Non-therapeutic use of antimicrobials in concentrated animal feeding operations, and, The presence of antibiotic-resistant and arsenic-resistant bacteria in environmental samples and retail meats

The development and persistence of antibiotic-resistant bacteria poses increasing challenges to public health. The use of antimicrobials in human medicine has influenced the emergence of antibiotic-resistant bacteria; however, the non-therapeutic use of antimicrobials for growth promotion in animal agriculture has contributed to this critical problem as well. The purpose of this dissertation was to provide additional data to the growing body of knowledge concerning the public health effects associated with the non-therapeutic use of antimicrobial animal growth promoters (AGPs) in swine and poultry production. Specifically, the objectives of this research were (1) To test Campylobacter jejuni isolated from retail poultry products for resistance to an arsenical AGP used in poultry production and to determine whether arsenic resistance is associated with antibiotic resistance in these isolates; (2) To determine whether the air within concentrated animal feeding operations (CAFOs) is an additional environmental source of human exposure to antibiotic-resistant bacteria; and (3) To determine the prevalence of antibiotic resistance genes among airborne bacteria isolated from a CAFO to shed light on the resistance gene reservoir potential of environmental CAFO-associated bacteria.; Objective 1 was accomplished by testing C. jejuni isolated from retail poultry products for resistance to an arsenical AGP, roxarsone, as well as its metabolites, arsenite (AsIII) and arsenate (AsV), using the minimal inhibitory concentration (MIC) agar dilution method in accordance with National Committee for Clinical Laboratory Standards (NCCLS) guidelines. After MICs were identified, odds ratios were calculated to determine whether arsenic resistance was associated with resistance to ciprofloxacin, another antimicrobial commonly used as an AGP. Objective 2 was achieved by sampling the air within a swine CAFO with an all-glass impinger, isolating Gram-positive bacteria from the air samples and testing the airborne bacteria for resistance to erythromycin, clindamycin, virginiamycin, tetracycline and vancomycin using the NCCLS agar dilution method. Objective 3 was accomplished by characterizing a subset of airborne gram-positive bacteria recovered from a swine CAFO for the specific macrolide, lincosamide, streptogramin (MLS) and tetracycline (tet) resistance genes that they carried using DNA-DNA hybridization, PCR, oligoprobe hybridization and sequencing.; Results of the Campylobacter aspect of this research demonstrated that all of the C. jejuni poultry isolates expressed phenotypic resistance to roxarsone, AsIII, and AsV.; This dissertation research provides the first evidence of phenotypic arsenic resistance in C. jejuni. It is the first study to investigate associations between arsenic resistance and antibiotic resistance in bacteria originating from CAFO environments where both arsenical AGPs and antibiotic AGPs are used non-therapeutically. (Abstract shortened by UMI.)...