of carbapenem antibiotics against such Multi-drug resistant strains.

Attenuation of quorum sensing regulated virulence functions and biofilm of pathogenic bacteria by medicinal plant Artemisia annua and its phytoconstituent 1, 8-cineole

The emergence of multidrug resistance (MDR) in bacterial pathogens is a serious public health concern. A significant therapeutic target for MDR infections is the quorum sensing-regulated bacterial pathogenicity. Determining the anti-quorum sensing abilities of certain medicinal plants against bacterial pathogens as well as the in-silico interactions of particular bioactive phytocompounds with QS and biofilm-associated proteins were the objectives of the present study. In this study, 6 medicinal plants were selected based on their ethnopharmacological usage, screened for Anti-QS activity and Artemisia annua leaf extract (AALE) demonstrated pigment inhibitory activity against Chromobacterium violaceum CV12472. Further, the methanol active fraction significantly inhibited the virulence factors (pyocyanin, pyoverdine, rhamnolipid and swarming motility) of Pseudomonas aeruginosa PAO1 and Serratia marcescens MTCC 97 at respective sub-MICs. The inhibition of biofilm was determined using a microtiter plate test and scanning electron microscopy. Biofilm formation was impaired by 70%, 72% and 74% in P. aeruginosa, C. violaceum and S. marcescens, respectively at 0.5xMIC of the extract. The phytochemical content of the extract was studied using GC-MS and 1, 8-cineole was identified as major bioactive compound. Furthermore, 1, 8-cineole was docked with quorum sensing (QS) proteins (LasI, LasR, CviR, and rhlR) and biofilm proteins (PilY1 and PilT). In silico docking and dynamics simulations studies suggested interactions with QS-receptors CviR', LasI, LasR, and biofilm proteins PilY1, PilT for anti-QS activity. Further, 1, 8-cineole demonstrated 66% and 51% reduction in violacein production and biofilm formation, respectively to validate the findings of computational analysis. Findings of the present investigation suggests that 1, 8-cineole plays a crucial role in the QS and biofilm inhibitory activity demonstrated by Artemisia annua extract. RESEARCH HIGHLIGHTS: Artemisia annua leaf extract (AALE) methanol fraction demonstrated broad-spectrum QS and biofilm inhibition Scanning electron microscopy (SEM) confirmed biofilm inhibition Molecular docking and simulation studies suggested positive interactions of 1,8-cineol with QS-receptors and biofilm proteins.

Study on the inhibitory effect of quercetin combined with gentamicin on the formation of Pseudomonas aeruginosa and its bioenvelope

OBJECTIVE

The potential effects of quercetin and gentamicin combination on the bacteriostatic activity and biofilm formation of Pseudomonas aeruginosa (PA) were examined, and the findings provided a theoretical basis for the development of quercetin as a new biofilm inhibitor.

METHODS

The minimum inhibitory concentration (MIC) of eight PAs was determined by microdilution method and the partial inhibitory concentration index (FICI) of the combined drug was analyzed by micro-dilution method. Thereafter, the lowest film inhibitory concentration (MBIC) of quercetin and gentamicin alone and in combination was evaluated by crystal violet staining. Finally, scanning electron microscopy (SEM) and laser confocal microscopy (CLSM) were used to decipher the inhibitory effect of the combination on biofilm formation.

OUTCOME

The antibacterial activity of quercetin alone was relatively weak, but after combination with gentamicin, the antibacterial activity was significantly enhanced, as evident by FICI of 0.28 and 0.53 and manifested as synergistic or additive effect, which indicated that quercetin can enhance gentamicin antibacterial activity. The results of crystal violet staining revealed that quercetin and gentamicin alone exhibited a similar biofilm formation inhibitory effect, but the inhibitory effect was substantially weaker, and the antibiofilm activity was stronger and exhibited a dose-dependent response after the combination of the two with 1/2FICI. The results of scanning electron microscopy and laser confocal microscopy also showed that the treatment of PA biofilm after combining quercetin and gentamicin with 1/2FICI could completely destroy the spatial structure of the complete biofilm, significantly reduce the thickness of bacteria, and markedly reduce the proportion of viable bacteria in the membrane.

