The in vitro antibacterial activities of 29 traditional medicinal plants used in respiratory ailments were assessed on multidrug resistant Gram-positive and Gram-negative bacteria isolated from the sore throat patients and two reference strains. The methanolic, n-hexane, and aqueous extracts were screened by the agar well diffusion assay. Bioactive fractions of effective extracts were identified on TLC coupled with bioautography, while their toxicity was determined using haemolytic assay against human erythrocytes. Qualitative and quantitative phytochemical analysis of effective extracts was also performed. Methanolic extract of 18 plants showed antimicrobial activity against test strains. Adhatoda vasica (ZI = 17–21 mm, MIC: 7.12–62.5 μg/mL), Althaea officinalis (ZI = 16–20 mm, MIC: 15.62–31.25 μg/mL), Cordia latifolia (ZI = 16–20 mm, MIC: 12.62–62.5 μg/mL), Origanum vulgare (ZI = 20–22 mm, MIC: 3–15.62 μg/mL), Thymus vulgaris (ZI = 21–25 mm, MIC: 7.81–31.25 μg/mL), and Ziziphus jujuba (ZI = 14–20 mm, MIC: 7.81–31.25 μg/mL) showed significant antibacterial activity. Alkaloid fractions of Adhatoda vasica, Cordia latifolia, and Origanum vulgare and flavonoid fraction of the Althaea officinalis, Origanum vulgare, Thymus Vulgaris, and Ziziphus jujuba exhibited antimicrobial activity. Effective plant extracts show 0.93–0.7% erythrocyte haemolysis. The results obtained from this study provide a scientific rationale for the traditional use of these herbs and laid the basis for future studies to explore novel antimicrobial compounds.

Nanoparticles (NPs) are being recognized as antibacterial agents due to their rapidly increasing multidrug resistance in bacterial pathogens. Hence, there is an unmet need to identify the natural antibacterial agent. The present study aimed to evaluate the antibacterial activity of sericin-conjugated silver NPs synthesized by using sericin as a reducing and capping agent. Synthesized NPs were characterized by scanning electron microscope, nanolaser particle size analyzer (BT-90), Fouriertransform infrared analysis, and energy-dispersive X-ray. The biogenic NPs significantly inhibited the growth of Escherichia coli (12-15 mm zone of inhibition), Staphylococcus aureus (14.6-15.4 mm zone of inhibition), and Klebsiella pneumoniae (12.5-18 mm zone of inhibition). The stability of naturally synthesized NPs was examined at various temperatures (i.e., 4°C, 37°C, and 55°C) and pH (i.e., 3, 7, and 11). Temperature variability did not significantly affect the efficacy of NPs. However, NPs performed better at higher pH levels. This study suggested that the sericinbased silver NPs are not only effective against bacteria, but they also maintain the stability at different ranges of temperature and pH. We concluded that the sericinconjugated silver NPs possess the remarkable antibacterial potential, which suggests their large-scale use as a cheap and stable antimicrobial agent in the future. K E Y W O R D Santibacterial activity, nanoparticles, sericin, silver

Microbial biofilm formation in dental unit water lines (DUWL) is a phenomenon that has been recognized for nearly four decades. Water delivered by DUWL can harbor high numbers of bacteria, including opportunistic pathogens. Biofilms on tubing within DUWL may serve as a reservoir for these microorganisms and should therefore be controlled. In this study, the effects of eight biocides were monitored on DUWL biofilms individually and in combination by epifluorescence microscopy and total viable counts (TVC). The effects of sodium dodecyl sulphate (SDS), hydrogen peroxide (H2O2), sodium hypochlorite (NaOCl), phenol (Phe), Tween 20 (Tw 20), ethylenediaminetetraacetic acid (EDTA), chlorohexidine gluconate (CHX), and povidine iodine (PI) were tested on DUWL biofilms alone and in combination. PI was found to have negligible effects on biofilm removal either applied alone or in combined form with CHX. Applying all biocides simultaneously did not completely eliminate viable bacteria nor did they remove biofilm. Overall, when combined, the biocides performed better than singly applied products. The most effective biocides were NaOCl and Phe (both alone and in combination).

The quorum sensing (QS) dependent behaviour of micro-organisms, in particular expression of virulence genes, biofilm formation and dispersal, have provided impetus for investigating practical approaches to interfere with microbial QS. This study tests Halomonas pacifica and Marinobacter hydrocarbonoclasticus, two halophilic marine micro-organism, for their AI-2 dependent QS signalling and the effect of two well-known quorum-sensing inhibitors (QSIs), patulin and penicillic acid, on biofilm formation. We report, for the first time, the successful amplification of a putative luxS gene in H. pacifica using degenerated primers and AI-2 dependent QS as well as inhibition using QSIs. Penicillic acid had a strong inhibitory effect on AI-2 induction of H. pacifica at non-growth inhibitory concentrations, while patulin has an adverse effect only at the highest concentration (25 μM). QSIs effect on biofilm forming capability was isolate specific, with maximum inhibition at 25 μM of patulin in H. pacifica. In M. hydrocarbonoclasticus, no adverse effects were noted at any tested concentration of either QSIs. Detection of bioluminescence and the presence of a putative luxS gene provide biochemical and genetic evidence for the production of a signalling molecule(s) which is the essential first step in characterizing H. pacifica QS. This study highlights the importance of AI-2 dependent QS in a marine setting, not previously reported. It further suggests that QSI compounds must be selected in the specific system in which they are to function, and they cannot easily be transferred from one QS system to another.

