Vanessa Silva

Coagulase-negative staphylococci (CoNSs) are major opportunistic pathogens in healthcare settings, particularly affecting immunocompromised patients and those with indwelling medical devices. Their growing antimicrobial resistance and ability to form biofilms present significant therapeutic challenges. This study analyzed 148 clinical CoNS isolates to determine species distribution, antimicrobial resistance, resistance genes, and biofilm production. Staphylococcus epidermidis was the most prevalent species (49.3%), followed by Staphylococcus hominis (27.0%) and Staphylococcus capitis (6.8%). Penicillin (83.8%), erythromycin (72.3%), and cefoxitin (66.2%) showed the highest resistance rates. Notably, 60.8% of isolates were resistant to fusidic acid and 45.3% to clindamycin, with inducible resistance in 12.1%. Among aminoglycosides, tobramycin resistance (45.3%) was most frequent. Resistance to ciprofloxacin and trimethoprim–sulfamethoxazole reached 45.9%, while mupirocin resistance was 17.6%. Among isolates resistant to penicillin and/or cefoxitin (n = 128), the mecA gene was detected in 69.5%; the mecC gene was absent. Only 38.5%% of mupirocin-resistant isolates carried the mupA gene. Trimethoprim resistance was mainly associated with dfrA (60.3%) and dfrG (14.7%). Biofilm super-producers accounted for 64.9% of isolates and non-producers for 7.4%, with no significant link between biofilm formation and antibiotic resistance. These findings reinforce the clinical relevance of multidrug-resistant, mupirocin-resistant, and biofilm-forming CoNSs, underscoring the need for improved surveillance and infection control.

Background/Objectives: Enterobacterales are widely distributed in animals and environmental matrices and represent important reservoirs of antimicrobial resistance within a One Health framework. Gulls are particularly relevant because of their synanthropic behavior and frequent contact with anthropogenic waste, which may facilitate the acquisition and dissemination of resistant bacteria. Therefore, this study aimed to investigate the diversity, genomic backgrounds, and resistance determinants of Enterobacterales recovered from gulls and coastal environments in Portugal. Methods: A total of 265 samples, including seagull feces, saltwater, stagnant water, and sand, were collected from four coastal locations. Enterobacterales isolates were recovered and characterized by whole-genome sequencing, and comparative genomic analyses were performed for selected chromosomal beta-lactamase regions. Results:Enterobacterales were recovered from 41 samples and comprised 11 Klebsiella spp., 11 Leclercia spp., 9 Enterobacter spp., and 3 Citrobacter spp. isolates. Isolates were recovered mainly from seagull feces, followed by sand, and Berlenga Grande and Miramar showed the highest diversity. Klebsiella spp. and Enterobacter spp. concentrated most clinically relevant resistance determinants, including chromosomal bla_SHV-like, bla_OXY-like, and bla_ACT-like genes. By contrast, Leclercia pneumoniae was mainly associated with sand and showed a limited resistome, whereas Citrobacter braakii carried relevant genes such as bla_CMY and qnrB10. Comparative genomic analysis showed conserved chromosomal contexts surrounding bla_SHV-like, bla_OXY-like, and bla_ACT-like regions. Conclusions: These findings indicate that gull-associated fecal contamination may play an important role in the introduction and dissemination of resistant Enterobacterales in coastal ecosystems, with subsequent spread to sand and water. Coastal gulls and beach-associated matrices may therefore act as relevant reservoirs and indicators of antimicrobial resistance circulation at the human–environment interface.

