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Exploring Copper (II) and Nickel (II) complexes for the control of antimicrobial-resistant Campylobacter jejuni and Escherichia coli

Thu, 26 Feb 2026 00:00:00 GMT

Title: Exploring Copper (II) and Nickel (II) complexes for the control of antimicrobial-resistant Campylobacter jejuni and Escherichia coli Abstract: Campylobacter jejuni and Escherichia coli are among the main pathogens associated with foodborne diseases, particularly those originating from poultry. The dissemination of multidrug-resistant strains and their ability to form biofilms favor the persistence of these microorganisms in industrial environments and reduce the effectiveness of conventional antimicrobials and sanitizers. In this context, this thesis aimed to evaluate the potential of two copper(II) complexes, [Cu(tta)(bipy)NO₃] and [Cu(tta)(phen)NO₃], and two nickel(II) complexes, [Ni(η²-NO₃)(bta)(phen)] and [Ni(η²-NO₃)(btacl)(phen)], as alternatives for the control of antimicrobial-resistant C. jejuni and E. coli, integrating phenotypic, genomic, and structural approaches. The thesis was organized into three chapters, with Chapter 1 dedicated to the theoretical framework and Chapters 2 and 3 structured as scientific articles. In Chapter 2, four metal complexes were evaluated against five resistant Campylobacter jejuni isolates. All isolates were classified as strong biofilm formers and exhibited a broad genomic repertoire, including 134 virulence genes and multiple determinants associated with resistance to antimicrobials, metals, and biocides. The complexes significantly reduced bacterial viability and biofilm formation, with particular emphasis on the [Ni(η²NO₃)(bta)(phen)] complex, which showed the lowest minimum bactericidal concentration (6.25 µg/mL) and promoted pronounced disruption of the extracellular matrix. Metabolomic analysis identified 408 compounds belonging to 14 chemical classes, revealing alterations consistent with oxidative stress, metabolic imbalance, and impairment of cellular integrity. In Chapter 3, ten Escherichia coli isolates from the poultry production chain were evaluated. Four isolates (40%) were classified as strong biofilm formers, and all exhibited a multidrug-resistant profile, with seven distinct resistance phenotypes. Genomic characterization revealed 28 antimicrobial resistance determinants, 280 virulence genes, 168 genes associated with resistance to metals and biocides, as well as 13 plasmid replicons. The complexes showed bactericidal activity against both planktonic (1.56–100 µg/mL) and sessile cells (25–400 µg/mL), again with superior performance of the [Ni(η²NO₃)(bta)(phen)] complex. Overall, the results demonstrate that metal complexes, particularly nickel(II)-based compounds, have high potential for the control of resistant bacteria associated with biofilms, contributing to the development of innovative strategies within the One Health framework.

Efeito do estresse por calor no desempenho reprodutivo de matrizes suínas nos trópicos e avaliação do limiar de ITU

Mon, 29 Dec 2025 00:00:00 GMT

Title: Efeito do estresse por calor no desempenho reprodutivo de matrizes suínas nos trópicos e avaliação do limiar de ITU Abstract: First, the study aimed to model and estimate the impact of the maximum temperature–humidity index (THImax) on the number of stillbirths in sows and to calculate the stress–comfort ratio (S/C). A total of 36,880 farrowings from sows in a commercial farm in Brazil were analyzed. Females were grouped according to parity as gilts, primiparous sows, sows with 2–5 parities, and sows with ≥6 parities. THImax on the day of farrowing was classified as ≤74 (thermal comfort), 75–78 (mild stress), 79–82 (moderate stress), and >82 (severe stress). The effect of THImax on the daily number of stillbirths was estimated using quasi-Poisson regression. The mean number of stillbirths per farrowing and per THImax category was analyzed by ANOVA, and the S/C ratio was subsequently calculated according to THImax categories. Out of a total of 1,826 days, 14.95% were classified as thermal comfort days. Multiparous sows (≥2 parities) showed a higher number of daily stillbirths under THImax >82, whereas primiparous sows showed higher values under THI <74. According to the S/C ratio (severe/comfort), increases in stillbirths of 20% in gilts, 7% in primiparous sows, 14% in sows with 2–5 parities, and 19% in sows with ≥6 parities were observed. The quasi-Poisson model indicated an increase in daily stillbirths in multiparous sows (≥2 parities) under THImax >82, and an S/C ratio greater than 1 across all parity groups, indicating an increased mean number of stillbirths per farrowing, particularly under severe heat stress conditions. In the second study, the objective was to model and estimate the effects of air temperature (Ta) and relative humidity (RH) on respiratory rate (RR), rectal temperature (RT), and surface temperature (ST) of sows, and to assess whether the current THI threshold underestimates or overestimates heat stress under tropical production conditions. A total of 98 sows from a commercial farm in Brazil were evaluated and grouped according to parity as gilts, primiparous sows, sows with 2–6 parities, and sows with 7–11 parities. The effects of environmental variables on thermophysiological responses were estimated using quasi-Poisson regression (RR) and Gaussian models (RT and ST). Increases in Ta and RH significantly affected RR, RT, and ST in sows with 2–6 parities, whereas in gilts, only ST was affected. When estimating RR, this variable was identified as the first physiological response to increase with rising Ta and RH in primiparous and multiparous sows (≥2 parities). In these groups, RR exceeded the physiological threshold (32 breaths·min⁻¹) while THI values were still below 74. In conclusion, heat stress affects sows differently according to parity, and the current THI threshold (74) underestimates the impact of heat stress on sows raised under tropical conditions.

