Miliane Moreira Soares de Souza

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.

This study investigated the identification, antimicrobial resistance patterns, and phenotypic and genotypic traits of 30 Klebsiella isolates recovered from diverse animal species and infection sites. MALDI-TOF MS demonstrated higher accuracy in species-level identification than conventional phenotypic approaches, revealing a predominance of Klebsiella pneumoniae (80%), followed by K. variicola , K. aerogenes , and K. oxytoca . Multidrug resistance was detected in 46.6% of isolates, while 43.3% were extended-spectrum β-lactamase (ESBL) producers carrying genes such as blaTEM, blaCTX, and blaSHV. One carbapenemase-producing isolate was confirmed, and carbapenemase-encoding genes (blaOXA-48, blaNDM, blaKPC) were identified in additional strains. Notably, hypermucoviscosity was observed in four isolates, including the first report of a hypermucoviscous K. variicola from a dog. These findings highlight the presence of antimicrobial-resistant Klebsiella isolates in animal sources and support the need for integrated One Health surveillance.

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.

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.

The Acinetobacter calcoaceticus-Acinetobacter baumannii (Acb) complex is a major concern in veterinary medicine due to its intrinsic resistance to various antimicrobial agents, including ampicillin, amoxicillin, amoxicillin-clavulanate, and carbapenems. The increasing prevalence of multidrug-resistant (MDR) strains, particularly those producing extended-spectrum beta-lactamases (ESBLs) and carbapenemases, has been observed in animals, with a significant number of urinary tract infections being associated with these pathogens. The present study identified Acb complex strains harboring one or more resistance genes for ESBL and carbapenemase production, highlighting the growing issue of bacterial resistance in veterinary clinical practice. Phenotypic resistance profiling revealed that some Acinetobacter complex strains can hydrolyze a wide range of beta-lactams, including penicillins and third- and fourth-generation cephalosporins, while remaining resistant to cephamycins and carbapenems. Most of the ESBLs belong to Ambler’s class A, and these enzymes can be inhibited by clavulanic acid, sulbactam, tazobactam, and avibactam. The spread of these resistant strains is largely attributed to clonal expansion and horizontal gene transfer, with CTX-M, SHV, and TEM-derived ESBLs being the most clinically significant. Despite advances in molecular diagnostic methods, correlating phenotypic and genotypic data remains a significant challenge. The present findings highlight discrepancies between the phenotypic resistance patterns and the presence of resistance genes, illustrating the complexity of diagnosing and treating infections caused by Acinetobacter species. Further studies are necessary to better understand the mechanisms of resistance, improve diagnostic accuracy, and address the increasing threat of MDR bacteria in the veterinary field.

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.

Escherichia coli is an essential bacteria as a human and animal pathogen, although this species can also be disseminated in the environment. The clinical laboratories use EMB agar (Eosin Methylene Blue) to identify E. coli from the observation of metallic green sheen. However, other bacterial species may show sheen when sown on EMB agar, or in some cases, the pH sample influences the presence of this sheen by E. coli. In this study, MALDI-TOF was used as the gold standard to detect E. coli from human, animal, and environmental samples by analyzing the presence of green glow on EMB agar. The positive predictive values (PPV) ​​were higher (above 85%) in human, animal, and environmental samples studied, and the negative predictive value (NPV) was variable between the samples. Specificity and sensitivity were also variables suggesting the influence of the pH of the samples in the presence of metallic green brightness. This work demonstrated that it is necessary to implement biochemical tests or, when possible, molecular assays to confirm E. coli since only the observation of the production of metallic green glow in EMB can generate false negative results in the identification of E. coli. Keywords: Biochemical tests; Escherichia coli; Laboratory Analysis; MALDI-TOF.

Bovine mastitis is the most common infectious disease in dairy herds and causes important economic losses. Various pathogens can cause the disease, with Staphylococcus aureus being one of the most significant. S. aureus can cause clinical, subclinical, and chronic forms of the disease due to a variety of virulence factors, including protein A, coagulase, toxins, and adhesins. The presence of methicillin-resistant S. aureus strains complicates treatment protocols and raises concerns about antimicrobial resistance. The genetic characterization of these strains, utilizing techniques such as molecular typing by pulsed-field gel electrophoresis (PFGE), reveals the existence of different genetic and virulence profiles, as well as the geographical variations in the distribution of these genotypes. The role of next-generation sequencing (NGS) technologies, functional genomics, and multi-omics approaches in the genetic research of bovine mastitis are highlighted, providing a complete understanding of its genetic basis and opening opportunities for targeted interventions and improved disease control strategies in the dairy industry. This review highlights the importance of understanding the genetic diversity and pathogenic mechanisms of S. aureus in bovine mastitis to develop effective disease management strategies and reduce economic losses in the dairy sector globally.

The emergence and spread of resistance to antimicrobials is one of the three main threats to public health in the 21st century. It must be analyzed using an integrated One Health approach, as it is a health risk shared by people, animals, and the environment. Among these, the necropsy space represents a point of cohesion, being an extremely relevant place for research and understanding the circulation of the bacterial microbiota and its resistance genes. The present study evaluated the occurrence of superbugs in samples from animals necropsied at the Federal Rural University of Rio de Janeiro, considering the priority criteria established by the World Health Organization (WHO). Of the 198 samples collected from 45 animals, 20 pet animals, 20 production animals and three wild animals, 325 strains were isolated, of which 51.38% (167/325) were Enterobacterales, 31.69% (103/325) Staphylococcus spp., 12.62% (41/325) Enterococcus spp., 2.46% (8/325) Streptococcus spp. and 1.85% (6/325) non-fermenting Gram-negative bacilli (NFGNB). In 29.13% (30/103) of Staphylococcus spp., the blaZ gene was detected, and in enterobacteria, the presence of bla _SHV was detected in 10.18% (17/167), bla _TEM in 6.59% (11/167) and bla _CTX-M-1 in 4.19% (7/167). These results reveal the occurrence of species characterized as critical superbugs by the WHO in the necropsy environment and reinforce the need to monitor these strains in the veterinary environment not only for the adoption of appropriate control and treatment measures for animals but also for the implementation of protocols safe for the disposal of their carcasses.

The aim of this study was to characterize bacterial species and their resistance and virulence profiles in a poultry production located in Rio de Janeiro, Brazil. Samples from 1-day-old chicks and broilers were evaluated using dependent and independent cultivation techniques. The 25 strains of Staphylococcus spp. presented the mecA gene. Of the 51 strains of Enterococcus spp., a strain of E. faecium presented the vanB gene, and one strain of E. faecalis presented vanA and vanB genes simultaneously. Analysis of scraped litter from wood used for poultry animals revealed the presence of a carbapenemase resistant gene, blaVIM, in one of the samples evaluated. Of the 44 Enterobacterales isolates, 45% (20/44) were extended-spectrum beta-lactamase (ESBL) producers. Of these, 9 (45%) tested positive for the blaSHV gene, 4 (20%) for the blaCTX gene, 3 (15%) for the blaTEM gene, 2 (10%) for the blaSHV and blaCTX genes and 2 (10%) for the blaSHV and blaTEM genes. Some virulence factors related to avian pathogenic Escherichia coli (APEC) were detected in the E. coli strains. The role of animal production in the emergence and spread of resistance genes is a matter of One Health, requiring studies to be carried out in animal environments.