Background/Objectives: Enterococcus spp. are important indicators of AMR and potential opportunistic pathogens. Urban green spaces, frequented by dogs and humans, may serve as reservoirs for resistant bacteria. This study assessed the occurrence, AMR profiles, and virulence traits of Enterococcus spp. in dog feces from urban green spaces in Porto (Portugal). Methods: In December 2023 and May 2024, 240 dog fecal samples were collected from 12 urban green spaces across Porto. Enterococcus spp. were isolated using selective culture, identified to species level, and tested for antimicrobial susceptibility following CLSI guidelines. PCR screening was performed for resistance genes (vanA, vanB, erm(A/B/C), vatD/E, tet(M/O/L/K)) and virulence genes (gelE, ace). Environmental and socioeconomic features, including vegetation density (NDVI), presence of water features, and neighborhood deprivation (EDI), were recorded to explore associations with bacterial occurrence and traits. Results: Thirty-two isolates were recovered, mainly E. faecium (n = 9) and E. faecalis (n = 7). High resistance rates were observed to tetracycline (56.3%) and quinupristin/dalfopristin (37.5%), with lower rates for vancomycin, teicoplanin, and ciprofloxacin (3.1%), and imipenem (6.3%). Tet(M) was the most prevalent resistance gene (40.6%), and gelE and ace were frequently detected, often co-occurring with resistance determinants. Distribution of resistance and virulence genes varied across green spaces, with widely used parks showing more isolates. Vegetation density and water features were not directly associated with bacterial recovery. Conclusions: Dog feces in urban green spaces contribute to localized AMR hotspots, acting as potential reservoirs of resistant and potentially pathogenic Enterococcus spp. These findings highlight the importance of One Health strategies for urban sanitation and AMR surveillance.

Apple by-products represent a valuable source of phenolic compounds with significant antimicrobial potential, aligning with sustainable strategies for waste valorisation within the circular bioeconomy. This review focuses on the phenolic profile and antimicrobial relevance of ‘Maçã de Alcobaça,’ a Protected Geographical Indication (PGI) apple variety from Portugal. The main phenolics identified include phloridzin, phloretin, chlorogenic acid, quercetin glycosides, catechin, epicatechin, and procyanidins, which exhibit broad-spectrum antibacterial activity, particularly against Gram-positive pathogens such as Staphylococcus aureus. Their structure–activity relationships and mechanisms of action, namely membrane disruption, enzyme inhibition, oxidative stress induction, and quorum sensing interference, are discussed. Different extraction methods and solvents influence phenolic yield and bioactivity, with ethyl acetate and hydromethanolic extracts generally showing stronger effects. Studies reveal the potential of phenolics to interact synergistically with antibiotics and the promising applications in food preservation, medical formulations, and antimicrobial packaging. Overall, apple-derived phenolics, particularly those derived from industrial by-products, have significant potential as natural antimicrobial agents. Further exploration of these phenolics in the context of One Health and antimicrobial resistance mitigation is recommended.

Klebsiella pneumoniae is an important pathogen associated with multidrug resistance and virulence in both human and animal populations. While its prevalence and resistance patterns are well documented in clinical settings, data on K. pneumoniae in food-producing animals remain scarce. This study aimed to isolate and characterize multidrug-resistant K. pneumoniae strains from healthy rabbits raised for human consumption, with a focus on antimicrobial resistance genes, plasmid content, and associated mobile genetic elements. A total of 295 fecal samples were collected from rabbits across 20 commercial farms in northern Portugal. Isolates were confirmed using MALDI-TOF MS, tested for hypermucoviscosity, and subjected to antimicrobial susceptibility testing (EUCAST). Whole-genome sequencing (WGS) was performed to determine sequence types (STs), resistance genes, plasmids, and resistance determinants for metals and biocides. Six K. pneumoniae isolates were recovered, showing extensive antimicrobial resistance profiles, including ESBL genes such as bla_CTX-M-15, bla_SHV-28, and bla_TEM-1. The most frequent ST was ST307. Multiple genes resistant to heavy metals were identified. Plasmid analysis revealed the presence of IncFII, IncN, and ColRNAI types. Network analysis showed clusters of genetically related isolates and highlighted shared resistance mechanisms. The presence of multidrug-resistant K. pneumoniae in healthy rabbits destined for human consumption underscores the zoonotic potential of this species and the need for surveillance in the animal–food–human interface. These findings contribute to a better understanding of resistance ecology in the context of One Health.

