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Novel Bacteriocin a Promising New Treatment for Resistant Listeria monocytogenes

SEP 05, 2019 | ALEXANDRA WARD
A novel bacteriocin appears promising as a new treatment option for antibiotic-resistant Listeria monocytogenes infection just as a multistate outbreak of the foodborne bacteria has claimed 2 lives in the United States.

With a fatality rate that can reach as high as 30%, L monocytogenes is considered a pressing public health threat that can have a serious impact on immunocompromised individuals and pregnant women, newborn children, and the elderly.

Because of its high mortality rate and increasing resistance to currently available antibiotics, treating L monocytogenes is becoming more and more challenging. But investigators with RMIT University in Melbourne, Australia, have discovered a promising new treatment in the form of a bacteriocin produced by Lactobacillus plantarum B21. The research team presented their findings at the American Society for Microbiology (ASM) and the European Society for Clinical Microbiology and Infectious Diseases (ESCMID) Conference on Drug Development to Meet the Challenge of Antimicrobial Resistance.

Investigators played with multiple culture conditions to find a set that would foster high bacterial growth and/or high bacteriocin production. They also used gas chromatography mass spectrometry (GC‐MS)-based metabolomics to evaluate cellular and functional behavior of L plantarum B21. The structure of bacteriocin was analyzed using 2‐dimensional nuclear magnetic resonance spectroscopy (NMR). In order to assess the effectiveness of bacteriocin against a range of target strains of bacteria, the team relied on well diffusion assays and electron microscopy.

“A lack of a major carbohydrate source was found to promote both bacteriocin production and long‐term robustness in L plantarum B21 cultures. GC‐MS data demonstrated significant (p <0.005) production of aspartic acid, glutamic acid, and alanine; these compounds may act as biomarkers of cell robustness. NMR indicates the bacteriocin to have a cyclic structure,” investigators report in the poster abstract.

Electron microscope data reveal that bacteriocin operates effectively by damaging the cell walls of target species, inducing cell perforation and blebbing, thus killing the cells.

“The B21 bacteriocin is ‘broad‐spectrum’ and effective against many gram‐positive organisms including known pathogens such as Listeria. The compound is safe, pH and temperature stable, and biodegrades quickly in the environment, meaning it is hard for target species to develop resistance,” the research team found.

“The use of bacteriocins such as those produced by the L plantarum B21 strain to fight strains of bacteria resistant to traditional antibiotics therefore shows great promise in the fight against antibiotic-resistant infections,” the team concluded.

For a list of states affected by the Listeria monocytogenes outbreak, consult the Contagion® Outbreak Monitor.

The poster, “Development of a Novel Bacteriocin from Lactobacillus plantarum as a Promising New Treatment for Antibiotic-Resistant Listeria monocytogenes,” was presented on Wednesday, September 4, 2019, at the 2019 ASM/ESCMID Conference in Boston, Massachusetts.
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