Irene da Silva Coelho

Background/Objectives: The Acinetobacter baumannii–calcoaceticus (Acb) complex comprises opportunistic pathogens of increasing relevance in human and veterinary medicine due to their capacity to acquire multidrug resistance. colistin, a last-resort antimicrobial for carbapenem-resistant A. baumannii (CRAB), is increasingly challenged by the emergence of resistance determinants, including those encoded by the mobilized colistin resistance (mcr) gene family. This study aimed to screen for mcr genes in Acb complex isolates recovered from animal and environmental sources in Rio de Janeiro State, Brazil. Methods: Thirty-five isolates obtained from dogs, cats, horses, and soil between 2018 and 2020 were genotypically identified using multiplex PCR. Of these, 23 successfully recovered isolates were screened for mcr variants (mcr-1 to mcr-9) by multiplex PCR. Results: Five isolates (21.7%) yielded amplicons of expected sizes consistent with the presence of mcr-associated determinants, including two consistent with mcr-7, one with mcr-8, and two with mcr-9. Because amplicon sequencing and phenotypic colistin susceptibility testing were not performed, these findings should be interpreted as preliminary molecular screening results. Conclusions: These findings indicate the presence of PCR-detectable mcr-associated genetic targets in isolates from animal and environmental sources, highlighting the need for further molecular characterization and integrated surveillance under a One Health framework.

Agricultural expansion, combined with poor soil management, can result in soil degradation, erosion, and nutrient depletion. Agroforestry systems (AFS) are sustainable alternatives that promote soil health, conserve biodiversity, and increase productive resilience. This study aimed to evaluate the physical, chemical, and biological attributes of soils under AFS and forests (FOR) in Paraty, Rio de Janeiro, located in the Atlantic Forest biome. In each area, mini-trenches were opened to collect five composite samples at 0–10 cm, with four replicates for chemical, physical, and biological analyses. Ecological similarities were observed between the AFS and FOR systems. While AFS was associated with fertility-related attributes and FOR with organic matter content, the biological components showed comparable patterns. Macrofaunal composition, β -glucosidase activity, abundance of arbuscular mycorrhizal fungi, and glomalin-related soil protein did not markedly differ between the systems. Only arylsulfatase levels were increased in the AFS group. The AFS maintained soil biological integrity, with fungal and bacterial communities exhibiting structures and diversities similar to those observed in the FOR. The fungal class Eurotiomycetes stood out in the AFS due to its higher abundance, while the families and genera Melanommataceae, Hygrophoraceae, Memnoniella, Hygrocybe, Myxarium, and Byssosphaeria were also enriched in this system. In bacterial communities, the class Acidobacteriae was more abundant in FOR, reflecting the influence of soil pH on bacterial composition. Overall, the evaluated AFS demonstrated potential as a strategy for ecological intensification and environmental conservation by maintaining soil and biological attributes comparable to those observed in the forest area while simultaneously enhancing soil fertility.

Poultry production generates substantial quantities of poultry litter, which can be applied to agricultural soils as organic fertilizer. Although this production system is sustainable, it can increase the microbial numbers and change ecological interactions and trophic networks in the soil. This study evaluated the composition, diversity, and structure of bacterial communities in poultry litter generated using conventional and organic production systems and subsequently composted under identical conditions for 125 days. Samples were collected before and after composting. Measurements included temperature, pH, electrical conductivity, and CO ₂ and NH ₃ emissions before and after composting. Total DNA was extracted, and the V3–V4 region of the 16S rRNA gene was sequenced using amplicon sequencing. The poultry litter reached temperatures around 65°C (±2°C) for 3 consecutive days, as established by Brazilian regulations for compost sanitization. The most abundant bacterial classes were Gammaproteobacteria and Alphaproteobacteria, representing 24.7% and 20.6% of the amplicon sequence variants, respectively. Among these groups, the orders Pseudomonales and Rhizobiales predominated. The order Enterobacterales was not detected in any of the poultry litter, before or after composting. Less abundant classes, such as Deltaproteobacteria, Bacilli, and Actinobacteria, showed reduced taxonomic diversity in both poultry litter after composting. Greater complexity and interconnection within the communities in both poultry litters were observed after composting. The bacterial community composition, diversity, and structure were influenced by both composting and the type of production system used. The impact of these remaining microorganisms on soil warrants further investigation because they can cause structural and functional changes in soil environments.

Histosols provide key ecosystem services, including carbon storage, hydrological regulation, and biodiversity support; however, the effects of conventional agriculture on their quality in tropical regions remain poorly understood. In this study, we evaluated the effects of different land-use systems on a Sapric Thionic Histosol in a coastal plain of Rio de Janeiro, Brazil, by comparing a conventional cropping system with a secondary forest under natural regeneration, both with approximately 25 years of contrasting land use. Soil chemical, physical, and biological attributes were evaluated, including microbial diversity, macrofauna, arbuscular mycorrhizal fungi, glomalin, and enzyme activities. Soil quality sub-indices (chemical, physical and biological) were integrated into an overall soil quality index. Conventional cultivation resulted in reduced soil pH, organic carbon, and fertility, whereas physical properties showed no significant changes. Agricultural use significantly altered microbial community structure, reduced bacterial richness and diversity, and shifted functional potential toward stress- and sulfur-related metabolic pathways. Biological indicators, including Oligochaeta, arbuscular mycorrhizal fungi, glomalin content, and enzymatic activity, were notably reduced under cultivation. Consequently, soil quality indices were significantly reduced in cultivated soils, demonstrating that agricultural use of tropical Histosols increases their susceptibility to degradation and is associated with pronounced shifts in microbial community structure, with implications for ecosystem functioning and stability.