CONCLUSION

The combination of quercetin and gentamicin can effectively inhibit the formation of PA as well as its biofilm, and exhibit synergistic and additive effects.

Phytochemicals as Invaluable Sources of Potent Antimicrobial Agents to Combat Antibiotic Resistance

Plants have been used for therapeutic purposes against various human ailments for several centuries. Plant-derived natural compounds have been implemented in clinics against microbial diseases. Unfortunately, the emergence of antimicrobial resistance has significantly reduced the efficacy of existing standard antimicrobials. The World Health Organization (WHO) has declared antimicrobial resistance as one of the top 10 global public health threats facing humanity. Therefore, it is the need of the hour to discover new antimicrobial agents against drug-resistant pathogens. In the present article, we have discussed the importance of plant metabolites in the context of their medicinal applications and elaborated on their mechanism of antimicrobial action against human pathogens. The WHO has categorized some drug-resistant bacteria and fungi as critical and high priority based on the need to develope new drugs, and we have considered the plant metabolites that target these bacteria and fungi. We have also emphasized the role of phytochemicals that target deadly viruses such as COVID-19, Ebola, and dengue. Additionally, we have also elaborated on the synergetic effect of plant-derived compounds with standard antimicrobials against clinically important microbes. Overall, this article provides an overview of the importance of considering phytogenous compounds in the development of antimicrobial compounds as therapeutic agents against drug-resistant microbes.

Biofilm formation and antibiotic sensitivity in Elizabethkingia anophelis

Elizabethkingia anophelis has recently gained global attention and is emerging as a cause of life-threatening nosocomial infections. The present study aimed to investigate the association between antimicrobial resistance and the ability to form biofilm among E. anophelis isolated from hospitalized patients in China. Over 10 years, a total of 197 non-duplicate E. anophelis strains were collected. Antibiotic susceptibility was determined by the standard agar dilution method as a reference assay according to the Clinical and Laboratory Standards Institute. The biofilm formation ability was assessed using a culture microtiter plate method, which was determined using a crystal violet assay. Culture plate results were cross-checked by scanning electron microscopy imaging analysis. Among the 197 isolates, all were multidrug-resistant, and 20 were extensively drug-resistant. Clinical E. anophelis showed high resistance to current antibiotics, and 99% of the isolates were resistant to at least seven antibiotics. The resistance rate for aztreonam, ceftazidime, imipenem, meropenem, trimethoprim-sulfamethoxazole, cefepime, and tetracycline was high as 100%, 99%, 99%, 99%, 99%, 95%, and 90%, respectively. However, the isolates exhibited the highest susceptibility to minocycline (100%), doxycycline (96%), and rifampin (94%). The biofilm formation results revealed that all strains could form biofilm. Among them, the proportions of strong, medium, and weak biofilm-forming strains were 41%, 42%, and 17%, respectively. Furthermore, the strains forming strong or moderate biofilm presented a statistically significant higher resistance than the weak formers (p < 0.05), especially for piperacillin, piperacillin-tazobactam, cefepime, amikacin, and ciprofloxacin. Although E. anophelis was notoriously resistant to large antibiotics, minocycline, doxycycline, and rifampin showed potent activity against this pathogen. The data in the present report revealed a positive association between biofilm formation and antibiotic resistance, which will provide a foundation for improved therapeutic strategies against E. anophelis infections in the future.

Naringenin Ultrafine Powder Was Prepared by a New Anti-Solvent Recrystallization Method

Raw naringenin directly isolated from plants is significantly limited by its poor dissolution rate and low bioavailability for clinical and in vivo studies. This study reported a method for the preparation of naringenin ultrafine powder (NUP) using a novel anti-solvent recrystallization process; preliminary experiments were conducted using six single-factor experiments. The response surface Box–Behnken (BBD) design was used to optimize the level of factors. The optimal preparation conditions of the DMP were obtained as follows: the feed rate was 40.82 mL/min, the solution concentration was 20.63 mg/mL, and the surfactant ratio was 0.62%. The minimum average particle size was 305.58 ± 0.37 nm in the derived optimum conditions. A scanning electron microscope was used to compare and analyze the appearance and morphology of the powder before and after preparation. The characterization results of FTIR, TG and XRD showed that no chemical change occurred in the powder before and after preparation. Through the simulated gastrointestinal juice digestion experiment, it was confirmed that the absorption rate of NUP was 2.96 times and 4.05 times higher than raw naringenin, respectively. Therefore, the results showed that the reduction in the particle size through the use of low-speed recrystallization could improve the absorption rate and provided a feasible approach for the further applications.

