Effectiveness of cleaners and sanitizers in killing Salmonella Newport in the gut of a free-living nematode, Caenorhabditis elegans

Abstract

Caenorhabditis elegans, a free-living nematode found in soil, has been shown to ingest human enteric pathogens, thereby potentially serving as a vector for preharvest contamination of fruits and vegetables. A study was undertaken to evaluate the efficacy of cleaners and sanitizers in killing Salmonella enterica serotype Newport in the gut of C. elegans. Adult worms were fed nalidixic acid-adapted cells of Escherichia coli OP50 (control) or Salmonella Newport for 24 h, washed, placed on paper discs, and incubated at temperatures of 4 or 20°C and relative humidities of 33 or 98% for 24 h. Two commercial cleaners (Enforce and K Foam Lo) and four sanitizers (2% acetic acid, 2% lactic acid, Sanova, and chlorine [50 and 200 μg/ml]) were applied to worms for 0, 2, or 10 min. Populations of E. coli and Salmonella Newport (CFU per worm) in untreated and treated worms were determined by sonicating worms in 0.1% peptone and surface plating suspensions of released cells on tryptic soy agar containing nalidixic acid. Populations of Salmonella Newport in worms exposed to 33 or 98% relative humidity at 4°C or 33% relative humidity at 20°C were significantly (P ≤ 0.05) lower than the number surviving exposure to 98% relative humidity at 20°C. In general, treatment of desiccated worms with cleaners and sanitizers was effective in significantly (P < 0.05) reducing the number of ingested Salmonella Newport. Results indicate that temperature and relative humidity influence the survival of Salmonella Newport in the gut of C. elegans, and cleaners and sanitizers may not eliminate the pathogen.