Telma de Sousa

SUMMARY: The ESKAPE group of pathogens represents one of the most critical threats to global health due to their capacity to evade antimicrobial treatments. This review provides a structured synthesis of the literature addressing antimicrobial resistance mechanisms, epidemiological relevance, clinical impact, and emerging strategies for containment within a One Health framework. Relevant studies and surveillance reports were analyzed to characterize the global distribution and burden of these organisms across human, animal, and environmental settings. The evidence indicates that ESKAPE pathogens remain leading causes of healthcare-associated infections while increasingly being identified in non-clinical reservoirs, highlighting the interconnected nature of antimicrobial resistance. Recent findings point to sustained high morbidity and mortality associated with these pathogens, driven by the expansion of multidrug-resistant lineages, and the limited effectiveness of current therapeutic options. Key challenges identified include gaps in surveillance integration, the spread of resistance determinants across sectors, and variability in infection control practices. Addressing these issues requires coordinated strategies that integrate surveillance, antimicrobial stewardship, infection prevention, and the development of novel therapeutics within a comprehensive One Health approach.

Livestock faeces constitute an important environmental interface within the One Health framework, as bacteria shed by animals are directly exposed to external environmental conditions, where they may persist and subsequently disseminate across the human, animal, and environmental sectors. The ability of these microorganisms to tolerate environmental stresses is therefore critical for their persistence and ecological distribution. In this study, the responses of 5 Pseudomonas putida, 15 Pseudomonas fulva, and 12 Alcaligenes faecalis isolates recovered from livestock faeces to different environmental stress conditions were investigated. Bacterial growth was evaluated under different temperatures, increasing NaCl concentrations, and carbon starvation, while biofilm formation was assessed using the microtiter plate assay. Growth was markedly affected by all stress conditions, although substantial variability was observed among isolates of the same species. Despite reduced growth under the most adverse conditions, all three species remained capable of growing across a wide range of environmental stresses. A. faecalis exhibited greater salt tolerance and biofilm-forming capacity than Pseudomonas spp., with biofilm formation detected in almost all isolates of both species. Furthermore, no statistically significant correlations were detected among the evaluated stress tolerance traits. These findings demonstrate that livestock-associated P. putida, P. fulva, and A. faecalis possess physiological characteristics that promote persistence under diverse environmental conditions, highlighting the potential role of livestock faeces as environmental reservoirs of opportunistic bacteria within the One Health context.

Species of the genus Streptococcus constitute important pathogens in human and veterinary medicine, being responsible for a wide spectrum of infections ranging from mild illnesses to severe invasive pathologies. Although β-lactams continue to be effective against most species, the global increase in resistance to macrolides, lincosamides, tetracyclines, and, in some cases, reduced susceptibility to penicillin represents a growing challenge for antimicrobial therapy. This review synthesizes the clinical and epidemiological landscape of antimicrobial resistance in the main Streptococcus species, including Streptococcus pyogenes, Streptococcus agalactiae, Streptococcus pneumoniae, Streptococcus dysgalactiae, and other species of clinical and veterinary relevance, addressing their epidemiological profiles, molecular mechanisms of resistance, and virulence factors. The main genetic determinants involved in resistance are discussed, namely the erm, mef, and tet genes, as well as the impact of alterations in penicillin-binding proteins, horizontal gene transfer, and biofilm formation on the persistence of infections and decreased therapeutic efficacy. Simultaneously, the main virulence factors are analyzed, including polysaccharide capsules, adhesins, toxins, extracellular enzymes, and immune response evasion mechanisms that contribute to the colonization, dissemination, and severity of infections. The importance of epidemiological and genomic surveillance, particularly through whole-genome sequencing, in monitoring the spread of resistant clones and identifying determinants of resistance and virulence is also highlighted. Taken together, the data highlight the need to strengthen programs for the rational use of antimicrobials, to promote integrated surveillance strategies from a One Health perspective, and to deepen knowledge about the interaction between antimicrobial resistance and virulence, in order to improve strategies for the prevention, diagnosis, and treatment of infections caused by Streptococcus spp.

