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The recurrent use of antibiotics has given the guideline so that bacteria will develop resistance to drugs used in medicine, which is why recent investigations have been directed to evaluate natural sources such as plants or fungi, which can fight the bacteria. Here the antibacterial activity of spent substrate of Pleurotus ostreatus combined with medicinal plants was evaluated. We designed six mixtures (barley straw, barley straw/Chenopodium ambrosioides L., barley straw/Mentha piperita L., barley straw/Rosmarinus officinalis L., barley straw/Litsea glaucescens Kunth and barley straw/Tagetes lucid Cav) to be used as a substrate of cultivation of mushroom. These were recovered after the harvest. We obtained aqueous extracts from spent substrates and resuspended them to different concentrations (25, 50 and 100 mg mL-1). These were tested for antibacterial activity against Staphylococcus epidermidis, Bacillus subtilis and Escherichia coli; as a positive control we used azithromycin, cephalexin and dicloxacillin. The protocol was a completely randomized assay with a factorial arrangement design. The data were analyzed with PROC GLM, SAS. The spent substrate from Pleurotus ostreatus that contained Mentha piperita L. presented the largest zone of inhibition against Staphylococcus epidermidis (40.00 mm) which was similar to control antibiotics (40.00 mm). Second in toxicity was the spent substrate from barley straw extract (33.33 mm). In conclusion, the results suggest that it is possible to use the spent substrate of Pleurotus ostreatus as source of extracts with antibacterial activity, being the best option the combination of barley straw with Mentha piperita L.

Nowadays, the uncontrolled use of antibiotics has created the problem of bacterial resistance to them, what has motivated the search for new alternatives of drug for the treatment of bacterial diseases. Here, we compare antimicrobial activity of spent substrate of mushroom Pleurotus ostreatus and Lentinula edodes, against Escherichia coli, Salmonella tiphymorium, Staphylococcus aureus and Micrococcus luteus. We designed two mixtures, barley straw to be used as a substrate of cultivation of mushroom Pleurotus ostreatus and oats or cedar for the cultivation of mushroom Lentinula edodes; and were obtained aqueous extracts from spent substrates; extracts were tested for antibacterial activity. The protocol was a completely randomized assay with a factorial arrangement design. The data were analyzed with PROC GLM, SAS. The results showed that in the case of Escherichia coli the greatest inhibition zone was of 12.66 mm at a concentration of 6 mg mL-1, with treatment of Lentinula edodes/Cedar; Salmonella tiphymorium showed a greatest inhibition zone of 31.10 mm to a concentration of 5.12 mg mL-1, with treatment of Pleurotus ostreatus/Barley straw; Staphylococcus aureus showed a greatest inhibition zone of 9.33 mm to a concentration of 100 mg mL-1, with the treatment of Lentinula edodes/Cedar and finaly, Micrococcus luteus showed a greatest inhibition zone of 15.00 mm to a concentration of 50 mg mL-1, with the treatment Lentinula edodes/Oats. In conclusion, the results suggest that it is possible to use indistinctly the spent substrate of Pleurotus ostreatus and Lentinula edodes as source of extracts with antibacterial activity.