Antibacterial activities of Lentinus squarrosulus (mont.) extracts against food borne pathogens

Abstract

Widespread cases of life threatening side effects and multiple-drug-resistance of food borne pathogens to conventional antibiotics have triggered the quest for naturally occurring antibacterial agents. This study was aimed at investigating the antibacterial properties of aqueous and methanol extracts of white rot mushroom (Lentinus squarrosulus) against food borne pathogens isolated from Tympanotonus fuscatus var. radula periwinkles. Isolation and identification of isolates were carried out using standard morphological characteristics and biochemical tests. The isolates were tentatively identified as Escherichia coli, Pseudomonas spp, Staphylococcus spp and Micrococcus spp. The preliminary phytochemical analysis of the mushroom extracts detected phytochemical constituents such as alkaloids, saponins, tannins, flavonoids, steroids, terpenoids, anthraquinones, proteins and starch. The antibiotic susceptibility profile using Kirby-Bauer disc diffusion method showed that all the isolates were resistant to at least more than two classes of conventional antibiotics. Agar well diffusion technique showed that the isolates were all susceptible to the aqueous extracts at all concentrations. E. coli was highly resistant to the methanol extracts even at 100mg/ mL. The aqueous extract was the most potent, exhibiting high zones of inhibition against Escherichia coli (15mm), Pseudomonas spp (18mm), Staphylococcus spp (20mm) and Micrococcus spp (22mm) at 100mg/  mL. At a concentration of 25mg/  mL the aqueous extract inhibited Escherichia coli (11mm), Pseudomonas spp (12mm), Staphylococcus spp (13mm) and Micrococcus spp (13mm) while the methanol extract showed no antibacterial activity against any of the isolates. The Minimum Inhibition Concentration (MIC) of the aqueous extract for all the isolates was 25mg/  mL except for E. coli which was 50mg/  mL. This study highlights the possibility of using the aqueous and methanol extracts of L. squarrosulus as raw materials in the food and pharmaceutical industries. Future studies should focus on the identification and purification of specific phytochemicals.