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United States Department of Agriculture

Agricultural Research Service

Research Project: MOLECULAR MICROBIOLOGY AND CONTROL OF ENTERIC PATHOGENS THAT CONTAMINATE FRESH PRODUCE

Location: Produce Safety and Microbiology Research

Title: Native protozoa decrease Escherichia coli O157:H7 in microcosms of wastewater from a dairy lagoon

Authors
item Ravva, Subbarao
item Sarreal, Chester
item Mandrell, Robert

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 2, 2010
Publication Date: N/A

Technical Abstract: Since protozoa constitute almost half of rumen microbial biomass and regulate rumen microbial ecosystem, we evaluated the influence of protozoa in wastewater from a dairy lagoon on the fate of pathogenic strains of Escherichia coli O157:H7 marked with antibiotic resistance. Protozoan populations in wastewater supplemented with E. coli O157:H7 were determined using the most-probable number method. Protozoa enriched from wastewater from dairy lagoons consumed an outbreak strain of E. coli O157:H7 preferentially as compared to aerobic bacteria. Protozoan populations increased 11-fold with 1.7 x 107 cells of E. coli O157:H7 per ml, and also increased with E. coli O157:H7 and coliform bacteria in wastewater supplemented with 10% LB broth. Both E. coli O157:H7 and ONT (O-nontypeable):H32 (persist in settling lagoons) strains were eliminated in wastewater, but ONT:H32 persisted when exposed to diffusible nutrients from wastewater without any competing organisms. Several types of native protozoa consumed E. coli O157:H7 within 2 h from wastewater. We isolated three protozoa and typed them by 18S sequencing as Vorticella microstoma, Platyophyra sp., Colpoda aspera; Platyophyra sp. and C. aspera acted as predators. Although we observed vacuoles containing live green-fluorescent protein labeled E. coli O157:H7 being expelled within three days, no E. coli O157:H7 either inside or outside the protozoa after seven days were detected by confocal microscopy. We conclude that enriching protozoa that eliminate pathogens such as E. coli O157:H7 is a potential strategy to obtain pathogen-free water for crop irrigations or washing lanes in free-stall dairies.

Last Modified: 8/30/2014
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