Evaluation of cattle exposed to high concentration of heavy metals and their relationship with changes in intestinal, ruminal and respiratory microbiota and the development of antimicrobial resistance

Author(s)

Natália Carrillo Gaeta

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD)
• Defense date: 2021-02-05

Examining board members

Lilian Gregory; Nilton Erbet Lincopan Huenuman; Luigi Jovane; Erika Ganda Ricotta; Huber Rizzo

• Advisor: Lilian Gregory

Abstract

Cases of environmental contamination originating from human errors are gaining more and more space in the media, alerting everyone to the fragility of the environment in the face of events. Technical and structural problems of dams were highlighted in the national and international media, which generated unimaginable consequences both for the environmental contamination and for the death of hundreds of people in the State of Minas Gerais, Brazil. In 2015, the mining municipality of Mariana was severely affected by the spill of over 43 million cubic meters of iron ore tailings due to the collapse of the Fundão dam. As a result, the region\'s environment also suffers from the continuous dumping of domestic and agricultural sewage, containing elements harmful to the environmental balance. Heavy metals can, by various mechanisms, trigger resistance to antibiotics and the modification of the microbiota, impacting the health of animals and, consequently, the economy of the region, in addition to causing negative consequences to human health. This study aimed to study dairy cattle raised in the region of Mariana, Minas Gerais (impacted by toxic waste), regarding health, the occurrence of bacterial resistance to antimicrobials, and possible changes in the microbiota of these animals. The river water was also evaluated for the presence of heavy metals and bacteria resistant to antimicrobials. Fourty-eight cattle females were studied, 28 raised in Mariana, Minas Gerais (F1), and 30 raised in Caldas, Minas Gerais (place without a history of environmental contamination) (F2). Samples of whole blood (to obtain serum), fecal and deep nasal swab, ruminal fluid, and water were obtained from both locations. The physical and renal and hepatic profiles of the animals were evaluated, as well as the concentration of heavy metals in serum and water using the x-ray fluorescence methodology. The intestinal, ruminal, and respiratory microbiome and resistome were studied and, finally, the presence of antimicrobial- resistant bacteria in the water samples. At the time of the visit to the properties, the animals did not show any clinical manifestation due to heavy metal poisoning. There was the detection of arsenic and aluminum in animals from both regions studied, in concentrations below the maximum safe limit for the species. As for the bovine metagenome, the F1 microbiome and resistome were different from F2. The relative abundance and prevalence of antimicrobial resistance genes were higher in F1 than in F2. F1 samples showed a high presence of antibiotics, metal, biocide, and multidrug resistance genes. The analysis of the river water indicated the presence of aluminum and iron in concentrations considered below the limit established by Organs regulatory agencies. The microbiological study of water revealed innumerable bacteria resistant to antibiotics and heavy metals such as arsenic and mercury and with genetic analysis, the occurrence of co-resistance was suggested. Knowing that heavy metal contamination affects the microbiome and animal resistome, water quality, and environmental balance, environmental actions concerning mining are necessary and urgent, such as adequate construction and maintenance of dams, searches for less harmful mineral extraction methods and with less production of tailings, adequate tailings treatment and continued evaluation of the presence and dissemination of resistance genes. These actions are fundamental to guarantee the environmental, animal, and food production system protection from the dangerous consequences resulting from the high dumping of contaminants. (AU)

• FAPESP's process: 16/23204-9 - Clinical evaluation of bovines exposed to high concentration of heavy metals and its relationship with intestinal, ruminal and respiratory microbiota change and the development of antibiotic resistance in bacteria
• Grantee: Natália Carrillo Gaeta
• Support Opportunities: Scholarships in Brazil - Doctorate