They show that an extract of the Chinese mushroom or shiitake reduces the virulence of one of the most resistant bacteria to antibiotics

Pseudomonas aeruginosa is one of the most antibiotic-resistant bacteria in existence today, according to the WHO

UGR scientists have demonstrated the modulating effect of a standardized extract of the mycelium of the fungus Lentinula edodes on the virulence of this bacterium

Scientists from the University of Granada (UGR) have shown that a standardized extract of the mycelium of the fungus Lentinula edodes, better known as the Chinese mushroom or shiitake, has a modulating effect on the virulence of the pathogen Pseudomonas aeruginosa, one of the most resistant bacteria to antibiotics currently available.

Pseudomonas aeruginosa is a bacterium belonging to the group of pathogenic gamma-proteobacteria, opportunistic in animals and plants. It is considered the cause of numerous cases of acute infections, frequently in patients with human immunodeficiency virus (HIV) infection, burn patients, critically ill patients and especially in patients with concomitant pathologies such as chronic obstructive pulmonary disease (COPD). ), bronchiectasis and cystic fibrosis, thus giving it great importance among the pathogens responsible for nosocomial infections due to its high morbidity and lethality values.

Also, Pseudomonas aeruginosa is not part of the human commensal gut microbiota. However, depletion after antibiotic treatment and its changes (dysbiosis) facilitate colonization of the intestinal tract by multidrug-resistant P. aeruginosa, due to its various resistance systems such as its secretion systems, its beta-lactamases, its motility, its ability to form biofilms and its quorum sensing mechanism.

In 2017, the WHO published a list of antibiotic-resistant bacteria as a priority to guide research towards the development of new antibiotics. In this list of priorities, P. aeruginosa, was placed in second place and the importance of the development of alternative agents against this bacterium was judged as critical.

Professors and researchers Daddaoua Abdelali, Olga Martínez Agustín and Fermín Sánchez de Medina, belonging to the Department of Biochemistry and Molecular Biology II and the Department of Pharmacology, respectively (both from the Faculty of Pharmacy of the University of Granada), members of the Center for Biomedical Research Network of Liver and Digestive Diseases (CIBERehd), of the Biosanitary Research Institute (IBS) and the Institute of Nutrition and Food Technology «José Mataix», have investigated the effect of a standardized extract of the mycelium of the fungus Lentinula edodes (AHCC ®) on the virulence of Pseudomonas aeruginosa within the framework of the FEDER project (30B572F301).

AHCC® is the name of a product derived from mushrooms with a high content of oligosaccharides, an enzymatically fermented extract from the mycelium of the basidiomycete Lentinula edodes. Its composition consists of various lipids, amino acids, minerals and, obviously, oligosaccharides, among which β-1,4-type glucans stand out. The acetylated forms of these oligosaccharides have a molecular weight of less than 5 kDa (OS size after acid hydrolysis), constituting what is believed to be the main active ingredient of AHCC®. This compound has been used as a supplement in humans, as well as a therapeutic agent, in addition to having demonstrated efficacy in terms of anti-inflammatory effects.

The UGR research group has experimentally shown that AHCC modulates the growth and pathogenicity of the P. aeruginosa PAO1 strain, inhibiting different virulence systems such as biofilm formation and motility. In addition, in co-cultures with eukaryotic cells, AHCC® reduced the secretion of proinflammatory cytokines (IL-6 and TNF) by inhibiting signal transduction pathways that modulate the inflammatory response of macrophages, as well as the internalization capacity of bacteria within cells. Intestinal epithelial (IEC18). Finally, quantitative analyzes using real-time quantitative PCR (RTqPCR) show that supplementation with AHCC® produces a decrease in the expression levels of genes involved in virulence.

"With this work, we intend to study the molecular bases that can support the use of oligosaccharides, more specifically AHCC®, as alternative compounds or adjuvants to conventional antibiotics used against P. aeruginosa," says Abdelali Daddaoua, one of the researchers at the Department of Biochemistry and Molecular Biology II responsible for this research work.

Bibliographic reference:

Mireia Tena-Garitaonaindia, Diego Ceacero-Heras, María Del Mar Maldonado Montoro, Fermín Sánchez de Medina, Olga Martínez-Augustin, Abdelali Daddaoua. A Standardized Extract of Lentinula edodes Cultured Mycelium Inhibits Pseudomonas aeruginosa Infectivity Mechanisms. Front Microbiol. 2022; 13:814448. doi: 10.3389/fmicb.2022.814448.