Wastewater treatment plants (WWTPs) are important interfaces for the persistence and dissemination of antimicrobial resistance genes (ARGs) in the environment. This study investigated colistin resistance and the presence of mobile colistin resistance (mcr) genes in Enterobacterales isolated from a poultry slaughterhouse WWTP in Brazil. Samples were collected from raw sewage, an equalization tank, and treated effluent. A total of 27 Enterobacter spp. isolates were identified, of which 70.4% showed resistance to colistin (MIC range: 2 to ≥512 mg/L). PCR screening detected mcr-1 in two isolates and mcr-10 in three isolates distributed across all treatment stages, including the final effluent. Whole-genome sequencing of a representative isolate from treated effluent identified Enterobacter vonholyi ST3343, carrying a plasmid-borne mcr-10 gene on an ~107 kb IncFII(Yp) plasmid, along with additional resistance determinants. Phylogenetic analysis supported the classification of this gene as a novel allele, mcr-10.6. The persistence of a clonal lineage harboring mcr-10.6 throughout the treatment system indicates that conventional wastewater treatment may not effectively eliminate clinically relevant ARGs. These findings highlight treated effluent as a potential route for environmental dissemination of colistin resistance and reinforce the need for improved monitoring and mitigation strategies within a One Health framework.

This study aimed to investigate the gradual adaptation of the fecal bacterial community and in vitro fermentative capacity of horses fed a complete extruded diet (CED). Twelve geldings weighing 370 kg were removed from a native pasture and fed coastcross hay ( Cynodon spp) for 7 days. In the second week, horses were assigned to two groups: one group was fed exclusively with coastcross hay (HAY) for 28 days and the other group fed with weekly increases of CED (30%, 60%, and 100%) to replace HAY. Fecal samples were collected on Days 7, 14, 21, and 28 for microbiota and in vitro fermentation analyses. CED intake reduces the relative abundance of phyla Fibrobacteres, Proteobacteria, Campilobacterota, Lentisphaerae, and SR1, while increasing Verrucomicrobia and Synergistetes. The fecal bacterial diversity was maintained until Day 21 (60% CED) but declined when hay was completely withdrawn. Equine fecal microbiota is diet‐dependent; the stability of microbial diversity is more closely linked to the presence of roughage than to CED intake. Also, the inclusion of CED affects its microbial abundance and the detection of bacterial groups able to alter in vitro fermentative activity.

Plant growth-promoting bacteria (PGPBs) offer a sustainable alternative for enhancing crop productivity in low-fertility tropical soils. In this study, 30 bacterial isolates were screened in vitro for multiple PGP traits, including phosphate solubilization (from aluminum phosphate—AlPO₄ and thermophosphate), potassium release from phonolite rock, siderophore production, indole-3-acetic acid (IAA) synthesis, ACC deaminase activity, and antagonism against Fusarium spp. Statistical analysis revealed significant differences (p < 0.05) among the isolates. The most efficient isolates demonstrated a solubilization capacity ranging from 24.0 to 45.2 mg L⁻¹ for thermophosphate and 21.7 to 23.5 mg L⁻¹ for potassium from phonolite. Among them, Pseudomonas azotoformans K22 showed the highest AlPO₄ solubilization (16.6 mg L⁻¹). IAA production among the isolates varied widely, from 1.34 to 9.65 µg mL⁻¹. Furthermore, 17 isolates produced carboxylate-type siderophores, and only Pseudomonas aeruginosa SS183 exhibited ACC deaminase activity, coupled with strong antifungal activity (91% inhibition). A composite performance index identified P. azotoformans K22, E. hormaechei SS150, S. sciuri SS120, and B. cereus SS18 and SS17 as the most promising isolates. This study provides a valuable foundation for characterizing plant growth-promoting traits and identifies key candidates for future validation and the development of microbial consortia.

Antimicrobial resistance is a global public health concern that requires an integrated approach including human, animal and environmental health. Agricultural environments, such as soil, animal waste and irrigation water, play crucial roles in the dynamics of antimicrobial resistance, as they act as reservoirs and pathways for disseminating resistance determinants. However, these agricultural environments are still often underestimated or neglected in many studies. This study aimed to address antimicrobial resistance in agricultural environments in Brazil and summarize the current state of knowledge about this issue in the country. Google Scholar, Google, ISI Web of Knowledge and Web of Science databases were searched for Portuguese, English and Spanish articles addressing antimicrobial resistance in agricultural environments in Brazil published through 2023. Different terms were used, and the findings were categorized according to the research questions posed. A total of 36 articles were found, 20 of which focused on antimicrobial resistance in animal waste from livestock production, 13 addressed antimicrobial resistance in agricultural soils, two considered both environments, and only one considered antimicrobial resistance associated with irrigation water in different agricultural environments. In all studies, diverse classes of resistant bacteria and antimicrobial resistance genes and mobile genetic elements were detected. However, the number of articles addressing this topic in Brazilian agricultural environments - in animal waste, followed by soils and, to a lesser degree, irrigation water - is still quite limited, revealing significant gaps to be filled. Therefore, it is essential to conduct more studies on antimicrobial resistance in these environments to elucidate their roles as reservoirs and sources of antimicrobial resistance and assess the risks to public health.