Effects of the U.S. Veterinary Feed Directive Final Rule on the Prevalence of Violative Antibiotic Residues and Antibiotic-Resistant Bacteria in Animal Products
Antibiotic-resistant is a public health concern. The dissertation objective was to assess the effect of the implementation of the Veterinary Feed Directive (VFD) rule changes on the prevalence of violative antibiotic residues and antibiotic-resistant bacteria in food-animal tissues, retail meats, and cecal samples from food animals compared to the pre-VFD rule change period in the U.S. To understand the effect of implemented VFD rule changes on violative antibiotic residues in food-animal tissues, inspector-generated sampling (IGS) data from the U.S. National Residue Surveillance Program (NRP) was analyzed. An important observation was that implementing VFD rule changes was associated with the decreased prevalence of violative sulfonamide and penicillin residues in food-animal tissues. However, implementing VFD rule changes did not significantly affect the prevalence of violative tetracycline residues in tissues. To further understand the effect of the VFD rule changes, retail meat surveillance data from the National Antimicrobial Resistance Monitoring System (NARMS) was analyzed. The results indicated that implementing VFD rule changes significantly reduced the prevalence of tetracycline-resistant Campylobacter and Escherichia in chicken and turkey meats. However, the study did not observe a significant effect on tetracycline-resistant Salmonella and Escherichia prevalence in beef and pork. To expand understandings of the effects of the VFD rule changes, cecal samples collected from food animals’ surveillance data in NARMS were analyzed. The results indicated that implementing VFD rule changes significantly reduced the prevalence of tetracycline-resistant Escherichia in cecal samples of chickens and turkey, and erythromycin-resistant Campylobacter in cecal samples of chickens. However, the study revealed that implementing VFD rule changes significantly increased tetracycline-resistant Escherichia in cecal samples of swine and erythromycin-resistant Campylobacter in cecal samples of cattle. In conclusion, implementing VFD rule changes significantly related to reducing the prevalence of tetracycline-resistant bacteria in meats and cecal samples of chickens and turkeys. Conversely, the implementation of VFD rule changes did not impact the prevalence of tetracycline-resistant bacteria in meats and cecal samples of cattle and swine, suggesting a potential surge in usage of injectable tetracycline, which is evident from the lack of reduction in the violative tetracycline residues in food animal tissues that should be further investigated