Antimicrobial resistance (AMR) is a global health crisis addressed through a One Health framework. However, recent European Union (EU) surveillance data reveals a marked divergence in progress between the human and animal sectors. This study analyzes the most recent monitoring reports (European Surveillance of Antimicrobial Consumption Network and European Sales and Use of Antimicrobials for Veterinary Medicine, 2024) to compare the effectiveness of mitigation strategies across sectors. The findings expose a clear paradox: while the veterinary sector has achieved a structural 24.3% reduction in antimicrobial sales in the EU since 2018, human medicine has recorded a 2% increase in overall consumption, diverging from established reduction targets. From a qualitative perspective, veterinary medicine has nearly eliminated the use of critically important antimicrobials in the AntiMicrobial Expert Group (AMEG) (category B), including polymyxins and third-generation cephalosporins, which now account for only 0.24% of total sales. In contrast, human medicine continues to struggle to contain antimicrobial resistance in key sentinel pathogens, notably Klebsiella pneumoniae and Escherichia coli. Furthermore, companion animals, representing 97.9% of non-food-producing animal biomass, emerge as a reservoir of antimicrobial-resistant bacteria due to the intensive use of broad-spectrum oral formulations. The results indicate that the veterinary regulatory model, centered on binding volume reduction and preventive strategies, has been more effective in reducing overall antimicrobial consumption compared to the voluntary, guideline-based stewardship approaches currently used in human medicine. Achieving meaningful control of antimicrobial resistance will require human medicine to adopt the same level of structural rigor already implemented in animal production systems.

A complex, dynamic microbiota inhabits cheese and cheesemaking environments. Such microorganisms can move across the dairy chain, from the microbiomes of production animals, through humans and environments which they interact with. These interactions impact all sectors of the One Health continuum. They may contribute to disseminate beneficial bacteria that enhance cheese quality, sustainability, and consumer health, but they also promote spread of pathogenic strains, along with their genetic determinants of virulence and antibiotic resistance across the milk and cheese production chain. This comprehensive, narrative review aims at providing a current view on cheese, its microbes, their roles, genetic determinants of virulence and antibiotic resistance, their relevance within the scope of the One Health approach and proposes using enterococci as sentinel microorganisms for monitoring AMR in cheese production chains.

Canine otitis externa is a common and recurrent ear infection in dogs, often caused by bacterial pathogens, and complicated by increasing antimicrobial resistance. The analysis of bacterial isolates from dogs with otitis externa revealed a predominance of Staphylococcus pseudintermedius, representing 41% of all cases, followed by Staphylococcus aureus (23%), and Pseudomonas aeruginosa (19%). Other less frequently isolated organisms included Escherichia coli, Streptococcus canis, and Proteus mirabilis. These results highlight the significant role of S. pseudintermedius in the pathogenesis of otitis externa in dogs, as well as the relevance of Gram-negative opportunistic pathogens like P. aeruginosa, which exhibits the highest recurrence rate, with 90% of the cases associated with highly resistant to β-lactams (93% for amoxicillin–clavulanic acid; >70% for third-generation cephalosporins). P. mirabilis showed complete resistance to tetracycline, partial resistance to doxycycline, and reduced susceptibility to carbapenems, nitrofurantoin, and polymyxin B. S. canis exhibited limited resistance to erythromycin and clindamycin, while S. epidermidis displayed extensive multidrug resistance, including β-lactams, fluoroquinolones, sulfonamides, and polymyxins. These findings highlight the high prevalence of multidrug-resistant pathogens in canine otitis externa, emphasizing the need for culture-guided therapy and raising concerns regarding One Health, due to potential zoonotic transmission and dissemination of genetic determinants of antimicrobial resistance.

