Banca de DEFESA: HOSANA DAU FERREIRA DE SOUZA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : HOSANA DAU FERREIRA DE SOUZA
DATE: 25/09/2025
TIME: 15:00
LOCAL: Google Meet
TITLE:

INVESTIGATION OF COLISTIN-RESISTANT ENTEROBACTERALES IN POULTRY SLAUGHTERHOUSE WASTEWATER: MICROBIOLOGICAL AND EPIDEMIOLOGICAL ASPECTS

KEY WORDS:

Bacterial resistance, Animal production, Water quality

PAGES: 85
BIG AREA: Ciências Agrárias
AREA: Medicina Veterinária
SUBÁREA: Medicina Veterinária Preventiva
SUMMARY:

Poultry production is one of the most important agricultural activities for the Brazilian economy and has shown significant growth over the past decade. In 2024, Brazil produced approximately 14.972 million tons of chicken meat, ranking as the second largest global producer and the world leader in exports within this sector. During poultry meat production, it is essential to consider that water consumption ranges from 5,000 to 21,000 liters per ton of meat, generating large volumes of effluents throughout the slaughtering chain. Additionally, poultry farming produces significant amounts of waste, including dead bird carcasses and poultry litter—a mixture of excreta, feathers, skin dander, and food remnants—which can impact water resources through excessive consumption, soil infiltration, and contamination of surface and groundwater.

The use of antimicrobials in animal production has become widespread as growth promoters, helping to control pathogens and enhance animal performance, often through continuous low-dose administration aimed at reducing carcass rejection and productivity losses. Despite their effectiveness, there is growing pressure to replace them due to the alarming rise in antimicrobial resistance. In this context, water becomes a potential route for the dissemination of multidrug-resistant bacteria, increasing the risk of transmission among animals, the environment, and even humans.

Among various classes of antimicrobials, polymyxins have been extensively used in veterinary medicine to control infectious processes and as growth promoters in livestock. Polymyxin resistance was once believed to arise solely from chromosomal regulatory changes and mutations. However, in 2015, the first mobile resistance gene (mcr-1) was identified on a plasmid in Escherichia coli in China. The presence of resistance to polymyxin E (colistin) in mobile genetic elements poses a significant risk to public health, as these elements can spread rapidly via horizontal gene transfer (HGT). The mcr-1 gene has been documented on at least five continents, but its origin, acquisition, emergence, and dissemination mechanisms remain poorly understood.

This study aimed to characterize colistin-resistant Enterobacterales in wastewater samples from the treatment plant of a poultry slaughterhouse located in the municipality of São José do Vale do Rio Preto, in the mountainous region of Rio de Janeiro State, Brazil. Sixteen water samples were collected at different points along the treatment flow. A total of 140 Enterobacterales strains were isolated and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The isolates were tested for colistin minimum inhibitory concentration (MIC) using broth microdilution; 39 were classified as resistant (MIC > 2 µg/mL). These were screened for the presence of mcr-1 to mcr-10 genes via conventional PCR. Sixteen isolates carried at least one of the targeted genes, with mcr-1 being detected in E. coli, Enterobacter spp., and Klebsiella spp. across all three sampling points, and mcr-10 being identified in Enterobacter bugandensis.

Positive isolates were subjected to clonal typing using Multilocus Sequence Typing (MLST). Additionally, E. coli strains were assigned to phylogenetic groups using the Clermont method. Finally, Enterobacter bugandensis and Klebsiella pneumoniae isolates obtained from treated effluent were selected for whole-genome sequencing. The identification of mcr genes in different Enterobacterales species throughout the treatment chain highlights the role of slaughterhouse wastewater as both a reservoir and a potential source of colistin resistance dissemination. The detection of such genes, even after wastewater treatment, underscores the need for continuous surveillance and the improvement of biosecurity strategies. This study contributes to the understanding of resistance dynamics in environments linked to animal production and supports public policy development aimed at mitigating the risks associated with the spread of resistance genes, particularly under the One Health framework

COMMITTEE MEMBERS:
Interna - 1722406 - SHANA DE MATTOS DE OLIVEIRA COELHO
Externa ao Programa - 1609810 - LIDIANE DE CASTRO SOARES - UFRRJExterno ao Programa - 1337836 - RAMON LOUREIRO PIMENTA - UFRRJExterna à Instituição - MAYSA BEATRIZ MANDETTA CLEMENTINO
Externa à Instituição - KAYLANE MONTENEGRO DA SILVA - FIOCRUZ
Externo à Instituição - ALEXANDER MACHADO CARDOSO
Externa à Instituição - DAYANNE ARAUJO DE MELO - UV