Degree

Doctor of Philosophy (PhD)

Department

Nutrition and Food Science

Document Type

Dissertation

Abstract

Catfish inspections have transitioned from the U.S. Food and Drug Administration (FDA) to the United States Department of Agriculture (USDA). The USDA Food Safety and Inspection Service (FSIS) and Food Emergency Response Network (FERN) consider it important to assess the food safety risk associated with consuming catfish in the United States. Surveillance of farm-raised and wild-caught catfish for pathogens is relevant as a public safety protocol. The purpose of this study was to detect the prevalence of Salmonella spp., identify and examine isolates for antibiotic resistance to clinical treatments, evaluate the effectiveness of antimicrobial chemical treatments against Salmonella enterica, and assess the presence of sanitary indicator organisms in raw wild-caught (WC) and farm-raised (FR) retail channel catfish carcasses. Catfish samples (n=240) were collected from retail markets in the southeast region of Louisiana for 24 months. Salmonella spp. detection was conducted using the USDA Microbiology Laboratory Guidebook (MLG) methods MLG 4.08 and MLG 4C.07. Presumptive positives were confirmed using biochemical assay and serological testing. Confirmed Salmonella positives were examined by VITEK®2 AST-GN69 in vitro for antibiotic resistance of 16 clinical antibiotic agents. Retail channel catfish inoculated with a combination of S. enterica strains (S. typhimurium, S. senftenberg, S. concord, S. infantis) (~ 5.5 log CFU ml/g) were tested with 12 antimicrobial chemical treatments and sterile ice water at 4°C for 8 days to examine the effectiveness of the treatments. Retail market channel catfish samples (n=120) were studied for the enumeration of aerobic plate count (APC), coliforms, and Escherichia coli (E. coli), Staphylococcus aureus and Salmonella spp. using appropriate selective and differential media. Salmonella spp. was detected and confirmed positive of 6 wild caught and 0 farm raised catfish. Salmonella isolates (n=6) expressed resistance to cefazolin, gentamicin, tobramycin out of 16 applied antibiotics. WC catfish has larger sanitation indicator microorganism load than FR catfish. There is a significant sanitation indicator bacteria difference among retail markets. Antimicrobial chemical treatments were effective at reducing S. enterica. Organic acid treatments were most influential in the eradication of S. enterica.

Committee Chair

Janes, Marlene

Available for download on Saturday, October 22, 2022

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