Y. enterocolitica is a cold-tolerant, foodborne pathogen that poses a significant risk to public health, with pigs identified as its main reservoir. This review explores the current knowledge on the epidemiology, transmission, and virulence of Y. enterocolitica in pigs, highlighting their central role in spreading the bacterium to humans—primarily through the consumption of raw or undercooked pork. The pathogen is frequently found in pig tonsils and intestines and can contaminate meat during slaughter. Among the various strains, bioserotype 4/O:3 is the most common cause of human illness. Y. enterocolitica carries a diverse set of virulence genes, such as ail, yst, inv, and yad, and evades immune responses. The review also covers major outbreaks, risk factors on farms and in slaughterhouses, and the limitations of current surveillance systems. Reducing the impact of Y. enterocolitica requires a One Health approach linking animal health, food safety, and public health.

This study aimed to assess the emergence and/or re-emergence of Tick-borne Diseases (TBD) in Portugal by linking the hemoparasite burden in companion animals to vector-borne disease dynamics through a One Health approach. Between 2015 and 2024, 1169 clinically suspected animals with hemoparasite infections, treated at the Hospital Veterinário de Santarém (HVS), underwent serological confirmation for Rickettsia conorii, Babesia canis, Ehrlichia spp., and Haemobartonella spp. A total of 3791 serological tests (3.2 tests per animal) were performed and 437 animals tested positive for at least one of the four hemoparasites under investigation. From 2020 to 2024, tests nearly tripled from 894 to 2883, raising positive cases and prevalence from 29.5% to 39.9%, especially for rickettsiosis and hemobartonellosis, indicating an increased circulation of their vectors. A national vector surveillance initiative identified Hyalomma spp., Rhipicephalus sanguineus, Ixodes ricinus, and Dermacentor sp. as primary tick vectors in Portugal for the hemoparasites mentioned above and for other agents like arbovirus, such as Crimean-Congo Hemorrhagic Fever Virus (CCHFV) and tick-borne encephalitis virus (TBEV). This study found that the vectors responsible for transmitting hemoparasitosis, given the high number of serologically positive cases detected in the HVS, represent an increasing risk for TBD. These findings highlight the relevance of companion animal monitoring as an early-warning component within a One Health surveillance approach.

Aquatic resistomes are important reservoirs of antibiotic resistance genes (ARGs) and their precursors, which can proliferate and dissipate in pathogenic microorganisms that affect humans and animals, especially due to anthropogenic pressures such as the intensive use of antibiotics in aquaculture, often without effective regulation. This review addresses the mechanisms of horizontal gene transfer (HGT) in the dissemination of ARGs through mobile genetic elements (MGEs). In freshwater, genera such as Aeromonas, Pseudomonas and Microcystis stand out as vectors of ARGs. In the context of One Health, it is essential to implement sound public policies and strict regulations on the use of antibiotics in aquaculture, and the use of monitoring tools such as environmental DNA (eDNA) and metagenomics allows for the early detection of ARGs, contributing to the protection of human, animal and environmental health.

Antimicrobial resistance (AMR) is a global health emergency. The growing levels of multidrug-resistant bacteria in companion animals represent a critical but under-recognized threat, as pets can act as reservoirs and vectors of resistant pathogens, and bacteria can spread between species. Despite living in close proximity to humans and sharing many of the same antibiotic classes, companion animals remain largely overlooked in the AMR control strategies. A major obstacle to combating AMR in Europe is the absence of a mandatory and uniform surveillance system. Without a standardized approach, data collection remains inconsistent, leading to knowledge gaps and hindering effective investigation and policymaking. Surveillance failures prevent a comprehensive understanding of resistance patterns, making it difficult to implement timely and evidence-based measures. Existing laws and regulations are insufficient to contain the growing threat of AMR. Current policies fail to enforce strict antimicrobial stewardship across all European countries and lack the necessary scope to address resistance effectively. Urgent action is required—Europe must implement stronger, harmonized surveillance systems, enforce stricter veterinary antimicrobial regulations, and develop more active and binding programs to curb resistance before it reaches an uncontrollable level. A One Health approach, recognizing the interconnectedness of human, animal, and environmental health, is essential.