Banca de DEFESA: NATALIA PEREIRA DE OLIVEIRA MACHADO

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : NATALIA PEREIRA DE OLIVEIRA MACHADO
DATE: 30/06/2026
TIME: 09:00
LOCAL: Sala 18 do PSA
TITLE:

Virulence factors and antimicrobial resistance in Pseudomonas spp. a One Health perspective

KEY WORDS:

Antibiotics. Agriculture. Colistin. Soil.

PAGES: 87
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SUMMARY:

The genus Pseudomonas comprises ubiquitous Gram-negative bacteria recognized for their high genetic plasticity and ability to accumulate both intrinsic and acquired genes associated with virulence and antimicrobial resistance (AMR). These determinants play a crucial role in bacterial colonization and persistence across diverse environments, including soil, water, animals, and humans. The circulation of these bacteria among different ecological niches facilitates the dissemination of such genes through horizontal gene transfer (HGT), making Pseudomonas an excellent model for investigating microbial adaptation and AMR dynamics across environmental and human-associated settings. In Chapter I, 53 Pseudomonas spp. isolates were analyzed, including 40 strains recovered from agricultural soils (n = 38) and native forest soils (n = 2) in São José do Vale do Rio Preto, Rio de Janeiro, Brazil, as well as 13 isolates obtained from saline soils collected in Guaratiba and the Região dos Lagos, Rio de Janeiro State. Among these isolates, 53% exhibited resistance to at least one antimicrobial agent, with the highest resistance rates observed for aztreonam (36%), ciprofloxacin (23%), and meropenem (19%). Multidrug resistance was detected among isolates from agricultural soils. Colistin resistance was confirmed in 19% of the isolates. The ten strains classified as resistant by both alternative methods (COL-AS and COL-DT) showed 100% categorical agreement (10/10) with the broth microdilution method (BMD), considered the gold standard. Furthermore, three isolates (SI276, SI277, and SI283) exhibited minimum inhibitory concentration (MIC) values exceeding the upper limit of the assay (>512 mg/L), which is remarkably high compared with the clinical resistance breakpoint (>4 mg/L). In addition, 89% of the isolates expressed at least one virulence-associated phenotype, with lipolytic (47%), proteolytic (45%), and hemolytic (32%) activities being the most prevalent. In Chapter II, an in silico analysis was conducted using 1,955 Pseudomonas genomes obtained from human, animal, soil, and water sources. Genomes of human and animal origin displayed greater abundance and diversity of antimicrobial resistance genes and virulence factors than those derived from environmental sources. A total of 249 distinct virulence genes were identified, with fliG and flgG being the most prevalent (99.4%). The most frequent acquired resistance genes were vanW (67%), blaOXA (64%), aph(3') (63.5%), and blaOXA50-like(63.2%). Moreover, a significant positive correlation was observed between the number of resistance genes and virulence factors (ρ = 0.67; p = 3.45 × 10⁻²⁵⁴). Collectively, these findings demonstrate that Pseudomonas spp. inhabiting different environments constitute important reservoirs of antimicrobial resistance genes and virulence determinants and are capable of expressing phenotypes consistent with these genetic traits. Based on both phenotypic and in silico analyses, natural and anthropogenically impacted environments may act as sources for the maintenance and dissemination of bacterial defense mechanisms. Therefore, continuous surveillance and integrated approaches based on the One Health framework are essential for monitoring and controlling the circulation of pathogenic microorganisms and antimicrobial resistance.

COMMITTEE MEMBERS:
Presidente - 1815763 - IRENE DA SILVA COELHO
Externa ao Programa - 1722406 - SHANA DE MATTOS DE OLIVEIRA COELHO - nullExterna à Instituição - SULAMITA SANTOS CORREA - EMBRAPA