Veterinary pharmaceuticals are routinely used in livestock production to treat diseases, prevent infections, and promote growth. However, the potential release of pharmaceuticals from agricultural activities has raised concerns because they may pose detrimental effects to the ecosystems and human health, for example fostering the evolution of antibiotic-resistant bacteria in the natural environment. A better understanding of the environmental fate of veterinary pharmaceuticals is critical to properly assess and mitigate their risks. This dissertation focuses on a major group of veterinary pharmaceuticals, ionophore antibiotics (IPAs), which is sold at over 4 million kilograms per year and constitutes more than one third of the total antibiotic consumption by the livestock industry in the U.S. Despite the extensive usage of IPAs, their environmental fate was not well-understood. Therefore, this study aimed at achieving a comprehensive understanding of the occurrence, persistence, and transformation of IPAs from poultry litter before and after applications to the agricultural lands. Three of the most commonly used members of IPAs were investigated in this study: monensin (MON), salinomycin (SAL), and narasin (NAR). Based on the common management practices of poultry litter, the potential abiotic and biotic transformation reactions of IPAs were examined under varying conditions relevant to the water-soil-litter systems. This dissertation consists of three sections. First, a robust analytical method was developed to quantify IPAs in various environmental compartments, especially in high organic-containing matrices such as poultry litter, and soil and runoff from litter-fertilized lands. Efforts were made to optimize the analytical method with respect to improving extraction recovery, reducing matrix effects, and validating a surrogate standard. Second, lab-scale experiments were set up to determine the chemical properties of IPAs in aqueous environments and to study the abiotic transformation of IPAs, including hydrolysis and photolysis. The results showed that IPAs are prone to hydrolytic transformation in acidic environments, which are likely to be encountered in acidic soils, alum-amended litter (alum: Al₂(SO₄)₃•12H₂O), and acidic runoff. Multiple transformation pathways were proposed based on the identified hydrolysis products. It is also noteworthy that the hydrolysis products of MON still exhibited a toxic effect on the selected microorganism (Bacillus subtilis). SAL and NAR were found to undergo direct photolysis under both UV light and sunlight irradiation. In natural water matrix, IPAs were also degraded by indirect photolysis with hydroxyl radicals generated by light-excited nitrate. Dissolved organic matter can shield IPAs from light and slow down their photolysis. Third, the biodegradation potential of IPAs was first tested in litter and soil microcosms. Factor analysis was conducted to delineate the interaction of water and temperature on IPA degradation in the litter. Litter-fertilized and non-fertilized soil microcosms were compared on the degradation of MON and SAL. Furthermore, the inhibition and biotransformation potential of IPAs were assessed under different redox conditions with litter-enriched cultures. Inhibition tests focused on examining IPAs’ impact on microbial community functions, including denitrification, sulfate-reduction, and methane production. Biodegradation tests were conducted with different electron acceptors, including oxygen, nitrate, sulfate, and organic carbons, with efforts to elucidate primary biotransformation products. On the basis of the results obtained in this study, several recommendations on litter management and IPA selection were made to help mitigate the release and transport of IPAs, as well as enhance their degradation. Overall, this study significantly improved the understanding of the environmental fate of IPAs and the obtained knowledge can aid proper selection of IPAs and management strategies in future applications to minimize the risks of antibiotic micropollutants in the environment.