Antibiofilm and anticancer activities of unripe and ripe Azadirachta indica (neem) seed extracts

BACKGROUND

Antibiotic resistances of pathogens and breast cancer warrant the search for new alternative strategies. Phytoextracts can eradicate microbe-borne diseases as well as cancer with lower side effects compared to conventional antibiotics.

AIM

Unripe and ripe Azadirachta indica (neem) seed extracts were explored as potential antibiofilm and anticancer agents in combating multidrug-resistant infectious bacteria as well as anticancer agents against the MDR breast cancer cell lines.

METHODS

Shed-dried neem seeds (both unripe and ripe) were pulverized and extracted using methanol. The chemical components were identified with FTIR and gas chromatography - mass spectrometry. Antibiofilm activity of neem seed extracts were assessed in terms of minimum biofilm inhibitory concentration (MBIC), minimum biofilm eradication concentration (MBEC), and fluorescence microscopic studies on Staphylococcus aureus and Vibrio cholerae. Bacterial cells were studied by fluorescence microscopy using acridine orange/ethidium bromide as the staining agents. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values were evaluated to observe the antibacterial activities. Cytotoxicity of the extracts against human blood lymphocytes and the anticancer activity against drug-resistant breast cancer cell lines were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and fluorescence-activated cell sorting (FACS) studies.

RESULTS

4-Ethyl-2-hydroxy-2-cyclopentene-1-one, phthalic acid, and 2-hexyl-tetrahydro thiophane were the major compounds in unripe neem seed, whereas 3,5-dihydroxy-6-methyl-2,3-dihydro-4-H-pyran-4-one and 4-ethylbenzamide were predominant in ripe neem seed. Triazine derivatives were also common for both the extracts. MBIC values of unripe and ripe neem seed extracts for S. aureus are 75 and 100 µg/mL, respectively, and for V. cholerae, they are 100 and 300 µg/mL, respectively. MBEC values of unripe and ripe seed extracts are 500 and 300 µg/mL, respectively for S. aureus and for V. cholerae the values are 700 and 500 µg/mL, respectively. Fluorescence microscopic studies at 16 and 24 h, after bacterial culture, demonstrate enhanced antibiofilm activity for the ripe seed extract than that of the unripe seeds for both the bacteria. MTT assay reveals lower cytotoxicity of both the extracts towards normal blood lymphocytes, and anticancer activity against breast cancer cell line (MDA-MB-231) with superior activity of ripe seed extract. FACS studies further supported higher anticancer activity for ripe seed extract.

CONCLUSIONS

Methanolic extract of neem seeds could substantially inhibit and eradicate biofilm along with their potent antibacterial and anticancer activities. Both the extracts showed higher antibiofilm and antibacterial activity against S. aureus (gram-positive) than V. cholerae (gram-negative). Moreover, ripe seed extract showed higher antibiofilm and anticancer activity than unripe extracts.

Development of Antibiofilm Therapeutics Strategies to Overcome Antimicrobial Drug Resistance