Despite the constantly increasing need for new antimicrobial agents, antibiotic drug discovery and development seem to have greatly decelerated in recent years. Presented with the significant problem of advancing antimicrobial resistance, the global scientific community has attempted to find alternative solutions; one of the most promising ones is the evaluation and use of old antibiotic compounds. A number of old antibiotic compounds, such as aminoglycosides, chloramphenicol, and tetracycline, are re-emerging as valuable alternatives for the treatment of difficult-to-treat infections. This study examined the in vitro potency for biofilm formation of five isolates (Klebsiella sp., Pseudomonas aeruginosa, Achromobacter sp., Klebsiella pneumoniae, and Bacillus pumilis) and the effects of antibiotics on these biofilms. Furthermore the quantitative analysis of planktonic, loosely attached cells, and their susceptibility to antibiotics was also determined. Twitching motility was observed to determine any effect in the biofilm forming capability of the isolates. All the isolates tested were efficient biofilm-forming strains in the polypropylene and borosilicate test tubes. Standard bacterial enumeration technique and CV staining produced equivalent results both in biofilm and planktonic assays. The biofilm formation of all the strains was affected in the presence of tetracycline or chloramphenicol. Highly significant decrease (P < 0.01) in biofilm formation was observed by treatment with chloramphenicol compared to tetracycline. In addition, the two antibiotics also affected adversely the planktonic and loosely attached cells of all isolates. Thus, testing the effects of older antibiotics on biofilms may supply useful information in addition to standard in vitro testing, particularly in diseases where biofilm formation is involved in the pathogenesis.

This study investigated the effect of patulin and penicillic acid, two known quorum-sensing inhibitors, and the common biocide ethylenediaminetetraacetic acid (EDTA) on the biofilm formation and auto-inducer (AI)-2 production of three isolates from dental unit water lines, Klebsiella sp., Bacillus subtilis and Bacillus cereus. Penicillic acid on its own had no effect on the biofilm formation of all isolates, whereas in combination with EDTA, it enhanced biofilm formation significantly in Klebsiella sp. and B. cereus. EDTA at concentrations greater than 10 microM promoted biofilm formation in B. cereus and B. subtilis. Patulin was found to promote biofilm formation in B. cereus up to 25 microM. A significant increase in biofilm formation was observed in B. cereus and B. subtilis at concentrations greater than 10 microM of patulin when combined with EDTA. The Vibrio harveyi BB170 AI-2 bioassay showed a positive response for Klebsiella sp. AI-2 production with a maximum fold induction at the late exponential growth phase. Addition of glucose prolonged the AI-2 production phase considerably. No significant effect of patulin, penicillic acid alone as well as in combination with EDTA was observed on AI-2 production by Klebsiella sp. The findings have important implications for the design of biofilm prevention and eradication strategies.

Colebrookea oppositifolia is a highly used medicinal plant and an enriched source of essential oils. Therefore, the present study was designed with the aim to extract the chemical constituents and to evaluate its antioxidant potential. Fresh plant parts were subjected to the extraction of volatile chemical constituents by maceration using n-hexane as the menstruum. The resulting n-hexane fractions were purified and then subjected to GC-MS and FTIR analysis. In-vitro antioxidant abilities were evaluated by, DPPH, total phenolic content (TPC), total flavonoid content (TFC) method against the standard solutions of (Gallic acid, Quercetin) as a positive control. The GC-MS analysis of leaves, stem and inflorescence showed a total of 100, 98 and 48 components out of which 47, 16 and 17 peaks were identified representing the 67.64 %, 73.16 % and 61.93 % of the total oily fractions, respectively. The FTIR spectrum indicated the presence of various functional groups. In-vitro antioxidant results exhibited that leaves showed the highest antioxidant potential by DPPH (3.365 ± 0.002), and the highest total phenolic content by FC method (203.00 ± 0.091). Foliar micromorphological features were found significant in the authentication of C. oppositifolia. Further pharmacognostic studies of this plant are recommended to evaluate its therapeutic potential.

Essential oils are produced as secondary metabolites by aromatic plants, predominantly belonging to families Apiaceae, Lamiaceae, Myrtaceae, and Rutaceae. The family Rutaceae has great economic importance for its numerous edible fruits and essential oils. In the present study, essential oils of seven plants of family Rutaceae, Aegle marmelos, Murraya koenigii, Citrus reticulata Blanco, Zanthoxylum armatum, Skimmia laureola, Murraya paniculata, and Boenninghausenia albiflora, were used for their toxicological assessment. Seven groups of selected essential oils-treated Wistar rats were established against control group (n = 5) that received water for 14 days; animals were offered feed and water ad libitum and treated with essential oils at 400 mg/kg body weight. Hematological studies revealed significant elevation in TEC in animals treated with essential oils of M. koenigii, S. laureola, and B. albiflora, while an elevation in PCV and depletion in MCV were observed in animals treated with M. paniculata and B. albiflora, respectively. Serological investigations demonstrated significant depletion in triglycerides and elevation in blood sodium level in animals treated with essential oils of A. marmelos and C. reticulata Blanco. Boenninghausenia albiflora affected many markers including RBC, MCV, triglycerides, HDL, LDL, urea, and sodium. In conclusion, all oils except B. albiflora can be considered safe for internal use.