Sternal bursitis is an underexplored lesion in poultry, often overlooked in microbiological diagnostics. In this study, we characterized 36 Escherichia coli isolates recovered from sternal bursitis in broiler chickens, combining phenotypic antimicrobial susceptibility testing, PCR-based screening, and whole genome sequencing (WGS). The genetic analysis revealed a diverse population spanning 15 sequence types, including ST155, ST201, and ST58. Resistance to tetracycline and ciprofloxacin was common, and several isolates carried genes encoding β-lactamases, including blaTEM-1B. Chromosomal mutations associated with quinolone and fosfomycin resistance (e.g., gyrA p.S83L, glpT_E448K) were also identified. WGS revealed a high number of virulence-associated genes per isolate (58–96), notably those linked to adhesion (fim, ecp clusters), secretion systems (T6SS), and iron acquisition (ent, fep, fes), suggesting strong pathogenic potential. Many isolates harbored virulence markers typical of ExPEC/APEC, such as iss, ompT, and traT, even in the absence of multidrug resistance. Our findings suggest that E. coli from sternal bursitis may act as reservoirs of resistance and virulence traits relevant to animal and public health. This highlights the need for including such lesions in genomic surveillance programs and reinforces the importance of integrated One Health approaches.

The overuse of antibiotics in livestock contributes to antimicrobial resistance and zoonotic risk. This study investigated 19 Escherichia coli isolates from broiler feces (Savinor, Portugal), characterizing resistance genes, virulence factors, integrases, and phylogenetic groups by PCR. Most isolates carried ampC, tetA, blaCTX-M, and qnrS; all harbored fimA, and six had int1. Phylogroup A predominated. Resistance was mainly found in commensal groups, highlighting adaptation to poultry environments. The findings underscore the need for regional antimicrobial resistance monitoring and One Health strategies. Stewardship, biosecurity, and alternative measures are vital to mitigate antimicrobial resistance spread and zoonotic potential.

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.

Introduction: Listeria monocytogenes is the causative agent of listeriosis, a serious infectious disease with one of the highest case fatality rates among foodborne diseases affecting humans. Objectives: This study investigated the prevalence, antimicrobial resistance pattern and biofilm production capacity of L. monocytogenes isolated in meats. Materials: A total of 75 samples were analyzed, including fresh meats and meat preparations, in Northern Portugal. Methods: The strains were identified using morphological and molecular methods. Antimicrobial resistance was determined using the Kirby–Bauer disk diffusion method, against a panel of 12 antibiotics and the presence of the respective antimicrobial resistance genes was investigated by polymerase chain reaction (PCR). The ability to form biofilms was evaluated by the microtiter biofilm assay. Results: The overall prevalence of L. monocytogenes among screened samples was 17.33%. The isolates were resistant to trimethoprim-sulfamethoxazole (85.71%), ciprofloxacin (38.10%), meropenem (33.33%), tetracycline and erythromycin (28.57%), rifampicin (23.81%), and kanamycin (14.29%). Six isolates (28.57%) exhibited a multidrug-resistance profile. All strains showed positive result for the virulence gene specific to listeriolysin O (hlyA). In the genotypic resistance analysis of the strains, the genes identified were tetK (23.81%), aadA, tetL, bla_OXA-48 (14.29%), ermC, and msr(A/B) (4.76%). All isolates had the ability to form biofilms, with no significant differences in biofilm biomass production at 24 h and 48 h. Some of these strains showed a high capacity for biofilm production. Conclusions: These findings raise public health concerns due to resistance to first-line antibiotics and the biofilm-forming capacity of these isolates, which pose risks to the food industry. Enhanced monitoring and surveillance are essential to guide public health strategies in order to mitigate the threat posed by L. monocytogenes in food.