Enterobacteria in feedlot waste and runoff

Area of Science:

• Environmental microbiology
• Food safety
• Veterinary science

Background:

• Beef cattle feedlot waste (FLW) management involves land application, potentially impacting microbial ecosystems.
• Enterobacteriaceae are a diverse group of bacteria, some of which can be pathogenic.

Purpose of the Study:

• To characterize the Enterobacteriaceae populations in beef cattle feedlot waste (FLW), runoff, and associated drainage ditch water.
• To assess the potential microbial hazards associated with FLW disposal.

Main Methods:

• Isolation and identification of Enterobacteriaceae from FLW, runoff, and drainage ditch water.
• Use of planting and enrichment techniques with seven different culture media.
• Serological testing to determine the pathogenicity of Escherichia coli isolates.

Main Results:

• FLW contained approximately 50 million enterobacteria per gram dry weight, with over 90% identified as Escherichia coli.
• Non-enteropathogenic Escherichia coli were predominant. Citrobacter and Enterobacter cloacae were also common.
• Enrichment techniques expanded the detected spectrum to include Proteus, Providencia, Klebsiella, Enterobacter aerogenes, Arizona, and one Salmonella isolate.
• Fewer enterobacteria were found in runoff and drainage ditch water, with similar dominant species.
• Salmonella and Arizona were not detected in runoff or drainage ditch water.

Conclusions:

• Beef cattle feedlot waste harbors a wide array of Enterobacteriaceae, posing a potential hazard if unsterilized waste is reused.
• While runoff and drainage ditch water showed reduced bacterial loads, the primary FLW bacteria persisted.
• Further research is needed to fully understand the implications of these findings for environmental and food safety.