Análise da estabilidade pré-analítica do paratormônio canino submetido à centrifugação refrigerada, convencional e com resfriamento adaptado

Mon, 26 Jan 2026 00:00:00 GMT

Title: Análise da estabilidade pré-analítica do paratormônio canino submetido à centrifugação refrigerada, convencional e com resfriamento adaptado Abstract: The measurement of parathyroid hormone (PTH) is challenging and can be significantly affected by pre-analytical factors. Refrigerated blood collection and centrifugation are recommended; however, access to specialized laboratory equipment is often limited. In this context, the present study aimed to evaluate the pre-analytical stability of canine PTH subjected to adapted cooled centrifugation (CTRes) and room-temperature centrifugation (CTA), in comparison with standard refrigerated centrifugation (CTRef). A total of 18 dogs were included, comprising nine animals in the control group (CG) and nine dogs with chronic kidney disease (GPTH) and suspected elevated PTH concentrations. Each dog underwent a single blood collection of 3 mL, which was equally aliquoted and processed using CTRef, CTRes (refrigerated centrifugation with frozen water tubes), and CTA. Plasma PTH (1–84) concentrations were determined using an immunoassay. Both CTRes and CTA demonstrated high agreement with CTRef in the quantification of PTH (1–84), with concordance rates of 98% and 96.1%, respectively, and minimal bias relative to CTRef when analyzed by a third-party laboratory. No significant differences were observed among the methods, indicating the feasibility of CTRes and CTA as alternative pre-analytical processing approaches. Therefore, sample processing using CTRes and CTA represents reliable alternatives to conventional refrigerated centrifugation (CTRef) for canine PTH measurement, particularly in resource- limited settings, supporting the diagnosis of mineral metabolism disorders, provided that blood samples are collected and transported under refrigerated conditions.

Implantação e avaliação de um sistema agroflorestal para recuperação de pastagem degradada no bioma Cerrado

Thu, 31 Jul 2025 00:00:00 GMT

Title: Implantação e avaliação de um sistema agroflorestal para recuperação de pastagem degradada no bioma Cerrado Abstract: The aim of this research is to present a agroforestry system (AFS) focused on improving the thermal quality of the environment and balancing the carbon budget. In the first manuscript, aimed to describe the costs, implementation and dynamics of changes in the thermal environment of an AFS in a degraded pasture of Urochloa decumbens in tropical environment. To do this, an AFS was planted in two rows 3 m apart in an isolated area 6 m wide and 90 m long. The rows were covered with cattle manure, fermented corn silage waste, composted calf bedding and NPK 08-28-16 formulation (250 g.m linear-1). The rows were planted with Eucalyptus grandis, Musa spp. AAB, Morus nigra, Manihot esculenta Crantz, Tithonia diversifolia and Dipteryx alata. The implementation cost was BRL 4312.28 (US$ 763.33), which was mainly comprised of the mechanized preparation of the area (29.90%) and labor (21.11%). Compared to the degraded pasture, there was a reduction in the temperature and humidity index (THI), black globe humid index (BGHI) and radiant thermal load (RTL) during the dry season within the AFS. The agroforestry model enable a low investment cost for the formation of natural shading and a reduction in heat stress factors from 16 months of implementation. In the second manuscript, aimed to develop a DPSIR tool for a degraded Urochloa decumbens pasture in the Cerrado biome and propose the implementation of a low-tech AFS as a mitigating action against carbon loss. A biodiverse AFS was developed in a degraded Urochloa decumbens pasture and, 36 years after its implementation, a DPSIR tool was developed for pasture degradation in the Cerrado, suggesting the use of the AFS as a response to the impacts generated by the process, highlighting the accumulation of carbon in the production system. It was observed that the Eucalyptus spp. plants in the SAF generated a stock of 4.567 Mg of C after 36 months of implementation. The DPSIR tool for pasture degradation processes in the Cerrado, which presents it as a multifactorial condition capable of generating risks to the environmental, economic and social sustainability of livestock production systems, but which allows the SAF to be adopted as a response to the environmental impacts generated. It is concluded that the low-tech AFS made it possible to partially mitigate the impacts caused by a degraded tropical pasture in the Cerrado biome.