A biofilm is a community of stable microorganisms encapsulated in an extracellular matrix produced by themselves. Many types of microorganisms that are found on living hosts or in the environment can form biofilms. These include pathogenic bacteria that can serve as a reservoir for persistent infections, and are culpable for leading to a broad spectrum of chronic illnesses and emergence of antibiotic resistance making them difficult to be treated. The absence of biofilm-targeting antibiotics in the drug discovery pipeline indicates an unmet opportunity for designing new biofilm inhibitors as antimicrobial agents using various strategies and targeting distinct stages of biofilm formation. The strategies available to control biofilm formation include targeting the enzymes and proteins specific to the microorganism and those involved in the adhesion pathways leading to formation of resistant biofilms. This review primarily focuses on the recent strategies and advances responsible for identifying a myriad of antibiofilm agents and their mechanism of biofilm inhibition, including extracellular polymeric substance synthesis inhibitors, adhesion inhibitors, quorum sensing inhibitors, efflux pump inhibitors, and cyclic diguanylate inhibitors. Furthermore, we present the structure–activity relationships (SAR) of these agents, including recently discovered biofilm inhibitors, nature-derived bioactive scaffolds, synthetic small molecules, antimicrobial peptides, bioactive compounds isolated from fungi, non-proteinogenic amino acids and antibiotics. We hope to fuel interest and focus research efforts on the development of agents targeting the uniquely complex, physical and chemical heterogeneous biofilms through a multipronged approach and combinatorial therapeutics for a more effective control and management of biofilms across diseases.

Antibacterial and Antibiofilm Effect of Ultrasound and Mild Heat Against a Multidrug-Resistant Klebsiella pneumoniae Stain Isolated from Meat of Yellow-Feathered Chicken

Klebsiella pneumoniae is an important foodborne pathogen with high biofilm-forming ability, which is continuously detected in food products in recent years. The antibacterial and antibiofilm activities and mechanism of ultrasonication in combination with heat treatment against K. pneumoniae were studied. K. pneumoniae planktonic and biofilm cells were treated with ultrasound (US), mild heat treatment (HT50, HT60, and HT70), and combinations of US and mild heat treatment (UH50, UH60, and UH70) for 5, 10, 20, 30, and 60 min. Results showed that the combination of US and mild heat treatment was more effective in inactivating K. pneumoniae planktonic and biofilm cells than the single treatment by counting viable bacteria. In addition, confocal laser scanning microscopy, scanning electron microscopy, and analysis of leakage of intracellular substances have revealed that the combination treatment effectively damaged the integrity of bacterial cell membrane and increased cell permeability, which led to the quick release of adenosine triphosphate (ATP) and macromolecular substances of nucleic acids and proteins. Moreover, the activities of respiratory chain dehydrogenase in planktonic and biofilm cells significantly decreased after UH treatment. The results indicated that ultrasonication and mild heat treatment had a synergistic effect on the inactivation of K. pneumoniae planktonic and biofilm cells by damaging the cell membrane and inhibiting intercellular cell respiration.

Isolation and molecular identification of biofilm producing P. aeruginosa and K. pneumoniae from urinary tract infections patient urine sample

BACKGROUND

Recent years, multi drug resistant pathogens and their pathogenicity were increased worldwide due to unauthorized consumption of antibiotics. In addition, correlation between multi drug resistant bacteria and biofilm formation is heightened due to the production of more virulence behavior. There is no better identification methods are available for detection of biofilm producing gram negative bacteria.

MATERIALS AND METHODS

In this research work, multi drug resistant strains of Pseudomonas aeruginosa (P. aeruginosa) and Klebsiella pneumoniae (K. pneumoniae) were identified based on the specific antibiotics and third generation cephalosporin discs by disc diffusion assay. Subsequently, biofilm forming ability of selected pathogens were identified tissue culture plate and tube test. Based on the multi-drug resistant ability and biofilm production, the molecular identification of P. aeruginosa and K. pneumoniae were confirmed by PCR using universal primers.

RESULTS AND CONCLUSIONS

No zone of inhibition present around the discs of muller hinton agar plates were confirm, selected P. aeruginosa and K. pneumoniae strains were multi drug resistant pathogens. Performed third generation cephalosporin antibiotics were also highly sensitive to selected pathogens of P. aeruginosa and K. pneumoniae. Further, biofilm forming ability of selected P. aeruginosa and K. pneumoniae was confirmed by tissue culture plate and tube methods. Finally, molecular identification of P. aeruginosa and K. pneumoniae was named as P. aeruginosa and K. pneumoniae. Our result was conclude, selected P. aeruginosa and K. pneumoniae as biofilm producing pathogens and also highly resistant to current antibiotics.