ISOLATION AND CHARACTERIZATION OF BACTERIOPHAGES OF LISTERIA SPP FROM WASTEWATER OF A DAIRY INDUSTRY

BLANCO FERNÁNDEZ, MD; BARRIOS, ME; CAMMARATA, RV; TORRES, C; MBAYED, VA

Simposio; IV Latin American Symposium on Environmental Virology; 2018

Bacteriophages and their endolysins, enzymes that degrade cell wall of bacteria, are emerging as alternative tools to inhibit growth of pathogen bacteria. Listeria spp, and specially Listeria monocytogenes is a foodborne pathogen that causes listeriosis: a serious invasive disease that affects both humans and a wide range of animals. Listeria spp is ubiquitous in the dairy farm environment, and could be present in dairy processing plants and wastewater. The aim of this work was to isolate bacteriophages infecting Listeria spp from the wastewater of a dairy industry. Treated and untreated wastewaters were sampled during a year in the inlet and outlet channels of the wastewater treatment plant from a dairy industry. Isolation of bacteriophages was performed after an enrichment step with different species and strains of Listeria spp: L. innocua, L. ivanovii and L. monocytogenes serotypes 1/2b and 4b. Bacteriophages infecting L. innocua and L. ivanovii were isolated (n=24) from 2 out of 12 samples. Bacteriophages were purified by performing five passages of isolated plaques. Host range was evaluated by spot tests against 5 collection strains and several field isolates of Listeria spp. Broad and narrow host range within Listeria genus was observed in different bacteriophages. Five of them were chosen for further characterization. After growth in liquid cultures (~ 1 x 109 pfu/ml), phages were concentrated by PEG precipitation and genome was extracted using phenol-chloroform and ethanol precipitation. Isolated bacteriophages possessed DNA genomes, with a genome length around 30 kb. Different restriction profiles were observed digesting DNA with NcoI and HpaI. Also, virus capsids were observed using TEM, showing small icosahedral capsids (40-60 nm) with none or short tails. All these observations could indicate their belonging to Podoviridae family. However, it has not been described so far that this bacteriophage family infects Listeria spp. Further experiments need to be carried out to identify and characterize these bacteriophages.