Antimicrobial and Immunomodulatory Effects of Aqueous Extracts of Edible Mushrooms Termitomyces striatus in Infected BALB/c Mice

Abstract

The worldwide increase in infectious diseases has resulted in the overuse of available antibiotics. The fight to effectively reduce morbidity and mortality has increased due to multidrug resistance. This calls for further investigation and the discovery of new antibiotics, as well as vaccines. Studies over the past few decades have proven that mushrooms and their active ingredients have positive impacts on a number of biological systems, with some mushrooms exhibiting a variety of characteristics. Synthetic immunomodulatory and antibiotic medications used to treat bacterial infections have been linked to a number of adverse effects, making alternative therapeutic agents necessary. This has necessitated the search for antimicrobial drugs with a new mechanisms of action that include immunomodulation. Immunomodulatory drugs from natural products like mushrooms would be a new novel drug in combating infections since they would work on the immune system without facing the problem of drug resistance. Termitomyces striatus is a wild edible mushroom that grows in many places worldwide Kenya included. T. striatus is used as food by people living in western Kenya. However, scientific data to validate the presence of phytochemical compounds, antimicrobial activity and immunomodulatory effects is lacking. The objective of this study was to determine the antimicrobial and immunomodulatory characteristics of T. striatus extract. The T. striatus mushrooms were collected from different parts of Kakamega county. They were dried, ground into a powder, and an aqueous extract was prepared using a freeze-drier. Standard laboratory procedures were used to determine phytochemical families of secondary metabolites. From powdered T. striatus, the aqueous extract was prepared. The disc-diffusion method was used to assess the antibacterial and antifungal properties. To determine the immunomodulatory effect of the mushroom extract, mice were grouped into four groups of twelve mice each as follows; normal control, positive control (levamisole), and extract-treated groups of 200 and 400mg/kg body weight (bw). To determine the effect of the extract on immunosuppression E. coli-infected mice were divided into five groups of fiteen mice each. They were negative control, positive control, and two extract-treated groups of mice were orally administered with 200μl of 2 ×108 CFU/mL of enterohemorrhagic Escherichia coli (EHEC). Blood was collected on different days and then total and differential WBC count analyzed, immunoglobulin G (IgG), interleukin-4 (IL-4) and interferon-gamma (INF-γ) levels were quantified using enzyme-linked immunosorbent assays (ELISA). In evaluation of reversal of experimentally induced leucopenia, mice were injected with cyclophosphamide and left for 3 days. The extracts (200 and 400mg/kg bw) and levamisole were administered, blood was collected for total and differential WBC counts for analysis. Mice were immunized by injecting 20µl of sheep red blood cells (SRBC) subcutaneously into the right foot pad in order to assess the impact of the extract on the immune response in delayed type hypersensitivity using SRBC as an antigen. After 7 days of treatment with different concentrations of extract, the left foot pad was injected with the SRBC. Left foot pad thickness measured before administration of extract and for a period of 48 hours. Data was analyzed using one-way analysis of variance and Bonferroni multiple comparisons. Level of significance was computed at p<0.05. The experiments for phytochemical profile revealed the presence of alkaloids, flavonoids, steroids, sterols, saponins and phenols. The aqueous extract of T. striatus exhibited antibacterial and antifungal activity against E. coli, P. auraginosa, S. aureus and B. subtilis, as well as C. albican. For immunomodulatory effect in BALB/c mice, the extract significantly (p<0.05) increased the levels of neutrophils and monocytes. When BALB/c mice were infected with EHEC, the extract significantly (p<0.05) reduced elevated levels of WBCs, neutrophils, monocytes, eosinophils and basophils, and significantly enhanced the levels of lymphocytes. Similarly, the extract significantly (p<0.05) reduced the levels of INF-γ, as well as significantly (p<0.05) elevated the levels of IL-4 and IgG. In the evaluation of immunosuppression, treatment with the extract significantly (p<0.05) ameliorated reduced levels of total and differential WBC counts following cyclophosphamide-induced immunosuppression in mice. Treatment using the extract also showed an increase in delayed hypersensitivity reaction following injection of SRBC in mice. The study concluded that the extract had phytochemicals associated with potent anti-microbial and immunomodulatory effects in EHEC-infected mice. The extract may therefore be used in the development of alternative antimicrobial and immunomodulatory agents. I have made a few changes in the abstract, though editorials