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2017-12-20T17:22:53Z No. of bitstreams: 1 fernandapyramidesdocoutogomes.pdf: 1744041 bytes, checksum: 559614bb5909c675c36516c829997921 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-12-21T10:42:28Z (GMT) No. of bitstreams: 1 fernandapyramidesdocoutogomes.pdf: 1744041 bytes, checksum: 559614bb5909c675c36516c829997921 (MD5) / Made available in DSpace on 2017-12-21T10:42:28Z (GMT). No. of bitstreams: 1 fernandapyramidesdocoutogomes.pdf: 1744041 bytes, checksum: 559614bb5909c675c36516c829997921 (MD5) Previous issue date: 2017-08-31 / A presença de resíduos de antimicrobianos em leite pode representar grave problema de saúde pública. Por este motivo, algumas medidas legais foram tomadas pelos órgãos competentes, como a venda de medicamentos antimicrobianos sob prescrição médica ou médico veterinária, a observância de Boas Práticas Agropecuárias, e a definição de limites máximos de resíduos (LMR) em alimentos de origem animal. No entanto, os LMR estabelecidos não visam os efeitos sobre tecnologia e fabricação de produtos lácteos, mas sim a proteção da saúde pública. Sob o aspecto tecnológico, as bactérias lácticas são indispensáveis na produção de derivados lácteos fermentados, pois promovem a acidificação controlada e melhoram a textura e o sabor do produto. Assim, a hipótese norteadora deste estudo é que resíduos de antimicrobianos em leite, mesmo abaixo do LMR, são capazes de alterar negativamente a resposta fermentativa das bactérias lácticas. Para tal, foram empregados cinco antimicrobianos (amoxicilina, ceftiofur, gentamicina, sulfametazina e tetraciclina, representante dos cinco principais grupos de antimicrobianos constantes do Plano Nacional de Controle de Resíduos e Contaminantes do Ministério da Agricultura, Pecuária e Abastecimento - MAPA), em cinco diferentes concentrações (0; 0,50; 0,75; 1,0 e 1,25 do respectivo LMR), que foram testados frente a três fermentos comerciais, DELVO® FRESH FC-211 (Lactococcus lactis subsp. lactis e Lactococcus lactis subsp. cremoris), DELVO® CHEESE CP-101 (Streptococcus thermophilus) e DELVO® FRESH YS-131 (Lactobacillus bulgaricus e Streptococcus thermophilus), amplamente utilizados na fabricação de queijos e iogurtes. O leite foi proveniente de três animais diferentes, comprovadamente não-tratados com antimicrobianos. Os controles e tratamentos experimentais foram analisados com respeito à cinética fermentativa. O efeito inibitório das substâncias antimicrobianos foi determinado pela variação na curva de acidificação, bem como quanto ao tempo para se atingir o pH final de referência de cada fermentação. Ceftiofur e tetraciclina inibiram a atividade de cultura contendo Streptococcus thermophilus, mesmo quando empregados em concentrações abaixo de seus respectivos LMR. A cultura composta por Lactococcus lactis ssp. lactis e Lactococcus lactis ssp. cremoris foi inibida pelos antimicrobianos ceftiofur e gentamicina, mesmo quando empregados em concentrações abaixo dos respectivos LMR. Ceftiofur também inibiu a cultura mista de Streptococcus thermophilus e Lactobacillus delbrueckii ssp. bulgaricus, em concentrações abaixo de seu LMR. Assim, os resultados do presente estudo indicam que concentrações abaixo do LMR de antimicrobianos em leite podem interferir negativamente na atividade fermentativa de bactérias lácticas. / The presence of antimicrobial residues in milk represents a serious public health problem. For this reason, some legal measures have been taken by the governments, as a sale of antimicrobial drugs under medical or veterinary medical prescription, observation of Good Agricultural Practices, and the definition of maximum residue limits (MRLs) in foods of animal origin. However, the established MRL do not take into account effects on technology and manufacturing of dairy products, but only the protection of public health. Under the technological aspect, lactic bacteria are indispensable in the production of fermented dairy products, because promote controlled acidification and improve the texture and flavor of the product. Thus, the guiding hypothesis of this study is that antimicrobial residues in milk, even below the MRL, are capable of negatively altering the fermentative response of lactic bacteria. Five antimicrobials (amoxicillin, ceftiofur, gentamicin, sulfamethazine and tetracycline, representing the five main antimicrobial groups included in the National Plan for the Control of Residues and Contaminants of the Ministry of Agriculture, Livestock and Supply (MAPA), in five different concentrations (0, 0.50, 0.75, 1.0 and 1.25 of the respective MRL), which were tested against three commercial lactic cultures, DELVO® FRESH FC-211 (Lactococcus lactis subsp. lactis e Lactococcus lactis subsp. cremoris), DELVO® CHEESE CP-101 (Streptococcus thermophilus) and DELVO® FRESH YS-131 (Lactobacillus bulgaricus e Streptococcus thermophilus). Widely used in the manufacture of cheeses and yogurts. The milk came from three different animals, proven untreated with antimicrobials. Experimental controls and treatments were analyzed with respect to fermentative kinetics. The inhibitory effect of the antimicrobial substances was determined by the variation in the acidification curve as well as the time to reach the final reference pH of each fermentation. Ceftiofur and tetracycline inhibited the culture activity containing Streptococcus thermophilus, even when employed at concentrations below their respective MRL. The culture composed of Lactococcus lactis ssp. lactis and Lactococcus lactis ssp. cremoris was inhibited by ceftiofur and gentamicin antimicrobials, even when used at concentrations below their MRL. Ceftiofur also inhibited the mixed culture of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus, at concentrations below its MRL. Thus, the results of the present study indicate that concentrations below the antimicrobial MRL in milk may negatively interfere with the fermentative activity of lactic acid bacteria.