Treatment of diarrheal infections is often challenged by development of drug resistance among the bacteria. The aim of this study was to investigate the antibacterial property of extracts of guava (Psidium guajava Linn.) leaves against diarrhea causing bacterial pathogens. Four extracts viz., ethanol, methanol, ethyl acetate and hot water extract of guava leaf were assayed for antibacterial activity against three selected bacterial pathogens along with four commercial antibiotics. The methanol extract exhibited substantial inhibitory activity (100 %) against both kinds of bacteria with a MIC of > 250 µg/ml in most cases. The ethanol extract demonstrated antibacterial activity ranging from 38 % to 65 % with the inhibition of clinical isolate of E. coli at concentrations > 500 µg/ml and both strains of V. cholerae at > 750 µg/ml respectively. The ethyl acetate and hot water extracts showed comparatively lesser response with MICs > 750 µg/ml in some cases. The commercial antibiotic Chloramphenicol exhibited absolute inhibitory action on Salmonella sp. and clinical isolate of V. cholerae. While Tetracycline and Gentamycin caused complete bactericidal action on both the strains of E. coli and V. cholerae respectively, the clinical isolate of E. coli was totally susceptible to Erythromycin. On the other hand significant percentages of resistances to these antibiotics ranging from 63 % to 88 % were also recorded. Six phytochemical compounds presumed to possess pharmacological properties were detected from methanol extract. The findings suggest that the methanol extract of guava leaf could serve as a potential source to explore promising drugs to control diarrheal infections.

A study was carried out to synthesize silver nanoparticles (Ag-NPs) using plant extracts and to explore their pharmaceutical application as antibacterial agents. Dried leaves of Mentha arvensis Linn. were powdered and extracts were prepared using three different organic solvents. Preliminary screening on antibacterial activity by agar well diffusion method indicated that the methanolic extract has superior potential than the other two. Phytochemical analysis of the leaf extract revealed that it possesses tannins, steroids, terpenoids and flavonoids. Ag-NPs prepared using this extract were of spherical to cuboidal shape ranging in size from 40 to 70 nm. It retained essential chemical groups and had the required surface plasmon resonance. Further to the antimicrobial assay, the Ag-NPs, in contrast to the whole methanolic leaf extract, showed better (100% vs. 80%) bactericidal activity against the indicator organisms. The zones of growth inhibition for gram positive bacteria ranged between 14±0.6 and 23±0.3, while it was between 12±0.6 and 22±0.2 for gram negative bacteria. The Ag-NPs presented the minimum inhibitory concentration values of 250 µg/mL for gram positive bacteria and 250 -500 µg/mL for gram negative bacteria. These findings suggest that the natural compounds present in M. arvensis L. possess the potency to facilitate the synthesis and antibacterial action of Ag-NPs.

Infection caused by Helicobacter pylori is considered as a serious health issue as it can cause severe damage of gastric mucosa, impair the digestive mechanism and even lead to neoplastic disease. Research studies have projected its survival in many parts of the body beyond the gastric system. The ability of these bacteria to withstand the gastric juice and change the surrounding conditions makes its survival in the stomach successful. As an outcome of H. pylori infection, there occurs the release of inflammatory mediators and immune modulators, which could cause further complications. Recent investigations on H. pylori have demonstrated the association of its infection with many systemic diseases including lung cancer, urticaria, type-1 diabetes, autoimmune diseases and so on. Autoimmune thyroiditis (AIT) is an organ-specific autoimmune disease, which occurs as a result of production of autoantibodies to thyroid gland leading to thyroid dysfunction. Antibodies of similar kind produced against H. pylori have been demonstrated for their occurrence in patients suffering with AIT in many studies. On the other hand, some of the studies have experimentally proved the lack of link between H. pylori infection and AIT. As the findings attributing H. pylori infection with the AIT are increasingly reported in recent years, this article reviews the concepts and controversies over their association.

Dried fishes are salted and sun dried fish products consumed by large population owing to their nutrient richness, flavor and long shelf life properties. Contamination of dried fishes by mycotoxin producing fungi pose serious threat to food safety and public health. A total of 27 samples belonging to three varieties of dried fishes collected in Chennai city, India were screened for the isolation of mycotoxin producing fungal contaminants. Mycological examination of samples revealed the prevalence of six types of fungi viz., A. parasiticus (27.27%), A. niger (22.72%), A. fumigatus (18.18%), Penicillium sp. (18.18%), Cladosporium sp. (9.09%) and Euratium sp. (4.54%). Detection using thin layer chromatography indicated that 18.18% of isolates belonging to A. parasiticus, A. fumigatus, Penicillium sp. were positive, while A. niger, Cladosporium sp., and Euratium sp.  were negative for mycotoxin production. Further to the bioassay with Artemia larvae, substantial lethality was observed with the mycotoxin of A. parasiticus (100%), followed that of by A. fumigatus and Penicillium sp. (each 50%). The HPLC studies indicated that the mycotoxin produced by A. parasiticus was Aflatoxin G2. Need for proper hygienic practices during processing and handling of dried fishes in order to avoid fungal contamination and likelihood mycotoxicosis in consumers has been suggested.

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